1 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
2 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
3 [<!ENTITY mdash "—">]>
5 - Copyright (C) 2004-2010 Internet Systems Consortium, Inc. ("ISC")
6 - Copyright (C) 2000-2003 Internet Software Consortium.
8 - Permission to use, copy, modify, and/or distribute this software for any
9 - purpose with or without fee is hereby granted, provided that the above
10 - copyright notice and this permission notice appear in all copies.
12 - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
13 - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
14 - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
15 - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
16 - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
17 - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
18 - PERFORMANCE OF THIS SOFTWARE.
21 <!-- File: $Id: Bv9ARM-book.xml,v 1.450.4.12 2010/08/16 22:27:17 marka Exp $ -->
22 <book xmlns:xi="http://www.w3.org/2001/XInclude">
23 <title>BIND 9 Administrator Reference Manual</title>
34 <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
41 <holder>Internet Software Consortium.</holder>
45 <chapter id="Bv9ARM.ch01">
46 <title>Introduction</title>
48 The Internet Domain Name System (<acronym>DNS</acronym>)
49 consists of the syntax
50 to specify the names of entities in the Internet in a hierarchical
51 manner, the rules used for delegating authority over names, and the
52 system implementation that actually maps names to Internet
53 addresses. <acronym>DNS</acronym> data is maintained in a
55 hierarchical databases.
59 <title>Scope of Document</title>
62 The Berkeley Internet Name Domain
63 (<acronym>BIND</acronym>) implements a
64 domain name server for a number of operating systems. This
65 document provides basic information about the installation and
66 care of the Internet Systems Consortium (<acronym>ISC</acronym>)
67 <acronym>BIND</acronym> version 9 software package for
68 system administrators.
72 This version of the manual corresponds to BIND version 9.7.
77 <title>Organization of This Document</title>
79 In this document, <emphasis>Chapter 1</emphasis> introduces
80 the basic <acronym>DNS</acronym> and <acronym>BIND</acronym> concepts. <emphasis>Chapter 2</emphasis>
81 describes resource requirements for running <acronym>BIND</acronym> in various
82 environments. Information in <emphasis>Chapter 3</emphasis> is
83 <emphasis>task-oriented</emphasis> in its presentation and is
84 organized functionally, to aid in the process of installing the
85 <acronym>BIND</acronym> 9 software. The task-oriented
86 section is followed by
87 <emphasis>Chapter 4</emphasis>, which contains more advanced
88 concepts that the system administrator may need for implementing
89 certain options. <emphasis>Chapter 5</emphasis>
90 describes the <acronym>BIND</acronym> 9 lightweight
91 resolver. The contents of <emphasis>Chapter 6</emphasis> are
92 organized as in a reference manual to aid in the ongoing
93 maintenance of the software. <emphasis>Chapter 7</emphasis> addresses
94 security considerations, and
95 <emphasis>Chapter 8</emphasis> contains troubleshooting help. The
96 main body of the document is followed by several
97 <emphasis>appendices</emphasis> which contain useful reference
98 information, such as a <emphasis>bibliography</emphasis> and
99 historic information related to <acronym>BIND</acronym>
105 <title>Conventions Used in This Document</title>
108 In this document, we use the following general typographic
114 <colspec colname="1" colnum="1" colwidth="3.000in"/>
115 <colspec colname="2" colnum="2" colwidth="2.625in"/>
120 <emphasis>To describe:</emphasis>
125 <emphasis>We use the style:</emphasis>
132 a pathname, filename, URL, hostname,
133 mailing list name, or new term or concept
138 <filename>Fixed width</filename>
151 <userinput>Fixed Width Bold</userinput>
163 <computeroutput>Fixed Width</computeroutput>
172 The following conventions are used in descriptions of the
173 <acronym>BIND</acronym> configuration file:<informaltable colsep="0" frame="all" rowsep="0">
174 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
175 <colspec colname="1" colnum="1" colsep="0" colwidth="3.000in"/>
176 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
179 <entry colname="1" colsep="1" rowsep="1">
181 <emphasis>To describe:</emphasis>
184 <entry colname="2" rowsep="1">
186 <emphasis>We use the style:</emphasis>
191 <entry colname="1" colsep="1" rowsep="1">
196 <entry colname="2" rowsep="1">
198 <literal>Fixed Width</literal>
203 <entry colname="1" colsep="1" rowsep="1">
208 <entry colname="2" rowsep="1">
210 <varname>Fixed Width</varname>
215 <entry colname="1" colsep="1">
222 <optional>Text is enclosed in square brackets</optional>
232 <title>The Domain Name System (<acronym>DNS</acronym>)</title>
234 The purpose of this document is to explain the installation
235 and upkeep of the <acronym>BIND</acronym> (Berkeley Internet
236 Name Domain) software package, and we
237 begin by reviewing the fundamentals of the Domain Name System
238 (<acronym>DNS</acronym>) as they relate to <acronym>BIND</acronym>.
242 <title>DNS Fundamentals</title>
245 The Domain Name System (DNS) is a hierarchical, distributed
246 database. It stores information for mapping Internet host names to
248 addresses and vice versa, mail routing information, and other data
249 used by Internet applications.
253 Clients look up information in the DNS by calling a
254 <emphasis>resolver</emphasis> library, which sends queries to one or
255 more <emphasis>name servers</emphasis> and interprets the responses.
256 The <acronym>BIND</acronym> 9 software distribution
258 name server, <command>named</command>, and a resolver
259 library, <command>liblwres</command>. The older
260 <command>libbind</command> resolver library is also available
261 from ISC as a separate download.
265 <title>Domains and Domain Names</title>
268 The data stored in the DNS is identified by <emphasis>domain names</emphasis> that are organized as a tree according to
269 organizational or administrative boundaries. Each node of the tree,
270 called a <emphasis>domain</emphasis>, is given a label. The domain
272 node is the concatenation of all the labels on the path from the
273 node to the <emphasis>root</emphasis> node. This is represented
274 in written form as a string of labels listed from right to left and
275 separated by dots. A label need only be unique within its parent
280 For example, a domain name for a host at the
281 company <emphasis>Example, Inc.</emphasis> could be
282 <literal>ourhost.example.com</literal>,
283 where <literal>com</literal> is the
284 top level domain to which
285 <literal>ourhost.example.com</literal> belongs,
286 <literal>example</literal> is
287 a subdomain of <literal>com</literal>, and
288 <literal>ourhost</literal> is the
293 For administrative purposes, the name space is partitioned into
294 areas called <emphasis>zones</emphasis>, each starting at a node and
295 extending down to the leaf nodes or to nodes where other zones
297 The data for each zone is stored in a <emphasis>name server</emphasis>, which answers queries about the zone using the
298 <emphasis>DNS protocol</emphasis>.
302 The data associated with each domain name is stored in the
303 form of <emphasis>resource records</emphasis> (<acronym>RR</acronym>s).
304 Some of the supported resource record types are described in
305 <xref linkend="types_of_resource_records_and_when_to_use_them"/>.
309 For more detailed information about the design of the DNS and
310 the DNS protocol, please refer to the standards documents listed in
311 <xref linkend="rfcs"/>.
318 To properly operate a name server, it is important to understand
319 the difference between a <emphasis>zone</emphasis>
320 and a <emphasis>domain</emphasis>.
324 As stated previously, a zone is a point of delegation in
325 the <acronym>DNS</acronym> tree. A zone consists of
326 those contiguous parts of the domain
327 tree for which a name server has complete information and over which
328 it has authority. It contains all domain names from a certain point
329 downward in the domain tree except those which are delegated to
330 other zones. A delegation point is marked by one or more
331 <emphasis>NS records</emphasis> in the
332 parent zone, which should be matched by equivalent NS records at
333 the root of the delegated zone.
337 For instance, consider the <literal>example.com</literal>
338 domain which includes names
339 such as <literal>host.aaa.example.com</literal> and
340 <literal>host.bbb.example.com</literal> even though
341 the <literal>example.com</literal> zone includes
342 only delegations for the <literal>aaa.example.com</literal> and
343 <literal>bbb.example.com</literal> zones. A zone can
345 exactly to a single domain, but could also include only part of a
346 domain, the rest of which could be delegated to other
347 name servers. Every name in the <acronym>DNS</acronym>
349 <emphasis>domain</emphasis>, even if it is
350 <emphasis>terminal</emphasis>, that is, has no
351 <emphasis>subdomains</emphasis>. Every subdomain is a domain and
352 every domain except the root is also a subdomain. The terminology is
353 not intuitive and we suggest that you read RFCs 1033, 1034 and 1035
355 gain a complete understanding of this difficult and subtle
360 Though <acronym>BIND</acronym> is called a "domain name
362 it deals primarily in terms of zones. The master and slave
363 declarations in the <filename>named.conf</filename> file
365 zones, not domains. When you ask some other site if it is willing to
366 be a slave server for your <emphasis>domain</emphasis>, you are
367 actually asking for slave service for some collection of zones.
372 <title>Authoritative Name Servers</title>
375 Each zone is served by at least
376 one <emphasis>authoritative name server</emphasis>,
377 which contains the complete data for the zone.
378 To make the DNS tolerant of server and network failures,
379 most zones have two or more authoritative servers, on
384 Responses from authoritative servers have the "authoritative
385 answer" (AA) bit set in the response packets. This makes them
386 easy to identify when debugging DNS configurations using tools like
387 <command>dig</command> (<xref linkend="diagnostic_tools"/>).
391 <title>The Primary Master</title>
394 The authoritative server where the master copy of the zone
395 data is maintained is called the
396 <emphasis>primary master</emphasis> server, or simply the
397 <emphasis>primary</emphasis>. Typically it loads the zone
398 contents from some local file edited by humans or perhaps
399 generated mechanically from some other local file which is
400 edited by humans. This file is called the
401 <emphasis>zone file</emphasis> or
402 <emphasis>master file</emphasis>.
406 In some cases, however, the master file may not be edited
407 by humans at all, but may instead be the result of
408 <emphasis>dynamic update</emphasis> operations.
413 <title>Slave Servers</title>
415 The other authoritative servers, the <emphasis>slave</emphasis>
416 servers (also known as <emphasis>secondary</emphasis> servers)
418 the zone contents from another server using a replication process
419 known as a <emphasis>zone transfer</emphasis>. Typically the data
421 transferred directly from the primary master, but it is also
423 to transfer it from another slave. In other words, a slave server
424 may itself act as a master to a subordinate slave server.
429 <title>Stealth Servers</title>
432 Usually all of the zone's authoritative servers are listed in
433 NS records in the parent zone. These NS records constitute
434 a <emphasis>delegation</emphasis> of the zone from the parent.
435 The authoritative servers are also listed in the zone file itself,
436 at the <emphasis>top level</emphasis> or <emphasis>apex</emphasis>
437 of the zone. You can list servers in the zone's top-level NS
438 records that are not in the parent's NS delegation, but you cannot
439 list servers in the parent's delegation that are not present at
440 the zone's top level.
444 A <emphasis>stealth server</emphasis> is a server that is
445 authoritative for a zone but is not listed in that zone's NS
446 records. Stealth servers can be used for keeping a local copy of
448 zone to speed up access to the zone's records or to make sure that
450 zone is available even if all the "official" servers for the zone
456 A configuration where the primary master server itself is a
457 stealth server is often referred to as a "hidden primary"
458 configuration. One use for this configuration is when the primary
460 is behind a firewall and therefore unable to communicate directly
461 with the outside world.
469 <title>Caching Name Servers</title>
472 - Terminology here is inconsistent. Probably ought to
473 - convert to using "recursive name server" everywhere
474 - with just a note about "caching" terminology.
478 The resolver libraries provided by most operating systems are
479 <emphasis>stub resolvers</emphasis>, meaning that they are not
481 performing the full DNS resolution process by themselves by talking
482 directly to the authoritative servers. Instead, they rely on a
484 name server to perform the resolution on their behalf. Such a
486 is called a <emphasis>recursive</emphasis> name server; it performs
487 <emphasis>recursive lookups</emphasis> for local clients.
491 To improve performance, recursive servers cache the results of
492 the lookups they perform. Since the processes of recursion and
493 caching are intimately connected, the terms
494 <emphasis>recursive server</emphasis> and
495 <emphasis>caching server</emphasis> are often used synonymously.
499 The length of time for which a record may be retained in
500 the cache of a caching name server is controlled by the
501 Time To Live (TTL) field associated with each resource record.
505 <title>Forwarding</title>
508 Even a caching name server does not necessarily perform
509 the complete recursive lookup itself. Instead, it can
510 <emphasis>forward</emphasis> some or all of the queries
511 that it cannot satisfy from its cache to another caching name
513 commonly referred to as a <emphasis>forwarder</emphasis>.
517 There may be one or more forwarders,
518 and they are queried in turn until the list is exhausted or an
520 is found. Forwarders are typically used when you do not
521 wish all the servers at a given site to interact directly with the
523 the Internet servers. A typical scenario would involve a number
524 of internal <acronym>DNS</acronym> servers and an
525 Internet firewall. Servers unable
526 to pass packets through the firewall would forward to the server
527 that can do it, and that server would query the Internet <acronym>DNS</acronym> servers
528 on the internal server's behalf.
535 <title>Name Servers in Multiple Roles</title>
538 The <acronym>BIND</acronym> name server can
539 simultaneously act as
540 a master for some zones, a slave for other zones, and as a caching
541 (recursive) server for a set of local clients.
545 However, since the functions of authoritative name service
546 and caching/recursive name service are logically separate, it is
547 often advantageous to run them on separate server machines.
549 A server that only provides authoritative name service
550 (an <emphasis>authoritative-only</emphasis> server) can run with
551 recursion disabled, improving reliability and security.
553 A server that is not authoritative for any zones and only provides
554 recursive service to local
555 clients (a <emphasis>caching-only</emphasis> server)
556 does not need to be reachable from the Internet at large and can
557 be placed inside a firewall.
565 <chapter id="Bv9ARM.ch02">
566 <title><acronym>BIND</acronym> Resource Requirements</title>
569 <title>Hardware requirements</title>
572 <acronym>DNS</acronym> hardware requirements have
573 traditionally been quite modest.
574 For many installations, servers that have been pensioned off from
575 active duty have performed admirably as <acronym>DNS</acronym> servers.
578 The DNSSEC features of <acronym>BIND</acronym> 9
579 may prove to be quite
580 CPU intensive however, so organizations that make heavy use of these
581 features may wish to consider larger systems for these applications.
582 <acronym>BIND</acronym> 9 is fully multithreaded, allowing
584 multiprocessor systems for installations that need it.
588 <title>CPU Requirements</title>
590 CPU requirements for <acronym>BIND</acronym> 9 range from
592 for serving of static zones without caching, to enterprise-class
593 machines if you intend to process many dynamic updates and DNSSEC
594 signed zones, serving many thousands of queries per second.
599 <title>Memory Requirements</title>
601 The memory of the server has to be large enough to fit the
602 cache and zones loaded off disk. The <command>max-cache-size</command>
603 option can be used to limit the amount of memory used by the cache,
604 at the expense of reducing cache hit rates and causing more <acronym>DNS</acronym>
606 Additionally, if additional section caching
607 (<xref linkend="acache"/>) is enabled,
608 the <command>max-acache-size</command> option can be used to
610 of memory used by the mechanism.
611 It is still good practice to have enough memory to load
612 all zone and cache data into memory — unfortunately, the best
614 to determine this for a given installation is to watch the name server
615 in operation. After a few weeks the server process should reach
616 a relatively stable size where entries are expiring from the cache as
617 fast as they are being inserted.
620 - Add something here about leaving overhead for attacks?
621 - How much overhead? Percentage?
626 <title>Name Server Intensive Environment Issues</title>
628 For name server intensive environments, there are two alternative
629 configurations that may be used. The first is where clients and
630 any second-level internal name servers query a main name server, which
631 has enough memory to build a large cache. This approach minimizes
632 the bandwidth used by external name lookups. The second alternative
633 is to set up second-level internal name servers to make queries
635 In this configuration, none of the individual machines needs to
636 have as much memory or CPU power as in the first alternative, but
637 this has the disadvantage of making many more external queries,
638 as none of the name servers share their cached data.
643 <title>Supported Operating Systems</title>
645 ISC <acronym>BIND</acronym> 9 compiles and runs on a large
647 of Unix-like operating systems and on
648 Microsoft Windows Server 2003 and 2008, and Windows XP and Vista.
650 list of supported systems, see the README file in the top level
652 of the BIND 9 source distribution.
657 <chapter id="Bv9ARM.ch03">
658 <title>Name Server Configuration</title>
660 In this chapter we provide some suggested configurations along
661 with guidelines for their use. We suggest reasonable values for
662 certain option settings.
665 <sect1 id="sample_configuration">
666 <title>Sample Configurations</title>
668 <title>A Caching-only Name Server</title>
670 The following sample configuration is appropriate for a caching-only
671 name server for use by clients internal to a corporation. All
673 from outside clients are refused using the <command>allow-query</command>
674 option. Alternatively, the same effect could be achieved using
680 // Two corporate subnets we wish to allow queries from.
681 acl corpnets { 192.168.4.0/24; 192.168.7.0/24; };
684 directory "/etc/namedb";
686 allow-query { corpnets; };
688 // Provide a reverse mapping for the loopback
690 zone "0.0.127.in-addr.arpa" {
692 file "localhost.rev";
700 <title>An Authoritative-only Name Server</title>
702 This sample configuration is for an authoritative-only server
703 that is the master server for "<filename>example.com</filename>"
704 and a slave for the subdomain "<filename>eng.example.com</filename>".
710 directory "/etc/namedb";
711 // Do not allow access to cache
712 allow-query-cache { none; };
713 // This is the default
714 allow-query { any; };
715 // Do not provide recursive service
719 // Provide a reverse mapping for the loopback
721 zone "0.0.127.in-addr.arpa" {
723 file "localhost.rev";
726 // We are the master server for example.com
729 file "example.com.db";
730 // IP addresses of slave servers allowed to
731 // transfer example.com
737 // We are a slave server for eng.example.com
738 zone "eng.example.com" {
740 file "eng.example.com.bk";
741 // IP address of eng.example.com master server
742 masters { 192.168.4.12; };
750 <title>Load Balancing</title>
752 - Add explanation of why load balancing is fragile at best
753 - and completely pointless in the general case.
757 A primitive form of load balancing can be achieved in
758 the <acronym>DNS</acronym> by using multiple records
759 (such as multiple A records) for one name.
763 For example, if you have three WWW servers with network addresses
764 of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the
765 following means that clients will connect to each machine one third
769 <informaltable colsep="0" rowsep="0">
770 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="2Level-table">
771 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
772 <colspec colname="2" colnum="2" colsep="0" colwidth="0.500in"/>
773 <colspec colname="3" colnum="3" colsep="0" colwidth="0.750in"/>
774 <colspec colname="4" colnum="4" colsep="0" colwidth="0.750in"/>
775 <colspec colname="5" colnum="5" colsep="0" colwidth="2.028in"/>
800 Resource Record (RR) Data
807 <literal>www</literal>
812 <literal>600</literal>
817 <literal>IN</literal>
827 <literal>10.0.0.1</literal>
837 <literal>600</literal>
842 <literal>IN</literal>
852 <literal>10.0.0.2</literal>
862 <literal>600</literal>
867 <literal>IN</literal>
877 <literal>10.0.0.3</literal>
885 When a resolver queries for these records, <acronym>BIND</acronym> will rotate
886 them and respond to the query with the records in a different
887 order. In the example above, clients will randomly receive
888 records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients
889 will use the first record returned and discard the rest.
892 For more detail on ordering responses, check the
893 <command>rrset-order</command> substatement in the
894 <command>options</command> statement, see
895 <xref endterm="rrset_ordering_title" linkend="rrset_ordering"/>.
901 <title>Name Server Operations</title>
904 <title>Tools for Use With the Name Server Daemon</title>
906 This section describes several indispensable diagnostic,
907 administrative and monitoring tools available to the system
908 administrator for controlling and debugging the name server
911 <sect3 id="diagnostic_tools">
912 <title>Diagnostic Tools</title>
914 The <command>dig</command>, <command>host</command>, and
915 <command>nslookup</command> programs are all command
917 for manually querying name servers. They differ in style and
923 <term id="dig"><command>dig</command></term>
926 The domain information groper (<command>dig</command>)
927 is the most versatile and complete of these lookup tools.
928 It has two modes: simple interactive
929 mode for a single query, and batch mode which executes a
931 each in a list of several query lines. All query options are
933 from the command line.
935 <cmdsynopsis label="Usage">
936 <command>dig</command>
937 <arg>@<replaceable>server</replaceable></arg>
938 <arg choice="plain"><replaceable>domain</replaceable></arg>
939 <arg><replaceable>query-type</replaceable></arg>
940 <arg><replaceable>query-class</replaceable></arg>
941 <arg>+<replaceable>query-option</replaceable></arg>
942 <arg>-<replaceable>dig-option</replaceable></arg>
943 <arg>%<replaceable>comment</replaceable></arg>
946 The usual simple use of <command>dig</command> will take the form
949 <command>dig @server domain query-type query-class</command>
952 For more information and a list of available commands and
953 options, see the <command>dig</command> man
960 <term><command>host</command></term>
963 The <command>host</command> utility emphasizes
965 and ease of use. By default, it converts
966 between host names and Internet addresses, but its
968 can be extended with the use of options.
970 <cmdsynopsis label="Usage">
971 <command>host</command>
972 <arg>-aCdlnrsTwv</arg>
973 <arg>-c <replaceable>class</replaceable></arg>
974 <arg>-N <replaceable>ndots</replaceable></arg>
975 <arg>-t <replaceable>type</replaceable></arg>
976 <arg>-W <replaceable>timeout</replaceable></arg>
977 <arg>-R <replaceable>retries</replaceable></arg>
978 <arg>-m <replaceable>flag</replaceable></arg>
981 <arg choice="plain"><replaceable>hostname</replaceable></arg>
982 <arg><replaceable>server</replaceable></arg>
985 For more information and a list of available commands and
986 options, see the <command>host</command> man
993 <term><command>nslookup</command></term>
995 <para><command>nslookup</command>
996 has two modes: interactive and
997 non-interactive. Interactive mode allows the user to
998 query name servers for information about various
999 hosts and domains or to print a list of hosts in a
1000 domain. Non-interactive mode is used to print just
1001 the name and requested information for a host or
1004 <cmdsynopsis label="Usage">
1005 <command>nslookup</command>
1006 <arg rep="repeat">-option</arg>
1008 <arg><replaceable>host-to-find</replaceable></arg>
1009 <arg>- <arg>server</arg></arg>
1013 Interactive mode is entered when no arguments are given (the
1014 default name server will be used) or when the first argument
1016 hyphen (`-') and the second argument is the host name or
1021 Non-interactive mode is used when the name or Internet
1023 of the host to be looked up is given as the first argument.
1025 optional second argument specifies the host name or address
1029 Due to its arcane user interface and frequently inconsistent
1030 behavior, we do not recommend the use of <command>nslookup</command>.
1031 Use <command>dig</command> instead.
1039 <sect3 id="admin_tools">
1040 <title>Administrative Tools</title>
1042 Administrative tools play an integral part in the management
1046 <varlistentry id="named-checkconf" xreflabel="Named Configuration Checking application">
1048 <term><command>named-checkconf</command></term>
1051 The <command>named-checkconf</command> program
1052 checks the syntax of a <filename>named.conf</filename> file.
1054 <cmdsynopsis label="Usage">
1055 <command>named-checkconf</command>
1057 <arg>-t <replaceable>directory</replaceable></arg>
1058 <arg><replaceable>filename</replaceable></arg>
1062 <varlistentry id="named-checkzone" xreflabel="Zone Checking application">
1064 <term><command>named-checkzone</command></term>
1067 The <command>named-checkzone</command> program
1068 checks a master file for
1069 syntax and consistency.
1071 <cmdsynopsis label="Usage">
1072 <command>named-checkzone</command>
1074 <arg>-c <replaceable>class</replaceable></arg>
1075 <arg>-o <replaceable>output</replaceable></arg>
1076 <arg>-t <replaceable>directory</replaceable></arg>
1077 <arg>-w <replaceable>directory</replaceable></arg>
1078 <arg>-k <replaceable>(ignore|warn|fail)</replaceable></arg>
1079 <arg>-n <replaceable>(ignore|warn|fail)</replaceable></arg>
1080 <arg>-W <replaceable>(ignore|warn)</replaceable></arg>
1081 <arg choice="plain"><replaceable>zone</replaceable></arg>
1082 <arg><replaceable>filename</replaceable></arg>
1086 <varlistentry id="named-compilezone" xreflabel="Zone Compilation application">
1087 <term><command>named-compilezone</command></term>
1090 Similar to <command>named-checkzone,</command> but
1091 it always dumps the zone content to a specified file
1092 (typically in a different format).
1096 <varlistentry id="rndc" xreflabel="Remote Name Daemon Control application">
1098 <term><command>rndc</command></term>
1101 The remote name daemon control
1102 (<command>rndc</command>) program allows the
1104 administrator to control the operation of a name server.
1105 Since <acronym>BIND</acronym> 9.2, <command>rndc</command>
1106 supports all the commands of the BIND 8 <command>ndc</command>
1107 utility except <command>ndc start</command> and
1108 <command>ndc restart</command>, which were also
1109 not supported in <command>ndc</command>'s
1111 If you run <command>rndc</command> without any
1113 it will display a usage message as follows:
1115 <cmdsynopsis label="Usage">
1116 <command>rndc</command>
1117 <arg>-c <replaceable>config</replaceable></arg>
1118 <arg>-s <replaceable>server</replaceable></arg>
1119 <arg>-p <replaceable>port</replaceable></arg>
1120 <arg>-y <replaceable>key</replaceable></arg>
1121 <arg choice="plain"><replaceable>command</replaceable></arg>
1122 <arg rep="repeat"><replaceable>command</replaceable></arg>
1124 <para>The <command>command</command>
1125 is one of the following:
1131 <term><userinput>reload</userinput></term>
1134 Reload configuration file and zones.
1140 <term><userinput>reload <replaceable>zone</replaceable>
1141 <optional><replaceable>class</replaceable>
1142 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1145 Reload the given zone.
1151 <term><userinput>refresh <replaceable>zone</replaceable>
1152 <optional><replaceable>class</replaceable>
1153 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1156 Schedule zone maintenance for the given zone.
1162 <term><userinput>retransfer <replaceable>zone</replaceable>
1164 <optional><replaceable>class</replaceable>
1165 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1168 Retransfer the given zone from the master.
1174 <term><userinput>sign <replaceable>zone</replaceable>
1175 <optional><replaceable>class</replaceable>
1176 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1179 Fetch all DNSSEC keys for the given zone
1180 from the key directory (see
1181 <command>key-directory</command> in
1182 <xref linkend="options"/>). If they are within
1183 their publication period, merge them into the
1184 zone's DNSKEY RRset. If the DNSKEY RRset
1185 is changed, then the zone is automatically
1186 re-signed with the new key set.
1189 This command requires that the
1190 <command>auto-dnssec</command> zone option to be set
1191 to <literal>allow</literal>,
1192 <literal>maintain</literal>, or
1193 <literal>create</literal>, and also requires
1194 the zone to be configured to allow dynamic DNS.
1195 See <xref linkend="dynamic_update_policies"/> for
1202 <term><userinput>loadkeys <replaceable>zone</replaceable>
1203 <optional><replaceable>class</replaceable>
1204 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1207 Fetch all DNSSEC keys for the given zone
1208 from the key directory (see
1209 <command>key-directory</command> in
1210 <xref linkend="options"/>). If they are within
1211 their publication period, merge them into the
1212 zone's DNSKEY RRset. Unlike <command>rndc
1213 sign</command>, however, the zone is not
1214 immediately re-signed by the new keys, but is
1215 allowed to incrementally re-sign over time.
1218 This command requires that the
1219 <command>auto-dnssec</command> zone option to
1220 be set to <literal>maintain</literal> or
1221 <literal>create</literal>, and also requires
1222 the zone to be configured to allow dynamic DNS.
1223 See <xref linkend="dynamic_update_policies"/> for
1230 <term><userinput>freeze
1231 <optional><replaceable>zone</replaceable>
1232 <optional><replaceable>class</replaceable>
1233 <optional><replaceable>view</replaceable></optional></optional></optional></userinput></term>
1236 Suspend updates to a dynamic zone. If no zone is
1238 then all zones are suspended. This allows manual
1239 edits to be made to a zone normally updated by dynamic
1241 also causes changes in the journal file to be synced
1243 and the journal file to be removed. All dynamic
1244 update attempts will
1245 be refused while the zone is frozen.
1251 <term><userinput>thaw
1252 <optional><replaceable>zone</replaceable>
1253 <optional><replaceable>class</replaceable>
1254 <optional><replaceable>view</replaceable></optional></optional></optional></userinput></term>
1257 Enable updates to a frozen dynamic zone. If no zone
1259 specified, then all frozen zones are enabled. This
1261 the server to reload the zone from disk, and
1262 re-enables dynamic updates
1263 after the load has completed. After a zone is thawed,
1265 will no longer be refused.
1271 <term><userinput>notify <replaceable>zone</replaceable>
1272 <optional><replaceable>class</replaceable>
1273 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1276 Resend NOTIFY messages for the zone.
1282 <term><userinput>reconfig</userinput></term>
1285 Reload the configuration file and load new zones,
1286 but do not reload existing zone files even if they
1288 This is faster than a full <command>reload</command> when there
1289 is a large number of zones because it avoids the need
1291 modification times of the zones files.
1297 <term><userinput>stats</userinput></term>
1300 Write server statistics to the statistics file.
1306 <term><userinput>querylog</userinput></term>
1309 Toggle query logging. Query logging can also be enabled
1310 by explicitly directing the <command>queries</command>
1311 <command>category</command> to a
1312 <command>channel</command> in the
1313 <command>logging</command> section of
1314 <filename>named.conf</filename> or by specifying
1315 <command>querylog yes;</command> in the
1316 <command>options</command> section of
1317 <filename>named.conf</filename>.
1323 <term><userinput>dumpdb
1324 <optional>-all|-cache|-zone</optional>
1325 <optional><replaceable>view ...</replaceable></optional></userinput></term>
1328 Dump the server's caches (default) and/or zones to
1330 dump file for the specified views. If no view is
1338 <term><userinput>secroots
1339 <optional><replaceable>view ...</replaceable></optional></userinput></term>
1342 Dump the server's security roots to the secroots
1343 file for the specified views. If no view is
1344 specified, security roots for all
1351 <term><userinput>stop <optional>-p</optional></userinput></term>
1354 Stop the server, making sure any recent changes
1355 made through dynamic update or IXFR are first saved to
1356 the master files of the updated zones.
1357 If <option>-p</option> is specified <command>named</command>'s process id is returned.
1358 This allows an external process to determine when <command>named</command>
1359 had completed stopping.
1365 <term><userinput>halt <optional>-p</optional></userinput></term>
1368 Stop the server immediately. Recent changes
1369 made through dynamic update or IXFR are not saved to
1370 the master files, but will be rolled forward from the
1371 journal files when the server is restarted.
1372 If <option>-p</option> is specified <command>named</command>'s process id is returned.
1373 This allows an external process to determine when <command>named</command>
1374 had completed halting.
1380 <term><userinput>trace</userinput></term>
1383 Increment the servers debugging level by one.
1389 <term><userinput>trace <replaceable>level</replaceable></userinput></term>
1392 Sets the server's debugging level to an explicit
1399 <term><userinput>notrace</userinput></term>
1402 Sets the server's debugging level to 0.
1408 <term><userinput>flush</userinput></term>
1411 Flushes the server's cache.
1417 <term><userinput>flushname</userinput> <replaceable>name</replaceable></term>
1420 Flushes the given name from the server's cache.
1426 <term><userinput>status</userinput></term>
1429 Display status of the server.
1430 Note that the number of zones includes the internal <command>bind/CH</command> zone
1431 and the default <command>./IN</command>
1432 hint zone if there is not an
1433 explicit root zone configured.
1439 <term><userinput>recursing</userinput></term>
1442 Dump the list of queries <command>named</command> is currently recursing
1449 <term><userinput>validation
1450 <optional>on|off</optional>
1451 <optional><replaceable>view ...</replaceable></optional>
1455 Enable or disable DNSSEC validation.
1456 Note <command>dnssec-enable</command> also needs to be
1457 set to <userinput>yes</userinput> to be effective.
1458 It defaults to enabled.
1464 <term><userinput>addzone
1465 <replaceable>zone</replaceable>
1466 <optional><replaceable>class</replaceable>
1467 <optional><replaceable>view</replaceable></optional></optional>
1468 <replaceable>configuration</replaceable>
1472 Add a zone while the server is running. This
1473 command requires the
1474 <command>allow-new-zones</command> option to be set
1475 to <userinput>yes</userinput>. The
1476 <replaceable>configuration</replaceable> string
1477 specified on the command line is the zone
1478 configuration text that would ordinarily be
1479 placed in <filename>named.conf</filename>.
1482 The configuration is saved in a file called
1483 <filename><replaceable>hash</replaceable>.nzf</filename>,
1484 where <replaceable>hash</replaceable> is a
1485 cryptographic hash generated from the name of
1486 the view. When <command>named</command> is
1487 restarted, the file will be loaded into the view
1488 configuration, so that zones that were added
1489 can persist after a restart.
1492 This sample <command>addzone</command> command
1493 would add the zone <literal>example.com</literal>
1494 to the default view:
1497 <prompt>$ </prompt><userinput>rndc addzone example.com '{ type master; file "example.com.db"; };'</userinput>
1500 (Note the brackets and semi-colon around the zone
1501 configuration text.)
1507 <term><userinput>delzone
1508 <replaceable>zone</replaceable>
1509 <optional><replaceable>class</replaceable>
1510 <optional><replaceable>view</replaceable></optional></optional>
1514 Delete a zone while the server is running.
1515 Only zones that were originally added via
1516 <command>rndc addzone</command> can be deleted
1525 A configuration file is required, since all
1526 communication with the server is authenticated with
1527 digital signatures that rely on a shared secret, and
1528 there is no way to provide that secret other than with a
1529 configuration file. The default location for the
1530 <command>rndc</command> configuration file is
1531 <filename>/etc/rndc.conf</filename>, but an
1533 location can be specified with the <option>-c</option>
1534 option. If the configuration file is not found,
1535 <command>rndc</command> will also look in
1536 <filename>/etc/rndc.key</filename> (or whatever
1537 <varname>sysconfdir</varname> was defined when
1538 the <acronym>BIND</acronym> build was
1540 The <filename>rndc.key</filename> file is
1542 running <command>rndc-confgen -a</command> as
1544 <xref linkend="controls_statement_definition_and_usage"/>.
1548 The format of the configuration file is similar to
1549 that of <filename>named.conf</filename>, but
1551 only four statements, the <command>options</command>,
1552 <command>key</command>, <command>server</command> and
1553 <command>include</command>
1554 statements. These statements are what associate the
1555 secret keys to the servers with which they are meant to
1556 be shared. The order of statements is not
1561 The <command>options</command> statement has
1563 <command>default-server</command>, <command>default-key</command>,
1564 and <command>default-port</command>.
1565 <command>default-server</command> takes a
1566 host name or address argument and represents the server
1568 be contacted if no <option>-s</option>
1569 option is provided on the command line.
1570 <command>default-key</command> takes
1571 the name of a key as its argument, as defined by a <command>key</command> statement.
1572 <command>default-port</command> specifies the
1574 <command>rndc</command> should connect if no
1575 port is given on the command line or in a
1576 <command>server</command> statement.
1580 The <command>key</command> statement defines a
1582 by <command>rndc</command> when authenticating
1584 <command>named</command>. Its syntax is
1586 <command>key</command> statement in <filename>named.conf</filename>.
1587 The keyword <userinput>key</userinput> is
1588 followed by a key name, which must be a valid
1589 domain name, though it need not actually be hierarchical;
1591 a string like "<userinput>rndc_key</userinput>" is a valid
1593 The <command>key</command> statement has two
1595 <command>algorithm</command> and <command>secret</command>.
1596 While the configuration parser will accept any string as the
1598 to algorithm, currently only the string "<userinput>hmac-md5</userinput>"
1599 has any meaning. The secret is a base-64 encoded string
1600 as specified in RFC 3548.
1604 The <command>server</command> statement
1606 defined using the <command>key</command>
1607 statement with a server.
1608 The keyword <userinput>server</userinput> is followed by a
1609 host name or address. The <command>server</command> statement
1610 has two clauses: <command>key</command> and <command>port</command>.
1611 The <command>key</command> clause specifies the
1613 to be used when communicating with this server, and the
1614 <command>port</command> clause can be used to
1615 specify the port <command>rndc</command> should
1621 A sample minimal configuration file is as follows:
1626 algorithm "hmac-md5";
1628 "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
1631 default-server 127.0.0.1;
1632 default-key rndc_key;
1637 This file, if installed as <filename>/etc/rndc.conf</filename>,
1638 would allow the command:
1642 <prompt>$ </prompt><userinput>rndc reload</userinput>
1646 to connect to 127.0.0.1 port 953 and cause the name server
1647 to reload, if a name server on the local machine were
1649 following controls statements:
1655 allow { localhost; } keys { rndc_key; };
1660 and it had an identical key statement for
1661 <literal>rndc_key</literal>.
1665 Running the <command>rndc-confgen</command>
1667 conveniently create a <filename>rndc.conf</filename>
1668 file for you, and also display the
1669 corresponding <command>controls</command>
1670 statement that you need to
1671 add to <filename>named.conf</filename>.
1673 you can run <command>rndc-confgen -a</command>
1675 a <filename>rndc.key</filename> file and not
1677 <filename>named.conf</filename> at all.
1688 <title>Signals</title>
1690 Certain UNIX signals cause the name server to take specific
1691 actions, as described in the following table. These signals can
1692 be sent using the <command>kill</command> command.
1694 <informaltable frame="all">
1696 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
1697 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
1701 <para><command>SIGHUP</command></para>
1705 Causes the server to read <filename>named.conf</filename> and
1706 reload the database.
1712 <para><command>SIGTERM</command></para>
1716 Causes the server to clean up and exit.
1722 <para><command>SIGINT</command></para>
1726 Causes the server to clean up and exit.
1737 <chapter id="Bv9ARM.ch04">
1738 <title>Advanced DNS Features</title>
1742 <title>Notify</title>
1744 <acronym>DNS</acronym> NOTIFY is a mechanism that allows master
1745 servers to notify their slave servers of changes to a zone's data. In
1746 response to a <command>NOTIFY</command> from a master server, the
1747 slave will check to see that its version of the zone is the
1748 current version and, if not, initiate a zone transfer.
1752 For more information about <acronym>DNS</acronym>
1753 <command>NOTIFY</command>, see the description of the
1754 <command>notify</command> option in <xref linkend="boolean_options"/> and
1755 the description of the zone option <command>also-notify</command> in
1756 <xref linkend="zone_transfers"/>. The <command>NOTIFY</command>
1757 protocol is specified in RFC 1996.
1761 As a slave zone can also be a master to other slaves, <command>named</command>,
1762 by default, sends <command>NOTIFY</command> messages for every zone
1763 it loads. Specifying <command>notify master-only;</command> will
1764 cause <command>named</command> to only send <command>NOTIFY</command> for master
1765 zones that it loads.
1770 <sect1 id="dynamic_update">
1771 <title>Dynamic Update</title>
1774 Dynamic Update is a method for adding, replacing or deleting
1775 records in a master server by sending it a special form of DNS
1776 messages. The format and meaning of these messages is specified
1781 Dynamic update is enabled by including an
1782 <command>allow-update</command> or an <command>update-policy</command>
1783 clause in the <command>zone</command> statement.
1787 If the zone's <command>update-policy</command> is set to
1788 <userinput>local</userinput>, updates to the zone
1789 will be permitted for the key <varname>local-ddns</varname>,
1790 which will be generated by <command>named</command> at startup.
1791 See <xref linkend="dynamic_update_policies"/> for more details.
1795 The <command>tkey-gssapi-credential</command> and
1796 <command>tkey-domain</command> clauses in the
1797 <command>options</command> statement enable the
1798 server to negotiate keys that can be matched against those
1799 in <command>update-policy</command> or
1800 <command>allow-update</command>.
1804 Updating of secure zones (zones using DNSSEC) follows RFC
1805 3007: RRSIG, NSEC and NSEC3 records affected by updates are
1806 automatically regenerated by the server using an online
1807 zone key. Update authorization is based on transaction
1808 signatures and an explicit server policy.
1811 <sect2 id="journal">
1812 <title>The journal file</title>
1815 All changes made to a zone using dynamic update are stored
1816 in the zone's journal file. This file is automatically created
1817 by the server when the first dynamic update takes place.
1818 The name of the journal file is formed by appending the extension
1819 <filename>.jnl</filename> to the name of the
1821 file unless specifically overridden. The journal file is in a
1822 binary format and should not be edited manually.
1826 The server will also occasionally write ("dump")
1827 the complete contents of the updated zone to its zone file.
1828 This is not done immediately after
1829 each dynamic update, because that would be too slow when a large
1830 zone is updated frequently. Instead, the dump is delayed by
1831 up to 15 minutes, allowing additional updates to take place.
1832 During the dump process, transient files will be created
1833 with the extensions <filename>.jnw</filename> and
1834 <filename>.jbk</filename>; under ordinary circumstances, these
1835 will be removed when the dump is complete, and can be safely
1840 When a server is restarted after a shutdown or crash, it will replay
1841 the journal file to incorporate into the zone any updates that
1843 place after the last zone dump.
1847 Changes that result from incoming incremental zone transfers are
1849 journalled in a similar way.
1853 The zone files of dynamic zones cannot normally be edited by
1854 hand because they are not guaranteed to contain the most recent
1855 dynamic changes — those are only in the journal file.
1856 The only way to ensure that the zone file of a dynamic zone
1857 is up to date is to run <command>rndc stop</command>.
1861 If you have to make changes to a dynamic zone
1862 manually, the following procedure will work: Disable dynamic updates
1864 <command>rndc freeze <replaceable>zone</replaceable></command>.
1865 This will also remove the zone's <filename>.jnl</filename> file
1866 and update the master file. Edit the zone file. Run
1867 <command>rndc thaw <replaceable>zone</replaceable></command>
1868 to reload the changed zone and re-enable dynamic updates.
1875 <sect1 id="incremental_zone_transfers">
1876 <title>Incremental Zone Transfers (IXFR)</title>
1879 The incremental zone transfer (IXFR) protocol is a way for
1880 slave servers to transfer only changed data, instead of having to
1881 transfer the entire zone. The IXFR protocol is specified in RFC
1882 1995. See <xref linkend="proposed_standards"/>.
1886 When acting as a master, <acronym>BIND</acronym> 9
1887 supports IXFR for those zones
1888 where the necessary change history information is available. These
1889 include master zones maintained by dynamic update and slave zones
1890 whose data was obtained by IXFR. For manually maintained master
1891 zones, and for slave zones obtained by performing a full zone
1892 transfer (AXFR), IXFR is supported only if the option
1893 <command>ixfr-from-differences</command> is set
1894 to <userinput>yes</userinput>.
1898 When acting as a slave, <acronym>BIND</acronym> 9 will
1899 attempt to use IXFR unless
1900 it is explicitly disabled. For more information about disabling
1901 IXFR, see the description of the <command>request-ixfr</command> clause
1902 of the <command>server</command> statement.
1907 <title>Split DNS</title>
1909 Setting up different views, or visibility, of the DNS space to
1910 internal and external resolvers is usually referred to as a
1911 <emphasis>Split DNS</emphasis> setup. There are several
1912 reasons an organization would want to set up its DNS this way.
1915 One common reason for setting up a DNS system this way is
1916 to hide "internal" DNS information from "external" clients on the
1917 Internet. There is some debate as to whether or not this is actually
1919 Internal DNS information leaks out in many ways (via email headers,
1920 for example) and most savvy "attackers" can find the information
1921 they need using other means.
1922 However, since listing addresses of internal servers that
1923 external clients cannot possibly reach can result in
1924 connection delays and other annoyances, an organization may
1925 choose to use a Split DNS to present a consistent view of itself
1926 to the outside world.
1929 Another common reason for setting up a Split DNS system is
1930 to allow internal networks that are behind filters or in RFC 1918
1931 space (reserved IP space, as documented in RFC 1918) to resolve DNS
1932 on the Internet. Split DNS can also be used to allow mail from outside
1933 back in to the internal network.
1936 <title>Example split DNS setup</title>
1938 Let's say a company named <emphasis>Example, Inc.</emphasis>
1939 (<literal>example.com</literal>)
1940 has several corporate sites that have an internal network with
1942 Internet Protocol (IP) space and an external demilitarized zone (DMZ),
1943 or "outside" section of a network, that is available to the public.
1946 <emphasis>Example, Inc.</emphasis> wants its internal clients
1947 to be able to resolve external hostnames and to exchange mail with
1948 people on the outside. The company also wants its internal resolvers
1949 to have access to certain internal-only zones that are not available
1950 at all outside of the internal network.
1953 In order to accomplish this, the company will set up two sets
1954 of name servers. One set will be on the inside network (in the
1956 IP space) and the other set will be on bastion hosts, which are
1958 hosts that can talk to both sides of its network, in the DMZ.
1961 The internal servers will be configured to forward all queries,
1962 except queries for <filename>site1.internal</filename>, <filename>site2.internal</filename>, <filename>site1.example.com</filename>,
1963 and <filename>site2.example.com</filename>, to the servers
1965 DMZ. These internal servers will have complete sets of information
1966 for <filename>site1.example.com</filename>, <filename>site2.example.com</filename>, <filename>site1.internal</filename>,
1967 and <filename>site2.internal</filename>.
1970 To protect the <filename>site1.internal</filename> and <filename>site2.internal</filename> domains,
1971 the internal name servers must be configured to disallow all queries
1972 to these domains from any external hosts, including the bastion
1976 The external servers, which are on the bastion hosts, will
1977 be configured to serve the "public" version of the <filename>site1</filename> and <filename>site2.example.com</filename> zones.
1978 This could include things such as the host records for public servers
1979 (<filename>www.example.com</filename> and <filename>ftp.example.com</filename>),
1980 and mail exchange (MX) records (<filename>a.mx.example.com</filename> and <filename>b.mx.example.com</filename>).
1983 In addition, the public <filename>site1</filename> and <filename>site2.example.com</filename> zones
1984 should have special MX records that contain wildcard (`*') records
1985 pointing to the bastion hosts. This is needed because external mail
1986 servers do not have any other way of looking up how to deliver mail
1987 to those internal hosts. With the wildcard records, the mail will
1988 be delivered to the bastion host, which can then forward it on to
1992 Here's an example of a wildcard MX record:
1994 <programlisting>* IN MX 10 external1.example.com.</programlisting>
1996 Now that they accept mail on behalf of anything in the internal
1997 network, the bastion hosts will need to know how to deliver mail
1998 to internal hosts. In order for this to work properly, the resolvers
2000 the bastion hosts will need to be configured to point to the internal
2001 name servers for DNS resolution.
2004 Queries for internal hostnames will be answered by the internal
2005 servers, and queries for external hostnames will be forwarded back
2006 out to the DNS servers on the bastion hosts.
2009 In order for all this to work properly, internal clients will
2010 need to be configured to query <emphasis>only</emphasis> the internal
2011 name servers for DNS queries. This could also be enforced via
2013 filtering on the network.
2016 If everything has been set properly, <emphasis>Example, Inc.</emphasis>'s
2017 internal clients will now be able to:
2022 Look up any hostnames in the <literal>site1</literal>
2024 <literal>site2.example.com</literal> zones.
2029 Look up any hostnames in the <literal>site1.internal</literal> and
2030 <literal>site2.internal</literal> domains.
2034 <simpara>Look up any hostnames on the Internet.</simpara>
2037 <simpara>Exchange mail with both internal and external people.</simpara>
2041 Hosts on the Internet will be able to:
2046 Look up any hostnames in the <literal>site1</literal>
2048 <literal>site2.example.com</literal> zones.
2053 Exchange mail with anyone in the <literal>site1</literal> and
2054 <literal>site2.example.com</literal> zones.
2060 Here is an example configuration for the setup we just
2061 described above. Note that this is only configuration information;
2062 for information on how to configure your zone files, see <xref linkend="sample_configuration"/>.
2066 Internal DNS server config:
2071 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
2073 acl externals { <varname>bastion-ips-go-here</varname>; };
2079 // forward to external servers
2081 <varname>bastion-ips-go-here</varname>;
2083 // sample allow-transfer (no one)
2084 allow-transfer { none; };
2085 // restrict query access
2086 allow-query { internals; externals; };
2087 // restrict recursion
2088 allow-recursion { internals; };
2093 // sample master zone
2094 zone "site1.example.com" {
2096 file "m/site1.example.com";
2097 // do normal iterative resolution (do not forward)
2099 allow-query { internals; externals; };
2100 allow-transfer { internals; };
2103 // sample slave zone
2104 zone "site2.example.com" {
2106 file "s/site2.example.com";
2107 masters { 172.16.72.3; };
2109 allow-query { internals; externals; };
2110 allow-transfer { internals; };
2113 zone "site1.internal" {
2115 file "m/site1.internal";
2117 allow-query { internals; };
2118 allow-transfer { internals; }
2121 zone "site2.internal" {
2123 file "s/site2.internal";
2124 masters { 172.16.72.3; };
2126 allow-query { internals };
2127 allow-transfer { internals; }
2132 External (bastion host) DNS server config:
2136 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
2138 acl externals { bastion-ips-go-here; };
2143 // sample allow-transfer (no one)
2144 allow-transfer { none; };
2145 // default query access
2146 allow-query { any; };
2147 // restrict cache access
2148 allow-query-cache { internals; externals; };
2149 // restrict recursion
2150 allow-recursion { internals; externals; };
2155 // sample slave zone
2156 zone "site1.example.com" {
2158 file "m/site1.foo.com";
2159 allow-transfer { internals; externals; };
2162 zone "site2.example.com" {
2164 file "s/site2.foo.com";
2165 masters { another_bastion_host_maybe; };
2166 allow-transfer { internals; externals; }
2171 In the <filename>resolv.conf</filename> (or equivalent) on
2172 the bastion host(s):
2177 nameserver 172.16.72.2
2178 nameserver 172.16.72.3
2179 nameserver 172.16.72.4
2187 This is a short guide to setting up Transaction SIGnatures
2188 (TSIG) based transaction security in <acronym>BIND</acronym>. It describes changes
2189 to the configuration file as well as what changes are required for
2190 different features, including the process of creating transaction
2191 keys and using transaction signatures with <acronym>BIND</acronym>.
2194 <acronym>BIND</acronym> primarily supports TSIG for server
2195 to server communication.
2196 This includes zone transfer, notify, and recursive query messages.
2197 Resolvers based on newer versions of <acronym>BIND</acronym> 8 have limited support
2202 TSIG can also be useful for dynamic update. A primary
2203 server for a dynamic zone should control access to the dynamic
2204 update service, but IP-based access control is insufficient.
2205 The cryptographic access control provided by TSIG
2206 is far superior. The <command>nsupdate</command>
2207 program supports TSIG via the <option>-k</option> and
2208 <option>-y</option> command line options or inline by use
2209 of the <command>key</command>.
2213 <title>Generate Shared Keys for Each Pair of Hosts</title>
2215 A shared secret is generated to be shared between <emphasis>host1</emphasis> and <emphasis>host2</emphasis>.
2216 An arbitrary key name is chosen: "host1-host2.". The key name must
2217 be the same on both hosts.
2220 <title>Automatic Generation</title>
2222 The following command will generate a 128-bit (16 byte) HMAC-SHA256
2223 key as described above. Longer keys are better, but shorter keys
2224 are easier to read. Note that the maximum key length is the digest
2225 length, here 256 bits.
2228 <userinput>dnssec-keygen -a hmac-sha256 -b 128 -n HOST host1-host2.</userinput>
2231 The key is in the file <filename>Khost1-host2.+163+00000.private</filename>.
2232 Nothing directly uses this file, but the base-64 encoded string
2233 following "<literal>Key:</literal>"
2234 can be extracted from the file and used as a shared secret:
2236 <programlisting>Key: La/E5CjG9O+os1jq0a2jdA==</programlisting>
2238 The string "<literal>La/E5CjG9O+os1jq0a2jdA==</literal>" can
2239 be used as the shared secret.
2243 <title>Manual Generation</title>
2245 The shared secret is simply a random sequence of bits, encoded
2246 in base-64. Most ASCII strings are valid base-64 strings (assuming
2247 the length is a multiple of 4 and only valid characters are used),
2248 so the shared secret can be manually generated.
2251 Also, a known string can be run through <command>mmencode</command> or
2252 a similar program to generate base-64 encoded data.
2257 <title>Copying the Shared Secret to Both Machines</title>
2259 This is beyond the scope of DNS. A secure transport mechanism
2260 should be used. This could be secure FTP, ssh, telephone, etc.
2264 <title>Informing the Servers of the Key's Existence</title>
2266 Imagine <emphasis>host1</emphasis> and <emphasis>host 2</emphasis>
2268 both servers. The following is added to each server's <filename>named.conf</filename> file:
2273 algorithm hmac-sha256;
2274 secret "La/E5CjG9O+os1jq0a2jdA==";
2279 The secret is the one generated above. Since this is a secret, it
2280 is recommended that either <filename>named.conf</filename> be
2281 non-world readable, or the key directive be added to a non-world
2282 readable file that is included by <filename>named.conf</filename>.
2285 At this point, the key is recognized. This means that if the
2286 server receives a message signed by this key, it can verify the
2287 signature. If the signature is successfully verified, the
2288 response is signed by the same key.
2293 <title>Instructing the Server to Use the Key</title>
2295 Since keys are shared between two hosts only, the server must
2296 be told when keys are to be used. The following is added to the <filename>named.conf</filename> file
2297 for <emphasis>host1</emphasis>, if the IP address of <emphasis>host2</emphasis> is
2303 keys { host1-host2. ;};
2308 Multiple keys may be present, but only the first is used.
2309 This directive does not contain any secrets, so it may be in a
2314 If <emphasis>host1</emphasis> sends a message that is a request
2315 to that address, the message will be signed with the specified key. <emphasis>host1</emphasis> will
2316 expect any responses to signed messages to be signed with the same
2320 A similar statement must be present in <emphasis>host2</emphasis>'s
2321 configuration file (with <emphasis>host1</emphasis>'s address) for <emphasis>host2</emphasis> to
2322 sign request messages to <emphasis>host1</emphasis>.
2326 <title>TSIG Key Based Access Control</title>
2328 <acronym>BIND</acronym> allows IP addresses and ranges
2329 to be specified in ACL
2331 <command>allow-{ query | transfer | update }</command>
2333 This has been extended to allow TSIG keys also. The above key would
2334 be denoted <command>key host1-host2.</command>
2337 An example of an <command>allow-update</command> directive would be:
2341 allow-update { key host1-host2. ;};
2345 This allows dynamic updates to succeed only if the request
2346 was signed by a key named "<command>host1-host2.</command>".
2350 See <xref linkend="dynamic_update_policies"/> for a discussion of
2351 the more flexible <command>update-policy</command> statement.
2356 <title>Errors</title>
2359 The processing of TSIG signed messages can result in
2360 several errors. If a signed message is sent to a non-TSIG aware
2361 server, a FORMERR (format error) will be returned, since the server will not
2362 understand the record. This is a result of misconfiguration,
2363 since the server must be explicitly configured to send a TSIG
2364 signed message to a specific server.
2368 If a TSIG aware server receives a message signed by an
2369 unknown key, the response will be unsigned with the TSIG
2370 extended error code set to BADKEY. If a TSIG aware server
2371 receives a message with a signature that does not validate, the
2372 response will be unsigned with the TSIG extended error code set
2373 to BADSIG. If a TSIG aware server receives a message with a time
2374 outside of the allowed range, the response will be signed with
2375 the TSIG extended error code set to BADTIME, and the time values
2376 will be adjusted so that the response can be successfully
2377 verified. In any of these cases, the message's rcode (response code) is set to
2378 NOTAUTH (not authenticated).
2386 <para><command>TKEY</command>
2387 is a mechanism for automatically generating a shared secret
2388 between two hosts. There are several "modes" of
2389 <command>TKEY</command> that specify how the key is generated
2390 or assigned. <acronym>BIND</acronym> 9 implements only one of
2391 these modes, the Diffie-Hellman key exchange. Both hosts are
2392 required to have a Diffie-Hellman KEY record (although this
2393 record is not required to be present in a zone). The
2394 <command>TKEY</command> process must use signed messages,
2395 signed either by TSIG or SIG(0). The result of
2396 <command>TKEY</command> is a shared secret that can be used to
2397 sign messages with TSIG. <command>TKEY</command> can also be
2398 used to delete shared secrets that it had previously
2403 The <command>TKEY</command> process is initiated by a
2405 or server by sending a signed <command>TKEY</command>
2407 (including any appropriate KEYs) to a TKEY-aware server. The
2408 server response, if it indicates success, will contain a
2409 <command>TKEY</command> record and any appropriate keys.
2411 this exchange, both participants have enough information to
2412 determine the shared secret; the exact process depends on the
2413 <command>TKEY</command> mode. When using the
2415 <command>TKEY</command> mode, Diffie-Hellman keys are
2417 and the shared secret is derived by both participants.
2422 <title>SIG(0)</title>
2425 <acronym>BIND</acronym> 9 partially supports DNSSEC SIG(0)
2426 transaction signatures as specified in RFC 2535 and RFC 2931.
2428 uses public/private keys to authenticate messages. Access control
2429 is performed in the same manner as TSIG keys; privileges can be
2430 granted or denied based on the key name.
2434 When a SIG(0) signed message is received, it will only be
2435 verified if the key is known and trusted by the server; the server
2436 will not attempt to locate and/or validate the key.
2440 SIG(0) signing of multiple-message TCP streams is not
2445 The only tool shipped with <acronym>BIND</acronym> 9 that
2446 generates SIG(0) signed messages is <command>nsupdate</command>.
2451 <title>DNSSEC</title>
2454 Cryptographic authentication of DNS information is possible
2455 through the DNS Security (<emphasis>DNSSEC-bis</emphasis>) extensions,
2456 defined in RFC 4033, RFC 4034, and RFC 4035.
2457 This section describes the creation and use of DNSSEC signed zones.
2461 In order to set up a DNSSEC secure zone, there are a series
2462 of steps which must be followed. <acronym>BIND</acronym>
2465 that are used in this process, which are explained in more detail
2466 below. In all cases, the <option>-h</option> option prints a
2467 full list of parameters. Note that the DNSSEC tools require the
2468 keyset files to be in the working directory or the
2469 directory specified by the <option>-d</option> option, and
2470 that the tools shipped with BIND 9.2.x and earlier are not compatible
2471 with the current ones.
2475 There must also be communication with the administrators of
2476 the parent and/or child zone to transmit keys. A zone's security
2477 status must be indicated by the parent zone for a DNSSEC capable
2478 resolver to trust its data. This is done through the presence
2479 or absence of a <literal>DS</literal> record at the
2485 For other servers to trust data in this zone, they must
2486 either be statically configured with this zone's zone key or the
2487 zone key of another zone above this one in the DNS tree.
2491 <title>Generating Keys</title>
2494 The <command>dnssec-keygen</command> program is used to
2499 A secure zone must contain one or more zone keys. The
2500 zone keys will sign all other records in the zone, as well as
2501 the zone keys of any secure delegated zones. Zone keys must
2502 have the same name as the zone, a name type of
2503 <command>ZONE</command>, and must be usable for
2505 It is recommended that zone keys use a cryptographic algorithm
2506 designated as "mandatory to implement" by the IETF; currently
2507 the only one is RSASHA1.
2511 The following command will generate a 768-bit RSASHA1 key for
2512 the <filename>child.example</filename> zone:
2516 <userinput>dnssec-keygen -a RSASHA1 -b 768 -n ZONE child.example.</userinput>
2520 Two output files will be produced:
2521 <filename>Kchild.example.+005+12345.key</filename> and
2522 <filename>Kchild.example.+005+12345.private</filename>
2524 12345 is an example of a key tag). The key filenames contain
2525 the key name (<filename>child.example.</filename>),
2527 is DSA, 1 is RSAMD5, 5 is RSASHA1, etc.), and the key tag (12345 in
2529 The private key (in the <filename>.private</filename>
2531 used to generate signatures, and the public key (in the
2532 <filename>.key</filename> file) is used for signature
2537 To generate another key with the same properties (but with
2538 a different key tag), repeat the above command.
2542 The <command>dnssec-keyfromlabel</command> program is used
2543 to get a key pair from a crypto hardware and build the key
2544 files. Its usage is similar to <command>dnssec-keygen</command>.
2548 The public keys should be inserted into the zone file by
2549 including the <filename>.key</filename> files using
2550 <command>$INCLUDE</command> statements.
2555 <title>Signing the Zone</title>
2558 The <command>dnssec-signzone</command> program is used
2563 Any <filename>keyset</filename> files corresponding to
2564 secure subzones should be present. The zone signer will
2565 generate <literal>NSEC</literal>, <literal>NSEC3</literal>
2566 and <literal>RRSIG</literal> records for the zone, as
2567 well as <literal>DS</literal> for the child zones if
2568 <literal>'-g'</literal> is specified. If <literal>'-g'</literal>
2569 is not specified, then DS RRsets for the secure child
2570 zones need to be added manually.
2574 The following command signs the zone, assuming it is in a
2575 file called <filename>zone.child.example</filename>. By
2576 default, all zone keys which have an available private key are
2577 used to generate signatures.
2581 <userinput>dnssec-signzone -o child.example zone.child.example</userinput>
2585 One output file is produced:
2586 <filename>zone.child.example.signed</filename>. This
2588 should be referenced by <filename>named.conf</filename>
2590 input file for the zone.
2593 <para><command>dnssec-signzone</command>
2594 will also produce a keyset and dsset files and optionally a
2595 dlvset file. These are used to provide the parent zone
2596 administrators with the <literal>DNSKEYs</literal> (or their
2597 corresponding <literal>DS</literal> records) that are the
2598 secure entry point to the zone.
2604 <title>Configuring Servers</title>
2607 To enable <command>named</command> to respond appropriately
2608 to DNS requests from DNSSEC aware clients,
2609 <command>dnssec-enable</command> must be set to yes.
2610 (This is the default setting.)
2614 To enable <command>named</command> to validate answers from
2615 other servers, the <command>dnssec-enable</command> and
2616 <command>dnssec-validation</command> options must both be
2617 set to yes (the default setting in <acronym>BIND</acronym> 9.5
2618 and later), and at least one trust anchor must be configured
2619 with a <command>trusted-keys</command> or
2620 <command>managed-keys</command> statement in
2621 <filename>named.conf</filename>.
2625 <command>trusted-keys</command> are copies of DNSKEY RRs
2626 for zones that are used to form the first link in the
2627 cryptographic chain of trust. All keys listed in
2628 <command>trusted-keys</command> (and corresponding zones)
2629 are deemed to exist and only the listed keys will be used
2630 to validated the DNSKEY RRset that they are from.
2634 <command>managed-keys</command> are trusted keys which are
2635 automatically kept up to date via RFC 5011 trust anchor
2640 <command>trusted-keys</command> and
2641 <command>managed-keys</command> are described in more detail
2642 later in this document.
2646 Unlike <acronym>BIND</acronym> 8, <acronym>BIND</acronym>
2647 9 does not verify signatures on load, so zone keys for
2648 authoritative zones do not need to be specified in the
2653 After DNSSEC gets established, a typical DNSSEC configuration
2654 will look something like the following. It has one or
2655 more public keys for the root. This allows answers from
2656 outside the organization to be validated. It will also
2657 have several keys for parts of the namespace the organization
2658 controls. These are here to ensure that <command>named</command>
2659 is immune to compromises in the DNSSEC components of the security
2666 "." initial-key 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS
2667 JxrGkxJWoZu6I7PzJu/E9gx4UC1zGAHlXKdE4zYIpRh
2668 aBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3zy2Xy
2669 4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYg
2670 hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp
2671 5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M/lUUVRbke
2672 g1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq
2673 66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ
2674 97S+LKUTpQcq27R7AT3/V5hRQxScINqwcz4jYqZD2fQ
2675 dgxbcDTClU0CRBdiieyLMNzXG3";
2679 /* Key for our organization's forward zone */
2680 example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6
2681 5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z
2682 GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb
2683 4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL
2684 kBOUKUf/mC7HvfwYH/Be22GnClrinKJp1O
2685 g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S
2686 TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq
2687 FxmAVZP20igTixin/1LcrgX/KMEGd/biuv
2688 F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm
2689 /oyWR8BW/hWdzOvnSCThlHf3xiYleDbt/o
2692 /* Key for our reverse zone. */
2693 2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwc
2694 xOdNax071L18QqZnQQQAVVr+i
2695 LhGTnNGp3HoWQLUIzKrJVZ3zg
2696 gy3WwNT6kZo6c0tszYqbtvchm
2697 gQC8CzKojM/W16i6MG/eafGU3
2698 siaOdS0yOI6BgPsw+YZdzlYMa
2699 IJGf4M4dyoKIhzdZyQ2bYQrjy
2700 Q4LB0lC7aOnsMyYKHHYeRvPxj
2701 IQXmdqgOJGq+vsevG06zW+1xg
2702 YJh9rCIfnm1GX/KMgxLPG2vXT
2703 D/RnLX+D3T3UL7HJYHJhAZD5L
2704 59VvjSPsZJHeDCUyWYrvPZesZ
2705 DIRvhDD52SKvbheeTJUm6Ehkz
2706 ytNN2SN96QRk8j/iI8ib";
2712 dnssec-validation yes;
2717 None of the keys listed in this example are valid. In particular,
2718 the root key is not valid.
2722 When DNSSEC validation is enabled and properly configured,
2723 the resolver will reject any answers from signed, secure zones
2724 which fail to validate, and will return SERVFAIL to the client.
2728 Responses may fail to validate for any of several reasons,
2729 including missing, expired, or invalid signatures, a key which
2730 does not match the DS RRset in the parent zone, or an insecure
2731 response from a zone which, according to its parent, should have
2737 When the validator receives a response from an unsigned zone
2738 that has a signed parent, it must confirm with the parent
2739 that the zone was intentionally left unsigned. It does
2740 this by verifying, via signed and validated NSEC/NSEC3 records,
2741 that the parent zone contains no DS records for the child.
2744 If the validator <emphasis>can</emphasis> prove that the zone
2745 is insecure, then the response is accepted. However, if it
2746 cannot, then it must assume an insecure response to be a
2747 forgery; it rejects the response and logs an error.
2750 The logged error reads "insecurity proof failed" and
2751 "got insecure response; parent indicates it should be secure".
2752 (Prior to BIND 9.7, the logged error was "not insecure".
2753 This referred to the zone, not the response.)
2760 <xi:include href="dnssec.xml"/>
2762 <xi:include href="managed-keys.xml"/>
2764 <xi:include href="pkcs11.xml"/>
2767 <title>IPv6 Support in <acronym>BIND</acronym> 9</title>
2770 <acronym>BIND</acronym> 9 fully supports all currently
2771 defined forms of IPv6 name to address and address to name
2772 lookups. It will also use IPv6 addresses to make queries when
2773 running on an IPv6 capable system.
2777 For forward lookups, <acronym>BIND</acronym> 9 supports
2778 only AAAA records. RFC 3363 deprecated the use of A6 records,
2779 and client-side support for A6 records was accordingly removed
2780 from <acronym>BIND</acronym> 9.
2781 However, authoritative <acronym>BIND</acronym> 9 name servers still
2782 load zone files containing A6 records correctly, answer queries
2783 for A6 records, and accept zone transfer for a zone containing A6
2788 For IPv6 reverse lookups, <acronym>BIND</acronym> 9 supports
2789 the traditional "nibble" format used in the
2790 <emphasis>ip6.arpa</emphasis> domain, as well as the older, deprecated
2791 <emphasis>ip6.int</emphasis> domain.
2792 Older versions of <acronym>BIND</acronym> 9
2793 supported the "binary label" (also known as "bitstring") format,
2794 but support of binary labels has been completely removed per
2796 Many applications in <acronym>BIND</acronym> 9 do not understand
2797 the binary label format at all any more, and will return an
2799 In particular, an authoritative <acronym>BIND</acronym> 9
2800 name server will not load a zone file containing binary labels.
2804 For an overview of the format and structure of IPv6 addresses,
2805 see <xref linkend="ipv6addresses"/>.
2809 <title>Address Lookups Using AAAA Records</title>
2812 The IPv6 AAAA record is a parallel to the IPv4 A record,
2813 and, unlike the deprecated A6 record, specifies the entire
2814 IPv6 address in a single record. For example,
2818 $ORIGIN example.com.
2819 host 3600 IN AAAA 2001:db8::1
2823 Use of IPv4-in-IPv6 mapped addresses is not recommended.
2824 If a host has an IPv4 address, use an A record, not
2825 a AAAA, with <literal>::ffff:192.168.42.1</literal> as
2830 <title>Address to Name Lookups Using Nibble Format</title>
2833 When looking up an address in nibble format, the address
2834 components are simply reversed, just as in IPv4, and
2835 <literal>ip6.arpa.</literal> is appended to the
2837 For example, the following would provide reverse name lookup for
2839 <literal>2001:db8::1</literal>.
2843 $ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
2844 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR (
2852 <chapter id="Bv9ARM.ch05">
2853 <title>The <acronym>BIND</acronym> 9 Lightweight Resolver</title>
2855 <title>The Lightweight Resolver Library</title>
2857 Traditionally applications have been linked with a stub resolver
2858 library that sends recursive DNS queries to a local caching name
2862 IPv6 once introduced new complexity into the resolution process,
2863 such as following A6 chains and DNAME records, and simultaneous
2864 lookup of IPv4 and IPv6 addresses. Though most of the complexity was
2865 then removed, these are hard or impossible
2866 to implement in a traditional stub resolver.
2869 <acronym>BIND</acronym> 9 therefore can also provide resolution
2870 services to local clients
2871 using a combination of a lightweight resolver library and a resolver
2872 daemon process running on the local host. These communicate using
2873 a simple UDP-based protocol, the "lightweight resolver protocol"
2874 that is distinct from and simpler than the full DNS protocol.
2878 <title>Running a Resolver Daemon</title>
2881 To use the lightweight resolver interface, the system must
2882 run the resolver daemon <command>lwresd</command> or a
2884 name server configured with a <command>lwres</command>
2889 By default, applications using the lightweight resolver library will
2891 UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
2893 address can be overridden by <command>lwserver</command>
2895 <filename>/etc/resolv.conf</filename>.
2899 The daemon currently only looks in the DNS, but in the future
2900 it may use other sources such as <filename>/etc/hosts</filename>,
2905 The <command>lwresd</command> daemon is essentially a
2906 caching-only name server that responds to requests using the
2908 resolver protocol rather than the DNS protocol. Because it needs
2909 to run on each host, it is designed to require no or minimal
2911 Unless configured otherwise, it uses the name servers listed on
2912 <command>nameserver</command> lines in <filename>/etc/resolv.conf</filename>
2913 as forwarders, but is also capable of doing the resolution
2918 The <command>lwresd</command> daemon may also be
2920 <filename>named.conf</filename> style configuration file,
2922 <filename>/etc/lwresd.conf</filename> by default. A name
2924 be configured to act as a lightweight resolver daemon using the
2925 <command>lwres</command> statement in <filename>named.conf</filename>.
2931 <chapter id="Bv9ARM.ch06">
2932 <title><acronym>BIND</acronym> 9 Configuration Reference</title>
2935 <acronym>BIND</acronym> 9 configuration is broadly similar
2936 to <acronym>BIND</acronym> 8; however, there are a few new
2938 of configuration, such as views. <acronym>BIND</acronym>
2939 8 configuration files should work with few alterations in <acronym>BIND</acronym>
2940 9, although more complex configurations should be reviewed to check
2941 if they can be more efficiently implemented using the new features
2942 found in <acronym>BIND</acronym> 9.
2946 <acronym>BIND</acronym> 4 configuration files can be
2947 converted to the new format
2948 using the shell script
2949 <filename>contrib/named-bootconf/named-bootconf.sh</filename>.
2951 <sect1 id="configuration_file_elements">
2952 <title>Configuration File Elements</title>
2954 Following is a list of elements used throughout the <acronym>BIND</acronym> configuration
2957 <informaltable colsep="0" rowsep="0">
2958 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
2959 <colspec colname="1" colnum="1" colsep="0" colwidth="1.855in"/>
2960 <colspec colname="2" colnum="2" colsep="0" colwidth="3.770in"/>
2965 <varname>acl_name</varname>
2970 The name of an <varname>address_match_list</varname> as
2971 defined by the <command>acl</command> statement.
2978 <varname>address_match_list</varname>
2983 A list of one or more
2984 <varname>ip_addr</varname>,
2985 <varname>ip_prefix</varname>, <varname>key_id</varname>,
2986 or <varname>acl_name</varname> elements, see
2987 <xref linkend="address_match_lists"/>.
2994 <varname>masters_list</varname>
2999 A named list of one or more <varname>ip_addr</varname>
3000 with optional <varname>key_id</varname> and/or
3001 <varname>ip_port</varname>.
3002 A <varname>masters_list</varname> may include other
3003 <varname>masters_lists</varname>.
3010 <varname>domain_name</varname>
3015 A quoted string which will be used as
3016 a DNS name, for example "<literal>my.test.domain</literal>".
3023 <varname>namelist</varname>
3028 A list of one or more <varname>domain_name</varname>
3036 <varname>dotted_decimal</varname>
3041 One to four integers valued 0 through
3042 255 separated by dots (`.'), such as <command>123</command>,
3043 <command>45.67</command> or <command>89.123.45.67</command>.
3050 <varname>ip4_addr</varname>
3055 An IPv4 address with exactly four elements
3056 in <varname>dotted_decimal</varname> notation.
3063 <varname>ip6_addr</varname>
3068 An IPv6 address, such as <command>2001:db8::1234</command>.
3069 IPv6 scoped addresses that have ambiguity on their
3070 scope zones must be disambiguated by an appropriate
3071 zone ID with the percent character (`%') as
3072 delimiter. It is strongly recommended to use
3073 string zone names rather than numeric identifiers,
3074 in order to be robust against system configuration
3075 changes. However, since there is no standard
3076 mapping for such names and identifier values,
3077 currently only interface names as link identifiers
3078 are supported, assuming one-to-one mapping between
3079 interfaces and links. For example, a link-local
3080 address <command>fe80::1</command> on the link
3081 attached to the interface <command>ne0</command>
3082 can be specified as <command>fe80::1%ne0</command>.
3083 Note that on most systems link-local addresses
3084 always have the ambiguity, and need to be
3092 <varname>ip_addr</varname>
3097 An <varname>ip4_addr</varname> or <varname>ip6_addr</varname>.
3104 <varname>ip_port</varname>
3109 An IP port <varname>number</varname>.
3110 The <varname>number</varname> is limited to 0
3111 through 65535, with values
3112 below 1024 typically restricted to use by processes running
3114 In some cases, an asterisk (`*') character can be used as a
3116 select a random high-numbered port.
3123 <varname>ip_prefix</varname>
3128 An IP network specified as an <varname>ip_addr</varname>,
3129 followed by a slash (`/') and then the number of bits in the
3131 Trailing zeros in a <varname>ip_addr</varname>
3133 For example, <command>127/8</command> is the
3134 network <command>127.0.0.0</command> with
3135 netmask <command>255.0.0.0</command> and <command>1.2.3.0/28</command> is
3136 network <command>1.2.3.0</command> with netmask <command>255.255.255.240</command>.
3139 When specifying a prefix involving a IPv6 scoped address
3140 the scope may be omitted. In that case the prefix will
3141 match packets from any scope.
3148 <varname>key_id</varname>
3153 A <varname>domain_name</varname> representing
3154 the name of a shared key, to be used for transaction
3162 <varname>key_list</varname>
3167 A list of one or more
3168 <varname>key_id</varname>s,
3169 separated by semicolons and ending with a semicolon.
3176 <varname>number</varname>
3181 A non-negative 32-bit integer
3182 (i.e., a number between 0 and 4294967295, inclusive).
3183 Its acceptable value might further
3184 be limited by the context in which it is used.
3191 <varname>path_name</varname>
3196 A quoted string which will be used as
3197 a pathname, such as <filename>zones/master/my.test.domain</filename>.
3204 <varname>port_list</varname>
3209 A list of an <varname>ip_port</varname> or a port
3211 A port range is specified in the form of
3212 <userinput>range</userinput> followed by
3213 two <varname>ip_port</varname>s,
3214 <varname>port_low</varname> and
3215 <varname>port_high</varname>, which represents
3216 port numbers from <varname>port_low</varname> through
3217 <varname>port_high</varname>, inclusive.
3218 <varname>port_low</varname> must not be larger than
3219 <varname>port_high</varname>.
3221 <userinput>range 1024 65535</userinput> represents
3222 ports from 1024 through 65535.
3223 In either case an asterisk (`*') character is not
3224 allowed as a valid <varname>ip_port</varname>.
3231 <varname>size_spec</varname>
3236 A number, the word <userinput>unlimited</userinput>,
3237 or the word <userinput>default</userinput>.
3240 An <varname>unlimited</varname> <varname>size_spec</varname> requests unlimited
3241 use, or the maximum available amount. A <varname>default size_spec</varname> uses
3242 the limit that was in force when the server was started.
3245 A <varname>number</varname> can optionally be
3246 followed by a scaling factor:
3247 <userinput>K</userinput> or <userinput>k</userinput>
3249 <userinput>M</userinput> or <userinput>m</userinput>
3251 <userinput>G</userinput> or <userinput>g</userinput> for gigabytes,
3252 which scale by 1024, 1024*1024, and 1024*1024*1024
3256 The value must be representable as a 64-bit unsigned integer
3257 (0 to 18446744073709551615, inclusive).
3258 Using <varname>unlimited</varname> is the best
3260 to safely set a really large number.
3267 <varname>yes_or_no</varname>
3272 Either <userinput>yes</userinput> or <userinput>no</userinput>.
3273 The words <userinput>true</userinput> and <userinput>false</userinput> are
3274 also accepted, as are the numbers <userinput>1</userinput>
3275 and <userinput>0</userinput>.
3282 <varname>dialup_option</varname>
3287 One of <userinput>yes</userinput>,
3288 <userinput>no</userinput>, <userinput>notify</userinput>,
3289 <userinput>notify-passive</userinput>, <userinput>refresh</userinput> or
3290 <userinput>passive</userinput>.
3291 When used in a zone, <userinput>notify-passive</userinput>,
3292 <userinput>refresh</userinput>, and <userinput>passive</userinput>
3293 are restricted to slave and stub zones.
3300 <sect2 id="address_match_lists">
3301 <title>Address Match Lists</title>
3303 <title>Syntax</title>
3305 <programlisting><varname>address_match_list</varname> = address_match_list_element ;
3306 <optional> address_match_list_element; ... </optional>
3307 <varname>address_match_list_element</varname> = <optional> ! </optional> (ip_address <optional>/length</optional> |
3308 key key_id | acl_name | { address_match_list } )
3313 <title>Definition and Usage</title>
3315 Address match lists are primarily used to determine access
3316 control for various server operations. They are also used in
3317 the <command>listen-on</command> and <command>sortlist</command>
3318 statements. The elements which constitute an address match
3319 list can be any of the following:
3323 <simpara>an IP address (IPv4 or IPv6)</simpara>
3326 <simpara>an IP prefix (in `/' notation)</simpara>
3330 a key ID, as defined by the <command>key</command>
3335 <simpara>the name of an address match list defined with
3336 the <command>acl</command> statement
3340 <simpara>a nested address match list enclosed in braces</simpara>
3345 Elements can be negated with a leading exclamation mark (`!'),
3346 and the match list names "any", "none", "localhost", and
3347 "localnets" are predefined. More information on those names
3348 can be found in the description of the acl statement.
3352 The addition of the key clause made the name of this syntactic
3353 element something of a misnomer, since security keys can be used
3354 to validate access without regard to a host or network address.
3355 Nonetheless, the term "address match list" is still used
3356 throughout the documentation.
3360 When a given IP address or prefix is compared to an address
3361 match list, the comparison takes place in approximately O(1)
3362 time. However, key comparisons require that the list of keys
3363 be traversed until a matching key is found, and therefore may
3368 The interpretation of a match depends on whether the list is being
3369 used for access control, defining <command>listen-on</command> ports, or in a
3370 <command>sortlist</command>, and whether the element was negated.
3374 When used as an access control list, a non-negated match
3375 allows access and a negated match denies access. If
3376 there is no match, access is denied. The clauses
3377 <command>allow-notify</command>,
3378 <command>allow-recursion</command>,
3379 <command>allow-recursion-on</command>,
3380 <command>allow-query</command>,
3381 <command>allow-query-on</command>,
3382 <command>allow-query-cache</command>,
3383 <command>allow-query-cache-on</command>,
3384 <command>allow-transfer</command>,
3385 <command>allow-update</command>,
3386 <command>allow-update-forwarding</command>, and
3387 <command>blackhole</command> all use address match
3388 lists. Similarly, the <command>listen-on</command> option will cause the
3389 server to refuse queries on any of the machine's
3390 addresses which do not match the list.
3394 Order of insertion is significant. If more than one element
3395 in an ACL is found to match a given IP address or prefix,
3396 preference will be given to the one that came
3397 <emphasis>first</emphasis> in the ACL definition.
3398 Because of this first-match behavior, an element that
3399 defines a subset of another element in the list should
3400 come before the broader element, regardless of whether
3401 either is negated. For example, in
3402 <command>1.2.3/24; ! 1.2.3.13;</command>
3403 the 1.2.3.13 element is completely useless because the
3404 algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
3405 element. Using <command>! 1.2.3.13; 1.2.3/24</command> fixes
3406 that problem by having 1.2.3.13 blocked by the negation, but
3407 all other 1.2.3.* hosts fall through.
3413 <title>Comment Syntax</title>
3416 The <acronym>BIND</acronym> 9 comment syntax allows for
3418 anywhere that whitespace may appear in a <acronym>BIND</acronym> configuration
3419 file. To appeal to programmers of all kinds, they can be written
3420 in the C, C++, or shell/perl style.
3424 <title>Syntax</title>
3427 <programlisting>/* This is a <acronym>BIND</acronym> comment as in C */</programlisting>
3428 <programlisting>// This is a <acronym>BIND</acronym> comment as in C++</programlisting>
3429 <programlisting># This is a <acronym>BIND</acronym> comment as in common UNIX shells
3430 # and perl</programlisting>
3434 <title>Definition and Usage</title>
3436 Comments may appear anywhere that whitespace may appear in
3437 a <acronym>BIND</acronym> configuration file.
3440 C-style comments start with the two characters /* (slash,
3441 star) and end with */ (star, slash). Because they are completely
3442 delimited with these characters, they can be used to comment only
3443 a portion of a line or to span multiple lines.
3446 C-style comments cannot be nested. For example, the following
3447 is not valid because the entire comment ends with the first */:
3451 <programlisting>/* This is the start of a comment.
3452 This is still part of the comment.
3453 /* This is an incorrect attempt at nesting a comment. */
3454 This is no longer in any comment. */
3460 C++-style comments start with the two characters // (slash,
3461 slash) and continue to the end of the physical line. They cannot
3462 be continued across multiple physical lines; to have one logical
3463 comment span multiple lines, each line must use the // pair.
3468 <programlisting>// This is the start of a comment. The next line
3469 // is a new comment, even though it is logically
3470 // part of the previous comment.
3475 Shell-style (or perl-style, if you prefer) comments start
3476 with the character <literal>#</literal> (number sign)
3477 and continue to the end of the
3478 physical line, as in C++ comments.
3484 <programlisting># This is the start of a comment. The next line
3485 # is a new comment, even though it is logically
3486 # part of the previous comment.
3493 You cannot use the semicolon (`;') character
3494 to start a comment such as you would in a zone file. The
3495 semicolon indicates the end of a configuration
3503 <sect1 id="Configuration_File_Grammar">
3504 <title>Configuration File Grammar</title>
3507 A <acronym>BIND</acronym> 9 configuration consists of
3508 statements and comments.
3509 Statements end with a semicolon. Statements and comments are the
3510 only elements that can appear without enclosing braces. Many
3511 statements contain a block of sub-statements, which are also
3512 terminated with a semicolon.
3516 The following statements are supported:
3519 <informaltable colsep="0" rowsep="0">
3520 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
3521 <colspec colname="1" colnum="1" colsep="0" colwidth="1.336in"/>
3522 <colspec colname="2" colnum="2" colsep="0" colwidth="3.778in"/>
3526 <para><command>acl</command></para>
3530 defines a named IP address
3531 matching list, for access control and other uses.
3537 <para><command>controls</command></para>
3541 declares control channels to be used
3542 by the <command>rndc</command> utility.
3548 <para><command>include</command></para>
3558 <para><command>key</command></para>
3562 specifies key information for use in
3563 authentication and authorization using TSIG.
3569 <para><command>logging</command></para>
3573 specifies what the server logs, and where
3574 the log messages are sent.
3580 <para><command>lwres</command></para>
3584 configures <command>named</command> to
3585 also act as a light-weight resolver daemon (<command>lwresd</command>).
3591 <para><command>masters</command></para>
3595 defines a named masters list for
3596 inclusion in stub and slave zone masters clauses.
3602 <para><command>options</command></para>
3606 controls global server configuration
3607 options and sets defaults for other statements.
3613 <para><command>server</command></para>
3617 sets certain configuration options on
3624 <para><command>statistics-channels</command></para>
3628 declares communication channels to get access to
3629 <command>named</command> statistics.
3635 <para><command>trusted-keys</command></para>
3639 defines trusted DNSSEC keys.
3645 <para><command>managed-keys</command></para>
3649 lists DNSSEC keys to be kept up to date
3650 using RFC 5011 trust anchor maintenance.
3656 <para><command>view</command></para>
3666 <para><command>zone</command></para>
3679 The <command>logging</command> and
3680 <command>options</command> statements may only occur once
3686 <title><command>acl</command> Statement Grammar</title>
3688 <programlisting><command>acl</command> acl-name {
3695 <title><command>acl</command> Statement Definition and
3699 The <command>acl</command> statement assigns a symbolic
3700 name to an address match list. It gets its name from a primary
3701 use of address match lists: Access Control Lists (ACLs).
3705 Note that an address match list's name must be defined
3706 with <command>acl</command> before it can be used
3707 elsewhere; no forward references are allowed.
3711 The following ACLs are built-in:
3714 <informaltable colsep="0" rowsep="0">
3715 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
3716 <colspec colname="1" colnum="1" colsep="0" colwidth="1.130in"/>
3717 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
3721 <para><command>any</command></para>
3731 <para><command>none</command></para>
3741 <para><command>localhost</command></para>
3745 Matches the IPv4 and IPv6 addresses of all network
3746 interfaces on the system.
3752 <para><command>localnets</command></para>
3756 Matches any host on an IPv4 or IPv6 network
3757 for which the system has an interface.
3758 Some systems do not provide a way to determine the prefix
3760 local IPv6 addresses.
3761 In such a case, <command>localnets</command>
3762 only matches the local
3763 IPv6 addresses, just like <command>localhost</command>.
3773 <title><command>controls</command> Statement Grammar</title>
3775 <programlisting><command>controls</command> {
3776 [ inet ( ip_addr | * ) [ port ip_port ]
3777 allow { <replaceable> address_match_list </replaceable> }
3778 keys { <replaceable>key_list</replaceable> }; ]
3780 [ unix <replaceable>path</replaceable> perm <replaceable>number</replaceable> owner <replaceable>number</replaceable> group <replaceable>number</replaceable>
3781 keys { <replaceable>key_list</replaceable> }; ]
3788 <sect2 id="controls_statement_definition_and_usage">
3789 <title><command>controls</command> Statement Definition and
3793 The <command>controls</command> statement declares control
3794 channels to be used by system administrators to control the
3795 operation of the name server. These control channels are
3796 used by the <command>rndc</command> utility to send
3797 commands to and retrieve non-DNS results from a name server.
3801 An <command>inet</command> control channel is a TCP socket
3802 listening at the specified <command>ip_port</command> on the
3803 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
3804 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
3805 interpreted as the IPv4 wildcard address; connections will be
3806 accepted on any of the system's IPv4 addresses.
3807 To listen on the IPv6 wildcard address,
3808 use an <command>ip_addr</command> of <literal>::</literal>.
3809 If you will only use <command>rndc</command> on the local host,
3810 using the loopback address (<literal>127.0.0.1</literal>
3811 or <literal>::1</literal>) is recommended for maximum security.
3815 If no port is specified, port 953 is used. The asterisk
3816 "<literal>*</literal>" cannot be used for <command>ip_port</command>.
3820 The ability to issue commands over the control channel is
3821 restricted by the <command>allow</command> and
3822 <command>keys</command> clauses.
3823 Connections to the control channel are permitted based on the
3824 <command>address_match_list</command>. This is for simple
3825 IP address based filtering only; any <command>key_id</command>
3826 elements of the <command>address_match_list</command>
3831 A <command>unix</command> control channel is a UNIX domain
3832 socket listening at the specified path in the file system.
3833 Access to the socket is specified by the <command>perm</command>,
3834 <command>owner</command> and <command>group</command> clauses.
3835 Note on some platforms (SunOS and Solaris) the permissions
3836 (<command>perm</command>) are applied to the parent directory
3837 as the permissions on the socket itself are ignored.
3841 The primary authorization mechanism of the command
3842 channel is the <command>key_list</command>, which
3843 contains a list of <command>key_id</command>s.
3844 Each <command>key_id</command> in the <command>key_list</command>
3845 is authorized to execute commands over the control channel.
3846 See <xref linkend="rndc"/> in <xref linkend="admin_tools"/>)
3847 for information about configuring keys in <command>rndc</command>.
3851 If no <command>controls</command> statement is present,
3852 <command>named</command> will set up a default
3853 control channel listening on the loopback address 127.0.0.1
3854 and its IPv6 counterpart ::1.
3855 In this case, and also when the <command>controls</command> statement
3856 is present but does not have a <command>keys</command> clause,
3857 <command>named</command> will attempt to load the command channel key
3858 from the file <filename>rndc.key</filename> in
3859 <filename>/etc</filename> (or whatever <varname>sysconfdir</varname>
3860 was specified as when <acronym>BIND</acronym> was built).
3861 To create a <filename>rndc.key</filename> file, run
3862 <userinput>rndc-confgen -a</userinput>.
3866 The <filename>rndc.key</filename> feature was created to
3867 ease the transition of systems from <acronym>BIND</acronym> 8,
3868 which did not have digital signatures on its command channel
3869 messages and thus did not have a <command>keys</command> clause.
3871 It makes it possible to use an existing <acronym>BIND</acronym> 8
3872 configuration file in <acronym>BIND</acronym> 9 unchanged,
3873 and still have <command>rndc</command> work the same way
3874 <command>ndc</command> worked in BIND 8, simply by executing the
3875 command <userinput>rndc-confgen -a</userinput> after BIND 9 is
3880 Since the <filename>rndc.key</filename> feature
3881 is only intended to allow the backward-compatible usage of
3882 <acronym>BIND</acronym> 8 configuration files, this
3884 have a high degree of configurability. You cannot easily change
3885 the key name or the size of the secret, so you should make a
3886 <filename>rndc.conf</filename> with your own key if you
3888 those things. The <filename>rndc.key</filename> file
3890 permissions set such that only the owner of the file (the user that
3891 <command>named</command> is running as) can access it.
3893 desire greater flexibility in allowing other users to access
3894 <command>rndc</command> commands, then you need to create
3896 <filename>rndc.conf</filename> file and make it group
3898 that contains the users who should have access.
3902 To disable the command channel, use an empty
3903 <command>controls</command> statement:
3904 <command>controls { };</command>.
3909 <title><command>include</command> Statement Grammar</title>
3910 <programlisting><command>include</command> <replaceable>filename</replaceable>;</programlisting>
3913 <title><command>include</command> Statement Definition and
3917 The <command>include</command> statement inserts the
3918 specified file at the point where the <command>include</command>
3919 statement is encountered. The <command>include</command>
3920 statement facilitates the administration of configuration
3922 by permitting the reading or writing of some things but not
3923 others. For example, the statement could include private keys
3924 that are readable only by the name server.
3929 <title><command>key</command> Statement Grammar</title>
3931 <programlisting><command>key</command> <replaceable>key_id</replaceable> {
3932 algorithm <replaceable>string</replaceable>;
3933 secret <replaceable>string</replaceable>;
3940 <title><command>key</command> Statement Definition and Usage</title>
3943 The <command>key</command> statement defines a shared
3944 secret key for use with TSIG (see <xref linkend="tsig"/>)
3945 or the command channel
3946 (see <xref linkend="controls_statement_definition_and_usage"/>).
3950 The <command>key</command> statement can occur at the
3952 of the configuration file or inside a <command>view</command>
3953 statement. Keys defined in top-level <command>key</command>
3954 statements can be used in all views. Keys intended for use in
3955 a <command>controls</command> statement
3956 (see <xref linkend="controls_statement_definition_and_usage"/>)
3957 must be defined at the top level.
3961 The <replaceable>key_id</replaceable>, also known as the
3962 key name, is a domain name uniquely identifying the key. It can
3963 be used in a <command>server</command>
3964 statement to cause requests sent to that
3965 server to be signed with this key, or in address match lists to
3966 verify that incoming requests have been signed with a key
3967 matching this name, algorithm, and secret.
3971 The <replaceable>algorithm_id</replaceable> is a string
3972 that specifies a security/authentication algorithm. Named
3973 supports <literal>hmac-md5</literal>,
3974 <literal>hmac-sha1</literal>, <literal>hmac-sha224</literal>,
3975 <literal>hmac-sha256</literal>, <literal>hmac-sha384</literal>
3976 and <literal>hmac-sha512</literal> TSIG authentication.
3977 Truncated hashes are supported by appending the minimum
3978 number of required bits preceded by a dash, e.g.
3979 <literal>hmac-sha1-80</literal>. The
3980 <replaceable>secret_string</replaceable> is the secret
3981 to be used by the algorithm, and is treated as a base-64
3987 <title><command>logging</command> Statement Grammar</title>
3989 <programlisting><command>logging</command> {
3990 [ <command>channel</command> <replaceable>channel_name</replaceable> {
3991 ( <command>file</command> <replaceable>path_name</replaceable>
3992 [ <command>versions</command> ( <replaceable>number</replaceable> | <command>unlimited</command> ) ]
3993 [ <command>size</command> <replaceable>size spec</replaceable> ]
3994 | <command>syslog</command> <replaceable>syslog_facility</replaceable>
3995 | <command>stderr</command>
3996 | <command>null</command> );
3997 [ <command>severity</command> (<option>critical</option> | <option>error</option> | <option>warning</option> | <option>notice</option> |
3998 <option>info</option> | <option>debug</option> [ <replaceable>level</replaceable> ] | <option>dynamic</option> ); ]
3999 [ <command>print-category</command> <option>yes</option> or <option>no</option>; ]
4000 [ <command>print-severity</command> <option>yes</option> or <option>no</option>; ]
4001 [ <command>print-time</command> <option>yes</option> or <option>no</option>; ]
4003 [ <command>category</command> <replaceable>category_name</replaceable> {
4004 <replaceable>channel_name</replaceable> ; [ <replaceable>channel_name</replaceable> ; ... ]
4013 <title><command>logging</command> Statement Definition and
4017 The <command>logging</command> statement configures a
4019 variety of logging options for the name server. Its <command>channel</command> phrase
4020 associates output methods, format options and severity levels with
4021 a name that can then be used with the <command>category</command> phrase
4022 to select how various classes of messages are logged.
4025 Only one <command>logging</command> statement is used to
4027 as many channels and categories as are wanted. If there is no <command>logging</command> statement,
4028 the logging configuration will be:
4031 <programlisting>logging {
4032 category default { default_syslog; default_debug; };
4033 category unmatched { null; };
4038 In <acronym>BIND</acronym> 9, the logging configuration
4039 is only established when
4040 the entire configuration file has been parsed. In <acronym>BIND</acronym> 8, it was
4041 established as soon as the <command>logging</command>
4043 was parsed. When the server is starting up, all logging messages
4044 regarding syntax errors in the configuration file go to the default
4045 channels, or to standard error if the "<option>-g</option>" option
4050 <title>The <command>channel</command> Phrase</title>
4053 All log output goes to one or more <emphasis>channels</emphasis>;
4054 you can make as many of them as you want.
4058 Every channel definition must include a destination clause that
4059 says whether messages selected for the channel go to a file, to a
4060 particular syslog facility, to the standard error stream, or are
4061 discarded. It can optionally also limit the message severity level
4062 that will be accepted by the channel (the default is
4063 <command>info</command>), and whether to include a
4064 <command>named</command>-generated time stamp, the
4066 and/or severity level (the default is not to include any).
4070 The <command>null</command> destination clause
4071 causes all messages sent to the channel to be discarded;
4072 in that case, other options for the channel are meaningless.
4076 The <command>file</command> destination clause directs
4078 to a disk file. It can include limitations
4079 both on how large the file is allowed to become, and how many
4081 of the file will be saved each time the file is opened.
4085 If you use the <command>versions</command> log file
4087 <command>named</command> will retain that many backup
4088 versions of the file by
4089 renaming them when opening. For example, if you choose to keep
4091 of the file <filename>lamers.log</filename>, then just
4093 <filename>lamers.log.1</filename> is renamed to
4094 <filename>lamers.log.2</filename>, <filename>lamers.log.0</filename> is renamed
4095 to <filename>lamers.log.1</filename>, and <filename>lamers.log</filename> is
4096 renamed to <filename>lamers.log.0</filename>.
4097 You can say <command>versions unlimited</command> to
4099 the number of versions.
4100 If a <command>size</command> option is associated with
4102 then renaming is only done when the file being opened exceeds the
4103 indicated size. No backup versions are kept by default; any
4105 log file is simply appended.
4109 The <command>size</command> option for files is used
4111 growth. If the file ever exceeds the size, then <command>named</command> will
4112 stop writing to the file unless it has a <command>versions</command> option
4113 associated with it. If backup versions are kept, the files are
4115 described above and a new one begun. If there is no
4116 <command>versions</command> option, no more data will
4117 be written to the log
4118 until some out-of-band mechanism removes or truncates the log to
4120 maximum size. The default behavior is not to limit the size of
4126 Example usage of the <command>size</command> and
4127 <command>versions</command> options:
4130 <programlisting>channel an_example_channel {
4131 file "example.log" versions 3 size 20m;
4138 The <command>syslog</command> destination clause
4140 channel to the system log. Its argument is a
4141 syslog facility as described in the <command>syslog</command> man
4142 page. Known facilities are <command>kern</command>, <command>user</command>,
4143 <command>mail</command>, <command>daemon</command>, <command>auth</command>,
4144 <command>syslog</command>, <command>lpr</command>, <command>news</command>,
4145 <command>uucp</command>, <command>cron</command>, <command>authpriv</command>,
4146 <command>ftp</command>, <command>local0</command>, <command>local1</command>,
4147 <command>local2</command>, <command>local3</command>, <command>local4</command>,
4148 <command>local5</command>, <command>local6</command> and
4149 <command>local7</command>, however not all facilities
4151 all operating systems.
4152 How <command>syslog</command> will handle messages
4154 this facility is described in the <command>syslog.conf</command> man
4155 page. If you have a system which uses a very old version of <command>syslog</command> that
4156 only uses two arguments to the <command>openlog()</command> function,
4157 then this clause is silently ignored.
4160 The <command>severity</command> clause works like <command>syslog</command>'s
4161 "priorities", except that they can also be used if you are writing
4162 straight to a file rather than using <command>syslog</command>.
4163 Messages which are not at least of the severity level given will
4164 not be selected for the channel; messages of higher severity
4169 If you are using <command>syslog</command>, then the <command>syslog.conf</command> priorities
4170 will also determine what eventually passes through. For example,
4171 defining a channel facility and severity as <command>daemon</command> and <command>debug</command> but
4172 only logging <command>daemon.warning</command> via <command>syslog.conf</command> will
4173 cause messages of severity <command>info</command> and
4174 <command>notice</command> to
4175 be dropped. If the situation were reversed, with <command>named</command> writing
4176 messages of only <command>warning</command> or higher,
4177 then <command>syslogd</command> would
4178 print all messages it received from the channel.
4182 The <command>stderr</command> destination clause
4184 channel to the server's standard error stream. This is intended
4186 use when the server is running as a foreground process, for
4188 when debugging a configuration.
4192 The server can supply extensive debugging information when
4193 it is in debugging mode. If the server's global debug level is
4195 than zero, then debugging mode will be active. The global debug
4196 level is set either by starting the <command>named</command> server
4197 with the <option>-d</option> flag followed by a positive integer,
4198 or by running <command>rndc trace</command>.
4199 The global debug level
4200 can be set to zero, and debugging mode turned off, by running <command>rndc
4201 notrace</command>. All debugging messages in the server have a debug
4202 level, and higher debug levels give more detailed output. Channels
4203 that specify a specific debug severity, for example:
4206 <programlisting>channel specific_debug_level {
4213 will get debugging output of level 3 or less any time the
4214 server is in debugging mode, regardless of the global debugging
4215 level. Channels with <command>dynamic</command>
4217 server's global debug level to determine what messages to print.
4220 If <command>print-time</command> has been turned on,
4222 the date and time will be logged. <command>print-time</command> may
4223 be specified for a <command>syslog</command> channel,
4225 pointless since <command>syslog</command> also logs
4227 time. If <command>print-category</command> is
4229 category of the message will be logged as well. Finally, if <command>print-severity</command> is
4230 on, then the severity level of the message will be logged. The <command>print-</command> options may
4231 be used in any combination, and will always be printed in the
4233 order: time, category, severity. Here is an example where all
4234 three <command>print-</command> options
4239 <computeroutput>28-Feb-2000 15:05:32.863 general: notice: running</computeroutput>
4243 There are four predefined channels that are used for
4244 <command>named</command>'s default logging as follows.
4246 used is described in <xref linkend="the_category_phrase"/>.
4249 <programlisting>channel default_syslog {
4250 // send to syslog's daemon facility
4252 // only send priority info and higher
4255 channel default_debug {
4256 // write to named.run in the working directory
4257 // Note: stderr is used instead of "named.run" if
4258 // the server is started with the '-f' option.
4260 // log at the server's current debug level
4264 channel default_stderr {
4267 // only send priority info and higher
4272 // toss anything sent to this channel
4278 The <command>default_debug</command> channel has the
4280 property that it only produces output when the server's debug
4282 nonzero. It normally writes to a file called <filename>named.run</filename>
4283 in the server's working directory.
4287 For security reasons, when the "<option>-u</option>"
4288 command line option is used, the <filename>named.run</filename> file
4289 is created only after <command>named</command> has
4291 new UID, and any debug output generated while <command>named</command> is
4292 starting up and still running as root is discarded. If you need
4293 to capture this output, you must run the server with the "<option>-g</option>"
4294 option and redirect standard error to a file.
4298 Once a channel is defined, it cannot be redefined. Thus you
4299 cannot alter the built-in channels directly, but you can modify
4300 the default logging by pointing categories at channels you have
4305 <sect3 id="the_category_phrase">
4306 <title>The <command>category</command> Phrase</title>
4309 There are many categories, so you can send the logs you want
4310 to see wherever you want, without seeing logs you don't want. If
4311 you don't specify a list of channels for a category, then log
4313 in that category will be sent to the <command>default</command> category
4314 instead. If you don't specify a default category, the following
4315 "default default" is used:
4318 <programlisting>category default { default_syslog; default_debug; };
4322 As an example, let's say you want to log security events to
4323 a file, but you also want keep the default logging behavior. You'd
4324 specify the following:
4327 <programlisting>channel my_security_channel {
4328 file "my_security_file";
4332 my_security_channel;
4338 To discard all messages in a category, specify the <command>null</command> channel:
4341 <programlisting>category xfer-out { null; };
4342 category notify { null; };
4346 Following are the available categories and brief descriptions
4347 of the types of log information they contain. More
4348 categories may be added in future <acronym>BIND</acronym> releases.
4350 <informaltable colsep="0" rowsep="0">
4351 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4352 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4353 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4357 <para><command>default</command></para>
4361 The default category defines the logging
4362 options for those categories where no specific
4363 configuration has been
4370 <para><command>general</command></para>
4374 The catch-all. Many things still aren't
4375 classified into categories, and they all end up here.
4381 <para><command>database</command></para>
4385 Messages relating to the databases used
4386 internally by the name server to store zone and cache
4393 <para><command>security</command></para>
4397 Approval and denial of requests.
4403 <para><command>config</command></para>
4407 Configuration file parsing and processing.
4413 <para><command>resolver</command></para>
4417 DNS resolution, such as the recursive
4418 lookups performed on behalf of clients by a caching name
4425 <para><command>xfer-in</command></para>
4429 Zone transfers the server is receiving.
4435 <para><command>xfer-out</command></para>
4439 Zone transfers the server is sending.
4445 <para><command>notify</command></para>
4449 The NOTIFY protocol.
4455 <para><command>client</command></para>
4459 Processing of client requests.
4465 <para><command>unmatched</command></para>
4469 Messages that <command>named</command> was unable to determine the
4470 class of or for which there was no matching <command>view</command>.
4471 A one line summary is also logged to the <command>client</command> category.
4472 This category is best sent to a file or stderr, by
4473 default it is sent to
4474 the <command>null</command> channel.
4480 <para><command>network</command></para>
4490 <para><command>update</command></para>
4500 <para><command>update-security</command></para>
4504 Approval and denial of update requests.
4510 <para><command>queries</command></para>
4514 Specify where queries should be logged to.
4517 At startup, specifying the category <command>queries</command> will also
4518 enable query logging unless <command>querylog</command> option has been
4523 The query log entry reports the client's IP
4524 address and port number, and the query name,
4525 class and type. Next it reports whether the
4526 Recursion Desired flag was set (+ if set, -
4527 if not set), if the query was signed (S),
4528 EDNS was in use (E), if TCP was used (T), if
4529 DO (DNSSEC Ok) was set (D), or if CD (Checking
4530 Disabled) was set (C). After this the
4531 destination address the query was sent to is
4536 <computeroutput>client 127.0.0.1#62536: query: www.example.com IN AAAA +SE</computeroutput>
4539 <computeroutput>client ::1#62537: query: www.example.net IN AAAA -SE</computeroutput>
4545 <para><command>query-errors</command></para>
4549 Information about queries that resulted in some
4556 <para><command>dispatch</command></para>
4560 Dispatching of incoming packets to the
4561 server modules where they are to be processed.
4567 <para><command>dnssec</command></para>
4571 DNSSEC and TSIG protocol processing.
4577 <para><command>lame-servers</command></para>
4581 Lame servers. These are misconfigurations
4582 in remote servers, discovered by BIND 9 when trying to
4583 query those servers during resolution.
4589 <para><command>delegation-only</command></para>
4593 Delegation only. Logs queries that have been
4594 forced to NXDOMAIN as the result of a
4595 delegation-only zone or a
4596 <command>delegation-only</command> in a hint
4597 or stub zone declaration.
4603 <para><command>edns-disabled</command></para>
4607 Log queries that have been forced to use plain
4608 DNS due to timeouts. This is often due to
4609 the remote servers not being RFC 1034 compliant
4610 (not always returning FORMERR or similar to
4611 EDNS queries and other extensions to the DNS
4612 when they are not understood). In other words, this is
4613 targeted at servers that fail to respond to
4614 DNS queries that they don't understand.
4617 Note: the log message can also be due to
4618 packet loss. Before reporting servers for
4619 non-RFC 1034 compliance they should be re-tested
4620 to determine the nature of the non-compliance.
4621 This testing should prevent or reduce the
4622 number of false-positive reports.
4625 Note: eventually <command>named</command> will have to stop
4626 treating such timeouts as due to RFC 1034 non
4627 compliance and start treating it as plain
4628 packet loss. Falsely classifying packet
4629 loss as due to RFC 1034 non compliance impacts
4630 on DNSSEC validation which requires EDNS for
4631 the DNSSEC records to be returned.
4640 <title>The <command>query-errors</command> Category</title>
4642 The <command>query-errors</command> category is
4643 specifically intended for debugging purposes: To identify
4644 why and how specific queries result in responses which
4646 Messages of this category are therefore only logged
4647 with <command>debug</command> levels.
4651 At the debug levels of 1 or higher, each response with the
4652 rcode of SERVFAIL is logged as follows:
4655 <computeroutput>client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</computeroutput>
4658 This means an error resulting in SERVFAIL was
4659 detected at line 3880 of source file
4660 <filename>query.c</filename>.
4661 Log messages of this level will particularly
4662 help identify the cause of SERVFAIL for an
4663 authoritative server.
4666 At the debug levels of 2 or higher, detailed context
4667 information of recursive resolutions that resulted in
4669 The log message will look like as follows:
4672 <!-- NOTE: newlines and some spaces added so this would fit on page -->
4674 fetch completed at resolver.c:2970 for www.example.com/A
4675 in 30.000183: timed out/success [domain:example.com,
4676 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
4677 badresp:1,adberr:0,findfail:0,valfail:0]
4681 The first part before the colon shows that a recursive
4682 resolution for AAAA records of www.example.com completed
4683 in 30.000183 seconds and the final result that led to the
4684 SERVFAIL was determined at line 2970 of source file
4685 <filename>resolver.c</filename>.
4688 The following part shows the detected final result and the
4689 latest result of DNSSEC validation.
4690 The latter is always success when no validation attempt
4692 In this example, this query resulted in SERVFAIL probably
4693 because all name servers are down or unreachable, leading
4694 to a timeout in 30 seconds.
4695 DNSSEC validation was probably not attempted.
4698 The last part enclosed in square brackets shows statistics
4699 information collected for this particular resolution
4701 The <varname>domain</varname> field shows the deepest zone
4702 that the resolver reached;
4703 it is the zone where the error was finally detected.
4704 The meaning of the other fields is summarized in the
4708 <informaltable colsep="0" rowsep="0">
4709 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4710 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4711 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4715 <para><varname>referral</varname></para>
4719 The number of referrals the resolver received
4720 throughout the resolution process.
4721 In the above example this is 2, which are most
4722 likely com and example.com.
4728 <para><varname>restart</varname></para>
4732 The number of cycles that the resolver tried
4733 remote servers at the <varname>domain</varname>
4735 In each cycle the resolver sends one query
4736 (possibly resending it, depending on the response)
4737 to each known name server of
4738 the <varname>domain</varname> zone.
4744 <para><varname>qrysent</varname></para>
4748 The number of queries the resolver sent at the
4749 <varname>domain</varname> zone.
4755 <para><varname>timeout</varname></para>
4759 The number of timeouts since the resolver
4760 received the last response.
4766 <para><varname>lame</varname></para>
4770 The number of lame servers the resolver detected
4771 at the <varname>domain</varname> zone.
4772 A server is detected to be lame either by an
4773 invalid response or as a result of lookup in
4774 BIND9's address database (ADB), where lame
4781 <para><varname>neterr</varname></para>
4785 The number of erroneous results that the
4786 resolver encountered in sending queries
4787 at the <varname>domain</varname> zone.
4788 One common case is the remote server is
4789 unreachable and the resolver receives an ICMP
4790 unreachable error message.
4796 <para><varname>badresp</varname></para>
4800 The number of unexpected responses (other than
4801 <varname>lame</varname>) to queries sent by the
4802 resolver at the <varname>domain</varname> zone.
4808 <para><varname>adberr</varname></para>
4812 Failures in finding remote server addresses
4813 of the <varname>domain</varname> zone in the ADB.
4814 One common case of this is that the remote
4815 server's name does not have any address records.
4821 <para><varname>findfail</varname></para>
4825 Failures of resolving remote server addresses.
4826 This is a total number of failures throughout
4827 the resolution process.
4833 <para><varname>valfail</varname></para>
4837 Failures of DNSSEC validation.
4838 Validation failures are counted throughout
4839 the resolution process (not limited to
4840 the <varname>domain</varname> zone), but should
4841 only happen in <varname>domain</varname>.
4849 At the debug levels of 3 or higher, the same messages
4850 as those at the debug 1 level are logged for other errors
4852 Note that negative responses such as NXDOMAIN are not
4853 regarded as errors here.
4856 At the debug levels of 4 or higher, the same messages
4857 as those at the debug 2 level are logged for other errors
4859 Unlike the above case of level 3, messages are logged for
4861 This is because any unexpected results can be difficult to
4862 debug in the recursion case.
4868 <title><command>lwres</command> Statement Grammar</title>
4871 This is the grammar of the <command>lwres</command>
4872 statement in the <filename>named.conf</filename> file:
4875 <programlisting><command>lwres</command> {
4876 <optional> listen-on { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
4877 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
4878 <optional> view <replaceable>view_name</replaceable>; </optional>
4879 <optional> search { <replaceable>domain_name</replaceable> ; <optional> <replaceable>domain_name</replaceable> ; ... </optional> }; </optional>
4880 <optional> ndots <replaceable>number</replaceable>; </optional>
4886 <title><command>lwres</command> Statement Definition and Usage</title>
4889 The <command>lwres</command> statement configures the
4891 server to also act as a lightweight resolver server. (See
4892 <xref linkend="lwresd"/>.) There may be multiple
4893 <command>lwres</command> statements configuring
4894 lightweight resolver servers with different properties.
4898 The <command>listen-on</command> statement specifies a
4900 addresses (and ports) that this instance of a lightweight resolver
4902 should accept requests on. If no port is specified, port 921 is
4904 If this statement is omitted, requests will be accepted on
4910 The <command>view</command> statement binds this
4912 lightweight resolver daemon to a view in the DNS namespace, so that
4914 response will be constructed in the same manner as a normal DNS
4916 matching this view. If this statement is omitted, the default view
4918 used, and if there is no default view, an error is triggered.
4922 The <command>search</command> statement is equivalent to
4924 <command>search</command> statement in
4925 <filename>/etc/resolv.conf</filename>. It provides a
4927 which are appended to relative names in queries.
4931 The <command>ndots</command> statement is equivalent to
4933 <command>ndots</command> statement in
4934 <filename>/etc/resolv.conf</filename>. It indicates the
4936 number of dots in a relative domain name that should result in an
4937 exact match lookup before search path elements are appended.
4941 <title><command>masters</command> Statement Grammar</title>
4944 <command>masters</command> <replaceable>name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> |
4945 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> };
4951 <title><command>masters</command> Statement Definition and
4953 <para><command>masters</command>
4954 lists allow for a common set of masters to be easily used by
4955 multiple stub and slave zones.
4960 <title><command>options</command> Statement Grammar</title>
4963 This is the grammar of the <command>options</command>
4964 statement in the <filename>named.conf</filename> file:
4967 <programlisting><command>options</command> {
4968 <optional> attach-cache <replaceable>cache_name</replaceable>; </optional>
4969 <optional> version <replaceable>version_string</replaceable>; </optional>
4970 <optional> hostname <replaceable>hostname_string</replaceable>; </optional>
4971 <optional> server-id <replaceable>server_id_string</replaceable>; </optional>
4972 <optional> directory <replaceable>path_name</replaceable>; </optional>
4973 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
4974 <optional> managed-keys-directory <replaceable>path_name</replaceable>; </optional>
4975 <optional> named-xfer <replaceable>path_name</replaceable>; </optional>
4976 <optional> tkey-gssapi-credential <replaceable>principal</replaceable>; </optional>
4977 <optional> tkey-domain <replaceable>domainname</replaceable>; </optional>
4978 <optional> tkey-dhkey <replaceable>key_name</replaceable> <replaceable>key_tag</replaceable>; </optional>
4979 <optional> cache-file <replaceable>path_name</replaceable>; </optional>
4980 <optional> dump-file <replaceable>path_name</replaceable>; </optional>
4981 <optional> bindkeys-file <replaceable>path_name</replaceable>; </optional>
4982 <optional> memstatistics <replaceable>yes_or_no</replaceable>; </optional>
4983 <optional> memstatistics-file <replaceable>path_name</replaceable>; </optional>
4984 <optional> pid-file <replaceable>path_name</replaceable>; </optional>
4985 <optional> recursing-file <replaceable>path_name</replaceable>; </optional>
4986 <optional> statistics-file <replaceable>path_name</replaceable>; </optional>
4987 <optional> zone-statistics <replaceable>yes_or_no</replaceable>; </optional>
4988 <optional> auth-nxdomain <replaceable>yes_or_no</replaceable>; </optional>
4989 <optional> deallocate-on-exit <replaceable>yes_or_no</replaceable>; </optional>
4990 <optional> dialup <replaceable>dialup_option</replaceable>; </optional>
4991 <optional> fake-iquery <replaceable>yes_or_no</replaceable>; </optional>
4992 <optional> fetch-glue <replaceable>yes_or_no</replaceable>; </optional>
4993 <optional> flush-zones-on-shutdown <replaceable>yes_or_no</replaceable>; </optional>
4994 <optional> has-old-clients <replaceable>yes_or_no</replaceable>; </optional>
4995 <optional> host-statistics <replaceable>yes_or_no</replaceable>; </optional>
4996 <optional> host-statistics-max <replaceable>number</replaceable>; </optional>
4997 <optional> minimal-responses <replaceable>yes_or_no</replaceable>; </optional>
4998 <optional> multiple-cnames <replaceable>yes_or_no</replaceable>; </optional>
4999 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable>; </optional>
5000 <optional> recursion <replaceable>yes_or_no</replaceable>; </optional>
5001 <optional> rfc2308-type1 <replaceable>yes_or_no</replaceable>; </optional>
5002 <optional> use-id-pool <replaceable>yes_or_no</replaceable>; </optional>
5003 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable>; </optional>
5004 <optional> ixfr-from-differences (<replaceable>yes_or_no</replaceable> | <constant>master</constant> | <constant>slave</constant>); </optional>
5005 <optional> dnssec-enable <replaceable>yes_or_no</replaceable>; </optional>
5006 <optional> dnssec-validation <replaceable>yes_or_no</replaceable>; </optional>
5007 <optional> dnssec-lookaside ( <replaceable>auto</replaceable> |
5008 <replaceable>domain</replaceable> trust-anchor <replaceable>domain</replaceable> ); </optional>
5009 <optional> dnssec-must-be-secure <replaceable>domain yes_or_no</replaceable>; </optional>
5010 <optional> dnssec-accept-expired <replaceable>yes_or_no</replaceable>; </optional>
5011 <optional> forward ( <replaceable>only</replaceable> | <replaceable>first</replaceable> ); </optional>
5012 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
5013 <optional> dual-stack-servers <optional>port <replaceable>ip_port</replaceable></optional> {
5014 ( <replaceable>domain_name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> |
5015 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ) ;
5017 <optional> check-names ( <replaceable>master</replaceable> | <replaceable>slave</replaceable> | <replaceable>response</replaceable> )
5018 ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5019 <optional> check-dup-records ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5020 <optional> check-mx ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5021 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
5022 <optional> check-integrity <replaceable>yes_or_no</replaceable>; </optional>
5023 <optional> check-mx-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5024 <optional> check-srv-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5025 <optional> check-sibling <replaceable>yes_or_no</replaceable>; </optional>
5026 <optional> allow-new-zones { <replaceable>yes_or_no</replaceable> }; </optional>
5027 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
5028 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
5029 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
5030 <optional> allow-query-cache { <replaceable>address_match_list</replaceable> }; </optional>
5031 <optional> allow-query-cache-on { <replaceable>address_match_list</replaceable> }; </optional>
5032 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
5033 <optional> allow-recursion { <replaceable>address_match_list</replaceable> }; </optional>
5034 <optional> allow-recursion-on { <replaceable>address_match_list</replaceable> }; </optional>
5035 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
5036 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
5037 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
5038 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
5039 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ;</optional>
5040 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
5041 <optional> allow-v6-synthesis { <replaceable>address_match_list</replaceable> }; </optional>
5042 <optional> blackhole { <replaceable>address_match_list</replaceable> }; </optional>
5043 <optional> use-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5044 <optional> avoid-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5045 <optional> use-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5046 <optional> avoid-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5047 <optional> listen-on <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
5048 <optional> listen-on-v6 <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
5049 <optional> query-source ( ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> )
5050 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
5051 <optional> address ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
5052 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
5053 <optional> query-source-v6 ( ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> )
5054 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
5055 <optional> address ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
5056 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
5057 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
5058 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
5059 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
5060 <optional> max-transfer-time-in <replaceable>number</replaceable>; </optional>
5061 <optional> max-transfer-time-out <replaceable>number</replaceable>; </optional>
5062 <optional> max-transfer-idle-in <replaceable>number</replaceable>; </optional>
5063 <optional> max-transfer-idle-out <replaceable>number</replaceable>; </optional>
5064 <optional> tcp-clients <replaceable>number</replaceable>; </optional>
5065 <optional> reserved-sockets <replaceable>number</replaceable>; </optional>
5066 <optional> recursive-clients <replaceable>number</replaceable>; </optional>
5067 <optional> serial-query-rate <replaceable>number</replaceable>; </optional>
5068 <optional> serial-queries <replaceable>number</replaceable>; </optional>
5069 <optional> tcp-listen-queue <replaceable>number</replaceable>; </optional>
5070 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable>; </optional>
5071 <optional> transfers-in <replaceable>number</replaceable>; </optional>
5072 <optional> transfers-out <replaceable>number</replaceable>; </optional>
5073 <optional> transfers-per-ns <replaceable>number</replaceable>; </optional>
5074 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5075 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5076 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5077 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
5078 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5079 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
5080 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
5081 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5082 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5083 <optional> notify-to-soa <replaceable>yes_or_no</replaceable> ; </optional>
5084 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
5085 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
5086 <optional> max-ixfr-log-size <replaceable>number</replaceable>; </optional>
5087 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
5088 <optional> coresize <replaceable>size_spec</replaceable> ; </optional>
5089 <optional> datasize <replaceable>size_spec</replaceable> ; </optional>
5090 <optional> files <replaceable>size_spec</replaceable> ; </optional>
5091 <optional> stacksize <replaceable>size_spec</replaceable> ; </optional>
5092 <optional> cleaning-interval <replaceable>number</replaceable>; </optional>
5093 <optional> heartbeat-interval <replaceable>number</replaceable>; </optional>
5094 <optional> interface-interval <replaceable>number</replaceable>; </optional>
5095 <optional> statistics-interval <replaceable>number</replaceable>; </optional>
5096 <optional> topology { <replaceable>address_match_list</replaceable> }</optional>;
5097 <optional> sortlist { <replaceable>address_match_list</replaceable> }</optional>;
5098 <optional> rrset-order { <replaceable>order_spec</replaceable> ; <optional> <replaceable>order_spec</replaceable> ; ... </optional> </optional> };
5099 <optional> lame-ttl <replaceable>number</replaceable>; </optional>
5100 <optional> max-ncache-ttl <replaceable>number</replaceable>; </optional>
5101 <optional> max-cache-ttl <replaceable>number</replaceable>; </optional>
5102 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
5103 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
5104 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
5105 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
5106 <optional> min-roots <replaceable>number</replaceable>; </optional>
5107 <optional> use-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
5108 <optional> provide-ixfr <replaceable>yes_or_no</replaceable>; </optional>
5109 <optional> request-ixfr <replaceable>yes_or_no</replaceable>; </optional>
5110 <optional> treat-cr-as-space <replaceable>yes_or_no</replaceable> ; </optional>
5111 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
5112 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
5113 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
5114 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
5115 <optional> port <replaceable>ip_port</replaceable>; </optional>
5116 <optional> additional-from-auth <replaceable>yes_or_no</replaceable> ; </optional>
5117 <optional> additional-from-cache <replaceable>yes_or_no</replaceable> ; </optional>
5118 <optional> random-device <replaceable>path_name</replaceable> ; </optional>
5119 <optional> max-cache-size <replaceable>size_spec</replaceable> ; </optional>
5120 <optional> match-mapped-addresses <replaceable>yes_or_no</replaceable>; </optional>
5121 <optional> filter-aaaa-on-v4 ( <replaceable>yes_or_no</replaceable> | <replaceable>break-dnssec</replaceable> ); </optional>
5122 <optional> filter-aaaa { <replaceable>address_match_list</replaceable> }; </optional>
5123 <optional> preferred-glue ( <replaceable>A</replaceable> | <replaceable>AAAA</replaceable> | <replaceable>NONE</replaceable> ); </optional>
5124 <optional> edns-udp-size <replaceable>number</replaceable>; </optional>
5125 <optional> max-udp-size <replaceable>number</replaceable>; </optional>
5126 <optional> root-delegation-only <optional> exclude { <replaceable>namelist</replaceable> } </optional> ; </optional>
5127 <optional> querylog <replaceable>yes_or_no</replaceable> ; </optional>
5128 <optional> disable-algorithms <replaceable>domain</replaceable> { <replaceable>algorithm</replaceable>;
5129 <optional> <replaceable>algorithm</replaceable>; </optional> }; </optional>
5130 <optional> acache-enable <replaceable>yes_or_no</replaceable> ; </optional>
5131 <optional> acache-cleaning-interval <replaceable>number</replaceable>; </optional>
5132 <optional> max-acache-size <replaceable>size_spec</replaceable> ; </optional>
5133 <optional> clients-per-query <replaceable>number</replaceable> ; </optional>
5134 <optional> max-clients-per-query <replaceable>number</replaceable> ; </optional>
5135 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
5136 <optional> empty-server <replaceable>name</replaceable> ; </optional>
5137 <optional> empty-contact <replaceable>name</replaceable> ; </optional>
5138 <optional> empty-zones-enable <replaceable>yes_or_no</replaceable> ; </optional>
5139 <optional> disable-empty-zone <replaceable>zone_name</replaceable> ; </optional>
5140 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
5141 <optional> zero-no-soa-ttl-cache <replaceable>yes_or_no</replaceable> ; </optional>
5142 <optional> deny-answer-addresses { <replaceable>address_match_list</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
5143 <optional> deny-answer-aliases { <replaceable>namelist</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
5149 <sect2 id="options">
5150 <title><command>options</command> Statement Definition and
5154 The <command>options</command> statement sets up global
5156 to be used by <acronym>BIND</acronym>. This statement
5158 once in a configuration file. If there is no <command>options</command>
5159 statement, an options block with each option set to its default will
5166 <term><command>attach-cache</command></term>
5169 Allows multiple views to share a single cache
5171 Each view has its own cache database by default, but
5172 if multiple views have the same operational policy
5173 for name resolution and caching, those views can
5174 share a single cache to save memory and possibly
5175 improve resolution efficiency by using this option.
5179 The <command>attach-cache</command> option
5180 may also be specified in <command>view</command>
5181 statements, in which case it overrides the
5182 global <command>attach-cache</command> option.
5186 The <replaceable>cache_name</replaceable> specifies
5187 the cache to be shared.
5188 When the <command>named</command> server configures
5189 views which are supposed to share a cache, it
5190 creates a cache with the specified name for the
5191 first view of these sharing views.
5192 The rest of the views will simply refer to the
5193 already created cache.
5197 One common configuration to share a cache would be to
5198 allow all views to share a single cache.
5199 This can be done by specifying
5200 the <command>attach-cache</command> as a global
5201 option with an arbitrary name.
5205 Another possible operation is to allow a subset of
5206 all views to share a cache while the others to
5207 retain their own caches.
5208 For example, if there are three views A, B, and C,
5209 and only A and B should share a cache, specify the
5210 <command>attach-cache</command> option as a view A (or
5211 B)'s option, referring to the other view name:
5216 // this view has its own cache
5220 // this view refers to A's cache
5224 // this view has its own cache
5230 Views that share a cache must have the same policy
5231 on configurable parameters that may affect caching.
5232 The current implementation requires the following
5233 configurable options be consistent among these
5235 <command>check-names</command>,
5236 <command>cleaning-interval</command>,
5237 <command>dnssec-accept-expired</command>,
5238 <command>dnssec-validation</command>,
5239 <command>max-cache-ttl</command>,
5240 <command>max-ncache-ttl</command>,
5241 <command>max-cache-size</command>, and
5242 <command>zero-no-soa-ttl</command>.
5246 Note that there may be other parameters that may
5247 cause confusion if they are inconsistent for
5248 different views that share a single cache.
5249 For example, if these views define different sets of
5250 forwarders that can return different answers for the
5251 same question, sharing the answer does not make
5252 sense or could even be harmful.
5253 It is administrator's responsibility to ensure
5254 configuration differences in different views do
5255 not cause disruption with a shared cache.
5262 <term><command>directory</command></term>
5265 The working directory of the server.
5266 Any non-absolute pathnames in the configuration file will be
5268 as relative to this directory. The default location for most
5270 output files (e.g. <filename>named.run</filename>)
5272 If a directory is not specified, the working directory
5273 defaults to `<filename>.</filename>', the directory from
5275 was started. The directory specified should be an absolute
5282 <term><command>key-directory</command></term>
5285 When performing dynamic update of secure zones, the
5286 directory where the public and private DNSSEC key files
5287 should be found, if different than the current working
5288 directory. (Note that this option has no effect on the
5289 paths for files containing non-DNSSEC keys such as
5290 <filename>bind.keys</filename>,
5291 <filename>rndc.key</filename> or
5292 <filename>session.key</filename>.)
5298 <term><command>managed-keys-directory</command></term>
5301 The directory used to hold the files used to track managed keys.
5302 By default it is the working directory. It there are no
5303 views then the file <filename>managed-keys.bind</filename>
5304 otherwise a SHA256 hash of the view name is used with
5305 <filename>.mkeys</filename> extension added.
5311 <term><command>named-xfer</command></term>
5314 <emphasis>This option is obsolete.</emphasis> It
5315 was used in <acronym>BIND</acronym> 8 to specify
5316 the pathname to the <command>named-xfer</command>
5317 program. In <acronym>BIND</acronym> 9, no separate
5318 <command>named-xfer</command> program is needed;
5319 its functionality is built into the name server.
5325 <term><command>tkey-gssapi-credential</command></term>
5328 The security credential with which the server should
5329 authenticate keys requested by the GSS-TSIG protocol.
5330 Currently only Kerberos 5 authentication is available
5331 and the credential is a Kerberos principal which
5332 the server can acquire through the default system
5333 key file, normally <filename>/etc/krb5.keytab</filename>.
5334 Normally this principal is of the form
5335 "<userinput>DNS/</userinput><varname>server.domain</varname>".
5336 To use GSS-TSIG, <command>tkey-domain</command>
5343 <term><command>tkey-domain</command></term>
5346 The domain appended to the names of all shared keys
5347 generated with <command>TKEY</command>. When a
5348 client requests a <command>TKEY</command> exchange,
5349 it may or may not specify the desired name for the
5350 key. If present, the name of the shared key will
5351 be <varname>client specified part</varname> +
5352 <varname>tkey-domain</varname>. Otherwise, the
5353 name of the shared key will be <varname>random hex
5354 digits</varname> + <varname>tkey-domain</varname>.
5355 In most cases, the <command>domainname</command>
5356 should be the server's domain name, or an otherwise
5357 non-existent subdomain like
5358 "_tkey.<varname>domainname</varname>". If you are
5359 using GSS-TSIG, this variable must be defined.
5365 <term><command>tkey-dhkey</command></term>
5368 The Diffie-Hellman key used by the server
5369 to generate shared keys with clients using the Diffie-Hellman
5371 of <command>TKEY</command>. The server must be
5373 public and private keys from files in the working directory.
5375 most cases, the keyname should be the server's host name.
5381 <term><command>cache-file</command></term>
5384 This is for testing only. Do not use.
5390 <term><command>dump-file</command></term>
5393 The pathname of the file the server dumps
5394 the database to when instructed to do so with
5395 <command>rndc dumpdb</command>.
5396 If not specified, the default is <filename>named_dump.db</filename>.
5402 <term><command>memstatistics-file</command></term>
5405 The pathname of the file the server writes memory
5406 usage statistics to on exit. If not specified,
5407 the default is <filename>named.memstats</filename>.
5413 <term><command>pid-file</command></term>
5416 The pathname of the file the server writes its process ID
5417 in. If not specified, the default is
5418 <filename>/var/run/named/named.pid</filename>.
5419 The PID file is used by programs that want to send signals to
5421 name server. Specifying <command>pid-file none</command> disables the
5422 use of a PID file — no file will be written and any
5423 existing one will be removed. Note that <command>none</command>
5424 is a keyword, not a filename, and therefore is not enclosed
5432 <term><command>recursing-file</command></term>
5435 The pathname of the file the server dumps
5436 the queries that are currently recursing when instructed
5437 to do so with <command>rndc recursing</command>.
5438 If not specified, the default is <filename>named.recursing</filename>.
5444 <term><command>statistics-file</command></term>
5447 The pathname of the file the server appends statistics
5448 to when instructed to do so using <command>rndc stats</command>.
5449 If not specified, the default is <filename>named.stats</filename> in the
5450 server's current directory. The format of the file is
5452 in <xref linkend="statsfile"/>.
5458 <term><command>bindkeys-file</command></term>
5461 The pathname of a file to override the built-in trusted
5462 keys provided by <command>named</command>.
5463 See the discussion of <command>dnssec-lookaside</command>
5464 for details. If not specified, the default is
5465 <filename>/etc/bind.keys</filename>.
5471 <term><command>secroots-file</command></term>
5474 The pathname of the file the server dumps
5475 security roots to when instructed to do so with
5476 <command>rndc secroots</command>.
5477 If not specified, the default is <filename>named.secroots</filename>.
5483 <term><command>session-keyfile</command></term>
5486 The pathname of the file into which to write a TSIG
5487 session key generated by <command>named</command> for use by
5488 <command>nsupdate -l</command>. If not specified, the
5489 default is <filename>/var/run/named/session.key</filename>.
5490 (See <xref linkend="dynamic_update_policies"/>, and in
5491 particular the discussion of the
5492 <command>update-policy</command> statement's
5493 <userinput>local</userinput> option for more
5494 information about this feature.)
5500 <term><command>session-keyname</command></term>
5503 The key name to use for the TSIG session key.
5504 If not specified, the default is "local-ddns".
5510 <term><command>session-keyalg</command></term>
5513 The algorithm to use for the TSIG session key.
5514 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
5515 hmac-sha384, hmac-sha512 and hmac-md5. If not
5516 specified, the default is hmac-sha256.
5522 <term><command>session-keyfile</command></term>
5525 The pathname of the file into which to write a session TSIG
5526 key for use by <command>nsupdate -l</command>. (See the
5527 discussion of the <command>update-policy</command>
5528 statement's <userinput>local</userinput> option for more
5529 details on this feature.)
5535 <term><command>port</command></term>
5538 The UDP/TCP port number the server uses for
5539 receiving and sending DNS protocol traffic.
5540 The default is 53. This option is mainly intended for server
5542 a server using a port other than 53 will not be able to
5550 <term><command>random-device</command></term>
5553 The source of entropy to be used by the server. Entropy is
5555 for DNSSEC operations, such as TKEY transactions and dynamic
5557 zones. This options specifies the device (or file) from which
5559 entropy. If this is a file, operations requiring entropy will
5561 file has been exhausted. If not specified, the default value
5563 <filename>/dev/random</filename>
5564 (or equivalent) when present, and none otherwise. The
5565 <command>random-device</command> option takes
5567 the initial configuration load at server startup time and
5568 is ignored on subsequent reloads.
5574 <term><command>preferred-glue</command></term>
5577 If specified, the listed type (A or AAAA) will be emitted
5579 in the additional section of a query response.
5580 The default is not to prefer any type (NONE).
5585 <varlistentry id="root_delegation_only">
5586 <term><command>root-delegation-only</command></term>
5589 Turn on enforcement of delegation-only in TLDs
5590 (top level domains) and root zones with an optional
5594 DS queries are expected to be made to and be answered by
5595 delegation only zones. Such queries and responses are
5596 treated as an exception to delegation-only processing
5597 and are not converted to NXDOMAIN responses provided
5598 a CNAME is not discovered at the query name.
5601 If a delegation only zone server also serves a child
5602 zone it is not always possible to determine whether
5603 an answer comes from the delegation only zone or the
5604 child zone. SOA NS and DNSKEY records are apex
5605 only records and a matching response that contains
5606 these records or DS is treated as coming from a
5607 child zone. RRSIG records are also examined to see
5608 if they are signed by a child zone or not. The
5609 authority section is also examined to see if there
5610 is evidence that the answer is from the child zone.
5611 Answers that are determined to be from a child zone
5612 are not converted to NXDOMAIN responses. Despite
5613 all these checks there is still a possibility of
5614 false negatives when a child zone is being served.
5617 Similarly false positives can arise from empty nodes
5618 (no records at the name) in the delegation only zone
5619 when the query type is not ANY.
5622 Note some TLDs are not delegation only (e.g. "DE", "LV",
5623 "US" and "MUSEUM"). This list is not exhaustive.
5628 root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
5636 <term><command>disable-algorithms</command></term>
5639 Disable the specified DNSSEC algorithms at and below the
5641 Multiple <command>disable-algorithms</command>
5642 statements are allowed.
5643 Only the most specific will be applied.
5649 <term><command>dnssec-lookaside</command></term>
5652 When set, <command>dnssec-lookaside</command> provides the
5653 validator with an alternate method to validate DNSKEY
5654 records at the top of a zone. When a DNSKEY is at or
5655 below a domain specified by the deepest
5656 <command>dnssec-lookaside</command>, and the normal DNSSEC
5657 validation has left the key untrusted, the trust-anchor
5658 will be appended to the key name and a DLV record will be
5659 looked up to see if it can validate the key. If the DLV
5660 record validates a DNSKEY (similarly to the way a DS
5661 record does) the DNSKEY RRset is deemed to be trusted.
5664 If <command>dnssec-lookaside</command> is set to
5665 <userinput>auto</userinput>, then built-in default
5666 values for the DLV domain and trust anchor will be
5667 used, along with a built-in key for validation.
5670 The default DLV key is stored in the file
5671 <filename>bind.keys</filename>, which
5672 <command>named</command> loads at startup if
5673 <command>dnssec-lookaside</command> is set to
5674 <constant>auto</constant>. A copy of that file is
5675 installed along with <acronym>BIND</acronym> 9, and is
5676 current as of the release date. If the DLV key expires, a
5677 new copy of <filename>bind.keys</filename> can be downloaded
5678 from <ulink>https://www.isc.org/solutions/dlv</ulink>.
5681 (To prevent problems if <filename>bind.keys</filename> is
5682 not found, the current key is also compiled in to
5683 <command>named</command>. Relying on this is not
5684 recommended, however, as it requires <command>named</command>
5685 to be recompiled with a new key when the DLV key expires.)
5688 NOTE: Using <filename>bind.keys</filename> to store
5689 locally-configured keys is possible, but not
5690 recommended, as the file will be overwritten whenever
5691 <acronym>BIND</acronym> 9 is re-installed or upgraded.
5697 <term><command>dnssec-must-be-secure</command></term>
5700 Specify hierarchies which must be or may not be secure
5701 (signed and validated). If <userinput>yes</userinput>,
5702 then <command>named</command> will only accept answers if
5703 they are secure. If <userinput>no</userinput>, then normal
5704 DNSSEC validation applies allowing for insecure answers to
5705 be accepted. The specified domain must be under a
5706 <command>trusted-keys</command> or
5707 <command>managed-keys</command> statement, or
5708 <command>dnssec-lookaside</command> must be active.
5715 <sect3 id="boolean_options">
5716 <title>Boolean Options</title>
5721 <term><command>allow-new-zones</command></term>
5724 If <userinput>yes</userinput>, then zones can be
5725 added at runtime via <command>rndc addzone</command>
5726 or deleted via <command>rndc delzone</command>.
5727 The default is <userinput>no</userinput>.
5733 <term><command>auth-nxdomain</command></term>
5736 If <userinput>yes</userinput>, then the <command>AA</command> bit
5737 is always set on NXDOMAIN responses, even if the server is
5739 authoritative. The default is <userinput>no</userinput>;
5741 a change from <acronym>BIND</acronym> 8. If you
5742 are using very old DNS software, you
5743 may need to set it to <userinput>yes</userinput>.
5749 <term><command>deallocate-on-exit</command></term>
5752 This option was used in <acronym>BIND</acronym>
5753 8 to enable checking
5754 for memory leaks on exit. <acronym>BIND</acronym> 9 ignores the option and always performs
5761 <term><command>memstatistics</command></term>
5764 Write memory statistics to the file specified by
5765 <command>memstatistics-file</command> at exit.
5766 The default is <userinput>no</userinput> unless
5767 '-m record' is specified on the command line in
5768 which case it is <userinput>yes</userinput>.
5774 <term><command>dialup</command></term>
5777 If <userinput>yes</userinput>, then the
5778 server treats all zones as if they are doing zone transfers
5780 a dial-on-demand dialup link, which can be brought up by
5782 originating from this server. This has different effects
5784 to zone type and concentrates the zone maintenance so that
5786 happens in a short interval, once every <command>heartbeat-interval</command> and
5787 hopefully during the one call. It also suppresses some of
5789 zone maintenance traffic. The default is <userinput>no</userinput>.
5792 The <command>dialup</command> option
5793 may also be specified in the <command>view</command> and
5794 <command>zone</command> statements,
5795 in which case it overrides the global <command>dialup</command>
5799 If the zone is a master zone, then the server will send out a
5801 request to all the slaves (default). This should trigger the
5803 number check in the slave (providing it supports NOTIFY)
5805 to verify the zone while the connection is active.
5806 The set of servers to which NOTIFY is sent can be controlled
5808 <command>notify</command> and <command>also-notify</command>.
5812 zone is a slave or stub zone, then the server will suppress
5814 "zone up to date" (refresh) queries and only perform them
5816 <command>heartbeat-interval</command> expires in
5821 Finer control can be achieved by using
5822 <userinput>notify</userinput> which only sends NOTIFY
5824 <userinput>notify-passive</userinput> which sends NOTIFY
5826 suppresses the normal refresh queries, <userinput>refresh</userinput>
5827 which suppresses normal refresh processing and sends refresh
5829 when the <command>heartbeat-interval</command>
5831 <userinput>passive</userinput> which just disables normal
5836 <informaltable colsep="0" rowsep="0">
5837 <tgroup cols="4" colsep="0" rowsep="0" tgroupstyle="4Level-table">
5838 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
5839 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
5840 <colspec colname="3" colnum="3" colsep="0" colwidth="1.150in"/>
5841 <colspec colname="4" colnum="4" colsep="0" colwidth="1.150in"/>
5867 <para><command>no</command> (default)</para>
5887 <para><command>yes</command></para>
5907 <para><command>notify</command></para>
5927 <para><command>refresh</command></para>
5947 <para><command>passive</command></para>
5967 <para><command>notify-passive</command></para>
5990 Note that normal NOTIFY processing is not affected by
5991 <command>dialup</command>.
5998 <term><command>fake-iquery</command></term>
6001 In <acronym>BIND</acronym> 8, this option
6002 enabled simulating the obsolete DNS query type
6003 IQUERY. <acronym>BIND</acronym> 9 never does
6010 <term><command>fetch-glue</command></term>
6013 This option is obsolete.
6014 In BIND 8, <userinput>fetch-glue yes</userinput>
6015 caused the server to attempt to fetch glue resource records
6017 didn't have when constructing the additional
6018 data section of a response. This is now considered a bad
6020 and BIND 9 never does it.
6026 <term><command>flush-zones-on-shutdown</command></term>
6029 When the nameserver exits due receiving SIGTERM,
6030 flush or do not flush any pending zone writes. The default
6032 <command>flush-zones-on-shutdown</command> <userinput>no</userinput>.
6038 <term><command>has-old-clients</command></term>
6041 This option was incorrectly implemented
6042 in <acronym>BIND</acronym> 8, and is ignored by <acronym>BIND</acronym> 9.
6043 To achieve the intended effect
6045 <command>has-old-clients</command> <userinput>yes</userinput>, specify
6046 the two separate options <command>auth-nxdomain</command> <userinput>yes</userinput>
6047 and <command>rfc2308-type1</command> <userinput>no</userinput> instead.
6053 <term><command>host-statistics</command></term>
6056 In BIND 8, this enables keeping of
6057 statistics for every host that the name server interacts
6059 Not implemented in BIND 9.
6065 <term><command>maintain-ixfr-base</command></term>
6068 <emphasis>This option is obsolete</emphasis>.
6069 It was used in <acronym>BIND</acronym> 8 to
6070 determine whether a transaction log was
6071 kept for Incremental Zone Transfer. <acronym>BIND</acronym> 9 maintains a transaction
6072 log whenever possible. If you need to disable outgoing
6074 transfers, use <command>provide-ixfr</command> <userinput>no</userinput>.
6080 <term><command>minimal-responses</command></term>
6083 If <userinput>yes</userinput>, then when generating
6084 responses the server will only add records to the authority
6085 and additional data sections when they are required (e.g.
6086 delegations, negative responses). This may improve the
6087 performance of the server.
6088 The default is <userinput>no</userinput>.
6094 <term><command>multiple-cnames</command></term>
6097 This option was used in <acronym>BIND</acronym> 8 to allow
6098 a domain name to have multiple CNAME records in violation of
6099 the DNS standards. <acronym>BIND</acronym> 9.2 onwards
6100 always strictly enforces the CNAME rules both in master
6101 files and dynamic updates.
6107 <term><command>notify</command></term>
6110 If <userinput>yes</userinput> (the default),
6111 DNS NOTIFY messages are sent when a zone the server is
6113 changes, see <xref linkend="notify"/>. The messages are
6115 servers listed in the zone's NS records (except the master
6117 in the SOA MNAME field), and to any servers listed in the
6118 <command>also-notify</command> option.
6121 If <userinput>master-only</userinput>, notifies are only
6124 If <userinput>explicit</userinput>, notifies are sent only
6126 servers explicitly listed using <command>also-notify</command>.
6127 If <userinput>no</userinput>, no notifies are sent.
6130 The <command>notify</command> option may also be
6131 specified in the <command>zone</command>
6133 in which case it overrides the <command>options notify</command> statement.
6134 It would only be necessary to turn off this option if it
6142 <term><command>notify-to-soa</command></term>
6145 If <userinput>yes</userinput> do not check the nameservers
6146 in the NS RRset against the SOA MNAME. Normally a NOTIFY
6147 message is not sent to the SOA MNAME (SOA ORIGIN) as it is
6148 supposed to contain the name of the ultimate master.
6149 Sometimes, however, a slave is listed as the SOA MNAME in
6150 hidden master configurations and in that case you would
6151 want the ultimate master to still send NOTIFY messages to
6152 all the nameservers listed in the NS RRset.
6158 <term><command>recursion</command></term>
6161 If <userinput>yes</userinput>, and a
6162 DNS query requests recursion, then the server will attempt
6164 all the work required to answer the query. If recursion is
6166 and the server does not already know the answer, it will
6168 referral response. The default is
6169 <userinput>yes</userinput>.
6170 Note that setting <command>recursion no</command> does not prevent
6171 clients from getting data from the server's cache; it only
6172 prevents new data from being cached as an effect of client
6174 Caching may still occur as an effect the server's internal
6175 operation, such as NOTIFY address lookups.
6176 See also <command>fetch-glue</command> above.
6182 <term><command>rfc2308-type1</command></term>
6185 Setting this to <userinput>yes</userinput> will
6186 cause the server to send NS records along with the SOA
6188 answers. The default is <userinput>no</userinput>.
6192 Not yet implemented in <acronym>BIND</acronym>
6200 <term><command>use-id-pool</command></term>
6203 <emphasis>This option is obsolete</emphasis>.
6204 <acronym>BIND</acronym> 9 always allocates query
6211 <term><command>zone-statistics</command></term>
6214 If <userinput>yes</userinput>, the server will collect
6215 statistical data on all zones (unless specifically turned
6217 on a per-zone basis by specifying <command>zone-statistics no</command>
6218 in the <command>zone</command> statement).
6219 The default is <userinput>no</userinput>.
6220 These statistics may be accessed
6221 using <command>rndc stats</command>, which will
6222 dump them to the file listed
6223 in the <command>statistics-file</command>. See
6224 also <xref linkend="statsfile"/>.
6230 <term><command>use-ixfr</command></term>
6233 <emphasis>This option is obsolete</emphasis>.
6234 If you need to disable IXFR to a particular server or
6236 the information on the <command>provide-ixfr</command> option
6237 in <xref linkend="server_statement_definition_and_usage"/>.
6239 <xref linkend="incremental_zone_transfers"/>.
6245 <term><command>provide-ixfr</command></term>
6248 See the description of
6249 <command>provide-ixfr</command> in
6250 <xref linkend="server_statement_definition_and_usage"/>.
6256 <term><command>request-ixfr</command></term>
6259 See the description of
6260 <command>request-ixfr</command> in
6261 <xref linkend="server_statement_definition_and_usage"/>.
6267 <term><command>treat-cr-as-space</command></term>
6270 This option was used in <acronym>BIND</acronym>
6272 the server treat carriage return ("<command>\r</command>") characters the same way
6273 as a space or tab character,
6274 to facilitate loading of zone files on a UNIX system that
6276 on an NT or DOS machine. In <acronym>BIND</acronym> 9, both UNIX "<command>\n</command>"
6277 and NT/DOS "<command>\r\n</command>" newlines
6278 are always accepted,
6279 and the option is ignored.
6285 <term><command>additional-from-auth</command></term>
6286 <term><command>additional-from-cache</command></term>
6290 These options control the behavior of an authoritative
6292 answering queries which have additional data, or when
6298 When both of these options are set to <userinput>yes</userinput>
6300 query is being answered from authoritative data (a zone
6301 configured into the server), the additional data section of
6303 reply will be filled in using data from other authoritative
6305 and from the cache. In some situations this is undesirable,
6307 as when there is concern over the correctness of the cache,
6309 in servers where slave zones may be added and modified by
6310 untrusted third parties. Also, avoiding
6311 the search for this additional data will speed up server
6313 at the possible expense of additional queries to resolve
6315 otherwise be provided in the additional section.
6319 For example, if a query asks for an MX record for host <literal>foo.example.com</literal>,
6320 and the record found is "<literal>MX 10 mail.example.net</literal>", normally the address
6321 records (A and AAAA) for <literal>mail.example.net</literal> will be provided as well,
6322 if known, even though they are not in the example.com zone.
6323 Setting these options to <command>no</command>
6324 disables this behavior and makes
6325 the server only search for additional data in the zone it
6330 These options are intended for use in authoritative-only
6331 servers, or in authoritative-only views. Attempts to set
6332 them to <command>no</command> without also
6334 <command>recursion no</command> will cause the
6336 ignore the options and log a warning message.
6340 Specifying <command>additional-from-cache no</command> actually
6341 disables the use of the cache not only for additional data
6343 but also when looking up the answer. This is usually the
6345 behavior in an authoritative-only server where the
6347 the cached data is an issue.
6351 When a name server is non-recursively queried for a name
6353 below the apex of any served zone, it normally answers with
6355 "upwards referral" to the root servers or the servers of
6357 known parent of the query name. Since the data in an
6359 comes from the cache, the server will not be able to provide
6361 referrals when <command>additional-from-cache no</command>
6362 has been specified. Instead, it will respond to such
6364 with REFUSED. This should not cause any problems since
6365 upwards referrals are not required for the resolution
6373 <term><command>match-mapped-addresses</command></term>
6376 If <userinput>yes</userinput>, then an
6377 IPv4-mapped IPv6 address will match any address match
6378 list entries that match the corresponding IPv4 address.
6381 This option was introduced to work around a kernel quirk
6382 in some operating systems that causes IPv4 TCP
6383 connections, such as zone transfers, to be accepted on an
6384 IPv6 socket using mapped addresses. This caused address
6385 match lists designed for IPv4 to fail to match. However,
6386 <command>named</command> now solves this problem
6387 internally. The use of this option is discouraged.
6393 <term><command>filter-aaaa-on-v4</command></term>
6396 This option is only available when
6397 <acronym>BIND</acronym> 9 is compiled with the
6398 <userinput>--enable-filter-aaaa</userinput> option on the
6399 "configure" command line. It is intended to help the
6400 transition from IPv4 to IPv6 by not giving IPv6 addresses
6401 to DNS clients unless they have connections to the IPv6
6402 Internet. This is not recommended unless absolutely
6403 necessary. The default is <userinput>no</userinput>.
6404 The <command>filter-aaaa-on-v4</command> option
6405 may also be specified in <command>view</command> statements
6406 to override the global <command>filter-aaaa-on-v4</command>
6410 If <userinput>yes</userinput>,
6411 the DNS client is at an IPv4 address, in <command>filter-aaaa</command>,
6412 and if the response does not include DNSSEC signatures,
6413 then all AAAA records are deleted from the response.
6414 This filtering applies to all responses and not only
6415 authoritative responses.
6418 If <userinput>break-dnssec</userinput>,
6419 then AAAA records are deleted even when dnssec is enabled.
6420 As suggested by the name, this makes the response not verify,
6421 because the DNSSEC protocol is designed detect deletions.
6424 This mechanism can erroneously cause other servers to
6425 not give AAAA records to their clients.
6426 A recursing server with both IPv6 and IPv4 network connections
6427 that queries an authoritative server using this mechanism
6428 via IPv4 will be denied AAAA records even if its client is
6432 This mechanism is applied to authoritative as well as
6433 non-authoritative records.
6434 A client using IPv4 that is not allowed recursion can
6435 erroneously be given AAAA records because the server is not
6436 allowed to check for A records.
6439 Some AAAA records are given to IPv4 clients in glue records.
6440 IPv4 clients that are servers can then erroneously
6441 answer requests for AAAA records received via IPv4.
6447 <term><command>ixfr-from-differences</command></term>
6450 When <userinput>yes</userinput> and the server loads a new version of a master
6451 zone from its zone file or receives a new version of a slave
6452 file by a non-incremental zone transfer, it will compare
6453 the new version to the previous one and calculate a set
6454 of differences. The differences are then logged in the
6455 zone's journal file such that the changes can be transmitted
6456 to downstream slaves as an incremental zone transfer.
6459 By allowing incremental zone transfers to be used for
6460 non-dynamic zones, this option saves bandwidth at the
6461 expense of increased CPU and memory consumption at the
6463 In particular, if the new version of a zone is completely
6464 different from the previous one, the set of differences
6465 will be of a size comparable to the combined size of the
6466 old and new zone version, and the server will need to
6467 temporarily allocate memory to hold this complete
6470 <para><command>ixfr-from-differences</command>
6471 also accepts <command>master</command> and
6472 <command>slave</command> at the view and options
6474 <command>ixfr-from-differences</command> to be enabled for
6475 all <command>master</command> or
6476 <command>slave</command> zones respectively.
6477 It is off by default.
6483 <term><command>multi-master</command></term>
6486 This should be set when you have multiple masters for a zone
6488 addresses refer to different machines. If <userinput>yes</userinput>, <command>named</command> will
6490 when the serial number on the master is less than what <command>named</command>
6492 has. The default is <userinput>no</userinput>.
6498 <term><command>dnssec-enable</command></term>
6501 Enable DNSSEC support in <command>named</command>. Unless set to <userinput>yes</userinput>,
6502 <command>named</command> behaves as if it does not support DNSSEC.
6503 The default is <userinput>yes</userinput>.
6509 <term><command>dnssec-validation</command></term>
6512 Enable DNSSEC validation in <command>named</command>.
6513 Note <command>dnssec-enable</command> also needs to be
6514 set to <userinput>yes</userinput> to be effective.
6515 The default is <userinput>yes</userinput>.
6521 <term><command>dnssec-accept-expired</command></term>
6524 Accept expired signatures when verifying DNSSEC signatures.
6525 The default is <userinput>no</userinput>.
6526 Setting this option to <userinput>yes</userinput>
6527 leaves <command>named</command> vulnerable to
6534 <term><command>querylog</command></term>
6537 Specify whether query logging should be started when <command>named</command>
6539 If <command>querylog</command> is not specified,
6540 then the query logging
6541 is determined by the presence of the logging category <command>queries</command>.
6547 <term><command>check-names</command></term>
6550 This option is used to restrict the character set and syntax
6552 certain domain names in master files and/or DNS responses
6554 from the network. The default varies according to usage
6556 <command>master</command> zones the default is <command>fail</command>.
6557 For <command>slave</command> zones the default
6558 is <command>warn</command>.
6559 For answers received from the network (<command>response</command>)
6560 the default is <command>ignore</command>.
6563 The rules for legal hostnames and mail domains are derived
6564 from RFC 952 and RFC 821 as modified by RFC 1123.
6566 <para><command>check-names</command>
6567 applies to the owner names of A, AAAA and MX records.
6568 It also applies to the domain names in the RDATA of NS, SOA,
6569 MX, and SRV records.
6570 It also applies to the RDATA of PTR records where the owner
6571 name indicated that it is a reverse lookup of a hostname
6572 (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
6578 <term><command>check-dup-records</command></term>
6581 Check master zones for records that are treated as different
6582 by DNSSEC but are semantically equal in plain DNS. The
6583 default is to <command>warn</command>. Other possible
6584 values are <command>fail</command> and
6585 <command>ignore</command>.
6591 <term><command>check-mx</command></term>
6594 Check whether the MX record appears to refer to a IP address.
6595 The default is to <command>warn</command>. Other possible
6596 values are <command>fail</command> and
6597 <command>ignore</command>.
6602 <term><command>check-mx</command></term>
6605 Check whether the MX record appears to refer to a IP address.
6606 The default is to <command>warn</command>. Other possible
6607 values are <command>fail</command> and
6608 <command>ignore</command>.
6614 <term><command>check-wildcard</command></term>
6617 This option is used to check for non-terminal wildcards.
6618 The use of non-terminal wildcards is almost always as a
6620 to understand the wildcard matching algorithm (RFC 1034).
6622 affects master zones. The default (<command>yes</command>) is to check
6623 for non-terminal wildcards and issue a warning.
6629 <term><command>check-integrity</command></term>
6632 Perform post load zone integrity checks on master
6633 zones. This checks that MX and SRV records refer
6634 to address (A or AAAA) records and that glue
6635 address records exist for delegated zones. For
6636 MX and SRV records only in-zone hostnames are
6637 checked (for out-of-zone hostnames use
6638 <command>named-checkzone</command>).
6639 For NS records only names below top of zone are
6640 checked (for out-of-zone names and glue consistency
6641 checks use <command>named-checkzone</command>).
6642 The default is <command>yes</command>.
6648 <term><command>check-mx-cname</command></term>
6651 If <command>check-integrity</command> is set then
6652 fail, warn or ignore MX records that refer
6653 to CNAMES. The default is to <command>warn</command>.
6659 <term><command>check-srv-cname</command></term>
6662 If <command>check-integrity</command> is set then
6663 fail, warn or ignore SRV records that refer
6664 to CNAMES. The default is to <command>warn</command>.
6670 <term><command>check-sibling</command></term>
6673 When performing integrity checks, also check that
6674 sibling glue exists. The default is <command>yes</command>.
6680 <term><command>zero-no-soa-ttl</command></term>
6683 When returning authoritative negative responses to
6684 SOA queries set the TTL of the SOA record returned in
6685 the authority section to zero.
6686 The default is <command>yes</command>.
6692 <term><command>zero-no-soa-ttl-cache</command></term>
6695 When caching a negative response to a SOA query
6696 set the TTL to zero.
6697 The default is <command>no</command>.
6703 <term><command>update-check-ksk</command></term>
6706 When set to the default value of <literal>yes</literal>,
6707 check the KSK bit in each key to determine how the key
6708 should be used when generating RRSIGs for a secure zone.
6711 Ordinarily, zone-signing keys (that is, keys without the
6712 KSK bit set) are used to sign the entire zone, while
6713 key-signing keys (keys with the KSK bit set) are only
6714 used to sign the DNSKEY RRset at the zone apex.
6715 However, if this option is set to <literal>no</literal>,
6716 then the KSK bit is ignored; KSKs are treated as if they
6717 were ZSKs and are used to sign the entire zone. This is
6718 similar to the <command>dnssec-signzone -z</command>
6719 command line option.
6722 When this option is set to <literal>yes</literal>, there
6723 must be at least two active keys for every algorithm
6724 represented in the DNSKEY RRset: at least one KSK and one
6725 ZSK per algorithm. If there is any algorithm for which
6726 this requirement is not met, this option will be ignored
6733 <term><command>dnssec-dnskey-kskonly</command></term>
6736 When this option and <command>update-check-ksk</command>
6737 are both set to <literal>yes</literal>, only key-signing
6738 keys (that is, keys with the KSK bit set) will be used
6739 to sign the DNSKEY RRset at the zone apex. Zone-signing
6740 keys (keys without the KSK bit set) will be used to sign
6741 the remainder of the zone, but not the DNSKEY RRset.
6742 This is similar to the
6743 <command>dnssec-signzone -x</command> command line option.
6746 The default is <command>no</command>. If
6747 <command>update-check-ksk</command> is set to
6748 <literal>no</literal>, this option is ignored.
6754 <term><command>try-tcp-refresh</command></term>
6757 Try to refresh the zone using TCP if UDP queries fail.
6758 For BIND 8 compatibility, the default is
6759 <command>yes</command>.
6765 <term><command>dnssec-secure-to-insecure</command></term>
6768 Allow a dynamic zone to transition from secure to
6769 insecure (i.e., signed to unsigned) by deleting all
6770 of the DNSKEY records. The default is <command>no</command>.
6771 If set to <command>yes</command>, and if the DNSKEY RRset
6772 at the zone apex is deleted, all RRSIG and NSEC records
6773 will be removed from the zone as well.
6776 If the zone uses NSEC3, then it is also necessary to
6777 delete the NSEC3PARAM RRset from the zone apex; this will
6778 cause the removal of all corresponding NSEC3 records.
6779 (It is expected that this requirement will be eliminated
6780 in a future release.)
6783 Note that if a zone has been configured with
6784 <command>auto-dnssec maintain</command> and the
6785 private keys remain accessible in the key repository,
6786 then the zone will be automatically signed again the
6787 next time <command>named</command> is started.
6797 <title>Forwarding</title>
6799 The forwarding facility can be used to create a large site-wide
6800 cache on a few servers, reducing traffic over links to external
6801 name servers. It can also be used to allow queries by servers that
6802 do not have direct access to the Internet, but wish to look up
6804 names anyway. Forwarding occurs only on those queries for which
6805 the server is not authoritative and does not have the answer in
6811 <term><command>forward</command></term>
6814 This option is only meaningful if the
6815 forwarders list is not empty. A value of <varname>first</varname>,
6816 the default, causes the server to query the forwarders
6818 if that doesn't answer the question, the server will then
6820 the answer itself. If <varname>only</varname> is
6822 server will only query the forwarders.
6828 <term><command>forwarders</command></term>
6831 Specifies the IP addresses to be used
6832 for forwarding. The default is the empty list (no
6841 Forwarding can also be configured on a per-domain basis, allowing
6842 for the global forwarding options to be overridden in a variety
6843 of ways. You can set particular domains to use different
6845 or have a different <command>forward only/first</command> behavior,
6846 or not forward at all, see <xref linkend="zone_statement_grammar"/>.
6851 <title>Dual-stack Servers</title>
6853 Dual-stack servers are used as servers of last resort to work
6855 problems in reachability due the lack of support for either IPv4
6857 on the host machine.
6862 <term><command>dual-stack-servers</command></term>
6865 Specifies host names or addresses of machines with access to
6866 both IPv4 and IPv6 transports. If a hostname is used, the
6868 to resolve the name using only the transport it has. If the
6870 stacked, then the <command>dual-stack-servers</command> have no effect unless
6871 access to a transport has been disabled on the command line
6872 (e.g. <command>named -4</command>).
6879 <sect3 id="access_control">
6880 <title>Access Control</title>
6883 Access to the server can be restricted based on the IP address
6884 of the requesting system. See <xref linkend="address_match_lists"/> for
6885 details on how to specify IP address lists.
6891 <term><command>allow-notify</command></term>
6894 Specifies which hosts are allowed to
6895 notify this server, a slave, of zone changes in addition
6896 to the zone masters.
6897 <command>allow-notify</command> may also be
6899 <command>zone</command> statement, in which case
6901 <command>options allow-notify</command>
6902 statement. It is only meaningful
6903 for a slave zone. If not specified, the default is to
6904 process notify messages
6905 only from a zone's master.
6911 <term><command>allow-query</command></term>
6914 Specifies which hosts are allowed to ask ordinary
6915 DNS questions. <command>allow-query</command> may
6916 also be specified in the <command>zone</command>
6917 statement, in which case it overrides the
6918 <command>options allow-query</command> statement.
6919 If not specified, the default is to allow queries
6924 <command>allow-query-cache</command> is now
6925 used to specify access to the cache.
6932 <term><command>allow-query-on</command></term>
6935 Specifies which local addresses can accept ordinary
6936 DNS questions. This makes it possible, for instance,
6937 to allow queries on internal-facing interfaces but
6938 disallow them on external-facing ones, without
6939 necessarily knowing the internal network's addresses.
6942 <command>allow-query-on</command> may
6943 also be specified in the <command>zone</command>
6944 statement, in which case it overrides the
6945 <command>options allow-query-on</command> statement.
6948 If not specified, the default is to allow queries
6953 <command>allow-query-cache</command> is
6954 used to specify access to the cache.
6961 <term><command>allow-query-cache</command></term>
6964 Specifies which hosts are allowed to get answers
6965 from the cache. If <command>allow-query-cache</command>
6966 is not set then <command>allow-recursion</command>
6967 is used if set, otherwise <command>allow-query</command>
6968 is used if set unless <command>recursion no;</command> is
6969 set in which case <command>none;</command> is used,
6970 otherwise the default (<command>localnets;</command>
6971 <command>localhost;</command>) is used.
6977 <term><command>allow-query-cache-on</command></term>
6980 Specifies which local addresses can give answers
6981 from the cache. If not specified, the default is
6982 to allow cache queries on any address,
6983 <command>localnets</command> and
6984 <command>localhost</command>.
6990 <term><command>allow-recursion</command></term>
6993 Specifies which hosts are allowed to make recursive
6994 queries through this server. If
6995 <command>allow-recursion</command> is not set
6996 then <command>allow-query-cache</command> is
6997 used if set, otherwise <command>allow-query</command>
6998 is used if set, otherwise the default
6999 (<command>localnets;</command>
7000 <command>localhost;</command>) is used.
7006 <term><command>allow-recursion-on</command></term>
7009 Specifies which local addresses can accept recursive
7010 queries. If not specified, the default is to allow
7011 recursive queries on all addresses.
7017 <term><command>allow-update</command></term>
7020 Specifies which hosts are allowed to
7021 submit Dynamic DNS updates for master zones. The default is
7023 updates from all hosts. Note that allowing updates based
7024 on the requestor's IP address is insecure; see
7025 <xref linkend="dynamic_update_security"/> for details.
7031 <term><command>allow-update-forwarding</command></term>
7034 Specifies which hosts are allowed to
7035 submit Dynamic DNS updates to slave zones to be forwarded to
7037 master. The default is <userinput>{ none; }</userinput>,
7039 means that no update forwarding will be performed. To
7041 update forwarding, specify
7042 <userinput>allow-update-forwarding { any; };</userinput>.
7043 Specifying values other than <userinput>{ none; }</userinput> or
7044 <userinput>{ any; }</userinput> is usually
7045 counterproductive, since
7046 the responsibility for update access control should rest
7048 master server, not the slaves.
7051 Note that enabling the update forwarding feature on a slave
7053 may expose master servers relying on insecure IP address
7055 access control to attacks; see <xref linkend="dynamic_update_security"/>
7062 <term><command>allow-v6-synthesis</command></term>
7065 This option was introduced for the smooth transition from
7067 to A6 and from "nibble labels" to binary labels.
7068 However, since both A6 and binary labels were then
7070 this option was also deprecated.
7071 It is now ignored with some warning messages.
7077 <term><command>allow-transfer</command></term>
7080 Specifies which hosts are allowed to
7081 receive zone transfers from the server. <command>allow-transfer</command> may
7082 also be specified in the <command>zone</command>
7084 case it overrides the <command>options allow-transfer</command> statement.
7085 If not specified, the default is to allow transfers to all
7092 <term><command>blackhole</command></term>
7095 Specifies a list of addresses that the
7096 server will not accept queries from or use to resolve a
7098 from these addresses will not be responded to. The default
7099 is <userinput>none</userinput>.
7105 <term><command>filter-aaaa</command></term>
7108 Specifies a list of addresses to which
7109 <command>filter-aaaa-on-v4</command>
7110 is applies. The default is <userinput>any</userinput>.
7120 <title>Interfaces</title>
7122 The interfaces and ports that the server will answer queries
7123 from may be specified using the <command>listen-on</command> option. <command>listen-on</command> takes
7124 an optional port and an <varname>address_match_list</varname>.
7125 The server will listen on all interfaces allowed by the address
7126 match list. If a port is not specified, port 53 will be used.
7129 Multiple <command>listen-on</command> statements are
7134 <programlisting>listen-on { 5.6.7.8; };
7135 listen-on port 1234 { !1.2.3.4; 1.2/16; };
7139 will enable the name server on port 53 for the IP address
7140 5.6.7.8, and on port 1234 of an address on the machine in net
7141 1.2 that is not 1.2.3.4.
7145 If no <command>listen-on</command> is specified, the
7146 server will listen on port 53 on all IPv4 interfaces.
7150 The <command>listen-on-v6</command> option is used to
7151 specify the interfaces and the ports on which the server will
7153 for incoming queries sent using IPv6.
7157 When <programlisting>{ any; }</programlisting> is
7159 as the <varname>address_match_list</varname> for the
7160 <command>listen-on-v6</command> option,
7161 the server does not bind a separate socket to each IPv6 interface
7162 address as it does for IPv4 if the operating system has enough API
7163 support for IPv6 (specifically if it conforms to RFC 3493 and RFC
7165 Instead, it listens on the IPv6 wildcard address.
7166 If the system only has incomplete API support for IPv6, however,
7167 the behavior is the same as that for IPv4.
7171 A list of particular IPv6 addresses can also be specified, in
7173 the server listens on a separate socket for each specified
7175 regardless of whether the desired API is supported by the system.
7179 Multiple <command>listen-on-v6</command> options can
7184 <programlisting>listen-on-v6 { any; };
7185 listen-on-v6 port 1234 { !2001:db8::/32; any; };
7189 will enable the name server on port 53 for any IPv6 addresses
7190 (with a single wildcard socket),
7191 and on port 1234 of IPv6 addresses that is not in the prefix
7192 2001:db8::/32 (with separate sockets for each matched address.)
7196 To make the server not listen on any IPv6 address, use
7199 <programlisting>listen-on-v6 { none; };
7203 If no <command>listen-on-v6</command> option is
7204 specified, the server will not listen on any IPv6 address
7205 unless <command>-6</command> is specified when <command>named</command> is
7206 invoked. If <command>-6</command> is specified then
7207 <command>named</command> will listen on port 53 on all IPv6 interfaces by default.
7211 <sect3 id="query_address">
7212 <title>Query Address</title>
7214 If the server doesn't know the answer to a question, it will
7215 query other name servers. <command>query-source</command> specifies
7216 the address and port used for such queries. For queries sent over
7217 IPv6, there is a separate <command>query-source-v6</command> option.
7218 If <command>address</command> is <command>*</command> (asterisk) or is omitted,
7219 a wildcard IP address (<command>INADDR_ANY</command>)
7224 If <command>port</command> is <command>*</command> or is omitted,
7225 a random port number from a pre-configured
7226 range is picked up and will be used for each query.
7227 The port range(s) is that specified in
7228 the <command>use-v4-udp-ports</command> (for IPv4)
7229 and <command>use-v6-udp-ports</command> (for IPv6)
7230 options, excluding the ranges specified in
7231 the <command>avoid-v4-udp-ports</command>
7232 and <command>avoid-v6-udp-ports</command> options, respectively.
7236 The defaults of the <command>query-source</command> and
7237 <command>query-source-v6</command> options
7241 <programlisting>query-source address * port *;
7242 query-source-v6 address * port *;
7246 If <command>use-v4-udp-ports</command> or
7247 <command>use-v6-udp-ports</command> is unspecified,
7248 <command>named</command> will check if the operating
7249 system provides a programming interface to retrieve the
7250 system's default range for ephemeral ports.
7251 If such an interface is available,
7252 <command>named</command> will use the corresponding system
7253 default range; otherwise, it will use its own defaults:
7256 <programlisting>use-v4-udp-ports { range 1024 65535; };
7257 use-v6-udp-ports { range 1024 65535; };
7261 Note: make sure the ranges be sufficiently large for
7262 security. A desirable size depends on various parameters,
7263 but we generally recommend it contain at least 16384 ports
7264 (14 bits of entropy).
7265 Note also that the system's default range when used may be
7266 too small for this purpose, and that the range may even be
7267 changed while <command>named</command> is running; the new
7268 range will automatically be applied when <command>named</command>
7271 configure <command>use-v4-udp-ports</command> and
7272 <command>use-v6-udp-ports</command> explicitly so that the
7273 ranges are sufficiently large and are reasonably
7274 independent from the ranges used by other applications.
7278 Note: the operational configuration
7279 where <command>named</command> runs may prohibit the use
7280 of some ports. For example, UNIX systems will not allow
7281 <command>named</command> running without a root privilege
7282 to use ports less than 1024.
7283 If such ports are included in the specified (or detected)
7284 set of query ports, the corresponding query attempts will
7285 fail, resulting in resolution failures or delay.
7286 It is therefore important to configure the set of ports
7287 that can be safely used in the expected operational environment.
7291 The defaults of the <command>avoid-v4-udp-ports</command> and
7292 <command>avoid-v6-udp-ports</command> options
7296 <programlisting>avoid-v4-udp-ports {};
7297 avoid-v6-udp-ports {};
7301 Note: BIND 9.5.0 introduced
7302 the <command>use-queryport-pool</command>
7303 option to support a pool of such random ports, but this
7304 option is now obsolete because reusing the same ports in
7305 the pool may not be sufficiently secure.
7306 For the same reason, it is generally strongly discouraged to
7307 specify a particular port for the
7308 <command>query-source</command> or
7309 <command>query-source-v6</command> options;
7310 it implicitly disables the use of randomized port numbers.
7315 <term><command>use-queryport-pool</command></term>
7318 This option is obsolete.
7324 <term><command>queryport-pool-ports</command></term>
7327 This option is obsolete.
7333 <term><command>queryport-pool-updateinterval</command></term>
7336 This option is obsolete.
7344 The address specified in the <command>query-source</command> option
7345 is used for both UDP and TCP queries, but the port applies only
7346 to UDP queries. TCP queries always use a random
7352 Solaris 2.5.1 and earlier does not support setting the source
7353 address for TCP sockets.
7358 See also <command>transfer-source</command> and
7359 <command>notify-source</command>.
7364 <sect3 id="zone_transfers">
7365 <title>Zone Transfers</title>
7367 <acronym>BIND</acronym> has mechanisms in place to
7368 facilitate zone transfers
7369 and set limits on the amount of load that transfers place on the
7370 system. The following options apply to zone transfers.
7376 <term><command>also-notify</command></term>
7379 Defines a global list of IP addresses of name servers
7380 that are also sent NOTIFY messages whenever a fresh copy of
7382 zone is loaded, in addition to the servers listed in the
7384 This helps to ensure that copies of the zones will
7385 quickly converge on stealth servers.
7386 Optionally, a port may be specified with each
7387 <command>also-notify</command> address to send
7388 the notify messages to a port other than the
7390 If an <command>also-notify</command> list
7391 is given in a <command>zone</command> statement,
7393 the <command>options also-notify</command>
7394 statement. When a <command>zone notify</command>
7396 is set to <command>no</command>, the IP
7397 addresses in the global <command>also-notify</command> list will
7398 not be sent NOTIFY messages for that zone. The default is
7400 list (no global notification list).
7406 <term><command>max-transfer-time-in</command></term>
7409 Inbound zone transfers running longer than
7410 this many minutes will be terminated. The default is 120
7412 (2 hours). The maximum value is 28 days (40320 minutes).
7418 <term><command>max-transfer-idle-in</command></term>
7421 Inbound zone transfers making no progress
7422 in this many minutes will be terminated. The default is 60
7424 (1 hour). The maximum value is 28 days (40320 minutes).
7430 <term><command>max-transfer-time-out</command></term>
7433 Outbound zone transfers running longer than
7434 this many minutes will be terminated. The default is 120
7436 (2 hours). The maximum value is 28 days (40320 minutes).
7442 <term><command>max-transfer-idle-out</command></term>
7445 Outbound zone transfers making no progress
7446 in this many minutes will be terminated. The default is 60
7448 hour). The maximum value is 28 days (40320 minutes).
7454 <term><command>serial-query-rate</command></term>
7457 Slave servers will periodically query master servers
7458 to find out if zone serial numbers have changed. Each such
7460 a minute amount of the slave server's network bandwidth. To
7462 amount of bandwidth used, BIND 9 limits the rate at which
7464 sent. The value of the <command>serial-query-rate</command> option,
7465 an integer, is the maximum number of queries sent per
7473 <term><command>serial-queries</command></term>
7476 In BIND 8, the <command>serial-queries</command>
7478 set the maximum number of concurrent serial number queries
7479 allowed to be outstanding at any given time.
7480 BIND 9 does not limit the number of outstanding
7481 serial queries and ignores the <command>serial-queries</command> option.
7482 Instead, it limits the rate at which the queries are sent
7483 as defined using the <command>serial-query-rate</command> option.
7489 <term><command>transfer-format</command></term>
7493 Zone transfers can be sent using two different formats,
7494 <command>one-answer</command> and
7495 <command>many-answers</command>.
7496 The <command>transfer-format</command> option is used
7497 on the master server to determine which format it sends.
7498 <command>one-answer</command> uses one DNS message per
7499 resource record transferred.
7500 <command>many-answers</command> packs as many resource
7501 records as possible into a message.
7502 <command>many-answers</command> is more efficient, but is
7503 only supported by relatively new slave servers,
7504 such as <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
7505 8.x and <acronym>BIND</acronym> 4.9.5 onwards.
7506 The <command>many-answers</command> format is also supported by
7507 recent Microsoft Windows nameservers.
7508 The default is <command>many-answers</command>.
7509 <command>transfer-format</command> may be overridden on a
7510 per-server basis by using the <command>server</command>
7518 <term><command>transfers-in</command></term>
7521 The maximum number of inbound zone transfers
7522 that can be running concurrently. The default value is <literal>10</literal>.
7523 Increasing <command>transfers-in</command> may
7524 speed up the convergence
7525 of slave zones, but it also may increase the load on the
7532 <term><command>transfers-out</command></term>
7535 The maximum number of outbound zone transfers
7536 that can be running concurrently. Zone transfer requests in
7538 of the limit will be refused. The default value is <literal>10</literal>.
7544 <term><command>transfers-per-ns</command></term>
7547 The maximum number of inbound zone transfers
7548 that can be concurrently transferring from a given remote
7550 The default value is <literal>2</literal>.
7551 Increasing <command>transfers-per-ns</command>
7553 speed up the convergence of slave zones, but it also may
7555 the load on the remote name server. <command>transfers-per-ns</command> may
7556 be overridden on a per-server basis by using the <command>transfers</command> phrase
7557 of the <command>server</command> statement.
7563 <term><command>transfer-source</command></term>
7565 <para><command>transfer-source</command>
7566 determines which local address will be bound to IPv4
7567 TCP connections used to fetch zones transferred
7568 inbound by the server. It also determines the
7569 source IPv4 address, and optionally the UDP port,
7570 used for the refresh queries and forwarded dynamic
7571 updates. If not set, it defaults to a system
7572 controlled value which will usually be the address
7573 of the interface "closest to" the remote end. This
7574 address must appear in the remote end's
7575 <command>allow-transfer</command> option for the
7576 zone being transferred, if one is specified. This
7578 <command>transfer-source</command> for all zones,
7579 but can be overridden on a per-view or per-zone
7580 basis by including a
7581 <command>transfer-source</command> statement within
7582 the <command>view</command> or
7583 <command>zone</command> block in the configuration
7588 Solaris 2.5.1 and earlier does not support setting the
7589 source address for TCP sockets.
7596 <term><command>transfer-source-v6</command></term>
7599 The same as <command>transfer-source</command>,
7600 except zone transfers are performed using IPv6.
7606 <term><command>alt-transfer-source</command></term>
7609 An alternate transfer source if the one listed in
7610 <command>transfer-source</command> fails and
7611 <command>use-alt-transfer-source</command> is
7615 If you do not wish the alternate transfer source
7616 to be used, you should set
7617 <command>use-alt-transfer-source</command>
7618 appropriately and you should not depend upon
7619 getting an answer back to the first refresh
7626 <term><command>alt-transfer-source-v6</command></term>
7629 An alternate transfer source if the one listed in
7630 <command>transfer-source-v6</command> fails and
7631 <command>use-alt-transfer-source</command> is
7638 <term><command>use-alt-transfer-source</command></term>
7641 Use the alternate transfer sources or not. If views are
7642 specified this defaults to <command>no</command>
7643 otherwise it defaults to
7644 <command>yes</command> (for BIND 8
7651 <term><command>notify-source</command></term>
7653 <para><command>notify-source</command>
7654 determines which local source address, and
7655 optionally UDP port, will be used to send NOTIFY
7656 messages. This address must appear in the slave
7657 server's <command>masters</command> zone clause or
7658 in an <command>allow-notify</command> clause. This
7659 statement sets the <command>notify-source</command>
7660 for all zones, but can be overridden on a per-zone or
7661 per-view basis by including a
7662 <command>notify-source</command> statement within
7663 the <command>zone</command> or
7664 <command>view</command> block in the configuration
7669 Solaris 2.5.1 and earlier does not support setting the
7670 source address for TCP sockets.
7677 <term><command>notify-source-v6</command></term>
7680 Like <command>notify-source</command>,
7681 but applies to notify messages sent to IPv6 addresses.
7691 <title>UDP Port Lists</title>
7693 <command>use-v4-udp-ports</command>,
7694 <command>avoid-v4-udp-ports</command>,
7695 <command>use-v6-udp-ports</command>, and
7696 <command>avoid-v6-udp-ports</command>
7697 specify a list of IPv4 and IPv6 UDP ports that will be
7698 used or not used as source ports for UDP messages.
7699 See <xref linkend="query_address"/> about how the
7700 available ports are determined.
7701 For example, with the following configuration
7705 use-v6-udp-ports { range 32768 65535; };
7706 avoid-v6-udp-ports { 40000; range 50000 60000; };
7710 UDP ports of IPv6 messages sent
7711 from <command>named</command> will be in one
7712 of the following ranges: 32768 to 39999, 40001 to 49999,
7717 <command>avoid-v4-udp-ports</command> and
7718 <command>avoid-v6-udp-ports</command> can be used
7719 to prevent <command>named</command> from choosing as its random source port a
7720 port that is blocked by your firewall or a port that is
7721 used by other applications;
7722 if a query went out with a source port blocked by a
7724 answer would not get by the firewall and the name server would
7725 have to query again.
7726 Note: the desired range can also be represented only with
7727 <command>use-v4-udp-ports</command> and
7728 <command>use-v6-udp-ports</command>, and the
7729 <command>avoid-</command> options are redundant in that
7730 sense; they are provided for backward compatibility and
7731 to possibly simplify the port specification.
7736 <title>Operating System Resource Limits</title>
7739 The server's usage of many system resources can be limited.
7740 Scaled values are allowed when specifying resource limits. For
7741 example, <command>1G</command> can be used instead of
7742 <command>1073741824</command> to specify a limit of
7744 gigabyte. <command>unlimited</command> requests
7745 unlimited use, or the
7746 maximum available amount. <command>default</command>
7748 that was in force when the server was started. See the description
7749 of <command>size_spec</command> in <xref linkend="configuration_file_elements"/>.
7753 The following options set operating system resource limits for
7754 the name server process. Some operating systems don't support
7756 any of the limits. On such systems, a warning will be issued if
7758 unsupported limit is used.
7764 <term><command>coresize</command></term>
7767 The maximum size of a core dump. The default
7768 is <literal>default</literal>.
7774 <term><command>datasize</command></term>
7777 The maximum amount of data memory the server
7778 may use. The default is <literal>default</literal>.
7779 This is a hard limit on server memory usage.
7780 If the server attempts to allocate memory in excess of this
7781 limit, the allocation will fail, which may in turn leave
7782 the server unable to perform DNS service. Therefore,
7783 this option is rarely useful as a way of limiting the
7784 amount of memory used by the server, but it can be used
7785 to raise an operating system data size limit that is
7786 too small by default. If you wish to limit the amount
7787 of memory used by the server, use the
7788 <command>max-cache-size</command> and
7789 <command>recursive-clients</command>
7796 <term><command>files</command></term>
7799 The maximum number of files the server
7800 may have open concurrently. The default is <literal>unlimited</literal>.
7806 <term><command>stacksize</command></term>
7809 The maximum amount of stack memory the server
7810 may use. The default is <literal>default</literal>.
7819 <sect3 id="server_resource_limits">
7820 <title>Server Resource Limits</title>
7823 The following options set limits on the server's
7824 resource consumption that are enforced internally by the
7825 server rather than the operating system.
7831 <term><command>max-ixfr-log-size</command></term>
7834 This option is obsolete; it is accepted
7835 and ignored for BIND 8 compatibility. The option
7836 <command>max-journal-size</command> performs a
7837 similar function in BIND 9.
7843 <term><command>max-journal-size</command></term>
7846 Sets a maximum size for each journal file
7847 (see <xref linkend="journal"/>). When the journal file
7849 the specified size, some of the oldest transactions in the
7851 will be automatically removed. The default is
7852 <literal>unlimited</literal>.
7853 This may also be set on a per-zone basis.
7859 <term><command>host-statistics-max</command></term>
7862 In BIND 8, specifies the maximum number of host statistics
7864 Not implemented in BIND 9.
7870 <term><command>recursive-clients</command></term>
7873 The maximum number of simultaneous recursive lookups
7874 the server will perform on behalf of clients. The default
7876 <literal>1000</literal>. Because each recursing
7878 bit of memory, on the order of 20 kilobytes, the value of
7880 <command>recursive-clients</command> option may
7881 have to be decreased
7882 on hosts with limited memory.
7888 <term><command>tcp-clients</command></term>
7891 The maximum number of simultaneous client TCP
7892 connections that the server will accept.
7893 The default is <literal>100</literal>.
7899 <term><command>reserved-sockets</command></term>
7902 The number of file descriptors reserved for TCP, stdio,
7903 etc. This needs to be big enough to cover the number of
7904 interfaces <command>named</command> listens on, <command>tcp-clients</command> as well as
7905 to provide room for outgoing TCP queries and incoming zone
7906 transfers. The default is <literal>512</literal>.
7907 The minimum value is <literal>128</literal> and the
7908 maximum value is <literal>128</literal> less than
7909 maxsockets (-S). This option may be removed in the future.
7912 This option has little effect on Windows.
7918 <term><command>max-cache-size</command></term>
7921 The maximum amount of memory to use for the
7922 server's cache, in bytes.
7923 When the amount of data in the cache
7924 reaches this limit, the server will cause records to expire
7925 prematurely based on an LRU based strategy so that
7926 the limit is not exceeded.
7927 A value of 0 is special, meaning that
7928 records are purged from the cache only when their
7930 Another special keyword <userinput>unlimited</userinput>
7931 means the maximum value of 32-bit unsigned integers
7932 (0xffffffff), which may not have the same effect as
7933 0 on machines that support more than 32 bits of
7935 Any positive values less than 2MB will be ignored reset
7937 In a server with multiple views, the limit applies
7938 separately to the cache of each view.
7945 <term><command>tcp-listen-queue</command></term>
7948 The listen queue depth. The default and minimum is 3.
7949 If the kernel supports the accept filter "dataready" this
7951 many TCP connections that will be queued in kernel space
7953 some data before being passed to accept. Values less than 3
7965 <title>Periodic Task Intervals</title>
7970 <term><command>cleaning-interval</command></term>
7973 This interval is effectively obsolete. Previously,
7974 the server would remove expired resource records
7975 from the cache every <command>cleaning-interval</command> minutes.
7976 <acronym>BIND</acronym> 9 now manages cache
7977 memory in a more sophisticated manner and does not
7978 rely on the periodic cleaning any more.
7979 Specifying this option therefore has no effect on
7980 the server's behavior.
7986 <term><command>heartbeat-interval</command></term>
7989 The server will perform zone maintenance tasks
7990 for all zones marked as <command>dialup</command> whenever this
7991 interval expires. The default is 60 minutes. Reasonable
7993 to 1 day (1440 minutes). The maximum value is 28 days
7995 If set to 0, no zone maintenance for these zones will occur.
8001 <term><command>interface-interval</command></term>
8004 The server will scan the network interface list
8005 every <command>interface-interval</command>
8006 minutes. The default
8007 is 60 minutes. The maximum value is 28 days (40320 minutes).
8008 If set to 0, interface scanning will only occur when
8009 the configuration file is loaded. After the scan, the
8011 begin listening for queries on any newly discovered
8012 interfaces (provided they are allowed by the
8013 <command>listen-on</command> configuration), and
8015 stop listening on interfaces that have gone away.
8021 <term><command>statistics-interval</command></term>
8024 Name server statistics will be logged
8025 every <command>statistics-interval</command>
8026 minutes. The default is
8027 60. The maximum value is 28 days (40320 minutes).
8028 If set to 0, no statistics will be logged.
8031 Not yet implemented in
8032 <acronym>BIND</acronym> 9.
8042 <sect3 id="topology">
8043 <title>Topology</title>
8046 All other things being equal, when the server chooses a name
8048 to query from a list of name servers, it prefers the one that is
8049 topologically closest to itself. The <command>topology</command> statement
8050 takes an <command>address_match_list</command> and
8052 in a special way. Each top-level list element is assigned a
8054 Non-negated elements get a distance based on their position in the
8055 list, where the closer the match is to the start of the list, the
8056 shorter the distance is between it and the server. A negated match
8057 will be assigned the maximum distance from the server. If there
8058 is no match, the address will get a distance which is further than
8059 any non-negated list element, and closer than any negated element.
8063 <programlisting>topology {
8070 will prefer servers on network 10 the most, followed by hosts
8071 on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
8072 exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
8073 is preferred least of all.
8076 The default topology is
8079 <programlisting> topology { localhost; localnets; };
8084 The <command>topology</command> option
8085 is not implemented in <acronym>BIND</acronym> 9.
8090 <sect3 id="the_sortlist_statement">
8092 <title>The <command>sortlist</command> Statement</title>
8095 The response to a DNS query may consist of multiple resource
8096 records (RRs) forming a resource records set (RRset).
8097 The name server will normally return the
8098 RRs within the RRset in an indeterminate order
8099 (but see the <command>rrset-order</command>
8100 statement in <xref linkend="rrset_ordering"/>).
8101 The client resolver code should rearrange the RRs as appropriate,
8102 that is, using any addresses on the local net in preference to
8104 However, not all resolvers can do this or are correctly
8106 When a client is using a local server, the sorting can be performed
8107 in the server, based on the client's address. This only requires
8108 configuring the name servers, not all the clients.
8112 The <command>sortlist</command> statement (see below)
8114 an <command>address_match_list</command> and
8116 more specifically than the <command>topology</command>
8118 does (<xref linkend="topology"/>).
8119 Each top level statement in the <command>sortlist</command> must
8120 itself be an explicit <command>address_match_list</command> with
8121 one or two elements. The first element (which may be an IP
8123 an IP prefix, an ACL name or a nested <command>address_match_list</command>)
8124 of each top level list is checked against the source address of
8125 the query until a match is found.
8128 Once the source address of the query has been matched, if
8129 the top level statement contains only one element, the actual
8131 element that matched the source address is used to select the
8133 in the response to move to the beginning of the response. If the
8134 statement is a list of two elements, then the second element is
8135 treated the same as the <command>address_match_list</command> in
8136 a <command>topology</command> statement. Each top
8138 is assigned a distance and the address in the response with the
8140 distance is moved to the beginning of the response.
8143 In the following example, any queries received from any of
8144 the addresses of the host itself will get responses preferring
8146 on any of the locally connected networks. Next most preferred are
8148 on the 192.168.1/24 network, and after that either the
8151 192.168.3/24 network with no preference shown between these two
8152 networks. Queries received from a host on the 192.168.1/24 network
8153 will prefer other addresses on that network to the 192.168.2/24
8155 192.168.3/24 networks. Queries received from a host on the
8157 or the 192.168.5/24 network will only prefer other addresses on
8158 their directly connected networks.
8161 <programlisting>sortlist {
8162 // IF the local host
8163 // THEN first fit on the following nets
8167 { 192.168.2/24; 192.168.3/24; }; }; };
8168 // IF on class C 192.168.1 THEN use .1, or .2 or .3
8171 { 192.168.2/24; 192.168.3/24; }; }; };
8172 // IF on class C 192.168.2 THEN use .2, or .1 or .3
8175 { 192.168.1/24; 192.168.3/24; }; }; };
8176 // IF on class C 192.168.3 THEN use .3, or .1 or .2
8179 { 192.168.1/24; 192.168.2/24; }; }; };
8180 // IF .4 or .5 THEN prefer that net
8181 { { 192.168.4/24; 192.168.5/24; };
8186 The following example will give reasonable behavior for the
8187 local host and hosts on directly connected networks. It is similar
8188 to the behavior of the address sort in <acronym>BIND</acronym> 4.9.x. Responses sent
8189 to queries from the local host will favor any of the directly
8191 networks. Responses sent to queries from any other hosts on a
8193 connected network will prefer addresses on that same network.
8195 to other queries will not be sorted.
8198 <programlisting>sortlist {
8199 { localhost; localnets; };
8205 <sect3 id="rrset_ordering">
8206 <title id="rrset_ordering_title">RRset Ordering</title>
8208 When multiple records are returned in an answer it may be
8209 useful to configure the order of the records placed into the
8211 The <command>rrset-order</command> statement permits
8213 of the ordering of the records in a multiple record response.
8214 See also the <command>sortlist</command> statement,
8215 <xref linkend="the_sortlist_statement"/>.
8219 An <command>order_spec</command> is defined as
8223 <optional>class <replaceable>class_name</replaceable></optional>
8224 <optional>type <replaceable>type_name</replaceable></optional>
8225 <optional>name <replaceable>"domain_name"</replaceable></optional>
8226 order <replaceable>ordering</replaceable>
8229 If no class is specified, the default is <command>ANY</command>.
8230 If no type is specified, the default is <command>ANY</command>.
8231 If no name is specified, the default is "<command>*</command>" (asterisk).
8234 The legal values for <command>ordering</command> are:
8236 <informaltable colsep="0" rowsep="0">
8237 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
8238 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
8239 <colspec colname="2" colnum="2" colsep="0" colwidth="3.750in"/>
8243 <para><command>fixed</command></para>
8247 Records are returned in the order they
8248 are defined in the zone file.
8254 <para><command>random</command></para>
8258 Records are returned in some random order.
8264 <para><command>cyclic</command></para>
8268 Records are returned in a cyclic round-robin order.
8271 If <acronym>BIND</acronym> is configured with the
8272 "--enable-fixed-rrset" option at compile time, then
8273 the initial ordering of the RRset will match the
8274 one specified in the zone file.
8285 <programlisting>rrset-order {
8286 class IN type A name "host.example.com" order random;
8292 will cause any responses for type A records in class IN that
8293 have "<literal>host.example.com</literal>" as a
8294 suffix, to always be returned
8295 in random order. All other records are returned in cyclic order.
8298 If multiple <command>rrset-order</command> statements
8300 they are not combined — the last one applies.
8305 In this release of <acronym>BIND</acronym> 9, the
8306 <command>rrset-order</command> statement does not support
8307 "fixed" ordering by default. Fixed ordering can be enabled
8308 at compile time by specifying "--enable-fixed-rrset" on
8309 the "configure" command line.
8315 <title>Tuning</title>
8320 <term><command>lame-ttl</command></term>
8323 Sets the number of seconds to cache a
8324 lame server indication. 0 disables caching. (This is
8325 <emphasis role="bold">NOT</emphasis> recommended.)
8326 The default is <literal>600</literal> (10 minutes) and the
8328 <literal>1800</literal> (30 minutes).
8332 Lame-ttl also controls the amount of time DNSSEC
8333 validation failures are cached. There is a minimum
8334 of 30 seconds applied to bad cache entries if the
8335 lame-ttl is set to less than 30 seconds.
8342 <term><command>max-ncache-ttl</command></term>
8345 To reduce network traffic and increase performance,
8346 the server stores negative answers. <command>max-ncache-ttl</command> is
8347 used to set a maximum retention time for these answers in
8349 in seconds. The default
8350 <command>max-ncache-ttl</command> is <literal>10800</literal> seconds (3 hours).
8351 <command>max-ncache-ttl</command> cannot exceed
8353 be silently truncated to 7 days if set to a greater value.
8359 <term><command>max-cache-ttl</command></term>
8362 Sets the maximum time for which the server will
8363 cache ordinary (positive) answers. The default is
8365 A value of zero may cause all queries to return
8366 SERVFAIL, because of lost caches of intermediate
8367 RRsets (such as NS and glue AAAA/A records) in the
8374 <term><command>min-roots</command></term>
8377 The minimum number of root servers that
8378 is required for a request for the root servers to be
8379 accepted. The default
8380 is <userinput>2</userinput>.
8384 Not implemented in <acronym>BIND</acronym> 9.
8391 <term><command>sig-validity-interval</command></term>
8394 Specifies the number of days into the future when
8395 DNSSEC signatures automatically generated as a
8396 result of dynamic updates (<xref
8397 linkend="dynamic_update"/>) will expire. There
8398 is an optional second field which specifies how
8399 long before expiry that the signatures will be
8400 regenerated. If not specified, the signatures will
8401 be regenerated at 1/4 of base interval. The second
8402 field is specified in days if the base interval is
8403 greater than 7 days otherwise it is specified in hours.
8404 The default base interval is <literal>30</literal> days
8405 giving a re-signing interval of 7 1/2 days. The maximum
8406 values are 10 years (3660 days).
8409 The signature inception time is unconditionally
8410 set to one hour before the current time to allow
8411 for a limited amount of clock skew.
8414 The <command>sig-validity-interval</command>
8415 should be, at least, several multiples of the SOA
8416 expire interval to allow for reasonable interaction
8417 between the various timer and expiry dates.
8423 <term><command>sig-signing-nodes</command></term>
8426 Specify the maximum number of nodes to be
8427 examined in each quantum when signing a zone with
8428 a new DNSKEY. The default is
8429 <literal>100</literal>.
8435 <term><command>sig-signing-signatures</command></term>
8438 Specify a threshold number of signatures that
8439 will terminate processing a quantum when signing
8440 a zone with a new DNSKEY. The default is
8441 <literal>10</literal>.
8447 <term><command>sig-signing-type</command></term>
8450 Specify a private RDATA type to be used when generating
8451 key signing records. The default is
8452 <literal>65535</literal>.
8455 It is expected that this parameter may be removed
8456 in a future version once there is a standard type.
8462 <term><command>min-refresh-time</command></term>
8463 <term><command>max-refresh-time</command></term>
8464 <term><command>min-retry-time</command></term>
8465 <term><command>max-retry-time</command></term>
8468 These options control the server's behavior on refreshing a
8470 (querying for SOA changes) or retrying failed transfers.
8471 Usually the SOA values for the zone are used, but these
8473 are set by the master, giving slave server administrators
8475 control over their contents.
8478 These options allow the administrator to set a minimum and
8480 refresh and retry time either per-zone, per-view, or
8482 These options are valid for slave and stub zones,
8483 and clamp the SOA refresh and retry times to the specified
8490 <term><command>edns-udp-size</command></term>
8493 Sets the advertised EDNS UDP buffer size in bytes
8494 to control the size of packets received.
8495 Valid values are 1024 to 4096 (values outside this range
8496 will be silently adjusted). The default value
8497 is 4096. The usual reason for setting
8498 <command>edns-udp-size</command> to a non-default
8499 value is to get UDP answers to pass through broken
8500 firewalls that block fragmented packets and/or
8501 block UDP packets that are greater than 512 bytes.
8504 <command>named</command> will fallback to using 512 bytes
8505 if it get a series of timeout at the initial value. 512
8506 bytes is not being offered to encourage sites to fix their
8507 firewalls. Small EDNS UDP sizes will result in the
8508 excessive use of TCP.
8514 <term><command>max-udp-size</command></term>
8517 Sets the maximum EDNS UDP message size
8518 <command>named</command> will send in bytes.
8519 Valid values are 512 to 4096 (values outside this
8520 range will be silently adjusted). The default
8521 value is 4096. The usual reason for setting
8522 <command>max-udp-size</command> to a non-default
8523 value is to get UDP answers to pass through broken
8524 firewalls that block fragmented packets and/or
8525 block UDP packets that are greater than 512 bytes.
8526 This is independent of the advertised receive
8527 buffer (<command>edns-udp-size</command>).
8530 Setting this to a low value will encourge additional
8531 TCP traffic to the nameserver.
8537 <term><command>masterfile-format</command></term>
8540 the file format of zone files (see
8541 <xref linkend="zonefile_format"/>).
8542 The default value is <constant>text</constant>, which is the
8543 standard textual representation. Files in other formats
8544 than <constant>text</constant> are typically expected
8545 to be generated by the <command>named-compilezone</command> tool.
8546 Note that when a zone file in a different format than
8547 <constant>text</constant> is loaded, <command>named</command>
8548 may omit some of the checks which would be performed for a
8549 file in the <constant>text</constant> format. In particular,
8550 <command>check-names</command> checks do not apply
8551 for the <constant>raw</constant> format. This means
8552 a zone file in the <constant>raw</constant> format
8553 must be generated with the same check level as that
8554 specified in the <command>named</command> configuration
8555 file. This statement sets the
8556 <command>masterfile-format</command> for all zones,
8557 but can be overridden on a per-zone or per-view basis
8558 by including a <command>masterfile-format</command>
8559 statement within the <command>zone</command> or
8560 <command>view</command> block in the configuration
8566 <varlistentry id="clients-per-query">
8567 <term><command>clients-per-query</command></term>
8568 <term><command>max-clients-per-query</command></term>
8571 initial value (minimum) and maximum number of recursive
8572 simultaneous clients for any given query
8573 (<qname,qtype,qclass>) that the server will accept
8574 before dropping additional clients. <command>named</command> will attempt to
8575 self tune this value and changes will be logged. The
8576 default values are 10 and 100.
8579 This value should reflect how many queries come in for
8580 a given name in the time it takes to resolve that name.
8581 If the number of queries exceed this value, <command>named</command> will
8582 assume that it is dealing with a non-responsive zone
8583 and will drop additional queries. If it gets a response
8584 after dropping queries, it will raise the estimate. The
8585 estimate will then be lowered in 20 minutes if it has
8589 If <command>clients-per-query</command> is set to zero,
8590 then there is no limit on the number of clients per query
8591 and no queries will be dropped.
8594 If <command>max-clients-per-query</command> is set to zero,
8595 then there is no upper bound other than imposed by
8596 <command>recursive-clients</command>.
8602 <term><command>notify-delay</command></term>
8605 The delay, in seconds, between sending sets of notify
8606 messages for a zone. The default is five (5) seconds.
8614 <sect3 id="builtin">
8615 <title>Built-in server information zones</title>
8618 The server provides some helpful diagnostic information
8619 through a number of built-in zones under the
8620 pseudo-top-level-domain <literal>bind</literal> in the
8621 <command>CHAOS</command> class. These zones are part
8623 built-in view (see <xref linkend="view_statement_grammar"/>) of
8625 <command>CHAOS</command> which is separate from the
8627 class <command>IN</command>; therefore, any global
8629 such as <command>allow-query</command> do not apply
8631 If you feel the need to disable these zones, use the options
8632 below, or hide the built-in <command>CHAOS</command>
8634 defining an explicit view of class <command>CHAOS</command>
8635 that matches all clients.
8641 <term><command>version</command></term>
8644 The version the server should report
8645 via a query of the name <literal>version.bind</literal>
8646 with type <command>TXT</command>, class <command>CHAOS</command>.
8647 The default is the real version number of this server.
8648 Specifying <command>version none</command>
8649 disables processing of the queries.
8655 <term><command>hostname</command></term>
8658 The hostname the server should report via a query of
8659 the name <filename>hostname.bind</filename>
8660 with type <command>TXT</command>, class <command>CHAOS</command>.
8661 This defaults to the hostname of the machine hosting the
8663 found by the gethostname() function. The primary purpose of such queries
8665 identify which of a group of anycast servers is actually
8666 answering your queries. Specifying <command>hostname none;</command>
8667 disables processing of the queries.
8673 <term><command>server-id</command></term>
8676 The ID the server should report when receiving a Name
8677 Server Identifier (NSID) query, or a query of the name
8678 <filename>ID.SERVER</filename> with type
8679 <command>TXT</command>, class <command>CHAOS</command>.
8680 The primary purpose of such queries is to
8681 identify which of a group of anycast servers is actually
8682 answering your queries. Specifying <command>server-id none;</command>
8683 disables processing of the queries.
8684 Specifying <command>server-id hostname;</command> will cause <command>named</command> to
8685 use the hostname as found by the gethostname() function.
8686 The default <command>server-id</command> is <command>none</command>.
8696 <title>Built-in Empty Zones</title>
8698 Named has some built-in empty zones (SOA and NS records only).
8699 These are for zones that should normally be answered locally
8700 and which queries should not be sent to the Internet's root
8701 servers. The official servers which cover these namespaces
8702 return NXDOMAIN responses to these queries. In particular,
8703 these cover the reverse namespace for addresses from RFC 1918 and
8704 RFC 3330. They also include the reverse namespace for IPv6 local
8705 address (locally assigned), IPv6 link local addresses, the IPv6
8706 loopback address and the IPv6 unknown address.
8709 Named will attempt to determine if a built-in zone already exists
8710 or is active (covered by a forward-only forwarding declaration)
8711 and will not create an empty zone in that case.
8714 The current list of empty zones is:
8716 <!-- XXX: The RFC1918 addresses are #defined out in sources currently.
8717 <listitem>10.IN-ADDR.ARPA</listitem>
8718 <listitem>16.172.IN-ADDR.ARPA</listitem>
8719 <listitem>17.172.IN-ADDR.ARPA</listitem>
8720 <listitem>18.172.IN-ADDR.ARPA</listitem>
8721 <listitem>19.172.IN-ADDR.ARPA</listitem>
8722 <listitem>20.172.IN-ADDR.ARPA</listitem>
8723 <listitem>21.172.IN-ADDR.ARPA</listitem>
8724 <listitem>22.172.IN-ADDR.ARPA</listitem>
8725 <listitem>23.172.IN-ADDR.ARPA</listitem>
8726 <listitem>24.172.IN-ADDR.ARPA</listitem>
8727 <listitem>25.172.IN-ADDR.ARPA</listitem>
8728 <listitem>26.172.IN-ADDR.ARPA</listitem>
8729 <listitem>27.172.IN-ADDR.ARPA</listitem>
8730 <listitem>28.172.IN-ADDR.ARPA</listitem>
8731 <listitem>29.172.IN-ADDR.ARPA</listitem>
8732 <listitem>30.172.IN-ADDR.ARPA</listitem>
8733 <listitem>31.172.IN-ADDR.ARPA</listitem>
8734 <listitem>168.192.IN-ADDR.ARPA</listitem>
8735 XXX: end of RFC1918 addresses #defined out -->
8736 <listitem>0.IN-ADDR.ARPA</listitem>
8737 <listitem>127.IN-ADDR.ARPA</listitem>
8738 <listitem>254.169.IN-ADDR.ARPA</listitem>
8739 <listitem>2.0.192.IN-ADDR.ARPA</listitem>
8740 <listitem>255.255.255.255.IN-ADDR.ARPA</listitem>
8741 <listitem>0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</listitem>
8742 <listitem>1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</listitem>
8743 <listitem>D.F.IP6.ARPA</listitem>
8744 <listitem>8.E.F.IP6.ARPA</listitem>
8745 <listitem>9.E.F.IP6.ARPA</listitem>
8746 <listitem>A.E.F.IP6.ARPA</listitem>
8747 <listitem>B.E.F.IP6.ARPA</listitem>
8751 Empty zones are settable at the view level and only apply to
8752 views of class IN. Disabled empty zones are only inherited
8753 from options if there are no disabled empty zones specified
8754 at the view level. To override the options list of disabled
8755 zones, you can disable the root zone at the view level, for example:
8757 disable-empty-zone ".";
8761 If you are using the address ranges covered here, you should
8762 already have reverse zones covering the addresses you use.
8763 In practice this appears to not be the case with many queries
8764 being made to the infrastructure servers for names in these
8765 spaces. So many in fact that sacrificial servers were needed
8766 to be deployed to channel the query load away from the
8767 infrastructure servers.
8770 The real parent servers for these zones should disable all
8771 empty zone under the parent zone they serve. For the real
8772 root servers, this is all built-in empty zones. This will
8773 enable them to return referrals to deeper in the tree.
8777 <term><command>empty-server</command></term>
8780 Specify what server name will appear in the returned
8781 SOA record for empty zones. If none is specified, then
8782 the zone's name will be used.
8788 <term><command>empty-contact</command></term>
8791 Specify what contact name will appear in the returned
8792 SOA record for empty zones. If none is specified, then
8799 <term><command>empty-zones-enable</command></term>
8802 Enable or disable all empty zones. By default, they
8809 <term><command>disable-empty-zone</command></term>
8812 Disable individual empty zones. By default, none are
8813 disabled. This option can be specified multiple times.
8821 <title>Additional Section Caching</title>
8824 The additional section cache, also called <command>acache</command>,
8825 is an internal cache to improve the response performance of BIND 9.
8826 When additional section caching is enabled, BIND 9 will
8827 cache an internal short-cut to the additional section content for
8829 Note that <command>acache</command> is an internal caching
8830 mechanism of BIND 9, and is not related to the DNS caching
8835 Additional section caching does not change the
8836 response content (except the RRsets ordering of the additional
8837 section, see below), but can improve the response performance
8839 It is particularly effective when BIND 9 acts as an authoritative
8840 server for a zone that has many delegations with many glue RRs.
8844 In order to obtain the maximum performance improvement
8845 from additional section caching, setting
8846 <command>additional-from-cache</command>
8847 to <command>no</command> is recommended, since the current
8848 implementation of <command>acache</command>
8849 does not short-cut of additional section information from the
8854 One obvious disadvantage of <command>acache</command> is
8855 that it requires much more
8856 memory for the internal cached data.
8857 Thus, if the response performance does not matter and memory
8858 consumption is much more critical, the
8859 <command>acache</command> mechanism can be
8860 disabled by setting <command>acache-enable</command> to
8861 <command>no</command>.
8862 It is also possible to specify the upper limit of memory
8864 for acache by using <command>max-acache-size</command>.
8868 Additional section caching also has a minor effect on the
8869 RRset ordering in the additional section.
8870 Without <command>acache</command>,
8871 <command>cyclic</command> order is effective for the additional
8872 section as well as the answer and authority sections.
8873 However, additional section caching fixes the ordering when it
8874 first caches an RRset for the additional section, and the same
8875 ordering will be kept in succeeding responses, regardless of the
8876 setting of <command>rrset-order</command>.
8877 The effect of this should be minor, however, since an
8878 RRset in the additional section
8879 typically only contains a small number of RRs (and in many cases
8880 it only contains a single RR), in which case the
8881 ordering does not matter much.
8885 The following is a summary of options related to
8886 <command>acache</command>.
8892 <term><command>acache-enable</command></term>
8895 If <command>yes</command>, additional section caching is
8896 enabled. The default value is <command>no</command>.
8902 <term><command>acache-cleaning-interval</command></term>
8905 The server will remove stale cache entries, based on an LRU
8907 algorithm, every <command>acache-cleaning-interval</command> minutes.
8908 The default is 60 minutes.
8909 If set to 0, no periodic cleaning will occur.
8915 <term><command>max-acache-size</command></term>
8918 The maximum amount of memory in bytes to use for the server's acache.
8919 When the amount of data in the acache reaches this limit,
8921 will clean more aggressively so that the limit is not
8923 In a server with multiple views, the limit applies
8925 acache of each view.
8926 The default is <literal>16M</literal>.
8936 <title>Content Filtering</title>
8938 <acronym>BIND</acronym> 9 provides the ability to filter
8939 out DNS responses from external DNS servers containing
8940 certain types of data in the answer section.
8941 Specifically, it can reject address (A or AAAA) records if
8942 the corresponding IPv4 or IPv6 addresses match the given
8943 <varname>address_match_list</varname> of the
8944 <command>deny-answer-addresses</command> option.
8945 It can also reject CNAME or DNAME records if the "alias"
8946 name (i.e., the CNAME alias or the substituted query name
8947 due to DNAME) matches the
8948 given <varname>namelist</varname> of the
8949 <command>deny-answer-aliases</command> option, where
8950 "match" means the alias name is a subdomain of one of
8951 the <varname>name_list</varname> elements.
8952 If the optional <varname>namelist</varname> is specified
8953 with <command>except-from</command>, records whose query name
8954 matches the list will be accepted regardless of the filter
8956 Likewise, if the alias name is a subdomain of the
8957 corresponding zone, the <command>deny-answer-aliases</command>
8958 filter will not apply;
8959 for example, even if "example.com" is specified for
8960 <command>deny-answer-aliases</command>,
8962 <programlisting>www.example.com. CNAME xxx.example.com.</programlisting>
8965 returned by an "example.com" server will be accepted.
8969 In the <varname>address_match_list</varname> of the
8970 <command>deny-answer-addresses</command> option, only
8971 <varname>ip_addr</varname>
8972 and <varname>ip_prefix</varname>
8974 any <varname>key_id</varname> will be silently ignored.
8978 If a response message is rejected due to the filtering,
8979 the entire message is discarded without being cached, and
8980 a SERVFAIL error will be returned to the client.
8984 This filtering is intended to prevent "DNS rebinding attacks," in
8985 which an attacker, in response to a query for a domain name the
8986 attacker controls, returns an IP address within your own network or
8987 an alias name within your own domain.
8988 A naive web browser or script could then serve as an
8989 unintended proxy, allowing the attacker
8990 to get access to an internal node of your local network
8991 that couldn't be externally accessed otherwise.
8992 See the paper available at
8994 http://portal.acm.org/citation.cfm?id=1315245.1315298
8996 for more details about the attacks.
9000 For example, if you own a domain named "example.net" and
9001 your internal network uses an IPv4 prefix 192.0.2.0/24,
9002 you might specify the following rules:
9005 <programlisting>deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
9006 deny-answer-aliases { "example.net"; };
9010 If an external attacker lets a web browser in your local
9011 network look up an IPv4 address of "attacker.example.com",
9012 the attacker's DNS server would return a response like this:
9015 <programlisting>attacker.example.com. A 192.0.2.1</programlisting>
9018 in the answer section.
9019 Since the rdata of this record (the IPv4 address) matches
9020 the specified prefix 192.0.2.0/24, this response will be
9025 On the other hand, if the browser looks up a legitimate
9026 internal web server "www.example.net" and the
9027 following response is returned to
9028 the <acronym>BIND</acronym> 9 server
9031 <programlisting>www.example.net. A 192.0.2.2</programlisting>
9034 it will be accepted since the owner name "www.example.net"
9035 matches the <command>except-from</command> element,
9040 Note that this is not really an attack on the DNS per se.
9041 In fact, there is nothing wrong for an "external" name to
9042 be mapped to your "internal" IP address or domain name
9043 from the DNS point of view.
9044 It might actually be provided for a legitimate purpose,
9045 such as for debugging.
9046 As long as the mapping is provided by the correct owner,
9047 it is not possible or does not make sense to detect
9048 whether the intent of the mapping is legitimate or not
9050 The "rebinding" attack must primarily be protected at the
9051 application that uses the DNS.
9052 For a large site, however, it may be difficult to protect
9053 all possible applications at once.
9054 This filtering feature is provided only to help such an
9055 operational environment;
9056 it is generally discouraged to turn it on unless you are
9057 very sure you have no other choice and the attack is a
9058 real threat for your applications.
9062 Care should be particularly taken if you want to use this
9063 option for addresses within 127.0.0.0/8.
9064 These addresses are obviously "internal", but many
9065 applications conventionally rely on a DNS mapping from
9066 some name to such an address.
9067 Filtering out DNS records containing this address
9068 spuriously can break such applications.
9073 <sect2 id="server_statement_grammar">
9074 <title><command>server</command> Statement Grammar</title>
9076 <programlisting><command>server</command> <replaceable>ip_addr[/prefixlen]</replaceable> {
9077 <optional> bogus <replaceable>yes_or_no</replaceable> ; </optional>
9078 <optional> provide-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9079 <optional> request-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9080 <optional> edns <replaceable>yes_or_no</replaceable> ; </optional>
9081 <optional> edns-udp-size <replaceable>number</replaceable> ; </optional>
9082 <optional> max-udp-size <replaceable>number</replaceable> ; </optional>
9083 <optional> transfers <replaceable>number</replaceable> ; </optional>
9084 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable> ; ]</optional>
9085 <optional> keys <replaceable>{ string ; <optional> string ; <optional>...</optional></optional> }</replaceable> ; </optional>
9086 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9087 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9088 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9089 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9090 <optional> query-source <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9091 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9092 <optional> query-source-v6 <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9093 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9094 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
9095 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
9096 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
9102 <sect2 id="server_statement_definition_and_usage">
9103 <title><command>server</command> Statement Definition and
9107 The <command>server</command> statement defines
9109 to be associated with a remote name server. If a prefix length is
9110 specified, then a range of servers is covered. Only the most
9112 server clause applies regardless of the order in
9113 <filename>named.conf</filename>.
9117 The <command>server</command> statement can occur at
9118 the top level of the
9119 configuration file or inside a <command>view</command>
9121 If a <command>view</command> statement contains
9122 one or more <command>server</command> statements, only
9124 apply to the view and any top-level ones are ignored.
9125 If a view contains no <command>server</command>
9127 any top-level <command>server</command> statements are
9133 If you discover that a remote server is giving out bad data,
9134 marking it as bogus will prevent further queries to it. The
9136 value of <command>bogus</command> is <command>no</command>.
9139 The <command>provide-ixfr</command> clause determines
9141 the local server, acting as master, will respond with an
9143 zone transfer when the given remote server, a slave, requests it.
9144 If set to <command>yes</command>, incremental transfer
9146 whenever possible. If set to <command>no</command>,
9148 to the remote server will be non-incremental. If not set, the
9150 of the <command>provide-ixfr</command> option in the
9152 global options block is used as a default.
9156 The <command>request-ixfr</command> clause determines
9158 the local server, acting as a slave, will request incremental zone
9159 transfers from the given remote server, a master. If not set, the
9160 value of the <command>request-ixfr</command> option in
9162 global options block is used as a default.
9166 IXFR requests to servers that do not support IXFR will
9168 fall back to AXFR. Therefore, there is no need to manually list
9169 which servers support IXFR and which ones do not; the global
9171 of <command>yes</command> should always work.
9172 The purpose of the <command>provide-ixfr</command> and
9173 <command>request-ixfr</command> clauses is
9174 to make it possible to disable the use of IXFR even when both
9176 and slave claim to support it, for example if one of the servers
9177 is buggy and crashes or corrupts data when IXFR is used.
9181 The <command>edns</command> clause determines whether
9182 the local server will attempt to use EDNS when communicating
9183 with the remote server. The default is <command>yes</command>.
9187 The <command>edns-udp-size</command> option sets the EDNS UDP size
9188 that is advertised by <command>named</command> when querying the remote server.
9189 Valid values are 512 to 4096 bytes (values outside this range will be
9190 silently adjusted). This option is useful when you wish to
9191 advertises a different value to this server than the value you
9192 advertise globally, for example, when there is a firewall at the
9193 remote site that is blocking large replies.
9197 The <command>max-udp-size</command> option sets the
9198 maximum EDNS UDP message size <command>named</command> will send. Valid
9199 values are 512 to 4096 bytes (values outside this range will
9200 be silently adjusted). This option is useful when you
9201 know that there is a firewall that is blocking large
9202 replies from <command>named</command>.
9206 The server supports two zone transfer methods. The first, <command>one-answer</command>,
9207 uses one DNS message per resource record transferred. <command>many-answers</command> packs
9208 as many resource records as possible into a message. <command>many-answers</command> is
9209 more efficient, but is only known to be understood by <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
9210 8.x, and patched versions of <acronym>BIND</acronym>
9211 4.9.5. You can specify which method
9212 to use for a server with the <command>transfer-format</command> option.
9213 If <command>transfer-format</command> is not
9214 specified, the <command>transfer-format</command>
9216 by the <command>options</command> statement will be
9220 <para><command>transfers</command>
9221 is used to limit the number of concurrent inbound zone
9222 transfers from the specified server. If no
9223 <command>transfers</command> clause is specified, the
9224 limit is set according to the
9225 <command>transfers-per-ns</command> option.
9229 The <command>keys</command> clause identifies a
9230 <command>key_id</command> defined by the <command>key</command> statement,
9231 to be used for transaction security (TSIG, <xref linkend="tsig"/>)
9232 when talking to the remote server.
9233 When a request is sent to the remote server, a request signature
9234 will be generated using the key specified here and appended to the
9235 message. A request originating from the remote server is not
9237 to be signed by this key.
9241 Although the grammar of the <command>keys</command>
9243 allows for multiple keys, only a single key per server is
9249 The <command>transfer-source</command> and
9250 <command>transfer-source-v6</command> clauses specify
9251 the IPv4 and IPv6 source
9252 address to be used for zone transfer with the remote server,
9254 For an IPv4 remote server, only <command>transfer-source</command> can
9256 Similarly, for an IPv6 remote server, only
9257 <command>transfer-source-v6</command> can be
9259 For more details, see the description of
9260 <command>transfer-source</command> and
9261 <command>transfer-source-v6</command> in
9262 <xref linkend="zone_transfers"/>.
9266 The <command>notify-source</command> and
9267 <command>notify-source-v6</command> clauses specify the
9268 IPv4 and IPv6 source address to be used for notify
9269 messages sent to remote servers, respectively. For an
9270 IPv4 remote server, only <command>notify-source</command>
9271 can be specified. Similarly, for an IPv6 remote server,
9272 only <command>notify-source-v6</command> can be specified.
9276 The <command>query-source</command> and
9277 <command>query-source-v6</command> clauses specify the
9278 IPv4 and IPv6 source address to be used for queries
9279 sent to remote servers, respectively. For an IPv4
9280 remote server, only <command>query-source</command> can
9281 be specified. Similarly, for an IPv6 remote server,
9282 only <command>query-source-v6</command> can be specified.
9287 <sect2 id="statschannels">
9288 <title><command>statistics-channels</command> Statement Grammar</title>
9290 <programlisting><command>statistics-channels</command> {
9291 [ inet ( ip_addr | * ) [ port ip_port ]
9292 [ allow { <replaceable> address_match_list </replaceable> } ]; ]
9299 <title><command>statistics-channels</command> Statement Definition and
9303 The <command>statistics-channels</command> statement
9304 declares communication channels to be used by system
9305 administrators to get access to statistics information of
9310 This statement intends to be flexible to support multiple
9311 communication protocols in the future, but currently only
9312 HTTP access is supported.
9313 It requires that BIND 9 be compiled with libxml2;
9314 the <command>statistics-channels</command> statement is
9315 still accepted even if it is built without the library,
9316 but any HTTP access will fail with an error.
9320 An <command>inet</command> control channel is a TCP socket
9321 listening at the specified <command>ip_port</command> on the
9322 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
9323 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
9324 interpreted as the IPv4 wildcard address; connections will be
9325 accepted on any of the system's IPv4 addresses.
9326 To listen on the IPv6 wildcard address,
9327 use an <command>ip_addr</command> of <literal>::</literal>.
9331 If no port is specified, port 80 is used for HTTP channels.
9332 The asterisk "<literal>*</literal>" cannot be used for
9333 <command>ip_port</command>.
9337 The attempt of opening a statistics channel is
9338 restricted by the optional <command>allow</command> clause.
9339 Connections to the statistics channel are permitted based on the
9340 <command>address_match_list</command>.
9341 If no <command>allow</command> clause is present,
9342 <command>named</command> accepts connection
9343 attempts from any address; since the statistics may
9344 contain sensitive internal information, it is highly
9345 recommended to restrict the source of connection requests
9350 If no <command>statistics-channels</command> statement is present,
9351 <command>named</command> will not open any communication channels.
9356 <sect2 id="trusted-keys">
9357 <title><command>trusted-keys</command> Statement Grammar</title>
9359 <programlisting><command>trusted-keys</command> {
9360 <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9361 <optional> <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9367 <title><command>trusted-keys</command> Statement Definition
9370 The <command>trusted-keys</command> statement defines
9371 DNSSEC security roots. DNSSEC is described in <xref
9372 linkend="DNSSEC"/>. A security root is defined when the
9373 public key for a non-authoritative zone is known, but
9374 cannot be securely obtained through DNS, either because
9375 it is the DNS root zone or because its parent zone is
9376 unsigned. Once a key has been configured as a trusted
9377 key, it is treated as if it had been validated and
9378 proven secure. The resolver attempts DNSSEC validation
9379 on all DNS data in subdomains of a security root.
9382 All keys (and corresponding zones) listed in
9383 <command>trusted-keys</command> are deemed to exist regardless
9384 of what parent zones say. Similarly for all keys listed in
9385 <command>trusted-keys</command> only those keys are
9386 used to validate the DNSKEY RRset. The parent's DS RRset
9390 The <command>trusted-keys</command> statement can contain
9391 multiple key entries, each consisting of the key's
9392 domain name, flags, protocol, algorithm, and the Base-64
9393 representation of the key data.
9394 Spaces, tabs, newlines and carriage returns are ignored
9395 in the key data, so the configuration may be split up into
9399 <command>trusted-keys</command> may be set at the top level
9400 of <filename>named.conf</filename> or within a view. If it is
9401 set in both places, they are additive: keys defined at the top
9402 level are inherited by all views, but keys defined in a view
9403 are only used within that view.
9408 <title><command>managed-keys</command> Statement Grammar</title>
9410 <programlisting><command>managed-keys</command> {
9411 <replaceable>string</replaceable> initial-key <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9412 <optional> <replaceable>string</replaceable> initial-key <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9417 <sect2 id="managed-keys">
9418 <title><command>managed-keys</command> Statement Definition
9421 The <command>managed-keys</command> statement, like
9422 <command>trusted-keys</command>, defines DNSSEC
9423 security roots. The difference is that
9424 <command>managed-keys</command> can be kept up to date
9425 automatically, without intervention from the resolver
9429 Suppose, for example, that a zone's key-signing
9430 key was compromised, and the zone owner had to revoke and
9431 replace the key. A resolver which had the old key in a
9432 <command>trusted-keys</command> statement would be
9433 unable to validate this zone any longer; it would
9434 reply with a SERVFAIL response code. This would
9435 continue until the resolver operator had updated the
9436 <command>trusted-keys</command> statement with the new key.
9439 If, however, the zone were listed in a
9440 <command>managed-keys</command> statement instead, then the
9441 zone owner could add a "stand-by" key to the zone in advance.
9442 <command>named</command> would store the stand-by key, and
9443 when the original key was revoked, <command>named</command>
9444 would be able to transition smoothly to the new key. It would
9445 also recognize that the old key had been revoked, and cease
9446 using that key to validate answers, minimizing the damage that
9447 the compromised key could do.
9450 A <command>managed-keys</command> statement contains a list of
9451 the keys to be managed, along with information about how the
9452 keys are to be initialized for the first time. The only
9453 initialization method currently supported (as of
9454 <acronym>BIND</acronym> 9.7.0) is <literal>initial-key</literal>.
9455 This means the <command>managed-keys</command> statement must
9456 contain a copy of the initializing key. (Future releases may
9457 allow keys to be initialized by other methods, eliminating this
9461 Consequently, a <command>managed-keys</command> statement
9462 appears similar to a <command>trusted-keys</command>, differing
9463 in the presence of the second field, containing the keyword
9464 <literal>initial-key</literal>. The difference is, whereas the
9465 keys listed in a <command>trusted-keys</command> continue to be
9466 trusted until they are removed from
9467 <filename>named.conf</filename>, an initializing key listed
9468 in a <command>managed-keys</command> statement is only trusted
9469 <emphasis>once</emphasis>: for as long as it takes to load the
9470 managed key database and start the RFC 5011 key maintenance
9474 The first time <command>named</command> runs with a managed key
9475 configured in <filename>named.conf</filename>, it fetches the
9476 DNSKEY RRset directly from the zone apex, and validates it
9477 using the key specified in the <command>managed-keys</command>
9478 statement. If the DNSKEY RRset is validly signed, then it is
9479 used as the basis for a new managed keys database.
9482 From that point on, whenever <command>named</command> runs, it
9483 sees the <command>managed-keys</command> statement, checks to
9484 make sure RFC 5011 key maintenance has already been initialized
9485 for the specified domain, and if so, it simply moves on. The
9486 key specified in the <command>managed-keys</command> is not
9487 used to validate answers; it has been superseded by the key or
9488 keys stored in the managed keys database.
9491 The next time <command>named</command> runs after a name
9492 has been <emphasis>removed</emphasis> from the
9493 <command>managed-keys</command> statement, the corresponding
9494 zone will be removed from the managed keys database,
9495 and RFC 5011 key maintenance will no longer be used for that
9499 <command>named</command> only maintains a single managed keys
9500 database; consequently, unlike <command>trusted-keys</command>,
9501 <command>managed-keys</command> may only be set at the top
9502 level of <filename>named.conf</filename>, not within a view.
9505 In the current implementation, the managed keys database is
9506 stored as a master-format zone file called
9507 <filename>managed-keys.bind</filename>. When the key database
9508 is changed, the zone is updated. As with any other dynamic
9509 zone, changes will be written into a journal file,
9510 <filename>managed-keys.bind.jnl</filename>. They are committed
9511 to the master file as soon as possible afterward; in the case
9512 of the managed key database, this will usually occur within 30
9513 seconds. So, whenever <command>named</command> is using
9514 automatic key maintenace, those two files can be expected to
9515 exist in the working directory. (For this reason among others,
9516 the working directory should be always be writable by
9517 <command>named</command>.)
9520 If the <command>dnssec-lookaside</command> option is
9521 set to <userinput>auto</userinput>, <command>named</command>
9522 will automatically initialize a managed key for the
9523 zone <literal>dlv.isc.org</literal>. The key that is
9524 used to initialize the key maintenance process is built
9525 into <command>named</command>, and can be overridden
9526 from <command>bindkeys-file</command>.
9530 <sect2 id="view_statement_grammar">
9531 <title><command>view</command> Statement Grammar</title>
9533 <programlisting><command>view</command> <replaceable>view_name</replaceable>
9534 <optional><replaceable>class</replaceable></optional> {
9535 match-clients { <replaceable>address_match_list</replaceable> };
9536 match-destinations { <replaceable>address_match_list</replaceable> };
9537 match-recursive-only <replaceable>yes_or_no</replaceable> ;
9538 <optional> <replaceable>view_option</replaceable>; ...</optional>
9539 <optional> <replaceable>zone_statement</replaceable>; ...</optional>
9545 <title><command>view</command> Statement Definition and Usage</title>
9548 The <command>view</command> statement is a powerful
9550 of <acronym>BIND</acronym> 9 that lets a name server
9551 answer a DNS query differently
9552 depending on who is asking. It is particularly useful for
9554 split DNS setups without having to run multiple servers.
9558 Each <command>view</command> statement defines a view
9560 DNS namespace that will be seen by a subset of clients. A client
9562 a view if its source IP address matches the
9563 <varname>address_match_list</varname> of the view's
9564 <command>match-clients</command> clause and its
9565 destination IP address matches
9566 the <varname>address_match_list</varname> of the
9568 <command>match-destinations</command> clause. If not
9570 <command>match-clients</command> and <command>match-destinations</command>
9571 default to matching all addresses. In addition to checking IP
9573 <command>match-clients</command> and <command>match-destinations</command>
9574 can also take <command>keys</command> which provide an
9576 client to select the view. A view can also be specified
9577 as <command>match-recursive-only</command>, which
9578 means that only recursive
9579 requests from matching clients will match that view.
9580 The order of the <command>view</command> statements is
9582 a client request will be resolved in the context of the first
9583 <command>view</command> that it matches.
9587 Zones defined within a <command>view</command>
9589 only be accessible to clients that match the <command>view</command>.
9590 By defining a zone of the same name in multiple views, different
9591 zone data can be given to different clients, for example,
9593 and "external" clients in a split DNS setup.
9597 Many of the options given in the <command>options</command> statement
9598 can also be used within a <command>view</command>
9600 apply only when resolving queries with that view. When no
9602 value is given, the value in the <command>options</command> statement
9603 is used as a default. Also, zone options can have default values
9605 in the <command>view</command> statement; these
9606 view-specific defaults
9607 take precedence over those in the <command>options</command> statement.
9611 Views are class specific. If no class is given, class IN
9612 is assumed. Note that all non-IN views must contain a hint zone,
9613 since only the IN class has compiled-in default hints.
9617 If there are no <command>view</command> statements in
9619 file, a default view that matches any client is automatically
9621 in class IN. Any <command>zone</command> statements
9623 the top level of the configuration file are considered to be part
9625 this default view, and the <command>options</command>
9627 apply to the default view. If any explicit <command>view</command>
9628 statements are present, all <command>zone</command>
9630 occur inside <command>view</command> statements.
9634 Here is an example of a typical split DNS setup implemented
9635 using <command>view</command> statements:
9638 <programlisting>view "internal" {
9639 // This should match our internal networks.
9640 match-clients { 10.0.0.0/8; };
9642 // Provide recursive service to internal
9646 // Provide a complete view of the example.com
9647 // zone including addresses of internal hosts.
9648 zone "example.com" {
9650 file "example-internal.db";
9655 // Match all clients not matched by the
9657 match-clients { any; };
9659 // Refuse recursive service to external clients.
9662 // Provide a restricted view of the example.com
9663 // zone containing only publicly accessible hosts.
9664 zone "example.com" {
9666 file "example-external.db";
9672 <sect2 id="zone_statement_grammar">
9673 <title><command>zone</command>
9674 Statement Grammar</title>
9676 <programlisting><command>zone</command> <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9678 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
9679 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
9680 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
9681 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
9682 <optional> update-policy <replaceable>local</replaceable> | { <replaceable>update_policy_rule</replaceable> <optional>...</optional> }; </optional>
9683 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
9684 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9685 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
9686 <optional> check-mx (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
9687 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
9688 <optional> check-integrity <replaceable>yes_or_no</replaceable> ; </optional>
9689 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
9690 <optional> file <replaceable>string</replaceable> ; </optional>
9691 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
9692 <optional> journal <replaceable>string</replaceable> ; </optional>
9693 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
9694 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
9695 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9696 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
9697 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
9698 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
9699 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
9700 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
9701 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
9702 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
9703 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
9704 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
9705 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
9706 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
9707 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9708 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9709 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
9710 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
9711 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
9712 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
9713 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
9714 <optional> database <replaceable>string</replaceable> ; </optional>
9715 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
9716 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
9717 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
9718 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
9719 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
9720 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>create</constant>|<constant>off</constant>; </optional>
9721 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
9724 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9726 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
9727 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
9728 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
9729 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
9730 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
9731 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
9732 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
9733 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ; </optional>
9734 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
9735 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
9736 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9737 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
9738 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
9739 <optional> file <replaceable>string</replaceable> ; </optional>
9740 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
9741 <optional> journal <replaceable>string</replaceable> ; </optional>
9742 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
9743 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
9744 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9745 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
9746 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
9747 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
9748 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
9749 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
9750 <optional>port <replaceable>ip_port</replaceable></optional>
9751 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
9752 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
9753 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
9754 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
9755 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
9756 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
9757 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
9758 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
9759 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
9760 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
9761 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9762 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9763 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9764 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
9765 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9766 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
9767 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9768 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9769 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
9770 <optional> database <replaceable>string</replaceable> ; </optional>
9771 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
9772 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
9773 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
9774 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
9775 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
9776 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
9779 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9781 file <replaceable>string</replaceable> ;
9782 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
9783 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional> // Not Implemented.
9786 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9788 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
9789 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
9790 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
9791 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
9792 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
9793 <optional> file <replaceable>string</replaceable> ; </optional>
9794 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
9795 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
9796 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9797 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
9798 <optional>port <replaceable>ip_port</replaceable></optional>
9799 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
9800 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
9801 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
9802 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
9803 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9804 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
9805 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9806 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9807 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
9808 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9809 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
9810 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
9811 <optional> database <replaceable>string</replaceable> ; </optional>
9812 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
9813 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
9814 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
9815 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
9816 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
9819 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9821 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
9822 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9823 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
9826 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9827 type delegation-only;
9834 <title><command>zone</command> Statement Definition and Usage</title>
9836 <title>Zone Types</title>
9837 <informaltable colsep="0" rowsep="0">
9838 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
9839 <!--colspec colname="1" colnum="1" colsep="0" colwidth="1.108in"/-->
9840 <!--colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/-->
9841 <colspec colname="1" colnum="1" colsep="0"/>
9842 <colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/>
9847 <varname>master</varname>
9852 The server has a master copy of the data
9853 for the zone and will be able to provide authoritative
9862 <varname>slave</varname>
9867 A slave zone is a replica of a master
9868 zone. The <command>masters</command> list
9869 specifies one or more IP addresses
9870 of master servers that the slave contacts to update
9871 its copy of the zone.
9872 Masters list elements can also be names of other
9874 By default, transfers are made from port 53 on the
9876 be changed for all servers by specifying a port number
9878 list of IP addresses, or on a per-server basis after
9880 Authentication to the master can also be done with
9881 per-server TSIG keys.
9882 If a file is specified, then the
9883 replica will be written to this file whenever the zone
9885 and reloaded from this file on a server restart. Use
9887 recommended, since it often speeds server startup and
9889 a needless waste of bandwidth. Note that for large
9891 tens or hundreds of thousands) of zones per server, it
9893 use a two-level naming scheme for zone filenames. For
9895 a slave server for the zone <literal>example.com</literal> might place
9896 the zone contents into a file called
9897 <filename>ex/example.com</filename> where <filename>ex/</filename> is
9898 just the first two letters of the zone name. (Most
9900 behave very slowly if you put 100000 files into
9901 a single directory.)
9908 <varname>stub</varname>
9913 A stub zone is similar to a slave zone,
9914 except that it replicates only the NS records of a
9916 of the entire zone. Stub zones are not a standard part
9918 they are a feature specific to the <acronym>BIND</acronym> implementation.
9922 Stub zones can be used to eliminate the need for glue
9924 in a parent zone at the expense of maintaining a stub
9926 a set of name server addresses in <filename>named.conf</filename>.
9927 This usage is not recommended for new configurations,
9929 supports it only in a limited way.
9930 In <acronym>BIND</acronym> 4/8, zone
9931 transfers of a parent zone
9932 included the NS records from stub children of that
9934 that, in some cases, users could get away with
9935 configuring child stubs
9936 only in the master server for the parent zone. <acronym>BIND</acronym>
9937 9 never mixes together zone data from different zones
9939 way. Therefore, if a <acronym>BIND</acronym> 9 master serving a parent
9940 zone has child stub zones configured, all the slave
9942 parent zone also need to have the same child stub
9948 Stub zones can also be used as a way of forcing the
9950 of a given domain to use a particular set of
9951 authoritative servers.
9952 For example, the caching name servers on a private
9954 RFC1918 addressing may be configured with stub zones
9956 <literal>10.in-addr.arpa</literal>
9957 to use a set of internal name servers as the
9959 servers for that domain.
9966 <varname>forward</varname>
9971 A "forward zone" is a way to configure
9972 forwarding on a per-domain basis. A <command>zone</command> statement
9973 of type <command>forward</command> can
9974 contain a <command>forward</command>
9975 and/or <command>forwarders</command>
9977 which will apply to queries within the domain given by
9979 name. If no <command>forwarders</command>
9980 statement is present or
9981 an empty list for <command>forwarders</command> is given, then no
9982 forwarding will be done for the domain, canceling the
9984 any forwarders in the <command>options</command> statement. Thus
9985 if you want to use this type of zone to change the
9987 global <command>forward</command> option
9988 (that is, "forward first"
9989 to, then "forward only", or vice versa, but want to
9991 servers as set globally) you need to re-specify the
9999 <varname>hint</varname>
10002 <entry colname="2">
10004 The initial set of root name servers is
10005 specified using a "hint zone". When the server starts
10007 the root hints to find a root name server and get the
10009 list of root name servers. If no hint zone is
10010 specified for class
10011 IN, the server uses a compiled-in default set of root
10013 Classes other than IN have no built-in defaults hints.
10018 <entry colname="1">
10020 <varname>delegation-only</varname>
10023 <entry colname="2">
10025 This is used to enforce the delegation-only
10026 status of infrastructure zones (e.g. COM,
10027 NET, ORG). Any answer that is received
10028 without an explicit or implicit delegation
10029 in the authority section will be treated
10030 as NXDOMAIN. This does not apply to the
10031 zone apex. This should not be applied to
10035 <varname>delegation-only</varname> has no
10036 effect on answers received from forwarders.
10039 See caveats in <xref linkend="root_delegation_only"/>.
10049 <title>Class</title>
10051 The zone's name may optionally be followed by a class. If
10052 a class is not specified, class <literal>IN</literal> (for <varname>Internet</varname>),
10053 is assumed. This is correct for the vast majority of cases.
10056 The <literal>hesiod</literal> class is
10057 named for an information service from MIT's Project Athena. It
10059 used to share information about various systems databases, such
10060 as users, groups, printers and so on. The keyword
10061 <literal>HS</literal> is
10062 a synonym for hesiod.
10065 Another MIT development is Chaosnet, a LAN protocol created
10066 in the mid-1970s. Zone data for it can be specified with the <literal>CHAOS</literal> class.
10071 <title>Zone Options</title>
10076 <term><command>allow-notify</command></term>
10079 See the description of
10080 <command>allow-notify</command> in <xref linkend="access_control"/>.
10086 <term><command>allow-query</command></term>
10089 See the description of
10090 <command>allow-query</command> in <xref linkend="access_control"/>.
10096 <term><command>allow-query-on</command></term>
10099 See the description of
10100 <command>allow-query-on</command> in <xref linkend="access_control"/>.
10106 <term><command>allow-transfer</command></term>
10109 See the description of <command>allow-transfer</command>
10110 in <xref linkend="access_control"/>.
10116 <term><command>allow-update</command></term>
10119 See the description of <command>allow-update</command>
10120 in <xref linkend="access_control"/>.
10126 <term><command>update-policy</command></term>
10129 Specifies a "Simple Secure Update" policy. See
10130 <xref linkend="dynamic_update_policies"/>.
10136 <term><command>allow-update-forwarding</command></term>
10139 See the description of <command>allow-update-forwarding</command>
10140 in <xref linkend="access_control"/>.
10146 <term><command>also-notify</command></term>
10149 Only meaningful if <command>notify</command>
10151 active for this zone. The set of machines that will
10153 <literal>DNS NOTIFY</literal> message
10154 for this zone is made up of all the listed name servers
10156 the primary master) for the zone plus any IP addresses
10158 with <command>also-notify</command>. A port
10160 with each <command>also-notify</command>
10161 address to send the notify
10162 messages to a port other than the default of 53.
10163 <command>also-notify</command> is not
10164 meaningful for stub zones.
10165 The default is the empty list.
10171 <term><command>check-names</command></term>
10174 This option is used to restrict the character set and
10176 certain domain names in master files and/or DNS responses
10178 network. The default varies according to zone type. For <command>master</command> zones the default is <command>fail</command>. For <command>slave</command>
10179 zones the default is <command>warn</command>.
10180 It is not implemented for <command>hint</command> zones.
10186 <term><command>check-mx</command></term>
10189 See the description of
10190 <command>check-mx</command> in <xref linkend="boolean_options"/>.
10196 <term><command>check-wildcard</command></term>
10199 See the description of
10200 <command>check-wildcard</command> in <xref linkend="boolean_options"/>.
10206 <term><command>check-integrity</command></term>
10209 See the description of
10210 <command>check-integrity</command> in <xref linkend="boolean_options"/>.
10216 <term><command>check-sibling</command></term>
10219 See the description of
10220 <command>check-sibling</command> in <xref linkend="boolean_options"/>.
10226 <term><command>zero-no-soa-ttl</command></term>
10229 See the description of
10230 <command>zero-no-soa-ttl</command> in <xref linkend="boolean_options"/>.
10236 <term><command>update-check-ksk</command></term>
10239 See the description of
10240 <command>update-check-ksk</command> in <xref linkend="boolean_options"/>.
10246 <term><command>dnssec-dnskey-kskonly</command></term>
10249 See the description of
10250 <command>dnssec-dnskey-kskonly</command> in <xref linkend="boolean_options"/>.
10256 <term><command>try-tcp-refresh</command></term>
10259 See the description of
10260 <command>try-tcp-refresh</command> in <xref linkend="boolean_options"/>.
10266 <term><command>database</command></term>
10269 Specify the type of database to be used for storing the
10270 zone data. The string following the <command>database</command> keyword
10271 is interpreted as a list of whitespace-delimited words.
10273 identifies the database type, and any subsequent words are
10275 as arguments to the database to be interpreted in a way
10277 to the database type.
10280 The default is <userinput>"rbt"</userinput>, BIND 9's
10282 red-black-tree database. This database does not take
10286 Other values are possible if additional database drivers
10287 have been linked into the server. Some sample drivers are
10289 with the distribution but none are linked in by default.
10295 <term><command>dialup</command></term>
10298 See the description of
10299 <command>dialup</command> in <xref linkend="boolean_options"/>.
10305 <term><command>delegation-only</command></term>
10308 The flag only applies to hint and stub zones. If set
10309 to <userinput>yes</userinput>, then the zone will also be
10310 treated as if it is also a delegation-only type zone.
10313 See caveats in <xref linkend="root_delegation_only"/>.
10319 <term><command>forward</command></term>
10322 Only meaningful if the zone has a forwarders
10323 list. The <command>only</command> value causes
10325 after trying the forwarders and getting no answer, while <command>first</command> would
10326 allow a normal lookup to be tried.
10332 <term><command>forwarders</command></term>
10335 Used to override the list of global forwarders.
10336 If it is not specified in a zone of type <command>forward</command>,
10337 no forwarding is done for the zone and the global options are
10344 <term><command>ixfr-base</command></term>
10347 Was used in <acronym>BIND</acronym> 8 to
10349 of the transaction log (journal) file for dynamic update
10351 <acronym>BIND</acronym> 9 ignores the option
10352 and constructs the name of the journal
10353 file by appending "<filename>.jnl</filename>"
10361 <term><command>ixfr-tmp-file</command></term>
10364 Was an undocumented option in <acronym>BIND</acronym> 8.
10365 Ignored in <acronym>BIND</acronym> 9.
10371 <term><command>journal</command></term>
10374 Allow the default journal's filename to be overridden.
10375 The default is the zone's filename with "<filename>.jnl</filename>" appended.
10376 This is applicable to <command>master</command> and <command>slave</command> zones.
10382 <term><command>max-journal-size</command></term>
10385 See the description of
10386 <command>max-journal-size</command> in <xref linkend="server_resource_limits"/>.
10392 <term><command>max-transfer-time-in</command></term>
10395 See the description of
10396 <command>max-transfer-time-in</command> in <xref linkend="zone_transfers"/>.
10402 <term><command>max-transfer-idle-in</command></term>
10405 See the description of
10406 <command>max-transfer-idle-in</command> in <xref linkend="zone_transfers"/>.
10412 <term><command>max-transfer-time-out</command></term>
10415 See the description of
10416 <command>max-transfer-time-out</command> in <xref linkend="zone_transfers"/>.
10422 <term><command>max-transfer-idle-out</command></term>
10425 See the description of
10426 <command>max-transfer-idle-out</command> in <xref linkend="zone_transfers"/>.
10432 <term><command>notify</command></term>
10435 See the description of
10436 <command>notify</command> in <xref linkend="boolean_options"/>.
10442 <term><command>notify-delay</command></term>
10445 See the description of
10446 <command>notify-delay</command> in <xref linkend="tuning"/>.
10452 <term><command>notify-to-soa</command></term>
10455 See the description of
10456 <command>notify-to-soa</command> in
10457 <xref linkend="boolean_options"/>.
10463 <term><command>pubkey</command></term>
10466 In <acronym>BIND</acronym> 8, this option was
10467 intended for specifying
10468 a public zone key for verification of signatures in DNSSEC
10470 zones when they are loaded from disk. <acronym>BIND</acronym> 9 does not verify signatures
10471 on load and ignores the option.
10477 <term><command>zone-statistics</command></term>
10480 If <userinput>yes</userinput>, the server will keep
10482 information for this zone, which can be dumped to the
10483 <command>statistics-file</command> defined in
10484 the server options.
10490 <term><command>sig-validity-interval</command></term>
10493 See the description of
10494 <command>sig-validity-interval</command> in <xref linkend="tuning"/>.
10500 <term><command>sig-signing-nodes</command></term>
10503 See the description of
10504 <command>sig-signing-nodes</command> in <xref linkend="tuning"/>.
10510 <term><command>sig-signing-signatures</command></term>
10513 See the description of
10514 <command>sig-signing-signatures</command> in <xref linkend="tuning"/>.
10520 <term><command>sig-signing-type</command></term>
10523 See the description of
10524 <command>sig-signing-type</command> in <xref linkend="tuning"/>.
10530 <term><command>transfer-source</command></term>
10533 See the description of
10534 <command>transfer-source</command> in <xref linkend="zone_transfers"/>.
10540 <term><command>transfer-source-v6</command></term>
10543 See the description of
10544 <command>transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
10550 <term><command>alt-transfer-source</command></term>
10553 See the description of
10554 <command>alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
10560 <term><command>alt-transfer-source-v6</command></term>
10563 See the description of
10564 <command>alt-transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
10570 <term><command>use-alt-transfer-source</command></term>
10573 See the description of
10574 <command>use-alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
10581 <term><command>notify-source</command></term>
10584 See the description of
10585 <command>notify-source</command> in <xref linkend="zone_transfers"/>.
10591 <term><command>notify-source-v6</command></term>
10594 See the description of
10595 <command>notify-source-v6</command> in <xref linkend="zone_transfers"/>.
10601 <term><command>min-refresh-time</command></term>
10602 <term><command>max-refresh-time</command></term>
10603 <term><command>min-retry-time</command></term>
10604 <term><command>max-retry-time</command></term>
10607 See the description in <xref linkend="tuning"/>.
10613 <term><command>ixfr-from-differences</command></term>
10616 See the description of
10617 <command>ixfr-from-differences</command> in <xref linkend="boolean_options"/>.
10618 (Note that the <command>ixfr-from-differences</command>
10619 <userinput>master</userinput> and
10620 <userinput>slave</userinput> choices are not
10621 available at the zone level.)
10627 <term><command>key-directory</command></term>
10630 See the description of
10631 <command>key-directory</command> in <xref linkend="options"/>.
10637 <term><command>auto-dnssec</command></term>
10640 Zones configured for dynamic DNS may also use this
10641 option to allow varying levels of autonatic DNSSEC key
10642 management. There are four possible settings:
10645 <command>auto-dnssec allow;</command> permits
10646 keys to be updated and the zone fully re-signed
10647 whenever the user issues the command <command>rndc sign
10648 <replaceable>zonename</replaceable></command>.
10651 <command>auto-dnssec maintain;</command> includes the
10652 above, but also automatically adjusts the zone's DNSSEC
10653 keys on schedule, according to the keys' timing metadata
10654 (see <xref linkend="man.dnyssec-keygen"/> and
10655 <xref linkend="man.dnssec-settime"/>). The command
10657 <replaceable>zonename</replaceable></command> causes
10658 <command>named</command> to load keys from the key
10659 repository and sign the zone with all keys that are
10661 <command>rndc loadkeys
10662 <replaceable>zonename</replaceable></command> causes
10663 <command>named</command> to load keys from the key
10664 repository and schedule key maintenance events to occur
10665 in the future, but it does not sign the full zone
10669 <command>auto-dnssec create;</command> includes the
10670 above, but also allows <command>named</command>
10671 to create new keys in the key repository when needed.
10672 (NOTE: This option is not yet implemented; the syntax is
10673 being reserved for future use.)
10676 The default setting is <command>auto-dnssec off</command>.
10682 <term><command>multi-master</command></term>
10685 See the description of <command>multi-master</command> in
10686 <xref linkend="boolean_options"/>.
10692 <term><command>masterfile-format</command></term>
10695 See the description of <command>masterfile-format</command>
10696 in <xref linkend="tuning"/>.
10702 <term><command>dnssec-secure-to-insecure</command></term>
10705 See the description of
10706 <command>dnssec-secure-to-insecure</command> in <xref linkend="boolean_options"/>.
10714 <sect3 id="dynamic_update_policies">
10715 <title>Dynamic Update Policies</title>
10716 <para><acronym>BIND</acronym> 9 supports two alternative
10717 methods of granting clients the right to perform
10718 dynamic updates to a zone, configured by the
10719 <command>allow-update</command> and
10720 <command>update-policy</command> option, respectively.
10723 The <command>allow-update</command> clause works the
10724 same way as in previous versions of <acronym>BIND</acronym>.
10725 It grants given clients the permission to update any
10726 record of any name in the zone.
10729 The <command>update-policy</command> clause
10730 allows more fine-grained control over what updates are
10731 allowed. A set of rules is specified, where each rule
10732 either grants or denies permissions for one or more
10733 names to be updated by one or more identities. If
10734 the dynamic update request message is signed (that is,
10735 it includes either a TSIG or SIG(0) record), the
10736 identity of the signer can be determined.
10739 Rules are specified in the <command>update-policy</command>
10740 zone option, and are only meaningful for master zones.
10741 When the <command>update-policy</command> statement
10742 is present, it is a configuration error for the
10743 <command>allow-update</command> statement to be
10744 present. The <command>update-policy</command> statement
10745 only examines the signer of a message; the source
10746 address is not relevant.
10749 There is a pre-defined <command>update-policy</command>
10750 rule which can be switched on with the command
10751 <command>update-policy local;</command>.
10752 Switching on this rule in a zone causes
10753 <command>named</command> to generate a TSIG session
10754 key and place it in a file, and to allow that key
10755 to update the zone. (By default, the file is
10756 <filename>/var/run/named/session.key</filename>, the key
10757 name is "local-ddns" and the key algorithm is HMAC-SHA256,
10758 but these values are configurable with the
10759 <command>session-keyfile</command>,
10760 <command>session-keyname</command> and
10761 <command>session-keyalg</command> options, respectively).
10764 A client running on the local system, and with appropriate
10765 permissions, may read that file and use the key to sign update
10766 requests. The zone's update policy will be set to allow that
10767 key to change any record within the zone. Assuming the
10768 key name is "local-ddns", this policy is equivalent to:
10771 <programlisting>update-policy { grant local-ddns zonesub any; };
10775 The command <command>nsupdate -l</command> sends update
10776 requests to localhost, and signs them using the session key.
10780 Other rule definitions look like this:
10784 ( <command>grant</command> | <command>deny</command> ) <replaceable>identity</replaceable> <replaceable>nametype</replaceable> <optional> <replaceable>name</replaceable> </optional> <optional> <replaceable>types</replaceable> </optional>
10788 Each rule grants or denies privileges. Once a message has
10789 successfully matched a rule, the operation is immediately
10790 granted or denied and no further rules are examined. A rule
10791 is matched when the signer matches the identity field, the
10792 name matches the name field in accordance with the nametype
10793 field, and the type matches the types specified in the type
10797 No signer is required for <replaceable>tcp-self</replaceable>
10798 or <replaceable>6to4-self</replaceable> however the standard
10799 reverse mapping / prefix conversion must match the identity
10803 The identity field specifies a name or a wildcard
10804 name. Normally, this is the name of the TSIG or
10805 SIG(0) key used to sign the update request. When a
10806 TKEY exchange has been used to create a shared secret,
10807 the identity of the shared secret is the same as the
10808 identity of the key used to authenticate the TKEY
10809 exchange. TKEY is also the negotiation method used
10810 by GSS-TSIG, which establishes an identity that is
10811 the Kerberos principal of the client, such as
10812 <userinput>"user@host.domain"</userinput>. When the
10813 <replaceable>identity</replaceable> field specifies
10814 a wildcard name, it is subject to DNS wildcard
10815 expansion, so the rule will apply to multiple identities.
10816 The <replaceable>identity</replaceable> field must
10817 contain a fully-qualified domain name.
10821 The <replaceable>nametype</replaceable> field has 13
10823 <varname>name</varname>, <varname>subdomain</varname>,
10824 <varname>wildcard</varname>, <varname>self</varname>,
10825 <varname>selfsub</varname>, <varname>selfwild</varname>,
10826 <varname>krb5-self</varname>, <varname>ms-self</varname>,
10827 <varname>krb5-subdomain</varname>,
10828 <varname>ms-subdomain</varname>,
10829 <varname>tcp-self</varname>, <varname>6to4-self</varname>,
10830 and <varname>zonesub</varname>.
10833 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
10834 <colspec colname="1" colnum="1" colsep="0" colwidth="0.819in"/>
10835 <colspec colname="2" colnum="2" colsep="0" colwidth="3.681in"/>
10838 <entry colname="1">
10840 <varname>name</varname>
10842 </entry> <entry colname="2">
10844 Exact-match semantics. This rule matches
10845 when the name being updated is identical
10846 to the contents of the
10847 <replaceable>name</replaceable> field.
10852 <entry colname="1">
10854 <varname>subdomain</varname>
10856 </entry> <entry colname="2">
10858 This rule matches when the name being updated
10859 is a subdomain of, or identical to, the
10860 contents of the <replaceable>name</replaceable>
10866 <entry colname="1">
10868 <varname>zonesub</varname>
10870 </entry> <entry colname="2">
10872 This rule is similar to subdomain, except that
10873 it matches when the name being updated is a
10874 subdomain of the zone in which the
10875 <command>update-policy</command> statement
10876 appears. This obviates the need to type the zone
10877 name twice, and enables the use of a standard
10878 <command>update-policy</command> statement in
10879 multiple zones without modification.
10882 When this rule is used, the
10883 <replaceable>name</replaceable> field is omitted.
10888 <entry colname="1">
10890 <varname>wildcard</varname>
10892 </entry> <entry colname="2">
10894 The <replaceable>name</replaceable> field
10895 is subject to DNS wildcard expansion, and
10896 this rule matches when the name being updated
10897 name is a valid expansion of the wildcard.
10902 <entry colname="1">
10904 <varname>self</varname>
10907 <entry colname="2">
10909 This rule matches when the name being updated
10910 matches the contents of the
10911 <replaceable>identity</replaceable> field.
10912 The <replaceable>name</replaceable> field
10913 is ignored, but should be the same as the
10914 <replaceable>identity</replaceable> field.
10915 The <varname>self</varname> nametype is
10916 most useful when allowing using one key per
10917 name to update, where the key has the same
10918 name as the name to be updated. The
10919 <replaceable>identity</replaceable> would
10920 be specified as <constant>*</constant> (an asterisk) in
10926 <entry colname="1">
10928 <varname>selfsub</varname>
10930 </entry> <entry colname="2">
10932 This rule is similar to <varname>self</varname>
10933 except that subdomains of <varname>self</varname>
10934 can also be updated.
10939 <entry colname="1">
10941 <varname>selfwild</varname>
10943 </entry> <entry colname="2">
10945 This rule is similar to <varname>self</varname>
10946 except that only subdomains of
10947 <varname>self</varname> can be updated.
10952 <entry colname="1">
10954 <varname>tcp-self</varname>
10956 </entry> <entry colname="2">
10958 Allow updates that have been sent via TCP and
10959 for which the standard mapping from the initiating
10960 IP address into the IN-ADDR.ARPA and IP6.ARPA
10961 namespaces match the name to be updated.
10964 It is theoretically possible to spoof these TCP
10970 <entry colname="1">
10972 <varname>6to4-self</varname>
10974 </entry> <entry colname="2">
10976 Allow the 6to4 prefix to be update by any TCP
10977 connection from the 6to4 network or from the
10978 corresponding IPv4 address. This is intended
10979 to allow NS or DNAME RRsets to be added to the
10983 It is theoretically possible to spoof these TCP
10993 In all cases, the <replaceable>name</replaceable>
10995 specify a fully-qualified domain name.
10999 If no types are explicitly specified, this rule matches
11000 all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
11001 may be specified by name, including "ANY" (ANY matches
11002 all types except NSEC and NSEC3, which can never be
11003 updated). Note that when an attempt is made to delete
11004 all records associated with a name, the rules are
11005 checked for each existing record type.
11011 <title>Zone File</title>
11012 <sect2 id="types_of_resource_records_and_when_to_use_them">
11013 <title>Types of Resource Records and When to Use Them</title>
11015 This section, largely borrowed from RFC 1034, describes the
11016 concept of a Resource Record (RR) and explains when each is used.
11017 Since the publication of RFC 1034, several new RRs have been
11019 and implemented in the DNS. These are also included.
11022 <title>Resource Records</title>
11025 A domain name identifies a node. Each node has a set of
11026 resource information, which may be empty. The set of resource
11027 information associated with a particular name is composed of
11028 separate RRs. The order of RRs in a set is not significant and
11029 need not be preserved by name servers, resolvers, or other
11030 parts of the DNS. However, sorting of multiple RRs is
11031 permitted for optimization purposes, for example, to specify
11032 that a particular nearby server be tried first. See <xref linkend="the_sortlist_statement"/> and <xref linkend="rrset_ordering"/>.
11036 The components of a Resource Record are:
11038 <informaltable colsep="0" rowsep="0">
11039 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11040 <colspec colname="1" colnum="1" colsep="0" colwidth="1.000in"/>
11041 <colspec colname="2" colnum="2" colsep="0" colwidth="3.500in"/>
11044 <entry colname="1">
11049 <entry colname="2">
11051 The domain name where the RR is found.
11056 <entry colname="1">
11061 <entry colname="2">
11063 An encoded 16-bit value that specifies
11064 the type of the resource record.
11069 <entry colname="1">
11074 <entry colname="2">
11076 The time-to-live of the RR. This field
11077 is a 32-bit integer in units of seconds, and is
11079 resolvers when they cache RRs. The TTL describes how
11081 be cached before it should be discarded.
11086 <entry colname="1">
11091 <entry colname="2">
11093 An encoded 16-bit value that identifies
11094 a protocol family or instance of a protocol.
11099 <entry colname="1">
11104 <entry colname="2">
11106 The resource data. The format of the
11107 data is type (and sometimes class) specific.
11115 The following are <emphasis>types</emphasis> of valid RRs:
11117 <informaltable colsep="0" rowsep="0">
11118 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11119 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
11120 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
11123 <entry colname="1">
11128 <entry colname="2">
11130 A host address. In the IN class, this is a
11131 32-bit IP address. Described in RFC 1035.
11136 <entry colname="1">
11141 <entry colname="2">
11143 IPv6 address. Described in RFC 1886.
11148 <entry colname="1">
11153 <entry colname="2">
11155 IPv6 address. This can be a partial
11156 address (a suffix) and an indirection to the name
11157 where the rest of the
11158 address (the prefix) can be found. Experimental.
11159 Described in RFC 2874.
11164 <entry colname="1">
11169 <entry colname="2">
11171 Location of AFS database servers.
11172 Experimental. Described in RFC 1183.
11177 <entry colname="1">
11182 <entry colname="2">
11184 Address prefix list. Experimental.
11185 Described in RFC 3123.
11190 <entry colname="1">
11195 <entry colname="2">
11197 Holds a digital certificate.
11198 Described in RFC 2538.
11203 <entry colname="1">
11208 <entry colname="2">
11210 Identifies the canonical name of an alias.
11211 Described in RFC 1035.
11216 <entry colname="1">
11221 <entry colname="2">
11223 Is used for identifying which DHCP client is
11224 associated with this name. Described in RFC 4701.
11229 <entry colname="1">
11234 <entry colname="2">
11236 Replaces the domain name specified with
11237 another name to be looked up, effectively aliasing an
11239 subtree of the domain name space rather than a single
11241 as in the case of the CNAME RR.
11242 Described in RFC 2672.
11247 <entry colname="1">
11252 <entry colname="2">
11254 Stores a public key associated with a signed
11255 DNS zone. Described in RFC 4034.
11260 <entry colname="1">
11265 <entry colname="2">
11267 Stores the hash of a public key associated with a
11268 signed DNS zone. Described in RFC 4034.
11273 <entry colname="1">
11278 <entry colname="2">
11280 Specifies the global position. Superseded by LOC.
11285 <entry colname="1">
11290 <entry colname="2">
11292 Identifies the CPU and OS used by a host.
11293 Described in RFC 1035.
11298 <entry colname="1">
11303 <entry colname="2">
11305 Provides a method for storing IPsec keying material in
11306 DNS. Described in RFC 4025.
11311 <entry colname="1">
11316 <entry colname="2">
11318 Representation of ISDN addresses.
11319 Experimental. Described in RFC 1183.
11324 <entry colname="1">
11329 <entry colname="2">
11331 Stores a public key associated with a
11332 DNS name. Used in original DNSSEC; replaced
11333 by DNSKEY in DNSSECbis, but still used with
11334 SIG(0). Described in RFCs 2535 and 2931.
11339 <entry colname="1">
11344 <entry colname="2">
11346 Identifies a key exchanger for this
11347 DNS name. Described in RFC 2230.
11352 <entry colname="1">
11357 <entry colname="2">
11359 For storing GPS info. Described in RFC 1876.
11365 <entry colname="1">
11370 <entry colname="2">
11372 Identifies a mail exchange for the domain with
11373 a 16-bit preference value (lower is better)
11374 followed by the host name of the mail exchange.
11375 Described in RFC 974, RFC 1035.
11380 <entry colname="1">
11385 <entry colname="2">
11387 Name authority pointer. Described in RFC 2915.
11392 <entry colname="1">
11397 <entry colname="2">
11399 A network service access point.
11400 Described in RFC 1706.
11405 <entry colname="1">
11410 <entry colname="2">
11412 The authoritative name server for the
11413 domain. Described in RFC 1035.
11418 <entry colname="1">
11423 <entry colname="2">
11425 Used in DNSSECbis to securely indicate that
11426 RRs with an owner name in a certain name interval do
11428 a zone and indicate what RR types are present for an
11430 Described in RFC 4034.
11435 <entry colname="1">
11440 <entry colname="2">
11442 Used in DNSSECbis to securely indicate that
11443 RRs with an owner name in a certain name
11444 interval do not exist in a zone and indicate
11445 what RR types are present for an existing
11446 name. NSEC3 differs from NSEC in that it
11447 prevents zone enumeration but is more
11448 computationally expensive on both the server
11449 and the client than NSEC. Described in RFC
11455 <entry colname="1">
11460 <entry colname="2">
11462 Used in DNSSECbis to tell the authoritative
11463 server which NSEC3 chains are available to use.
11464 Described in RFC 5155.
11469 <entry colname="1">
11474 <entry colname="2">
11476 Used in DNSSEC to securely indicate that
11477 RRs with an owner name in a certain name interval do
11479 a zone and indicate what RR types are present for an
11481 Used in original DNSSEC; replaced by NSEC in
11483 Described in RFC 2535.
11488 <entry colname="1">
11493 <entry colname="2">
11495 A pointer to another part of the domain
11496 name space. Described in RFC 1035.
11501 <entry colname="1">
11506 <entry colname="2">
11508 Provides mappings between RFC 822 and X.400
11509 addresses. Described in RFC 2163.
11514 <entry colname="1">
11519 <entry colname="2">
11521 Information on persons responsible
11522 for the domain. Experimental. Described in RFC 1183.
11527 <entry colname="1">
11532 <entry colname="2">
11534 Contains DNSSECbis signature data. Described
11540 <entry colname="1">
11545 <entry colname="2">
11547 Route-through binding for hosts that
11548 do not have their own direct wide area network
11550 Experimental. Described in RFC 1183.
11555 <entry colname="1">
11560 <entry colname="2">
11562 Contains DNSSEC signature data. Used in
11563 original DNSSEC; replaced by RRSIG in
11564 DNSSECbis, but still used for SIG(0).
11565 Described in RFCs 2535 and 2931.
11570 <entry colname="1">
11575 <entry colname="2">
11577 Identifies the start of a zone of authority.
11578 Described in RFC 1035.
11583 <entry colname="1">
11588 <entry colname="2">
11590 Contains the Sender Policy Framework information
11591 for a given email domain. Described in RFC 4408.
11596 <entry colname="1">
11601 <entry colname="2">
11603 Information about well known network
11604 services (replaces WKS). Described in RFC 2782.
11609 <entry colname="1">
11614 <entry colname="2">
11616 Provides a way to securely publish a secure shell key's
11617 fingerprint. Described in RFC 4255.
11622 <entry colname="1">
11627 <entry colname="2">
11629 Text records. Described in RFC 1035.
11634 <entry colname="1">
11639 <entry colname="2">
11641 Information about which well known
11642 network services, such as SMTP, that a domain
11643 supports. Historical.
11648 <entry colname="1">
11653 <entry colname="2">
11655 Representation of X.25 network addresses.
11656 Experimental. Described in RFC 1183.
11664 The following <emphasis>classes</emphasis> of resource records
11665 are currently valid in the DNS:
11667 <informaltable colsep="0" rowsep="0"><tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11668 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
11669 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
11673 <entry colname="1">
11678 <entry colname="2">
11686 <entry colname="1">
11691 <entry colname="2">
11693 Chaosnet, a LAN protocol created at MIT in the
11695 Rarely used for its historical purpose, but reused for
11697 built-in server information zones, e.g.,
11698 <literal>version.bind</literal>.
11704 <entry colname="1">
11709 <entry colname="2">
11711 Hesiod, an information service
11712 developed by MIT's Project Athena. It is used to share
11714 about various systems databases, such as users,
11726 The owner name is often implicit, rather than forming an
11728 part of the RR. For example, many name servers internally form
11730 or hash structures for the name space, and chain RRs off nodes.
11731 The remaining RR parts are the fixed header (type, class, TTL)
11732 which is consistent for all RRs, and a variable part (RDATA)
11734 fits the needs of the resource being described.
11737 The meaning of the TTL field is a time limit on how long an
11738 RR can be kept in a cache. This limit does not apply to
11740 data in zones; it is also timed out, but by the refreshing
11742 for the zone. The TTL is assigned by the administrator for the
11743 zone where the data originates. While short TTLs can be used to
11744 minimize caching, and a zero TTL prohibits caching, the
11746 of Internet performance suggest that these times should be on
11748 order of days for the typical host. If a change can be
11750 the TTL can be reduced prior to the change to minimize
11752 during the change, and then increased back to its former value
11757 The data in the RDATA section of RRs is carried as a combination
11758 of binary strings and domain names. The domain names are
11760 used as "pointers" to other data in the DNS.
11764 <title>Textual expression of RRs</title>
11766 RRs are represented in binary form in the packets of the DNS
11767 protocol, and are usually represented in highly encoded form
11769 stored in a name server or resolver. In the examples provided
11771 RFC 1034, a style similar to that used in master files was
11773 in order to show the contents of RRs. In this format, most RRs
11774 are shown on a single line, although continuation lines are
11779 The start of the line gives the owner of the RR. If a line
11780 begins with a blank, then the owner is assumed to be the same as
11781 that of the previous RR. Blank lines are often included for
11785 Following the owner, we list the TTL, type, and class of the
11786 RR. Class and type use the mnemonics defined above, and TTL is
11787 an integer before the type field. In order to avoid ambiguity
11789 parsing, type and class mnemonics are disjoint, TTLs are
11791 and the type mnemonic is always last. The IN class and TTL
11793 are often omitted from examples in the interests of clarity.
11796 The resource data or RDATA section of the RR are given using
11797 knowledge of the typical representation for the data.
11800 For example, we might show the RRs carried in a message as:
11802 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11803 <colspec colname="1" colnum="1" colsep="0" colwidth="1.381in"/>
11804 <colspec colname="2" colnum="2" colsep="0" colwidth="1.020in"/>
11805 <colspec colname="3" colnum="3" colsep="0" colwidth="2.099in"/>
11808 <entry colname="1">
11810 <literal>ISI.EDU.</literal>
11813 <entry colname="2">
11815 <literal>MX</literal>
11818 <entry colname="3">
11820 <literal>10 VENERA.ISI.EDU.</literal>
11825 <entry colname="1">
11828 <entry colname="2">
11830 <literal>MX</literal>
11833 <entry colname="3">
11835 <literal>10 VAXA.ISI.EDU</literal>
11840 <entry colname="1">
11842 <literal>VENERA.ISI.EDU</literal>
11845 <entry colname="2">
11847 <literal>A</literal>
11850 <entry colname="3">
11852 <literal>128.9.0.32</literal>
11857 <entry colname="1">
11860 <entry colname="2">
11862 <literal>A</literal>
11865 <entry colname="3">
11867 <literal>10.1.0.52</literal>
11872 <entry colname="1">
11874 <literal>VAXA.ISI.EDU</literal>
11877 <entry colname="2">
11879 <literal>A</literal>
11882 <entry colname="3">
11884 <literal>10.2.0.27</literal>
11889 <entry colname="1">
11892 <entry colname="2">
11894 <literal>A</literal>
11897 <entry colname="3">
11899 <literal>128.9.0.33</literal>
11907 The MX RRs have an RDATA section which consists of a 16-bit
11908 number followed by a domain name. The address RRs use a
11910 IP address format to contain a 32-bit internet address.
11913 The above example shows six RRs, with two RRs at each of three
11917 Similarly we might see:
11919 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11920 <colspec colname="1" colnum="1" colsep="0" colwidth="1.491in"/>
11921 <colspec colname="2" colnum="2" colsep="0" colwidth="1.067in"/>
11922 <colspec colname="3" colnum="3" colsep="0" colwidth="2.067in"/>
11925 <entry colname="1">
11927 <literal>XX.LCS.MIT.EDU.</literal>
11930 <entry colname="2">
11932 <literal>IN A</literal>
11935 <entry colname="3">
11937 <literal>10.0.0.44</literal>
11942 <entry colname="1"/>
11943 <entry colname="2">
11945 <literal>CH A</literal>
11948 <entry colname="3">
11950 <literal>MIT.EDU. 2420</literal>
11958 This example shows two addresses for
11959 <literal>XX.LCS.MIT.EDU</literal>, each of a different class.
11965 <title>Discussion of MX Records</title>
11968 As described above, domain servers store information as a
11969 series of resource records, each of which contains a particular
11970 piece of information about a given domain name (which is usually,
11971 but not always, a host). The simplest way to think of a RR is as
11972 a typed pair of data, a domain name matched with a relevant datum,
11973 and stored with some additional type information to help systems
11974 determine when the RR is relevant.
11978 MX records are used to control delivery of email. The data
11979 specified in the record is a priority and a domain name. The
11981 controls the order in which email delivery is attempted, with the
11982 lowest number first. If two priorities are the same, a server is
11983 chosen randomly. If no servers at a given priority are responding,
11984 the mail transport agent will fall back to the next largest
11986 Priority numbers do not have any absolute meaning — they are
11988 only respective to other MX records for that domain name. The
11990 name given is the machine to which the mail will be delivered.
11991 It <emphasis>must</emphasis> have an associated address record
11992 (A or AAAA) — CNAME is not sufficient.
11995 For a given domain, if there is both a CNAME record and an
11996 MX record, the MX record is in error, and will be ignored.
11998 the mail will be delivered to the server specified in the MX
12000 pointed to by the CNAME.
12003 <informaltable colsep="0" rowsep="0">
12004 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12005 <colspec colname="1" colnum="1" colsep="0" colwidth="1.708in"/>
12006 <colspec colname="2" colnum="2" colsep="0" colwidth="0.444in"/>
12007 <colspec colname="3" colnum="3" colsep="0" colwidth="0.444in"/>
12008 <colspec colname="4" colnum="4" colsep="0" colwidth="0.976in"/>
12009 <colspec colname="5" colnum="5" colsep="0" colwidth="1.553in"/>
12012 <entry colname="1">
12014 <literal>example.com.</literal>
12017 <entry colname="2">
12019 <literal>IN</literal>
12022 <entry colname="3">
12024 <literal>MX</literal>
12027 <entry colname="4">
12029 <literal>10</literal>
12032 <entry colname="5">
12034 <literal>mail.example.com.</literal>
12039 <entry colname="1">
12042 <entry colname="2">
12044 <literal>IN</literal>
12047 <entry colname="3">
12049 <literal>MX</literal>
12052 <entry colname="4">
12054 <literal>10</literal>
12057 <entry colname="5">
12059 <literal>mail2.example.com.</literal>
12064 <entry colname="1">
12067 <entry colname="2">
12069 <literal>IN</literal>
12072 <entry colname="3">
12074 <literal>MX</literal>
12077 <entry colname="4">
12079 <literal>20</literal>
12082 <entry colname="5">
12084 <literal>mail.backup.org.</literal>
12089 <entry colname="1">
12091 <literal>mail.example.com.</literal>
12094 <entry colname="2">
12096 <literal>IN</literal>
12099 <entry colname="3">
12101 <literal>A</literal>
12104 <entry colname="4">
12106 <literal>10.0.0.1</literal>
12109 <entry colname="5">
12114 <entry colname="1">
12116 <literal>mail2.example.com.</literal>
12119 <entry colname="2">
12121 <literal>IN</literal>
12124 <entry colname="3">
12126 <literal>A</literal>
12129 <entry colname="4">
12131 <literal>10.0.0.2</literal>
12134 <entry colname="5">
12140 </informaltable><para>
12141 Mail delivery will be attempted to <literal>mail.example.com</literal> and
12142 <literal>mail2.example.com</literal> (in
12143 any order), and if neither of those succeed, delivery to <literal>mail.backup.org</literal> will
12147 <sect2 id="Setting_TTLs">
12148 <title>Setting TTLs</title>
12150 The time-to-live of the RR field is a 32-bit integer represented
12151 in units of seconds, and is primarily used by resolvers when they
12152 cache RRs. The TTL describes how long a RR can be cached before it
12153 should be discarded. The following three types of TTL are
12155 used in a zone file.
12157 <informaltable colsep="0" rowsep="0">
12158 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12159 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
12160 <colspec colname="2" colnum="2" colsep="0" colwidth="4.375in"/>
12163 <entry colname="1">
12168 <entry colname="2">
12170 The last field in the SOA is the negative
12171 caching TTL. This controls how long other servers will
12172 cache no-such-domain
12173 (NXDOMAIN) responses from you.
12176 The maximum time for
12177 negative caching is 3 hours (3h).
12182 <entry colname="1">
12187 <entry colname="2">
12189 The $TTL directive at the top of the
12190 zone file (before the SOA) gives a default TTL for every
12192 a specific TTL set.
12197 <entry colname="1">
12202 <entry colname="2">
12204 Each RR can have a TTL as the second
12205 field in the RR, which will control how long other
12215 All of these TTLs default to units of seconds, though units
12216 can be explicitly specified, for example, <literal>1h30m</literal>.
12220 <title>Inverse Mapping in IPv4</title>
12222 Reverse name resolution (that is, translation from IP address
12223 to name) is achieved by means of the <emphasis>in-addr.arpa</emphasis> domain
12224 and PTR records. Entries in the in-addr.arpa domain are made in
12225 least-to-most significant order, read left to right. This is the
12226 opposite order to the way IP addresses are usually written. Thus,
12227 a machine with an IP address of 10.1.2.3 would have a
12229 in-addr.arpa name of
12230 3.2.1.10.in-addr.arpa. This name should have a PTR resource record
12231 whose data field is the name of the machine or, optionally,
12233 PTR records if the machine has more than one name. For example,
12234 in the <optional>example.com</optional> domain:
12236 <informaltable colsep="0" rowsep="0">
12237 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12238 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
12239 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
12242 <entry colname="1">
12244 <literal>$ORIGIN</literal>
12247 <entry colname="2">
12249 <literal>2.1.10.in-addr.arpa</literal>
12254 <entry colname="1">
12256 <literal>3</literal>
12259 <entry colname="2">
12261 <literal>IN PTR foo.example.com.</literal>
12270 The <command>$ORIGIN</command> lines in the examples
12271 are for providing context to the examples only — they do not
12273 appear in the actual usage. They are only used here to indicate
12274 that the example is relative to the listed origin.
12279 <title>Other Zone File Directives</title>
12281 The Master File Format was initially defined in RFC 1035 and
12282 has subsequently been extended. While the Master File Format
12284 is class independent all records in a Master File must be of the
12289 Master File Directives include <command>$ORIGIN</command>, <command>$INCLUDE</command>,
12290 and <command>$TTL.</command>
12293 <title>The <command>@</command> (at-sign)</title>
12295 When used in the label (or name) field, the asperand or
12296 at-sign (@) symbol represents the current origin.
12297 At the start of the zone file, it is the
12298 <<varname>zone_name</varname>> (followed by
12303 <title>The <command>$ORIGIN</command> Directive</title>
12305 Syntax: <command>$ORIGIN</command>
12306 <replaceable>domain-name</replaceable>
12307 <optional><replaceable>comment</replaceable></optional>
12309 <para><command>$ORIGIN</command>
12310 sets the domain name that will be appended to any
12311 unqualified records. When a zone is first read in there
12312 is an implicit <command>$ORIGIN</command>
12313 <<varname>zone_name</varname>><command>.</command>
12314 (followed by trailing dot).
12315 The current <command>$ORIGIN</command> is appended to
12316 the domain specified in the <command>$ORIGIN</command>
12317 argument if it is not absolute.
12321 $ORIGIN example.com.
12322 WWW CNAME MAIN-SERVER
12330 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
12335 <title>The <command>$INCLUDE</command> Directive</title>
12337 Syntax: <command>$INCLUDE</command>
12338 <replaceable>filename</replaceable>
12340 <replaceable>origin</replaceable> </optional>
12341 <optional> <replaceable>comment</replaceable> </optional>
12344 Read and process the file <filename>filename</filename> as
12345 if it were included into the file at this point. If <command>origin</command> is
12346 specified the file is processed with <command>$ORIGIN</command> set
12347 to that value, otherwise the current <command>$ORIGIN</command> is
12351 The origin and the current domain name
12352 revert to the values they had prior to the <command>$INCLUDE</command> once
12353 the file has been read.
12357 RFC 1035 specifies that the current origin should be restored
12359 an <command>$INCLUDE</command>, but it is silent
12360 on whether the current
12361 domain name should also be restored. BIND 9 restores both of
12363 This could be construed as a deviation from RFC 1035, a
12369 <title>The <command>$TTL</command> Directive</title>
12371 Syntax: <command>$TTL</command>
12372 <replaceable>default-ttl</replaceable>
12374 <replaceable>comment</replaceable> </optional>
12377 Set the default Time To Live (TTL) for subsequent records
12378 with undefined TTLs. Valid TTLs are of the range 0-2147483647
12381 <para><command>$TTL</command>
12382 is defined in RFC 2308.
12387 <title><acronym>BIND</acronym> Master File Extension: the <command>$GENERATE</command> Directive</title>
12389 Syntax: <command>$GENERATE</command>
12390 <replaceable>range</replaceable>
12391 <replaceable>lhs</replaceable>
12392 <optional><replaceable>ttl</replaceable></optional>
12393 <optional><replaceable>class</replaceable></optional>
12394 <replaceable>type</replaceable>
12395 <replaceable>rhs</replaceable>
12396 <optional><replaceable>comment</replaceable></optional>
12398 <para><command>$GENERATE</command>
12399 is used to create a series of resource records that only
12400 differ from each other by an
12401 iterator. <command>$GENERATE</command> can be used to
12402 easily generate the sets of records required to support
12403 sub /24 reverse delegations described in RFC 2317:
12404 Classless IN-ADDR.ARPA delegation.
12407 <programlisting>$ORIGIN 0.0.192.IN-ADDR.ARPA.
12408 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
12409 $GENERATE 1-127 $ CNAME $.0</programlisting>
12415 <programlisting>0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
12416 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
12417 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
12418 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
12420 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
12424 Generate a set of A and MX records. Note the MX's right hand
12425 side is a quoted string. The quotes will be stripped when the
12426 right hand side is processed.
12431 $GENERATE 1-127 HOST-$ A 1.2.3.$
12432 $GENERATE 1-127 HOST-$ MX "0 ."</programlisting>
12438 <programlisting>HOST-1.EXAMPLE. A 1.2.3.1
12439 HOST-1.EXAMPLE. MX 0 .
12440 HOST-2.EXAMPLE. A 1.2.3.2
12441 HOST-2.EXAMPLE. MX 0 .
12442 HOST-3.EXAMPLE. A 1.2.3.3
12443 HOST-3.EXAMPLE. MX 0 .
12445 HOST-127.EXAMPLE. A 1.2.3.127
12446 HOST-127.EXAMPLE. MX 0 .
12449 <informaltable colsep="0" rowsep="0">
12450 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12451 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
12452 <colspec colname="2" colnum="2" colsep="0" colwidth="4.250in"/>
12455 <entry colname="1">
12456 <para><command>range</command></para>
12458 <entry colname="2">
12460 This can be one of two forms: start-stop
12461 or start-stop/step. If the first form is used, then step
12463 1. All of start, stop and step must be positive.
12468 <entry colname="1">
12469 <para><command>lhs</command></para>
12471 <entry colname="2">
12473 describes the owner name of the resource records
12474 to be created. Any single <command>$</command>
12476 symbols within the <command>lhs</command> string
12477 are replaced by the iterator value.
12479 To get a $ in the output, you need to escape the
12480 <command>$</command> using a backslash
12481 <command>\</command>,
12482 e.g. <command>\$</command>. The
12483 <command>$</command> may optionally be followed
12484 by modifiers which change the offset from the
12485 iterator, field width and base.
12487 Modifiers are introduced by a
12488 <command>{</command> (left brace) immediately following the
12489 <command>$</command> as
12490 <command>${offset[,width[,base]]}</command>.
12491 For example, <command>${-20,3,d}</command>
12492 subtracts 20 from the current value, prints the
12493 result as a decimal in a zero-padded field of
12496 Available output forms are decimal
12497 (<command>d</command>), octal
12498 (<command>o</command>), hexadecimal
12499 (<command>x</command> or <command>X</command>
12500 for uppercase) and nibble
12501 (<command>n</command> or <command>N</command>\
12502 for uppercase). The default modifier is
12503 <command>${0,0,d}</command>. If the
12504 <command>lhs</command> is not absolute, the
12505 current <command>$ORIGIN</command> is appended
12509 In nibble mode the value will be treated as
12510 if it was a reversed hexadecimal string
12511 with each hexadecimal digit as a separate
12512 label. The width field includes the label
12516 For compatibility with earlier versions,
12517 <command>$$</command> is still recognized as
12518 indicating a literal $ in the output.
12523 <entry colname="1">
12524 <para><command>ttl</command></para>
12526 <entry colname="2">
12528 Specifies the time-to-live of the generated records. If
12529 not specified this will be inherited using the
12530 normal TTL inheritance rules.
12532 <para><command>class</command>
12533 and <command>ttl</command> can be
12534 entered in either order.
12539 <entry colname="1">
12540 <para><command>class</command></para>
12542 <entry colname="2">
12544 Specifies the class of the generated records.
12545 This must match the zone class if it is
12548 <para><command>class</command>
12549 and <command>ttl</command> can be
12550 entered in either order.
12555 <entry colname="1">
12556 <para><command>type</command></para>
12558 <entry colname="2">
12565 <entry colname="1">
12566 <para><command>rhs</command></para>
12568 <entry colname="2">
12570 <command>rhs</command>, optionally, quoted string.
12578 The <command>$GENERATE</command> directive is a <acronym>BIND</acronym> extension
12579 and not part of the standard zone file format.
12582 BIND 8 does not support the optional TTL and CLASS fields.
12586 <sect2 id="zonefile_format">
12587 <title>Additional File Formats</title>
12589 In addition to the standard textual format, BIND 9
12590 supports the ability to read or dump to zone files in
12591 other formats. The <constant>raw</constant> format is
12592 currently available as an additional format. It is a
12593 binary format representing BIND 9's internal data
12594 structure directly, thereby remarkably improving the
12598 For a primary server, a zone file in the
12599 <constant>raw</constant> format is expected to be
12600 generated from a textual zone file by the
12601 <command>named-compilezone</command> command. For a
12602 secondary server or for a dynamic zone, it is automatically
12603 generated (if this format is specified by the
12604 <command>masterfile-format</command> option) when
12605 <command>named</command> dumps the zone contents after
12606 zone transfer or when applying prior updates.
12609 If a zone file in a binary format needs manual modification,
12610 it first must be converted to a textual form by the
12611 <command>named-compilezone</command> command. All
12612 necessary modification should go to the text file, which
12613 should then be converted to the binary form by the
12614 <command>named-compilezone</command> command again.
12617 Although the <constant>raw</constant> format uses the
12618 network byte order and avoids architecture-dependent
12619 data alignment so that it is as much portable as
12620 possible, it is primarily expected to be used inside
12621 the same single system. In order to export a zone
12622 file in the <constant>raw</constant> format or make a
12623 portable backup of the file, it is recommended to
12624 convert the file to the standard textual representation.
12629 <sect1 id="statistics">
12630 <title>BIND9 Statistics</title>
12632 <acronym>BIND</acronym> 9 maintains lots of statistics
12633 information and provides several interfaces for users to
12634 get access to the statistics.
12635 The available statistics include all statistics counters
12636 that were available in <acronym>BIND</acronym> 8 and
12637 are meaningful in <acronym>BIND</acronym> 9,
12638 and other information that is considered useful.
12642 The statistics information is categorized into the following
12646 <informaltable frame="all">
12648 <colspec colname="1" colnum="1" colsep="0" colwidth="3.300in"/>
12649 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
12653 <entry colname="1">
12654 <para>Incoming Requests</para>
12656 <entry colname="2">
12658 The number of incoming DNS requests for each OPCODE.
12664 <entry colname="1">
12665 <para>Incoming Queries</para>
12667 <entry colname="2">
12669 The number of incoming queries for each RR type.
12675 <entry colname="1">
12676 <para>Outgoing Queries</para>
12678 <entry colname="2">
12680 The number of outgoing queries for each RR
12681 type sent from the internal resolver.
12682 Maintained per view.
12688 <entry colname="1">
12689 <para>Name Server Statistics</para>
12691 <entry colname="2">
12693 Statistics counters about incoming request processing.
12699 <entry colname="1">
12700 <para>Zone Maintenance Statistics</para>
12702 <entry colname="2">
12704 Statistics counters regarding zone maintenance
12705 operations such as zone transfers.
12711 <entry colname="1">
12712 <para>Resolver Statistics</para>
12714 <entry colname="2">
12716 Statistics counters about name resolution
12717 performed in the internal resolver.
12718 Maintained per view.
12724 <entry colname="1">
12725 <para>Cache DB RRsets</para>
12727 <entry colname="2">
12729 The number of RRsets per RR type and nonexistent
12730 names stored in the cache database.
12731 If the exclamation mark (!) is printed for a RR
12732 type, it means that particular type of RRset is
12733 known to be nonexistent (this is also known as
12735 Maintained per view.
12741 <entry colname="1">
12742 <para>Socket I/O Statistics</para>
12744 <entry colname="2">
12746 Statistics counters about network related events.
12756 A subset of Name Server Statistics is collected and shown
12757 per zone for which the server has the authority when
12758 <command>zone-statistics</command> is set to
12759 <userinput>yes</userinput>.
12760 These statistics counters are shown with their zone and view
12762 In some cases the view names are omitted for the default view.
12766 There are currently two user interfaces to get access to the
12768 One is in the plain text format dumped to the file specified
12769 by the <command>statistics-file</command> configuration option.
12770 The other is remotely accessible via a statistics channel
12771 when the <command>statistics-channels</command> statement
12772 is specified in the configuration file
12773 (see <xref linkend="statschannels"/>.)
12776 <sect3 id="statsfile">
12777 <title>The Statistics File</title>
12779 The text format statistics dump begins with a line, like:
12782 <command>+++ Statistics Dump +++ (973798949)</command>
12785 The number in parentheses is a standard
12786 Unix-style timestamp, measured as seconds since January 1, 1970.
12789 that line is a set of statistics information, which is categorized
12790 as described above.
12791 Each section begins with a line, like:
12795 <command>++ Name Server Statistics ++</command>
12799 Each section consists of lines, each containing the statistics
12800 counter value followed by its textual description.
12801 See below for available counters.
12802 For brevity, counters that have a value of 0 are not shown
12803 in the statistics file.
12807 The statistics dump ends with the line where the
12808 number is identical to the number in the beginning line; for example:
12811 <command>--- Statistics Dump --- (973798949)</command>
12815 <sect2 id="statistics_counters">
12816 <title>Statistics Counters</title>
12818 The following tables summarize statistics counters that
12819 <acronym>BIND</acronym> 9 provides.
12820 For each row of the tables, the leftmost column is the
12821 abbreviated symbol name of that counter.
12822 These symbols are shown in the statistics information
12823 accessed via an HTTP statistics channel.
12824 The rightmost column gives the description of the counter,
12825 which is also shown in the statistics file
12826 (but, in this document, possibly with slight modification
12827 for better readability).
12828 Additional notes may also be provided in this column.
12829 When a middle column exists between these two columns,
12830 it gives the corresponding counter name of the
12831 <acronym>BIND</acronym> 8 statistics, if applicable.
12835 <title>Name Server Statistics Counters</title>
12837 <informaltable colsep="0" rowsep="0">
12838 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12839 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
12840 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
12841 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
12844 <entry colname="1">
12846 <emphasis>Symbol</emphasis>
12849 <entry colname="2">
12851 <emphasis>BIND8 Symbol</emphasis>
12854 <entry colname="3">
12856 <emphasis>Description</emphasis>
12862 <entry colname="1">
12863 <para><command>Requestv4</command></para>
12865 <entry colname="2">
12866 <para><command>RQ</command></para>
12868 <entry colname="3">
12870 IPv4 requests received.
12871 Note: this also counts non query requests.
12876 <entry colname="1">
12877 <para><command>Requestv6</command></para>
12879 <entry colname="2">
12880 <para><command>RQ</command></para>
12882 <entry colname="3">
12884 IPv6 requests received.
12885 Note: this also counts non query requests.
12890 <entry colname="1">
12891 <para><command>ReqEdns0</command></para>
12893 <entry colname="2">
12894 <para><command></command></para>
12896 <entry colname="3">
12898 Requests with EDNS(0) received.
12903 <entry colname="1">
12904 <para><command>ReqBadEDNSVer</command></para>
12906 <entry colname="2">
12907 <para><command></command></para>
12909 <entry colname="3">
12911 Requests with unsupported EDNS version received.
12916 <entry colname="1">
12917 <para><command>ReqTSIG</command></para>
12919 <entry colname="2">
12920 <para><command></command></para>
12922 <entry colname="3">
12924 Requests with TSIG received.
12929 <entry colname="1">
12930 <para><command>ReqSIG0</command></para>
12932 <entry colname="2">
12933 <para><command></command></para>
12935 <entry colname="3">
12937 Requests with SIG(0) received.
12942 <entry colname="1">
12943 <para><command>ReqBadSIG</command></para>
12945 <entry colname="2">
12946 <para><command></command></para>
12948 <entry colname="3">
12950 Requests with invalid (TSIG or SIG(0)) signature.
12955 <entry colname="1">
12956 <para><command>ReqTCP</command></para>
12958 <entry colname="2">
12959 <para><command>RTCP</command></para>
12961 <entry colname="3">
12963 TCP requests received.
12968 <entry colname="1">
12969 <para><command>AuthQryRej</command></para>
12971 <entry colname="2">
12972 <para><command>RUQ</command></para>
12974 <entry colname="3">
12976 Authoritative (non recursive) queries rejected.
12981 <entry colname="1">
12982 <para><command>RecQryRej</command></para>
12984 <entry colname="2">
12985 <para><command>RURQ</command></para>
12987 <entry colname="3">
12989 Recursive queries rejected.
12994 <entry colname="1">
12995 <para><command>XfrRej</command></para>
12997 <entry colname="2">
12998 <para><command>RUXFR</command></para>
13000 <entry colname="3">
13002 Zone transfer requests rejected.
13007 <entry colname="1">
13008 <para><command>UpdateRej</command></para>
13010 <entry colname="2">
13011 <para><command>RUUpd</command></para>
13013 <entry colname="3">
13015 Dynamic update requests rejected.
13020 <entry colname="1">
13021 <para><command>Response</command></para>
13023 <entry colname="2">
13024 <para><command>SAns</command></para>
13026 <entry colname="3">
13033 <entry colname="1">
13034 <para><command>RespTruncated</command></para>
13036 <entry colname="2">
13037 <para><command></command></para>
13039 <entry colname="3">
13041 Truncated responses sent.
13046 <entry colname="1">
13047 <para><command>RespEDNS0</command></para>
13049 <entry colname="2">
13050 <para><command></command></para>
13052 <entry colname="3">
13054 Responses with EDNS(0) sent.
13059 <entry colname="1">
13060 <para><command>RespTSIG</command></para>
13062 <entry colname="2">
13063 <para><command></command></para>
13065 <entry colname="3">
13067 Responses with TSIG sent.
13072 <entry colname="1">
13073 <para><command>RespSIG0</command></para>
13075 <entry colname="2">
13076 <para><command></command></para>
13078 <entry colname="3">
13080 Responses with SIG(0) sent.
13085 <entry colname="1">
13086 <para><command>QrySuccess</command></para>
13088 <entry colname="2">
13089 <para><command></command></para>
13091 <entry colname="3">
13093 Queries resulted in a successful answer.
13094 This means the query which returns a NOERROR response
13095 with at least one answer RR.
13096 This corresponds to the
13097 <command>success</command> counter
13098 of previous versions of
13099 <acronym>BIND</acronym> 9.
13104 <entry colname="1">
13105 <para><command>QryAuthAns</command></para>
13107 <entry colname="2">
13108 <para><command></command></para>
13110 <entry colname="3">
13112 Queries resulted in authoritative answer.
13117 <entry colname="1">
13118 <para><command>QryNoauthAns</command></para>
13120 <entry colname="2">
13121 <para><command>SNaAns</command></para>
13123 <entry colname="3">
13125 Queries resulted in non authoritative answer.
13130 <entry colname="1">
13131 <para><command>QryReferral</command></para>
13133 <entry colname="2">
13134 <para><command></command></para>
13136 <entry colname="3">
13138 Queries resulted in referral answer.
13139 This corresponds to the
13140 <command>referral</command> counter
13141 of previous versions of
13142 <acronym>BIND</acronym> 9.
13147 <entry colname="1">
13148 <para><command>QryNxrrset</command></para>
13150 <entry colname="2">
13151 <para><command></command></para>
13153 <entry colname="3">
13155 Queries resulted in NOERROR responses with no data.
13156 This corresponds to the
13157 <command>nxrrset</command> counter
13158 of previous versions of
13159 <acronym>BIND</acronym> 9.
13164 <entry colname="1">
13165 <para><command>QrySERVFAIL</command></para>
13167 <entry colname="2">
13168 <para><command>SFail</command></para>
13170 <entry colname="3">
13172 Queries resulted in SERVFAIL.
13177 <entry colname="1">
13178 <para><command>QryFORMERR</command></para>
13180 <entry colname="2">
13181 <para><command>SFErr</command></para>
13183 <entry colname="3">
13185 Queries resulted in FORMERR.
13190 <entry colname="1">
13191 <para><command>QryNXDOMAIN</command></para>
13193 <entry colname="2">
13194 <para><command>SNXD</command></para>
13196 <entry colname="3">
13198 Queries resulted in NXDOMAIN.
13199 This corresponds to the
13200 <command>nxdomain</command> counter
13201 of previous versions of
13202 <acronym>BIND</acronym> 9.
13207 <entry colname="1">
13208 <para><command>QryRecursion</command></para>
13210 <entry colname="2">
13211 <para><command>RFwdQ</command></para>
13213 <entry colname="3">
13215 Queries which caused the server
13216 to perform recursion in order to find the final answer.
13217 This corresponds to the
13218 <command>recursion</command> counter
13219 of previous versions of
13220 <acronym>BIND</acronym> 9.
13225 <entry colname="1">
13226 <para><command>QryDuplicate</command></para>
13228 <entry colname="2">
13229 <para><command>RDupQ</command></para>
13231 <entry colname="3">
13233 Queries which the server attempted to
13234 recurse but discovered an existing query with the same
13235 IP address, port, query ID, name, type and class
13236 already being processed.
13237 This corresponds to the
13238 <command>duplicate</command> counter
13239 of previous versions of
13240 <acronym>BIND</acronym> 9.
13245 <entry colname="1">
13246 <para><command>QryDropped</command></para>
13248 <entry colname="2">
13249 <para><command></command></para>
13251 <entry colname="3">
13253 Recursive queries for which the server
13254 discovered an excessive number of existing
13255 recursive queries for the same name, type and
13256 class and were subsequently dropped.
13257 This is the number of dropped queries due to
13258 the reason explained with the
13259 <command>clients-per-query</command>
13261 <command>max-clients-per-query</command>
13263 (see the description about
13264 <xref linkend="clients-per-query"/>.)
13265 This corresponds to the
13266 <command>dropped</command> counter
13267 of previous versions of
13268 <acronym>BIND</acronym> 9.
13273 <entry colname="1">
13274 <para><command>QryFailure</command></para>
13276 <entry colname="2">
13277 <para><command></command></para>
13279 <entry colname="3">
13281 Other query failures.
13282 This corresponds to the
13283 <command>failure</command> counter
13284 of previous versions of
13285 <acronym>BIND</acronym> 9.
13286 Note: this counter is provided mainly for
13287 backward compatibility with the previous versions.
13288 Normally a more fine-grained counters such as
13289 <command>AuthQryRej</command> and
13290 <command>RecQryRej</command>
13291 that would also fall into this counter are provided,
13292 and so this counter would not be of much
13293 interest in practice.
13298 <entry colname="1">
13299 <para><command>XfrReqDone</command></para>
13301 <entry colname="2">
13302 <para><command></command></para>
13304 <entry colname="3">
13306 Requested zone transfers completed.
13311 <entry colname="1">
13312 <para><command>UpdateReqFwd</command></para>
13314 <entry colname="2">
13315 <para><command></command></para>
13317 <entry colname="3">
13319 Update requests forwarded.
13324 <entry colname="1">
13325 <para><command>UpdateRespFwd</command></para>
13327 <entry colname="2">
13328 <para><command></command></para>
13330 <entry colname="3">
13332 Update responses forwarded.
13337 <entry colname="1">
13338 <para><command>UpdateFwdFail</command></para>
13340 <entry colname="2">
13341 <para><command></command></para>
13343 <entry colname="3">
13345 Dynamic update forward failed.
13350 <entry colname="1">
13351 <para><command>UpdateDone</command></para>
13353 <entry colname="2">
13354 <para><command></command></para>
13356 <entry colname="3">
13358 Dynamic updates completed.
13363 <entry colname="1">
13364 <para><command>UpdateFail</command></para>
13366 <entry colname="2">
13367 <para><command></command></para>
13369 <entry colname="3">
13371 Dynamic updates failed.
13376 <entry colname="1">
13377 <para><command>UpdateBadPrereq</command></para>
13379 <entry colname="2">
13380 <para><command></command></para>
13382 <entry colname="3">
13384 Dynamic updates rejected due to prerequisite failure.
13394 <title>Zone Maintenance Statistics Counters</title>
13396 <informaltable colsep="0" rowsep="0">
13397 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13398 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
13399 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
13402 <entry colname="1">
13404 <emphasis>Symbol</emphasis>
13407 <entry colname="2">
13409 <emphasis>Description</emphasis>
13415 <entry colname="1">
13416 <para><command>NotifyOutv4</command></para>
13418 <entry colname="2">
13420 IPv4 notifies sent.
13425 <entry colname="1">
13426 <para><command>NotifyOutv6</command></para>
13428 <entry colname="2">
13430 IPv6 notifies sent.
13435 <entry colname="1">
13436 <para><command>NotifyInv4</command></para>
13438 <entry colname="2">
13440 IPv4 notifies received.
13445 <entry colname="1">
13446 <para><command>NotifyInv6</command></para>
13448 <entry colname="2">
13450 IPv6 notifies received.
13455 <entry colname="1">
13456 <para><command>NotifyRej</command></para>
13458 <entry colname="2">
13460 Incoming notifies rejected.
13465 <entry colname="1">
13466 <para><command>SOAOutv4</command></para>
13468 <entry colname="2">
13470 IPv4 SOA queries sent.
13475 <entry colname="1">
13476 <para><command>SOAOutv6</command></para>
13478 <entry colname="2">
13480 IPv6 SOA queries sent.
13485 <entry colname="1">
13486 <para><command>AXFRReqv4</command></para>
13488 <entry colname="2">
13490 IPv4 AXFR requested.
13495 <entry colname="1">
13496 <para><command>AXFRReqv6</command></para>
13498 <entry colname="2">
13500 IPv6 AXFR requested.
13505 <entry colname="1">
13506 <para><command>IXFRReqv4</command></para>
13508 <entry colname="2">
13510 IPv4 IXFR requested.
13515 <entry colname="1">
13516 <para><command>IXFRReqv6</command></para>
13518 <entry colname="2">
13520 IPv6 IXFR requested.
13525 <entry colname="1">
13526 <para><command>XfrSuccess</command></para>
13528 <entry colname="2">
13530 Zone transfer requests succeeded.
13535 <entry colname="1">
13536 <para><command>XfrFail</command></para>
13538 <entry colname="2">
13540 Zone transfer requests failed.
13550 <title>Resolver Statistics Counters</title>
13552 <informaltable colsep="0" rowsep="0">
13553 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13554 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
13555 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
13556 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
13559 <entry colname="1">
13561 <emphasis>Symbol</emphasis>
13564 <entry colname="2">
13566 <emphasis>BIND8 Symbol</emphasis>
13569 <entry colname="3">
13571 <emphasis>Description</emphasis>
13577 <entry colname="1">
13578 <para><command>Queryv4</command></para>
13580 <entry colname="2">
13581 <para><command>SFwdQ</command></para>
13583 <entry colname="3">
13590 <entry colname="1">
13591 <para><command>Queryv6</command></para>
13593 <entry colname="2">
13594 <para><command>SFwdQ</command></para>
13596 <entry colname="3">
13603 <entry colname="1">
13604 <para><command>Responsev4</command></para>
13606 <entry colname="2">
13607 <para><command>RR</command></para>
13609 <entry colname="3">
13611 IPv4 responses received.
13616 <entry colname="1">
13617 <para><command>Responsev6</command></para>
13619 <entry colname="2">
13620 <para><command>RR</command></para>
13622 <entry colname="3">
13624 IPv6 responses received.
13629 <entry colname="1">
13630 <para><command>NXDOMAIN</command></para>
13632 <entry colname="2">
13633 <para><command>RNXD</command></para>
13635 <entry colname="3">
13642 <entry colname="1">
13643 <para><command>SERVFAIL</command></para>
13645 <entry colname="2">
13646 <para><command>RFail</command></para>
13648 <entry colname="3">
13655 <entry colname="1">
13656 <para><command>FORMERR</command></para>
13658 <entry colname="2">
13659 <para><command>RFErr</command></para>
13661 <entry colname="3">
13668 <entry colname="1">
13669 <para><command>OtherError</command></para>
13671 <entry colname="2">
13672 <para><command>RErr</command></para>
13674 <entry colname="3">
13676 Other errors received.
13681 <entry colname="1">
13682 <para><command>EDNS0Fail</command></para>
13684 <entry colname="2">
13685 <para><command></command></para>
13687 <entry colname="3">
13689 EDNS(0) query failures.
13694 <entry colname="1">
13695 <para><command>Mismatch</command></para>
13697 <entry colname="2">
13698 <para><command>RDupR</command></para>
13700 <entry colname="3">
13702 Mismatch responses received.
13703 The DNS ID, response's source address,
13704 and/or the response's source port does not
13705 match what was expected.
13706 (The port must be 53 or as defined by
13707 the <command>port</command> option.)
13708 This may be an indication of a cache
13714 <entry colname="1">
13715 <para><command>Truncated</command></para>
13717 <entry colname="2">
13718 <para><command></command></para>
13720 <entry colname="3">
13722 Truncated responses received.
13727 <entry colname="1">
13728 <para><command>Lame</command></para>
13730 <entry colname="2">
13731 <para><command>RLame</command></para>
13733 <entry colname="3">
13735 Lame delegations received.
13740 <entry colname="1">
13741 <para><command>Retry</command></para>
13743 <entry colname="2">
13744 <para><command>SDupQ</command></para>
13746 <entry colname="3">
13748 Query retries performed.
13753 <entry colname="1">
13754 <para><command>QueryAbort</command></para>
13756 <entry colname="2">
13757 <para><command></command></para>
13759 <entry colname="3">
13761 Queries aborted due to quota control.
13766 <entry colname="1">
13767 <para><command>QuerySockFail</command></para>
13769 <entry colname="2">
13770 <para><command></command></para>
13772 <entry colname="3">
13774 Failures in opening query sockets.
13775 One common reason for such failures is a
13776 failure of opening a new socket due to a
13777 limitation on file descriptors.
13782 <entry colname="1">
13783 <para><command>QueryTimeout</command></para>
13785 <entry colname="2">
13786 <para><command></command></para>
13788 <entry colname="3">
13795 <entry colname="1">
13796 <para><command>GlueFetchv4</command></para>
13798 <entry colname="2">
13799 <para><command>SSysQ</command></para>
13801 <entry colname="3">
13803 IPv4 NS address fetches invoked.
13808 <entry colname="1">
13809 <para><command>GlueFetchv6</command></para>
13811 <entry colname="2">
13812 <para><command>SSysQ</command></para>
13814 <entry colname="3">
13816 IPv6 NS address fetches invoked.
13821 <entry colname="1">
13822 <para><command>GlueFetchv4Fail</command></para>
13824 <entry colname="2">
13825 <para><command></command></para>
13827 <entry colname="3">
13829 IPv4 NS address fetch failed.
13834 <entry colname="1">
13835 <para><command>GlueFetchv6Fail</command></para>
13837 <entry colname="2">
13838 <para><command></command></para>
13840 <entry colname="3">
13842 IPv6 NS address fetch failed.
13847 <entry colname="1">
13848 <para><command>ValAttempt</command></para>
13850 <entry colname="2">
13851 <para><command></command></para>
13853 <entry colname="3">
13855 DNSSEC validation attempted.
13860 <entry colname="1">
13861 <para><command>ValOk</command></para>
13863 <entry colname="2">
13864 <para><command></command></para>
13866 <entry colname="3">
13868 DNSSEC validation succeeded.
13873 <entry colname="1">
13874 <para><command>ValNegOk</command></para>
13876 <entry colname="2">
13877 <para><command></command></para>
13879 <entry colname="3">
13881 DNSSEC validation on negative information succeeded.
13886 <entry colname="1">
13887 <para><command>ValFail</command></para>
13889 <entry colname="2">
13890 <para><command></command></para>
13892 <entry colname="3">
13894 DNSSEC validation failed.
13899 <entry colname="1">
13900 <para><command>QryRTTnn</command></para>
13902 <entry colname="2">
13903 <para><command></command></para>
13905 <entry colname="3">
13907 Frequency table on round trip times (RTTs) of
13909 Each <command>nn</command> specifies the corresponding
13912 <command>nn_1</command>,
13913 <command>nn_2</command>,
13915 <command>nn_m</command>,
13916 the value of <command>nn_i</command> is the
13917 number of queries whose RTTs are between
13918 <command>nn_(i-1)</command> (inclusive) and
13919 <command>nn_i</command> (exclusive) milliseconds.
13920 For the sake of convenience we define
13921 <command>nn_0</command> to be 0.
13922 The last entry should be represented as
13923 <command>nn_m+</command>, which means the
13924 number of queries whose RTTs are equal to or over
13925 <command>nn_m</command> milliseconds.
13936 <title>Socket I/O Statistics Counters</title>
13939 Socket I/O statistics counters are defined per socket
13941 <command>UDP4</command> (UDP/IPv4),
13942 <command>UDP6</command> (UDP/IPv6),
13943 <command>TCP4</command> (TCP/IPv4),
13944 <command>TCP6</command> (TCP/IPv6),
13945 <command>Unix</command> (Unix Domain), and
13946 <command>FDwatch</command> (sockets opened outside the
13948 In the following table <command><TYPE></command>
13949 represents a socket type.
13950 Not all counters are available for all socket types;
13951 exceptions are noted in the description field.
13954 <informaltable colsep="0" rowsep="0">
13955 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13956 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
13957 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
13960 <entry colname="1">
13962 <emphasis>Symbol</emphasis>
13965 <entry colname="2">
13967 <emphasis>Description</emphasis>
13973 <entry colname="1">
13974 <para><command><TYPE>Open</command></para>
13976 <entry colname="2">
13978 Sockets opened successfully.
13979 This counter is not applicable to the
13980 <command>FDwatch</command> type.
13985 <entry colname="1">
13986 <para><command><TYPE>OpenFail</command></para>
13988 <entry colname="2">
13990 Failures of opening sockets.
13991 This counter is not applicable to the
13992 <command>FDwatch</command> type.
13997 <entry colname="1">
13998 <para><command><TYPE>Close</command></para>
14000 <entry colname="2">
14007 <entry colname="1">
14008 <para><command><TYPE>BindFail</command></para>
14010 <entry colname="2">
14012 Failures of binding sockets.
14017 <entry colname="1">
14018 <para><command><TYPE>ConnFail</command></para>
14020 <entry colname="2">
14022 Failures of connecting sockets.
14027 <entry colname="1">
14028 <para><command><TYPE>Conn</command></para>
14030 <entry colname="2">
14032 Connections established successfully.
14037 <entry colname="1">
14038 <para><command><TYPE>AcceptFail</command></para>
14040 <entry colname="2">
14042 Failures of accepting incoming connection requests.
14043 This counter is not applicable to the
14044 <command>UDP</command> and
14045 <command>FDwatch</command> types.
14050 <entry colname="1">
14051 <para><command><TYPE>Accept</command></para>
14053 <entry colname="2">
14055 Incoming connections successfully accepted.
14056 This counter is not applicable to the
14057 <command>UDP</command> and
14058 <command>FDwatch</command> types.
14063 <entry colname="1">
14064 <para><command><TYPE>SendErr</command></para>
14066 <entry colname="2">
14068 Errors in socket send operations.
14069 This counter corresponds
14070 to <command>SErr</command> counter of
14071 <command>BIND</command> 8.
14076 <entry colname="1">
14077 <para><command><TYPE>RecvErr</command></para>
14079 <entry colname="2">
14081 Errors in socket receive operations.
14082 This includes errors of send operations on a
14083 connected UDP socket notified by an ICMP error
14093 <title>Compatibility with <emphasis>BIND</emphasis> 8 Counters</title>
14095 Most statistics counters that were available
14096 in <command>BIND</command> 8 are also supported in
14097 <command>BIND</command> 9 as shown in the above tables.
14098 Here are notes about other counters that do not appear
14104 <term><command>RFwdR,SFwdR</command></term>
14107 These counters are not supported
14108 because <command>BIND</command> 9 does not adopt
14109 the notion of <emphasis>forwarding</emphasis>
14110 as <command>BIND</command> 8 did.
14116 <term><command>RAXFR</command></term>
14119 This counter is accessible in the Incoming Queries section.
14125 <term><command>RIQ</command></term>
14128 This counter is accessible in the Incoming Requests section.
14134 <term><command>ROpts</command></term>
14137 This counter is not supported
14138 because <command>BIND</command> 9 does not care
14139 about IP options in the first place.
14149 <chapter id="Bv9ARM.ch07">
14150 <title><acronym>BIND</acronym> 9 Security Considerations</title>
14151 <sect1 id="Access_Control_Lists">
14152 <title>Access Control Lists</title>
14154 Access Control Lists (ACLs) are address match lists that
14155 you can set up and nickname for future use in <command>allow-notify</command>,
14156 <command>allow-query</command>, <command>allow-query-on</command>,
14157 <command>allow-recursion</command>, <command>allow-recursion-on</command>,
14158 <command>blackhole</command>, <command>allow-transfer</command>,
14162 Using ACLs allows you to have finer control over who can access
14163 your name server, without cluttering up your config files with huge
14164 lists of IP addresses.
14167 It is a <emphasis>good idea</emphasis> to use ACLs, and to
14168 control access to your server. Limiting access to your server by
14169 outside parties can help prevent spoofing and denial of service (DoS) attacks against
14173 Here is an example of how to properly apply ACLs:
14177 // Set up an ACL named "bogusnets" that will block
14178 // RFC1918 space and some reserved space, which is
14179 // commonly used in spoofing attacks.
14181 0.0.0.0/8; 1.0.0.0/8; 2.0.0.0/8; 192.0.2.0/24;
14182 224.0.0.0/3; 10.0.0.0/8; 172.16.0.0/12;
14186 // Set up an ACL called our-nets. Replace this with the
14187 // real IP numbers.
14188 acl our-nets { x.x.x.x/24; x.x.x.x/21; };
14192 allow-query { our-nets; };
14193 allow-recursion { our-nets; };
14195 blackhole { bogusnets; };
14199 zone "example.com" {
14201 file "m/example.com";
14202 allow-query { any; };
14207 This allows recursive queries of the server from the outside
14208 unless recursion has been previously disabled.
14211 For more information on how to use ACLs to protect your server,
14212 see the <emphasis>AUSCERT</emphasis> advisory at:
14215 <ulink url="ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos"
14216 >ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos</ulink>
14220 <title><command>Chroot</command> and <command>Setuid</command></title>
14222 On UNIX servers, it is possible to run <acronym>BIND</acronym>
14223 in a <emphasis>chrooted</emphasis> environment (using
14224 the <command>chroot()</command> function) by specifying
14225 the "<option>-t</option>" option for <command>named</command>.
14226 This can help improve system security by placing
14227 <acronym>BIND</acronym> in a "sandbox", which will limit
14228 the damage done if a server is compromised.
14231 Another useful feature in the UNIX version of <acronym>BIND</acronym> is the
14232 ability to run the daemon as an unprivileged user ( <option>-u</option> <replaceable>user</replaceable> ).
14233 We suggest running as an unprivileged user when using the <command>chroot</command> feature.
14236 Here is an example command line to load <acronym>BIND</acronym> in a <command>chroot</command> sandbox,
14237 <command>/var/named</command>, and to run <command>named</command> <command>setuid</command> to
14241 <userinput>/usr/local/sbin/named -u 202 -t /var/named</userinput>
14245 <title>The <command>chroot</command> Environment</title>
14248 In order for a <command>chroot</command> environment
14250 work properly in a particular directory
14251 (for example, <filename>/var/named</filename>),
14252 you will need to set up an environment that includes everything
14253 <acronym>BIND</acronym> needs to run.
14254 From <acronym>BIND</acronym>'s point of view, <filename>/var/named</filename> is
14255 the root of the filesystem. You will need to adjust the values of
14257 like <command>directory</command> and <command>pid-file</command> to account
14261 Unlike with earlier versions of BIND, you typically will
14262 <emphasis>not</emphasis> need to compile <command>named</command>
14263 statically nor install shared libraries under the new root.
14264 However, depending on your operating system, you may need
14265 to set up things like
14266 <filename>/dev/zero</filename>,
14267 <filename>/dev/random</filename>,
14268 <filename>/dev/log</filename>, and
14269 <filename>/etc/localtime</filename>.
14274 <title>Using the <command>setuid</command> Function</title>
14277 Prior to running the <command>named</command> daemon,
14279 the <command>touch</command> utility (to change file
14281 modification times) or the <command>chown</command>
14283 set the user id and/or group id) on files
14284 to which you want <acronym>BIND</acronym>
14288 Note that if the <command>named</command> daemon is running as an
14289 unprivileged user, it will not be able to bind to new restricted
14290 ports if the server is reloaded.
14295 <sect1 id="dynamic_update_security">
14296 <title>Dynamic Update Security</title>
14299 Access to the dynamic
14300 update facility should be strictly limited. In earlier versions of
14301 <acronym>BIND</acronym>, the only way to do this was
14303 address of the host requesting the update, by listing an IP address
14305 network prefix in the <command>allow-update</command>
14307 This method is insecure since the source address of the update UDP
14309 is easily forged. Also note that if the IP addresses allowed by the
14310 <command>allow-update</command> option include the
14312 server which performs forwarding of dynamic updates, the master can
14314 trivially attacked by sending the update to the slave, which will
14315 forward it to the master with its own source IP address causing the
14316 master to approve it without question.
14320 For these reasons, we strongly recommend that updates be
14321 cryptographically authenticated by means of transaction signatures
14322 (TSIG). That is, the <command>allow-update</command>
14324 list only TSIG key names, not IP addresses or network
14325 prefixes. Alternatively, the new <command>update-policy</command>
14326 option can be used.
14330 Some sites choose to keep all dynamically-updated DNS data
14331 in a subdomain and delegate that subdomain to a separate zone. This
14332 way, the top-level zone containing critical data such as the IP
14334 of public web and mail servers need not allow dynamic update at
14341 <chapter id="Bv9ARM.ch08">
14342 <title>Troubleshooting</title>
14344 <title>Common Problems</title>
14346 <title>It's not working; how can I figure out what's wrong?</title>
14349 The best solution to solving installation and
14350 configuration issues is to take preventative measures by setting
14351 up logging files beforehand. The log files provide a
14352 source of hints and information that can be used to figure out
14353 what went wrong and how to fix the problem.
14359 <title>Incrementing and Changing the Serial Number</title>
14362 Zone serial numbers are just numbers — they aren't
14363 date related. A lot of people set them to a number that
14364 represents a date, usually of the form YYYYMMDDRR.
14365 Occasionally they will make a mistake and set them to a
14366 "date in the future" then try to correct them by setting
14367 them to the "current date". This causes problems because
14368 serial numbers are used to indicate that a zone has been
14369 updated. If the serial number on the slave server is
14370 lower than the serial number on the master, the slave
14371 server will attempt to update its copy of the zone.
14375 Setting the serial number to a lower number on the master
14376 server than the slave server means that the slave will not perform
14377 updates to its copy of the zone.
14381 The solution to this is to add 2147483647 (2^31-1) to the
14382 number, reload the zone and make sure all slaves have updated to
14383 the new zone serial number, then reset the number to what you want
14384 it to be, and reload the zone again.
14389 <title>Where Can I Get Help?</title>
14392 The Internet Systems Consortium
14393 (<acronym>ISC</acronym>) offers a wide range
14394 of support and service agreements for <acronym>BIND</acronym> and <acronym>DHCP</acronym> servers. Four
14395 levels of premium support are available and each level includes
14396 support for all <acronym>ISC</acronym> programs,
14397 significant discounts on products
14398 and training, and a recognized priority on bug fixes and
14399 non-funded feature requests. In addition, <acronym>ISC</acronym> offers a standard
14400 support agreement package which includes services ranging from bug
14401 fix announcements to remote support. It also includes training in
14402 <acronym>BIND</acronym> and <acronym>DHCP</acronym>.
14406 To discuss arrangements for support, contact
14407 <ulink url="mailto:info@isc.org">info@isc.org</ulink> or visit the
14408 <acronym>ISC</acronym> web page at
14409 <ulink url="http://www.isc.org/services/support/"
14410 >http://www.isc.org/services/support/</ulink>
14415 <appendix id="Bv9ARM.ch09">
14416 <title>Appendices</title>
14418 <title>Acknowledgments</title>
14419 <sect2 id="historical_dns_information">
14420 <title>A Brief History of the <acronym>DNS</acronym> and <acronym>BIND</acronym></title>
14423 Although the "official" beginning of the Domain Name
14424 System occurred in 1984 with the publication of RFC 920, the
14425 core of the new system was described in 1983 in RFCs 882 and
14426 883. From 1984 to 1987, the ARPAnet (the precursor to today's
14427 Internet) became a testbed of experimentation for developing the
14428 new naming/addressing scheme in a rapidly expanding,
14429 operational network environment. New RFCs were written and
14430 published in 1987 that modified the original documents to
14431 incorporate improvements based on the working model. RFC 1034,
14432 "Domain Names-Concepts and Facilities", and RFC 1035, "Domain
14433 Names-Implementation and Specification" were published and
14434 became the standards upon which all <acronym>DNS</acronym> implementations are
14439 The first working domain name server, called "Jeeves", was
14440 written in 1983-84 by Paul Mockapetris for operation on DEC
14442 machines located at the University of Southern California's
14444 Sciences Institute (USC-ISI) and SRI International's Network
14446 Center (SRI-NIC). A <acronym>DNS</acronym> server for
14447 Unix machines, the Berkeley Internet
14448 Name Domain (<acronym>BIND</acronym>) package, was
14449 written soon after by a group of
14450 graduate students at the University of California at Berkeley
14452 a grant from the US Defense Advanced Research Projects
14457 Versions of <acronym>BIND</acronym> through
14458 4.8.3 were maintained by the Computer
14459 Systems Research Group (CSRG) at UC Berkeley. Douglas Terry, Mark
14460 Painter, David Riggle and Songnian Zhou made up the initial <acronym>BIND</acronym>
14461 project team. After that, additional work on the software package
14462 was done by Ralph Campbell. Kevin Dunlap, a Digital Equipment
14464 employee on loan to the CSRG, worked on <acronym>BIND</acronym> for 2 years, from 1985
14465 to 1987. Many other people also contributed to <acronym>BIND</acronym> development
14466 during that time: Doug Kingston, Craig Partridge, Smoot
14468 Mike Muuss, Jim Bloom and Mike Schwartz. <acronym>BIND</acronym> maintenance was subsequently
14469 handled by Mike Karels and Øivind Kure.
14472 <acronym>BIND</acronym> versions 4.9 and 4.9.1 were
14473 released by Digital Equipment
14474 Corporation (now Compaq Computer Corporation). Paul Vixie, then
14475 a DEC employee, became <acronym>BIND</acronym>'s
14476 primary caretaker. He was assisted
14477 by Phil Almquist, Robert Elz, Alan Barrett, Paul Albitz, Bryan
14479 Partan, Andy Cherenson, Tom Limoncelli, Berthold Paffrath, Fuat
14480 Baran, Anant Kumar, Art Harkin, Win Treese, Don Lewis, Christophe
14481 Wolfhugel, and others.
14484 In 1994, <acronym>BIND</acronym> version 4.9.2 was sponsored by
14485 Vixie Enterprises. Paul
14486 Vixie became <acronym>BIND</acronym>'s principal
14487 architect/programmer.
14490 <acronym>BIND</acronym> versions from 4.9.3 onward
14491 have been developed and maintained
14492 by the Internet Systems Consortium and its predecessor,
14493 the Internet Software Consortium, with support being provided
14497 As co-architects/programmers, Bob Halley and
14498 Paul Vixie released the first production-ready version of
14499 <acronym>BIND</acronym> version 8 in May 1997.
14502 BIND version 9 was released in September 2000 and is a
14503 major rewrite of nearly all aspects of the underlying
14507 BIND versions 4 and 8 are officially deprecated.
14508 No additional development is done
14509 on BIND version 4 or BIND version 8.
14512 <acronym>BIND</acronym> development work is made
14513 possible today by the sponsorship
14514 of several corporations, and by the tireless work efforts of
14515 numerous individuals.
14520 <title>General <acronym>DNS</acronym> Reference Information</title>
14521 <sect2 id="ipv6addresses">
14522 <title>IPv6 addresses (AAAA)</title>
14524 IPv6 addresses are 128-bit identifiers for interfaces and
14525 sets of interfaces which were introduced in the <acronym>DNS</acronym> to facilitate
14526 scalable Internet routing. There are three types of addresses: <emphasis>Unicast</emphasis>,
14527 an identifier for a single interface;
14528 <emphasis>Anycast</emphasis>,
14529 an identifier for a set of interfaces; and <emphasis>Multicast</emphasis>,
14530 an identifier for a set of interfaces. Here we describe the global
14531 Unicast address scheme. For more information, see RFC 3587,
14532 "Global Unicast Address Format."
14535 IPv6 unicast addresses consist of a
14536 <emphasis>global routing prefix</emphasis>, a
14537 <emphasis>subnet identifier</emphasis>, and an
14538 <emphasis>interface identifier</emphasis>.
14541 The global routing prefix is provided by the
14542 upstream provider or ISP, and (roughly) corresponds to the
14543 IPv4 <emphasis>network</emphasis> section
14544 of the address range.
14546 The subnet identifier is for local subnetting, much the
14547 same as subnetting an
14548 IPv4 /16 network into /24 subnets.
14550 The interface identifier is the address of an individual
14551 interface on a given network; in IPv6, addresses belong to
14552 interfaces rather than to machines.
14555 The subnetting capability of IPv6 is much more flexible than
14556 that of IPv4: subnetting can be carried out on bit boundaries,
14557 in much the same way as Classless InterDomain Routing
14558 (CIDR), and the DNS PTR representation ("nibble" format)
14559 makes setting up reverse zones easier.
14562 The Interface Identifier must be unique on the local link,
14563 and is usually generated automatically by the IPv6
14564 implementation, although it is usually possible to
14565 override the default setting if necessary. A typical IPv6
14566 address might look like:
14567 <command>2001:db8:201:9:a00:20ff:fe81:2b32</command>
14570 IPv6 address specifications often contain long strings
14571 of zeros, so the architects have included a shorthand for
14573 them. The double colon (`::') indicates the longest possible
14575 of zeros that can fit, and can be used only once in an address.
14579 <sect1 id="bibliography">
14580 <title>Bibliography (and Suggested Reading)</title>
14582 <title>Request for Comments (RFCs)</title>
14584 Specification documents for the Internet protocol suite, including
14585 the <acronym>DNS</acronym>, are published as part of
14586 the Request for Comments (RFCs)
14587 series of technical notes. The standards themselves are defined
14588 by the Internet Engineering Task Force (IETF) and the Internet
14589 Engineering Steering Group (IESG). RFCs can be obtained online via FTP at:
14592 <ulink url="ftp://www.isi.edu/in-notes/">
14593 ftp://www.isi.edu/in-notes/RFC<replaceable>xxxx</replaceable>.txt
14597 (where <replaceable>xxxx</replaceable> is
14598 the number of the RFC). RFCs are also available via the Web at:
14601 <ulink url="http://www.ietf.org/rfc/"
14602 >http://www.ietf.org/rfc/</ulink>.
14606 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
14607 <title>Standards</title>
14609 <abbrev>RFC974</abbrev>
14611 <surname>Partridge</surname>
14612 <firstname>C.</firstname>
14614 <title>Mail Routing and the Domain System</title>
14615 <pubdate>January 1986</pubdate>
14618 <abbrev>RFC1034</abbrev>
14620 <surname>Mockapetris</surname>
14621 <firstname>P.V.</firstname>
14623 <title>Domain Names — Concepts and Facilities</title>
14624 <pubdate>November 1987</pubdate>
14627 <abbrev>RFC1035</abbrev>
14629 <surname>Mockapetris</surname>
14630 <firstname>P. V.</firstname>
14631 </author> <title>Domain Names — Implementation and
14632 Specification</title>
14633 <pubdate>November 1987</pubdate>
14636 <bibliodiv id="proposed_standards" xreflabel="Proposed Standards">
14638 <title>Proposed Standards</title>
14639 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
14641 <abbrev>RFC2181</abbrev>
14643 <surname>Elz</surname>
14644 <firstname>R., R. Bush</firstname>
14646 <title>Clarifications to the <acronym>DNS</acronym>
14647 Specification</title>
14648 <pubdate>July 1997</pubdate>
14651 <abbrev>RFC2308</abbrev>
14653 <surname>Andrews</surname>
14654 <firstname>M.</firstname>
14656 <title>Negative Caching of <acronym>DNS</acronym>
14658 <pubdate>March 1998</pubdate>
14661 <abbrev>RFC1995</abbrev>
14663 <surname>Ohta</surname>
14664 <firstname>M.</firstname>
14666 <title>Incremental Zone Transfer in <acronym>DNS</acronym></title>
14667 <pubdate>August 1996</pubdate>
14670 <abbrev>RFC1996</abbrev>
14672 <surname>Vixie</surname>
14673 <firstname>P.</firstname>
14675 <title>A Mechanism for Prompt Notification of Zone Changes</title>
14676 <pubdate>August 1996</pubdate>
14679 <abbrev>RFC2136</abbrev>
14682 <surname>Vixie</surname>
14683 <firstname>P.</firstname>
14686 <firstname>S.</firstname>
14687 <surname>Thomson</surname>
14690 <firstname>Y.</firstname>
14691 <surname>Rekhter</surname>
14694 <firstname>J.</firstname>
14695 <surname>Bound</surname>
14698 <title>Dynamic Updates in the Domain Name System</title>
14699 <pubdate>April 1997</pubdate>
14702 <abbrev>RFC2671</abbrev>
14705 <firstname>P.</firstname>
14706 <surname>Vixie</surname>
14709 <title>Extension Mechanisms for DNS (EDNS0)</title>
14710 <pubdate>August 1997</pubdate>
14713 <abbrev>RFC2672</abbrev>
14716 <firstname>M.</firstname>
14717 <surname>Crawford</surname>
14720 <title>Non-Terminal DNS Name Redirection</title>
14721 <pubdate>August 1999</pubdate>
14724 <abbrev>RFC2845</abbrev>
14727 <surname>Vixie</surname>
14728 <firstname>P.</firstname>
14731 <firstname>O.</firstname>
14732 <surname>Gudmundsson</surname>
14735 <firstname>D.</firstname>
14736 <surname>Eastlake</surname>
14737 <lineage>3rd</lineage>
14740 <firstname>B.</firstname>
14741 <surname>Wellington</surname>
14744 <title>Secret Key Transaction Authentication for <acronym>DNS</acronym> (TSIG)</title>
14745 <pubdate>May 2000</pubdate>
14748 <abbrev>RFC2930</abbrev>
14751 <firstname>D.</firstname>
14752 <surname>Eastlake</surname>
14753 <lineage>3rd</lineage>
14756 <title>Secret Key Establishment for DNS (TKEY RR)</title>
14757 <pubdate>September 2000</pubdate>
14760 <abbrev>RFC2931</abbrev>
14763 <firstname>D.</firstname>
14764 <surname>Eastlake</surname>
14765 <lineage>3rd</lineage>
14768 <title>DNS Request and Transaction Signatures (SIG(0)s)</title>
14769 <pubdate>September 2000</pubdate>
14772 <abbrev>RFC3007</abbrev>
14775 <firstname>B.</firstname>
14776 <surname>Wellington</surname>
14779 <title>Secure Domain Name System (DNS) Dynamic Update</title>
14780 <pubdate>November 2000</pubdate>
14783 <abbrev>RFC3645</abbrev>
14786 <firstname>S.</firstname>
14787 <surname>Kwan</surname>
14790 <firstname>P.</firstname>
14791 <surname>Garg</surname>
14794 <firstname>J.</firstname>
14795 <surname>Gilroy</surname>
14798 <firstname>L.</firstname>
14799 <surname>Esibov</surname>
14802 <firstname>J.</firstname>
14803 <surname>Westhead</surname>
14806 <firstname>R.</firstname>
14807 <surname>Hall</surname>
14810 <title>Generic Security Service Algorithm for Secret
14811 Key Transaction Authentication for DNS
14813 <pubdate>October 2003</pubdate>
14817 <title><acronym>DNS</acronym> Security Proposed Standards</title>
14819 <abbrev>RFC3225</abbrev>
14822 <firstname>D.</firstname>
14823 <surname>Conrad</surname>
14826 <title>Indicating Resolver Support of DNSSEC</title>
14827 <pubdate>December 2001</pubdate>
14830 <abbrev>RFC3833</abbrev>
14833 <firstname>D.</firstname>
14834 <surname>Atkins</surname>
14837 <firstname>R.</firstname>
14838 <surname>Austein</surname>
14841 <title>Threat Analysis of the Domain Name System (DNS)</title>
14842 <pubdate>August 2004</pubdate>
14845 <abbrev>RFC4033</abbrev>
14848 <firstname>R.</firstname>
14849 <surname>Arends</surname>
14852 <firstname>R.</firstname>
14853 <surname>Austein</surname>
14856 <firstname>M.</firstname>
14857 <surname>Larson</surname>
14860 <firstname>D.</firstname>
14861 <surname>Massey</surname>
14864 <firstname>S.</firstname>
14865 <surname>Rose</surname>
14868 <title>DNS Security Introduction and Requirements</title>
14869 <pubdate>March 2005</pubdate>
14872 <abbrev>RFC4034</abbrev>
14875 <firstname>R.</firstname>
14876 <surname>Arends</surname>
14879 <firstname>R.</firstname>
14880 <surname>Austein</surname>
14883 <firstname>M.</firstname>
14884 <surname>Larson</surname>
14887 <firstname>D.</firstname>
14888 <surname>Massey</surname>
14891 <firstname>S.</firstname>
14892 <surname>Rose</surname>
14895 <title>Resource Records for the DNS Security Extensions</title>
14896 <pubdate>March 2005</pubdate>
14899 <abbrev>RFC4035</abbrev>
14902 <firstname>R.</firstname>
14903 <surname>Arends</surname>
14906 <firstname>R.</firstname>
14907 <surname>Austein</surname>
14910 <firstname>M.</firstname>
14911 <surname>Larson</surname>
14914 <firstname>D.</firstname>
14915 <surname>Massey</surname>
14918 <firstname>S.</firstname>
14919 <surname>Rose</surname>
14922 <title>Protocol Modifications for the DNS
14923 Security Extensions</title>
14924 <pubdate>March 2005</pubdate>
14928 <title>Other Important RFCs About <acronym>DNS</acronym>
14929 Implementation</title>
14931 <abbrev>RFC1535</abbrev>
14933 <surname>Gavron</surname>
14934 <firstname>E.</firstname>
14936 <title>A Security Problem and Proposed Correction With Widely
14937 Deployed <acronym>DNS</acronym> Software.</title>
14938 <pubdate>October 1993</pubdate>
14941 <abbrev>RFC1536</abbrev>
14944 <surname>Kumar</surname>
14945 <firstname>A.</firstname>
14948 <firstname>J.</firstname>
14949 <surname>Postel</surname>
14952 <firstname>C.</firstname>
14953 <surname>Neuman</surname>
14956 <firstname>P.</firstname>
14957 <surname>Danzig</surname>
14960 <firstname>S.</firstname>
14961 <surname>Miller</surname>
14964 <title>Common <acronym>DNS</acronym> Implementation
14965 Errors and Suggested Fixes</title>
14966 <pubdate>October 1993</pubdate>
14969 <abbrev>RFC1982</abbrev>
14972 <surname>Elz</surname>
14973 <firstname>R.</firstname>
14976 <firstname>R.</firstname>
14977 <surname>Bush</surname>
14980 <title>Serial Number Arithmetic</title>
14981 <pubdate>August 1996</pubdate>
14984 <abbrev>RFC4074</abbrev>
14987 <surname>Morishita</surname>
14988 <firstname>Y.</firstname>
14991 <firstname>T.</firstname>
14992 <surname>Jinmei</surname>
14995 <title>Common Misbehaviour Against <acronym>DNS</acronym>
14996 Queries for IPv6 Addresses</title>
14997 <pubdate>May 2005</pubdate>
15001 <title>Resource Record Types</title>
15003 <abbrev>RFC1183</abbrev>
15006 <surname>Everhart</surname>
15007 <firstname>C.F.</firstname>
15010 <firstname>L. A.</firstname>
15011 <surname>Mamakos</surname>
15014 <firstname>R.</firstname>
15015 <surname>Ullmann</surname>
15018 <firstname>P.</firstname>
15019 <surname>Mockapetris</surname>
15022 <title>New <acronym>DNS</acronym> RR Definitions</title>
15023 <pubdate>October 1990</pubdate>
15026 <abbrev>RFC1706</abbrev>
15029 <surname>Manning</surname>
15030 <firstname>B.</firstname>
15033 <firstname>R.</firstname>
15034 <surname>Colella</surname>
15037 <title><acronym>DNS</acronym> NSAP Resource Records</title>
15038 <pubdate>October 1994</pubdate>
15041 <abbrev>RFC2168</abbrev>
15044 <surname>Daniel</surname>
15045 <firstname>R.</firstname>
15048 <firstname>M.</firstname>
15049 <surname>Mealling</surname>
15052 <title>Resolution of Uniform Resource Identifiers using
15053 the Domain Name System</title>
15054 <pubdate>June 1997</pubdate>
15057 <abbrev>RFC1876</abbrev>
15060 <surname>Davis</surname>
15061 <firstname>C.</firstname>
15064 <firstname>P.</firstname>
15065 <surname>Vixie</surname>
15068 <firstname>T.</firstname>
15069 <firstname>Goodwin</firstname>
15072 <firstname>I.</firstname>
15073 <surname>Dickinson</surname>
15076 <title>A Means for Expressing Location Information in the
15078 Name System</title>
15079 <pubdate>January 1996</pubdate>
15082 <abbrev>RFC2052</abbrev>
15085 <surname>Gulbrandsen</surname>
15086 <firstname>A.</firstname>
15089 <firstname>P.</firstname>
15090 <surname>Vixie</surname>
15093 <title>A <acronym>DNS</acronym> RR for Specifying the
15096 <pubdate>October 1996</pubdate>
15099 <abbrev>RFC2163</abbrev>
15101 <surname>Allocchio</surname>
15102 <firstname>A.</firstname>
15104 <title>Using the Internet <acronym>DNS</acronym> to
15106 Conformant Global Address Mapping</title>
15107 <pubdate>January 1998</pubdate>
15110 <abbrev>RFC2230</abbrev>
15112 <surname>Atkinson</surname>
15113 <firstname>R.</firstname>
15115 <title>Key Exchange Delegation Record for the <acronym>DNS</acronym></title>
15116 <pubdate>October 1997</pubdate>
15119 <abbrev>RFC2536</abbrev>
15121 <surname>Eastlake</surname>
15122 <firstname>D.</firstname>
15123 <lineage>3rd</lineage>
15125 <title>DSA KEYs and SIGs in the Domain Name System (DNS)</title>
15126 <pubdate>March 1999</pubdate>
15129 <abbrev>RFC2537</abbrev>
15131 <surname>Eastlake</surname>
15132 <firstname>D.</firstname>
15133 <lineage>3rd</lineage>
15135 <title>RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)</title>
15136 <pubdate>March 1999</pubdate>
15139 <abbrev>RFC2538</abbrev>
15142 <surname>Eastlake</surname>
15143 <firstname>D.</firstname>
15144 <lineage>3rd</lineage>
15147 <surname>Gudmundsson</surname>
15148 <firstname>O.</firstname>
15151 <title>Storing Certificates in the Domain Name System (DNS)</title>
15152 <pubdate>March 1999</pubdate>
15155 <abbrev>RFC2539</abbrev>
15158 <surname>Eastlake</surname>
15159 <firstname>D.</firstname>
15160 <lineage>3rd</lineage>
15163 <title>Storage of Diffie-Hellman Keys in the Domain Name System (DNS)</title>
15164 <pubdate>March 1999</pubdate>
15167 <abbrev>RFC2540</abbrev>
15170 <surname>Eastlake</surname>
15171 <firstname>D.</firstname>
15172 <lineage>3rd</lineage>
15175 <title>Detached Domain Name System (DNS) Information</title>
15176 <pubdate>March 1999</pubdate>
15179 <abbrev>RFC2782</abbrev>
15181 <surname>Gulbrandsen</surname>
15182 <firstname>A.</firstname>
15185 <surname>Vixie</surname>
15186 <firstname>P.</firstname>
15189 <surname>Esibov</surname>
15190 <firstname>L.</firstname>
15192 <title>A DNS RR for specifying the location of services (DNS SRV)</title>
15193 <pubdate>February 2000</pubdate>
15196 <abbrev>RFC2915</abbrev>
15198 <surname>Mealling</surname>
15199 <firstname>M.</firstname>
15202 <surname>Daniel</surname>
15203 <firstname>R.</firstname>
15205 <title>The Naming Authority Pointer (NAPTR) DNS Resource Record</title>
15206 <pubdate>September 2000</pubdate>
15209 <abbrev>RFC3110</abbrev>
15211 <surname>Eastlake</surname>
15212 <firstname>D.</firstname>
15213 <lineage>3rd</lineage>
15215 <title>RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)</title>
15216 <pubdate>May 2001</pubdate>
15219 <abbrev>RFC3123</abbrev>
15221 <surname>Koch</surname>
15222 <firstname>P.</firstname>
15224 <title>A DNS RR Type for Lists of Address Prefixes (APL RR)</title>
15225 <pubdate>June 2001</pubdate>
15228 <abbrev>RFC3596</abbrev>
15231 <surname>Thomson</surname>
15232 <firstname>S.</firstname>
15235 <firstname>C.</firstname>
15236 <surname>Huitema</surname>
15239 <firstname>V.</firstname>
15240 <surname>Ksinant</surname>
15243 <firstname>M.</firstname>
15244 <surname>Souissi</surname>
15247 <title><acronym>DNS</acronym> Extensions to support IP
15249 <pubdate>October 2003</pubdate>
15252 <abbrev>RFC3597</abbrev>
15254 <surname>Gustafsson</surname>
15255 <firstname>A.</firstname>
15257 <title>Handling of Unknown DNS Resource Record (RR) Types</title>
15258 <pubdate>September 2003</pubdate>
15262 <title><acronym>DNS</acronym> and the Internet</title>
15264 <abbrev>RFC1101</abbrev>
15266 <surname>Mockapetris</surname>
15267 <firstname>P. V.</firstname>
15269 <title><acronym>DNS</acronym> Encoding of Network Names
15270 and Other Types</title>
15271 <pubdate>April 1989</pubdate>
15274 <abbrev>RFC1123</abbrev>
15276 <surname>Braden</surname>
15277 <surname>R.</surname>
15279 <title>Requirements for Internet Hosts - Application and
15281 <pubdate>October 1989</pubdate>
15284 <abbrev>RFC1591</abbrev>
15286 <surname>Postel</surname>
15287 <firstname>J.</firstname>
15289 <title>Domain Name System Structure and Delegation</title>
15290 <pubdate>March 1994</pubdate>
15293 <abbrev>RFC2317</abbrev>
15296 <surname>Eidnes</surname>
15297 <firstname>H.</firstname>
15300 <firstname>G.</firstname>
15301 <surname>de Groot</surname>
15304 <firstname>P.</firstname>
15305 <surname>Vixie</surname>
15308 <title>Classless IN-ADDR.ARPA Delegation</title>
15309 <pubdate>March 1998</pubdate>
15312 <abbrev>RFC2826</abbrev>
15315 <surname>Internet Architecture Board</surname>
15318 <title>IAB Technical Comment on the Unique DNS Root</title>
15319 <pubdate>May 2000</pubdate>
15322 <abbrev>RFC2929</abbrev>
15325 <surname>Eastlake</surname>
15326 <firstname>D.</firstname>
15327 <lineage>3rd</lineage>
15330 <surname>Brunner-Williams</surname>
15331 <firstname>E.</firstname>
15334 <surname>Manning</surname>
15335 <firstname>B.</firstname>
15338 <title>Domain Name System (DNS) IANA Considerations</title>
15339 <pubdate>September 2000</pubdate>
15343 <title><acronym>DNS</acronym> Operations</title>
15345 <abbrev>RFC1033</abbrev>
15347 <surname>Lottor</surname>
15348 <firstname>M.</firstname>
15350 <title>Domain administrators operations guide.</title>
15351 <pubdate>November 1987</pubdate>
15354 <abbrev>RFC1537</abbrev>
15356 <surname>Beertema</surname>
15357 <firstname>P.</firstname>
15359 <title>Common <acronym>DNS</acronym> Data File
15360 Configuration Errors</title>
15361 <pubdate>October 1993</pubdate>
15364 <abbrev>RFC1912</abbrev>
15366 <surname>Barr</surname>
15367 <firstname>D.</firstname>
15369 <title>Common <acronym>DNS</acronym> Operational and
15370 Configuration Errors</title>
15371 <pubdate>February 1996</pubdate>
15374 <abbrev>RFC2010</abbrev>
15377 <surname>Manning</surname>
15378 <firstname>B.</firstname>
15381 <firstname>P.</firstname>
15382 <surname>Vixie</surname>
15385 <title>Operational Criteria for Root Name Servers.</title>
15386 <pubdate>October 1996</pubdate>
15389 <abbrev>RFC2219</abbrev>
15392 <surname>Hamilton</surname>
15393 <firstname>M.</firstname>
15396 <firstname>R.</firstname>
15397 <surname>Wright</surname>
15400 <title>Use of <acronym>DNS</acronym> Aliases for
15401 Network Services.</title>
15402 <pubdate>October 1997</pubdate>
15406 <title>Internationalized Domain Names</title>
15408 <abbrev>RFC2825</abbrev>
15411 <surname>IAB</surname>
15414 <surname>Daigle</surname>
15415 <firstname>R.</firstname>
15418 <title>A Tangled Web: Issues of I18N, Domain Names,
15419 and the Other Internet protocols</title>
15420 <pubdate>May 2000</pubdate>
15423 <abbrev>RFC3490</abbrev>
15426 <surname>Faltstrom</surname>
15427 <firstname>P.</firstname>
15430 <surname>Hoffman</surname>
15431 <firstname>P.</firstname>
15434 <surname>Costello</surname>
15435 <firstname>A.</firstname>
15438 <title>Internationalizing Domain Names in Applications (IDNA)</title>
15439 <pubdate>March 2003</pubdate>
15442 <abbrev>RFC3491</abbrev>
15445 <surname>Hoffman</surname>
15446 <firstname>P.</firstname>
15449 <surname>Blanchet</surname>
15450 <firstname>M.</firstname>
15453 <title>Nameprep: A Stringprep Profile for Internationalized Domain Names</title>
15454 <pubdate>March 2003</pubdate>
15457 <abbrev>RFC3492</abbrev>
15460 <surname>Costello</surname>
15461 <firstname>A.</firstname>
15464 <title>Punycode: A Bootstring encoding of Unicode
15465 for Internationalized Domain Names in
15466 Applications (IDNA)</title>
15467 <pubdate>March 2003</pubdate>
15471 <title>Other <acronym>DNS</acronym>-related RFCs</title>
15474 Note: the following list of RFCs, although
15475 <acronym>DNS</acronym>-related, are not
15476 concerned with implementing software.
15480 <abbrev>RFC1464</abbrev>
15482 <surname>Rosenbaum</surname>
15483 <firstname>R.</firstname>
15485 <title>Using the Domain Name System To Store Arbitrary String
15487 <pubdate>May 1993</pubdate>
15490 <abbrev>RFC1713</abbrev>
15492 <surname>Romao</surname>
15493 <firstname>A.</firstname>
15495 <title>Tools for <acronym>DNS</acronym> Debugging</title>
15496 <pubdate>November 1994</pubdate>
15499 <abbrev>RFC1794</abbrev>
15501 <surname>Brisco</surname>
15502 <firstname>T.</firstname>
15504 <title><acronym>DNS</acronym> Support for Load
15506 <pubdate>April 1995</pubdate>
15509 <abbrev>RFC2240</abbrev>
15511 <surname>Vaughan</surname>
15512 <firstname>O.</firstname>
15514 <title>A Legal Basis for Domain Name Allocation</title>
15515 <pubdate>November 1997</pubdate>
15518 <abbrev>RFC2345</abbrev>
15521 <surname>Klensin</surname>
15522 <firstname>J.</firstname>
15525 <firstname>T.</firstname>
15526 <surname>Wolf</surname>
15529 <firstname>G.</firstname>
15530 <surname>Oglesby</surname>
15533 <title>Domain Names and Company Name Retrieval</title>
15534 <pubdate>May 1998</pubdate>
15537 <abbrev>RFC2352</abbrev>
15539 <surname>Vaughan</surname>
15540 <firstname>O.</firstname>
15542 <title>A Convention For Using Legal Names as Domain Names</title>
15543 <pubdate>May 1998</pubdate>
15546 <abbrev>RFC3071</abbrev>
15549 <surname>Klensin</surname>
15550 <firstname>J.</firstname>
15553 <title>Reflections on the DNS, RFC 1591, and Categories of Domains</title>
15554 <pubdate>February 2001</pubdate>
15557 <abbrev>RFC3258</abbrev>
15560 <surname>Hardie</surname>
15561 <firstname>T.</firstname>
15564 <title>Distributing Authoritative Name Servers via
15565 Shared Unicast Addresses</title>
15566 <pubdate>April 2002</pubdate>
15569 <abbrev>RFC3901</abbrev>
15572 <surname>Durand</surname>
15573 <firstname>A.</firstname>
15576 <firstname>J.</firstname>
15577 <surname>Ihren</surname>
15580 <title>DNS IPv6 Transport Operational Guidelines</title>
15581 <pubdate>September 2004</pubdate>
15585 <title>Obsolete and Unimplemented Experimental RFC</title>
15587 <abbrev>RFC1712</abbrev>
15590 <surname>Farrell</surname>
15591 <firstname>C.</firstname>
15594 <firstname>M.</firstname>
15595 <surname>Schulze</surname>
15598 <firstname>S.</firstname>
15599 <surname>Pleitner</surname>
15602 <firstname>D.</firstname>
15603 <surname>Baldoni</surname>
15606 <title><acronym>DNS</acronym> Encoding of Geographical
15608 <pubdate>November 1994</pubdate>
15611 <abbrev>RFC2673</abbrev>
15614 <surname>Crawford</surname>
15615 <firstname>M.</firstname>
15618 <title>Binary Labels in the Domain Name System</title>
15619 <pubdate>August 1999</pubdate>
15622 <abbrev>RFC2874</abbrev>
15625 <surname>Crawford</surname>
15626 <firstname>M.</firstname>
15629 <surname>Huitema</surname>
15630 <firstname>C.</firstname>
15633 <title>DNS Extensions to Support IPv6 Address Aggregation
15634 and Renumbering</title>
15635 <pubdate>July 2000</pubdate>
15639 <title>Obsoleted DNS Security RFCs</title>
15642 Most of these have been consolidated into RFC4033,
15643 RFC4034 and RFC4035 which collectively describe DNSSECbis.
15647 <abbrev>RFC2065</abbrev>
15650 <surname>Eastlake</surname>
15651 <lineage>3rd</lineage>
15652 <firstname>D.</firstname>
15655 <firstname>C.</firstname>
15656 <surname>Kaufman</surname>
15659 <title>Domain Name System Security Extensions</title>
15660 <pubdate>January 1997</pubdate>
15663 <abbrev>RFC2137</abbrev>
15665 <surname>Eastlake</surname>
15666 <lineage>3rd</lineage>
15667 <firstname>D.</firstname>
15669 <title>Secure Domain Name System Dynamic Update</title>
15670 <pubdate>April 1997</pubdate>
15673 <abbrev>RFC2535</abbrev>
15676 <surname>Eastlake</surname>
15677 <lineage>3rd</lineage>
15678 <firstname>D.</firstname>
15681 <title>Domain Name System Security Extensions</title>
15682 <pubdate>March 1999</pubdate>
15685 <abbrev>RFC3008</abbrev>
15688 <surname>Wellington</surname>
15689 <firstname>B.</firstname>
15692 <title>Domain Name System Security (DNSSEC)
15693 Signing Authority</title>
15694 <pubdate>November 2000</pubdate>
15697 <abbrev>RFC3090</abbrev>
15700 <surname>Lewis</surname>
15701 <firstname>E.</firstname>
15704 <title>DNS Security Extension Clarification on Zone Status</title>
15705 <pubdate>March 2001</pubdate>
15708 <abbrev>RFC3445</abbrev>
15711 <surname>Massey</surname>
15712 <firstname>D.</firstname>
15715 <surname>Rose</surname>
15716 <firstname>S.</firstname>
15719 <title>Limiting the Scope of the KEY Resource Record (RR)</title>
15720 <pubdate>December 2002</pubdate>
15723 <abbrev>RFC3655</abbrev>
15726 <surname>Wellington</surname>
15727 <firstname>B.</firstname>
15730 <surname>Gudmundsson</surname>
15731 <firstname>O.</firstname>
15734 <title>Redefinition of DNS Authenticated Data (AD) bit</title>
15735 <pubdate>November 2003</pubdate>
15738 <abbrev>RFC3658</abbrev>
15741 <surname>Gudmundsson</surname>
15742 <firstname>O.</firstname>
15745 <title>Delegation Signer (DS) Resource Record (RR)</title>
15746 <pubdate>December 2003</pubdate>
15749 <abbrev>RFC3755</abbrev>
15752 <surname>Weiler</surname>
15753 <firstname>S.</firstname>
15756 <title>Legacy Resolver Compatibility for Delegation Signer (DS)</title>
15757 <pubdate>May 2004</pubdate>
15760 <abbrev>RFC3757</abbrev>
15763 <surname>Kolkman</surname>
15764 <firstname>O.</firstname>
15767 <surname>Schlyter</surname>
15768 <firstname>J.</firstname>
15771 <surname>Lewis</surname>
15772 <firstname>E.</firstname>
15775 <title>Domain Name System KEY (DNSKEY) Resource Record
15776 (RR) Secure Entry Point (SEP) Flag</title>
15777 <pubdate>April 2004</pubdate>
15780 <abbrev>RFC3845</abbrev>
15783 <surname>Schlyter</surname>
15784 <firstname>J.</firstname>
15787 <title>DNS Security (DNSSEC) NextSECure (NSEC) RDATA Format</title>
15788 <pubdate>August 2004</pubdate>
15793 <sect2 id="internet_drafts">
15794 <title>Internet Drafts</title>
15796 Internet Drafts (IDs) are rough-draft working documents of
15797 the Internet Engineering Task Force. They are, in essence, RFCs
15798 in the preliminary stages of development. Implementors are
15800 to regard IDs as archival, and they should not be quoted or cited
15801 in any formal documents unless accompanied by the disclaimer that
15802 they are "works in progress." IDs have a lifespan of six months
15803 after which they are deleted unless updated by their authors.
15807 <title>Other Documents About <acronym>BIND</acronym></title>
15813 <surname>Albitz</surname>
15814 <firstname>Paul</firstname>
15817 <firstname>Cricket</firstname>
15818 <surname>Liu</surname>
15821 <title><acronym>DNS</acronym> and <acronym>BIND</acronym></title>
15824 <holder>Sebastopol, CA: O'Reilly and Associates</holder>
15831 <xi:include href="libdns.xml"/>
15836 <reference id="Bv9ARM.ch10">
15837 <title>Manual pages</title>
15838 <xi:include href="../../bin/dig/dig.docbook"/>
15839 <xi:include href="../../bin/dig/host.docbook"/>
15840 <xi:include href="../../bin/dnssec/dnssec-dsfromkey.docbook"/>
15841 <xi:include href="../../bin/dnssec/dnssec-keyfromlabel.docbook"/>
15842 <xi:include href="../../bin/dnssec/dnssec-keygen.docbook"/>
15843 <xi:include href="../../bin/dnssec/dnssec-revoke.docbook"/>
15844 <xi:include href="../../bin/dnssec/dnssec-settime.docbook"/>
15845 <xi:include href="../../bin/dnssec/dnssec-signzone.docbook"/>
15846 <xi:include href="../../bin/check/named-checkconf.docbook"/>
15847 <xi:include href="../../bin/check/named-checkzone.docbook"/>
15848 <xi:include href="../../bin/named/named.docbook"/>
15849 <xi:include href="../../bin/tools/named-journalprint.docbook"/>
15850 <!-- named.conf.docbook and others? -->
15851 <xi:include href="../../bin/nsupdate/nsupdate.docbook"/>
15852 <xi:include href="../../bin/rndc/rndc.docbook"/>
15853 <xi:include href="../../bin/rndc/rndc.conf.docbook"/>
15854 <xi:include href="../../bin/confgen/rndc-confgen.docbook"/>
15855 <xi:include href="../../bin/confgen/ddns-confgen.docbook"/>
15856 <xi:include href="../../bin/tools/arpaname.docbook"/>
15857 <xi:include href="../../bin/tools/genrandom.docbook"/>
15858 <xi:include href="../../bin/tools/isc-hmac-fixup.docbook"/>
15859 <xi:include href="../../bin/tools/nsec3hash.docbook"/>