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18 <!-- Converted by db4-upgrade version 1.0 -->
19 <book xmlns="http://docbook.org/ns/docbook" version="5.0">
21 <title>BIND 9 Administrator Reference Manual</title>
35 <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
42 <holder>Internet Software Consortium.</holder>
44 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="releaseinfo.xml"/>
47 <chapter xml:id="Bv9ARM.ch01"><info><title>Introduction</title></info>
50 The Internet Domain Name System (<acronym>DNS</acronym>)
51 consists of the syntax
52 to specify the names of entities in the Internet in a hierarchical
53 manner, the rules used for delegating authority over names, and the
54 system implementation that actually maps names to Internet
55 addresses. <acronym>DNS</acronym> data is maintained in a
57 hierarchical databases.
60 <section xml:id="doc_scope"><info><title>Scope of Document</title></info>
63 The Berkeley Internet Name Domain
64 (<acronym>BIND</acronym>) implements a
65 domain name server for a number of operating systems. This
66 document provides basic information about the installation and
67 care of the Internet Systems Consortium (<acronym>ISC</acronym>)
68 <acronym>BIND</acronym> version 9 software package for
69 system administrators.
71 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="pkgversion.xml"/>
74 <section xml:id="organization"><info><title>Organization of This Document</title></info>
77 In this document, <emphasis>Chapter 1</emphasis> introduces
78 the basic <acronym>DNS</acronym> and <acronym>BIND</acronym> concepts. <emphasis>Chapter 2</emphasis>
79 describes resource requirements for running <acronym>BIND</acronym> in various
80 environments. Information in <emphasis>Chapter 3</emphasis> is
81 <emphasis>task-oriented</emphasis> in its presentation and is
82 organized functionally, to aid in the process of installing the
83 <acronym>BIND</acronym> 9 software. The task-oriented
84 section is followed by
85 <emphasis>Chapter 4</emphasis>, which contains more advanced
86 concepts that the system administrator may need for implementing
87 certain options. <emphasis>Chapter 5</emphasis>
88 describes the <acronym>BIND</acronym> 9 lightweight
89 resolver. The contents of <emphasis>Chapter 6</emphasis> are
90 organized as in a reference manual to aid in the ongoing
91 maintenance of the software. <emphasis>Chapter 7</emphasis> addresses
92 security considerations, and
93 <emphasis>Chapter 8</emphasis> contains troubleshooting help. The
94 main body of the document is followed by several
95 <emphasis>appendices</emphasis> which contain useful reference
96 information, such as a <emphasis>bibliography</emphasis> and
97 historic information related to <acronym>BIND</acronym>
102 <section xml:id="conventions"><info><title>Conventions Used in This Document</title></info>
105 In this document, we use the following general typographic
111 <colspec colname="1" colnum="1" colwidth="3.000in"/>
112 <colspec colname="2" colnum="2" colwidth="2.625in"/>
117 <emphasis>To describe:</emphasis>
122 <emphasis>We use the style:</emphasis>
129 a pathname, filename, URL, hostname,
130 mailing list name, or new term or concept
135 <filename>Fixed width</filename>
148 <userinput>Fixed Width Bold</userinput>
160 <computeroutput>Fixed Width</computeroutput>
169 The following conventions are used in descriptions of the
170 <acronym>BIND</acronym> configuration file:<informaltable colsep="0" frame="all" rowsep="0">
171 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
172 <colspec colname="1" colnum="1" colsep="0" colwidth="3.000in"/>
173 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
176 <entry colname="1" colsep="1" rowsep="1">
178 <emphasis>To describe:</emphasis>
181 <entry colname="2" rowsep="1">
183 <emphasis>We use the style:</emphasis>
188 <entry colname="1" colsep="1" rowsep="1">
193 <entry colname="2" rowsep="1">
195 <literal>Fixed Width</literal>
200 <entry colname="1" colsep="1" rowsep="1">
205 <entry colname="2" rowsep="1">
207 <varname>Fixed Width</varname>
212 <entry colname="1" colsep="1">
219 <optional>Text is enclosed in square brackets</optional>
228 <section xml:id="dns_overview"><info><title>The Domain Name System (<acronym>DNS</acronym>)</title></info>
231 The purpose of this document is to explain the installation
232 and upkeep of the <acronym>BIND</acronym> (Berkeley Internet
233 Name Domain) software package, and we
234 begin by reviewing the fundamentals of the Domain Name System
235 (<acronym>DNS</acronym>) as they relate to <acronym>BIND</acronym>.
238 <section xml:id="dns_fundamentals"><info><title>DNS Fundamentals</title></info>
241 The Domain Name System (DNS) is a hierarchical, distributed
242 database. It stores information for mapping Internet host names to
244 addresses and vice versa, mail routing information, and other data
245 used by Internet applications.
249 Clients look up information in the DNS by calling a
250 <emphasis>resolver</emphasis> library, which sends queries to one or
251 more <emphasis>name servers</emphasis> and interprets the responses.
252 The <acronym>BIND</acronym> 9 software distribution
254 name server, <command>named</command>, and a resolver
255 library, <command>liblwres</command>. The older
256 <command>libbind</command> resolver library is also available
257 from ISC as a separate download.
261 <section xml:id="domain_names"><info><title>Domains and Domain Names</title></info>
264 The data stored in the DNS is identified by <emphasis>domain names</emphasis> that are organized as a tree according to
265 organizational or administrative boundaries. Each node of the tree,
266 called a <emphasis>domain</emphasis>, is given a label. The domain
268 node is the concatenation of all the labels on the path from the
269 node to the <emphasis>root</emphasis> node. This is represented
270 in written form as a string of labels listed from right to left and
271 separated by dots. A label need only be unique within its parent
276 For example, a domain name for a host at the
277 company <emphasis>Example, Inc.</emphasis> could be
278 <literal>ourhost.example.com</literal>,
279 where <literal>com</literal> is the
280 top level domain to which
281 <literal>ourhost.example.com</literal> belongs,
282 <literal>example</literal> is
283 a subdomain of <literal>com</literal>, and
284 <literal>ourhost</literal> is the
289 For administrative purposes, the name space is partitioned into
290 areas called <emphasis>zones</emphasis>, each starting at a node and
291 extending down to the leaf nodes or to nodes where other zones
293 The data for each zone is stored in a <emphasis>name server</emphasis>, which answers queries about the zone using the
294 <emphasis>DNS protocol</emphasis>.
298 The data associated with each domain name is stored in the
299 form of <emphasis>resource records</emphasis> (<acronym>RR</acronym>s).
300 Some of the supported resource record types are described in
301 <xref linkend="types_of_resource_records_and_when_to_use_them"/>.
305 For more detailed information about the design of the DNS and
306 the DNS protocol, please refer to the standards documents listed in
307 <xref linkend="rfcs"/>.
311 <section xml:id="zones"><info><title>Zones</title></info>
314 To properly operate a name server, it is important to understand
315 the difference between a <emphasis>zone</emphasis>
316 and a <emphasis>domain</emphasis>.
320 As stated previously, a zone is a point of delegation in
321 the <acronym>DNS</acronym> tree. A zone consists of
322 those contiguous parts of the domain
323 tree for which a name server has complete information and over which
324 it has authority. It contains all domain names from a certain point
325 downward in the domain tree except those which are delegated to
326 other zones. A delegation point is marked by one or more
327 <emphasis>NS records</emphasis> in the
328 parent zone, which should be matched by equivalent NS records at
329 the root of the delegated zone.
333 For instance, consider the <literal>example.com</literal>
334 domain which includes names
335 such as <literal>host.aaa.example.com</literal> and
336 <literal>host.bbb.example.com</literal> even though
337 the <literal>example.com</literal> zone includes
338 only delegations for the <literal>aaa.example.com</literal> and
339 <literal>bbb.example.com</literal> zones. A zone can
341 exactly to a single domain, but could also include only part of a
342 domain, the rest of which could be delegated to other
343 name servers. Every name in the <acronym>DNS</acronym>
345 <emphasis>domain</emphasis>, even if it is
346 <emphasis>terminal</emphasis>, that is, has no
347 <emphasis>subdomains</emphasis>. Every subdomain is a domain and
348 every domain except the root is also a subdomain. The terminology is
349 not intuitive and we suggest that you read RFCs 1033, 1034 and 1035
351 gain a complete understanding of this difficult and subtle
356 Though <acronym>BIND</acronym> is called a "domain name
358 it deals primarily in terms of zones. The master and slave
359 declarations in the <filename>named.conf</filename> file
361 zones, not domains. When you ask some other site if it is willing to
362 be a slave server for your <emphasis>domain</emphasis>, you are
363 actually asking for slave service for some collection of zones.
367 <section xml:id="auth_servers"><info><title>Authoritative Name Servers</title></info>
370 Each zone is served by at least
371 one <emphasis>authoritative name server</emphasis>,
372 which contains the complete data for the zone.
373 To make the DNS tolerant of server and network failures,
374 most zones have two or more authoritative servers, on
379 Responses from authoritative servers have the "authoritative
380 answer" (AA) bit set in the response packets. This makes them
381 easy to identify when debugging DNS configurations using tools like
382 <command>dig</command> (<xref linkend="diagnostic_tools"/>).
385 <section xml:id="primary_master"><info><title>The Primary Master</title></info>
388 The authoritative server where the master copy of the zone
389 data is maintained is called the
390 <emphasis>primary master</emphasis> server, or simply the
391 <emphasis>primary</emphasis>. Typically it loads the zone
392 contents from some local file edited by humans or perhaps
393 generated mechanically from some other local file which is
394 edited by humans. This file is called the
395 <emphasis>zone file</emphasis> or
396 <emphasis>master file</emphasis>.
400 In some cases, however, the master file may not be edited
401 by humans at all, but may instead be the result of
402 <emphasis>dynamic update</emphasis> operations.
406 <section xml:id="slave_server"><info><title>Slave Servers</title></info>
409 The other authoritative servers, the <emphasis>slave</emphasis>
410 servers (also known as <emphasis>secondary</emphasis> servers)
412 the zone contents from another server using a replication process
413 known as a <emphasis>zone transfer</emphasis>. Typically the data
415 transferred directly from the primary master, but it is also
417 to transfer it from another slave. In other words, a slave server
418 may itself act as a master to a subordinate slave server.
422 <section xml:id="stealth_server"><info><title>Stealth Servers</title></info>
425 Usually all of the zone's authoritative servers are listed in
426 NS records in the parent zone. These NS records constitute
427 a <emphasis>delegation</emphasis> of the zone from the parent.
428 The authoritative servers are also listed in the zone file itself,
429 at the <emphasis>top level</emphasis> or <emphasis>apex</emphasis>
430 of the zone. You can list servers in the zone's top-level NS
431 records that are not in the parent's NS delegation, but you cannot
432 list servers in the parent's delegation that are not present at
433 the zone's top level.
437 A <emphasis>stealth server</emphasis> is a server that is
438 authoritative for a zone but is not listed in that zone's NS
439 records. Stealth servers can be used for keeping a local copy of
441 zone to speed up access to the zone's records or to make sure that
443 zone is available even if all the "official" servers for the zone
449 A configuration where the primary master server itself is a
450 stealth server is often referred to as a "hidden primary"
451 configuration. One use for this configuration is when the primary
453 is behind a firewall and therefore unable to communicate directly
454 with the outside world.
460 <section xml:id="cache_servers"><info><title>Caching Name Servers</title></info>
463 - Terminology here is inconsistent. Probably ought to
464 - convert to using "recursive name server" everywhere
465 - with just a note about "caching" terminology.
469 The resolver libraries provided by most operating systems are
470 <emphasis>stub resolvers</emphasis>, meaning that they are not
472 performing the full DNS resolution process by themselves by talking
473 directly to the authoritative servers. Instead, they rely on a
475 name server to perform the resolution on their behalf. Such a
477 is called a <emphasis>recursive</emphasis> name server; it performs
478 <emphasis>recursive lookups</emphasis> for local clients.
482 To improve performance, recursive servers cache the results of
483 the lookups they perform. Since the processes of recursion and
484 caching are intimately connected, the terms
485 <emphasis>recursive server</emphasis> and
486 <emphasis>caching server</emphasis> are often used synonymously.
490 The length of time for which a record may be retained in
491 the cache of a caching name server is controlled by the
492 Time To Live (TTL) field associated with each resource record.
495 <section xml:id="forwarder"><info><title>Forwarding</title></info>
498 Even a caching name server does not necessarily perform
499 the complete recursive lookup itself. Instead, it can
500 <emphasis>forward</emphasis> some or all of the queries
501 that it cannot satisfy from its cache to another caching name
503 commonly referred to as a <emphasis>forwarder</emphasis>.
507 There may be one or more forwarders,
508 and they are queried in turn until the list is exhausted or an
510 is found. Forwarders are typically used when you do not
511 wish all the servers at a given site to interact directly with the
513 the Internet servers. A typical scenario would involve a number
514 of internal <acronym>DNS</acronym> servers and an
515 Internet firewall. Servers unable
516 to pass packets through the firewall would forward to the server
517 that can do it, and that server would query the Internet <acronym>DNS</acronym> servers
518 on the internal server's behalf.
524 <section xml:id="multi_role"><info><title>Name Servers in Multiple Roles</title></info>
527 The <acronym>BIND</acronym> name server can
528 simultaneously act as
529 a master for some zones, a slave for other zones, and as a caching
530 (recursive) server for a set of local clients.
534 However, since the functions of authoritative name service
535 and caching/recursive name service are logically separate, it is
536 often advantageous to run them on separate server machines.
538 A server that only provides authoritative name service
539 (an <emphasis>authoritative-only</emphasis> server) can run with
540 recursion disabled, improving reliability and security.
542 A server that is not authoritative for any zones and only provides
543 recursive service to local
544 clients (a <emphasis>caching-only</emphasis> server)
545 does not need to be reachable from the Internet at large and can
546 be placed inside a firewall.
554 <chapter xml:id="Bv9ARM.ch02"><info><title><acronym>BIND</acronym> Resource Requirements</title></info>
556 <section xml:id="hw_req"><info><title>Hardware requirements</title></info>
558 <acronym>DNS</acronym> hardware requirements have
559 traditionally been quite modest.
560 For many installations, servers that have been pensioned off from
561 active duty have performed admirably as <acronym>DNS</acronym> servers.
564 The DNSSEC features of <acronym>BIND</acronym> 9
565 may prove to be quite
566 CPU intensive however, so organizations that make heavy use of these
567 features may wish to consider larger systems for these applications.
568 <acronym>BIND</acronym> 9 is fully multithreaded, allowing
570 multiprocessor systems for installations that need it.
573 <section xml:id="cpu_req"><info><title>CPU Requirements</title></info>
575 CPU requirements for <acronym>BIND</acronym> 9 range from
577 for serving of static zones without caching, to enterprise-class
578 machines if you intend to process many dynamic updates and DNSSEC
579 signed zones, serving many thousands of queries per second.
582 <section xml:id="mem_req"><info><title>Memory Requirements</title></info>
584 The memory of the server has to be large enough to fit the
585 cache and zones loaded off disk. The <command>max-cache-size</command>
586 option can be used to limit the amount of memory used by the cache,
587 at the expense of reducing cache hit rates and causing more <acronym>DNS</acronym>
589 Additionally, if additional section caching
590 (<xref linkend="acache"/>) is enabled,
591 the <command>max-acache-size</command> option can be used to
593 of memory used by the mechanism.
594 It is still good practice to have enough memory to load
595 all zone and cache data into memory — unfortunately, the best
597 to determine this for a given installation is to watch the name server
598 in operation. After a few weeks the server process should reach
599 a relatively stable size where entries are expiring from the cache as
600 fast as they are being inserted.
603 - Add something here about leaving overhead for attacks?
604 - How much overhead? Percentage?
608 <section xml:id="intensive_env"><info><title>Name Server Intensive Environment Issues</title></info>
611 For name server intensive environments, there are two alternative
612 configurations that may be used. The first is where clients and
613 any second-level internal name servers query a main name server, which
614 has enough memory to build a large cache. This approach minimizes
615 the bandwidth used by external name lookups. The second alternative
616 is to set up second-level internal name servers to make queries
618 In this configuration, none of the individual machines needs to
619 have as much memory or CPU power as in the first alternative, but
620 this has the disadvantage of making many more external queries,
621 as none of the name servers share their cached data.
625 <section xml:id="supported_os"><info><title>Supported Operating Systems</title></info>
628 ISC <acronym>BIND</acronym> 9 compiles and runs on a large
630 of Unix-like operating systems and on
631 Microsoft Windows Server 2003 and 2008, and Windows XP and Vista.
633 list of supported systems, see the README file in the top level
635 of the BIND 9 source distribution.
640 <chapter xml:id="Bv9ARM.ch03"><info><title>Name Server Configuration</title></info>
643 In this chapter we provide some suggested configurations along
644 with guidelines for their use. We suggest reasonable values for
645 certain option settings.
648 <section xml:id="sample_configuration"><info><title>Sample Configurations</title></info>
650 <section xml:id="cache_only_sample"><info><title>A Caching-only Name Server</title></info>
653 The following sample configuration is appropriate for a caching-only
654 name server for use by clients internal to a corporation. All
656 from outside clients are refused using the <command>allow-query</command>
657 option. Alternatively, the same effect could be achieved using
663 // Two corporate subnets we wish to allow queries from.
664 acl corpnets { 192.168.4.0/24; 192.168.7.0/24; };
667 directory "/etc/namedb";
669 allow-query { corpnets; };
671 // Provide a reverse mapping for the loopback
673 zone "0.0.127.in-addr.arpa" {
675 file "localhost.rev";
682 <section xml:id="auth_only_sample"><info><title>An Authoritative-only Name Server</title></info>
685 This sample configuration is for an authoritative-only server
686 that is the master server for "<filename>example.com</filename>"
687 and a slave for the subdomain "<filename>eng.example.com</filename>".
693 directory "/etc/namedb";
694 // Do not allow access to cache
695 allow-query-cache { none; };
696 // This is the default
697 allow-query { any; };
698 // Do not provide recursive service
702 // Provide a reverse mapping for the loopback
704 zone "0.0.127.in-addr.arpa" {
706 file "localhost.rev";
709 // We are the master server for example.com
712 file "example.com.db";
713 // IP addresses of slave servers allowed to
714 // transfer example.com
720 // We are a slave server for eng.example.com
721 zone "eng.example.com" {
723 file "eng.example.com.bk";
724 // IP address of eng.example.com master server
725 masters { 192.168.4.12; };
732 <section xml:id="load_balancing"><info><title>Load Balancing</title></info>
735 - Add explanation of why load balancing is fragile at best
736 - and completely pointless in the general case.
740 A primitive form of load balancing can be achieved in
741 the <acronym>DNS</acronym> by using multiple records
742 (such as multiple A records) for one name.
746 For example, if you have three WWW servers with network addresses
747 of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the
748 following means that clients will connect to each machine one third
752 <informaltable colsep="0" rowsep="0">
753 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="2Level-table">
754 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
755 <colspec colname="2" colnum="2" colsep="0" colwidth="0.500in"/>
756 <colspec colname="3" colnum="3" colsep="0" colwidth="0.750in"/>
757 <colspec colname="4" colnum="4" colsep="0" colwidth="0.750in"/>
758 <colspec colname="5" colnum="5" colsep="0" colwidth="2.028in"/>
783 Resource Record (RR) Data
790 <literal>www</literal>
795 <literal>600</literal>
800 <literal>IN</literal>
810 <literal>10.0.0.1</literal>
820 <literal>600</literal>
825 <literal>IN</literal>
835 <literal>10.0.0.2</literal>
845 <literal>600</literal>
850 <literal>IN</literal>
860 <literal>10.0.0.3</literal>
868 When a resolver queries for these records, <acronym>BIND</acronym> will rotate
869 them and respond to the query with the records in a different
870 order. In the example above, clients will randomly receive
871 records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients
872 will use the first record returned and discard the rest.
875 For more detail on ordering responses, check the
876 <command>rrset-order</command> sub-statement in the
877 <command>options</command> statement, see
878 <xref endterm="rrset_ordering_title" linkend="rrset_ordering"/>.
883 <section xml:id="ns_operations"><info><title>Name Server Operations</title></info>
885 <section xml:id="tools"><info><title>Tools for Use With the Name Server Daemon</title></info>
887 This section describes several indispensable diagnostic,
888 administrative and monitoring tools available to the system
889 administrator for controlling and debugging the name server
892 <section xml:id="diagnostic_tools"><info><title>Diagnostic Tools</title></info>
894 The <command>dig</command>, <command>host</command>, and
895 <command>nslookup</command> programs are all command
897 for manually querying name servers. They differ in style and
903 <term xml:id="dig"><command>dig</command></term>
906 The domain information groper (<command>dig</command>)
907 is the most versatile and complete of these lookup tools.
908 It has two modes: simple interactive
909 mode for a single query, and batch mode which executes a
911 each in a list of several query lines. All query options are
913 from the command line.
915 <cmdsynopsis label="Usage" sepchar=" ">
916 <command>dig</command>
917 <arg choice="opt" rep="norepeat">@<replaceable>server</replaceable></arg>
918 <arg choice="plain" rep="norepeat"><replaceable>domain</replaceable></arg>
919 <arg choice="opt" rep="norepeat"><replaceable>query-type</replaceable></arg>
920 <arg choice="opt" rep="norepeat"><replaceable>query-class</replaceable></arg>
921 <arg choice="opt" rep="norepeat">+<replaceable>query-option</replaceable></arg>
922 <arg choice="opt" rep="norepeat">-<replaceable>dig-option</replaceable></arg>
923 <arg choice="opt" rep="norepeat">%<replaceable>comment</replaceable></arg>
926 The usual simple use of <command>dig</command> will take the form
929 <command>dig @server domain query-type query-class</command>
932 For more information and a list of available commands and
933 options, see the <command>dig</command> man
940 <term><command>host</command></term>
943 The <command>host</command> utility emphasizes
945 and ease of use. By default, it converts
946 between host names and Internet addresses, but its
948 can be extended with the use of options.
950 <cmdsynopsis label="Usage" sepchar=" ">
951 <command>host</command>
952 <arg choice="opt" rep="norepeat">-aCdlnrsTwv</arg>
953 <arg choice="opt" rep="norepeat">-c <replaceable>class</replaceable></arg>
954 <arg choice="opt" rep="norepeat">-N <replaceable>ndots</replaceable></arg>
955 <arg choice="opt" rep="norepeat">-t <replaceable>type</replaceable></arg>
956 <arg choice="opt" rep="norepeat">-W <replaceable>timeout</replaceable></arg>
957 <arg choice="opt" rep="norepeat">-R <replaceable>retries</replaceable></arg>
958 <arg choice="opt" rep="norepeat">-m <replaceable>flag</replaceable></arg>
959 <arg choice="opt" rep="norepeat">-4</arg>
960 <arg choice="opt" rep="norepeat">-6</arg>
961 <arg choice="plain" rep="norepeat"><replaceable>hostname</replaceable></arg>
962 <arg choice="opt" rep="norepeat"><replaceable>server</replaceable></arg>
965 For more information and a list of available commands and
966 options, see the <command>host</command> man
973 <term><command>nslookup</command></term>
975 <para><command>nslookup</command>
976 has two modes: interactive and
977 non-interactive. Interactive mode allows the user to
978 query name servers for information about various
979 hosts and domains or to print a list of hosts in a
980 domain. Non-interactive mode is used to print just
981 the name and requested information for a host or
984 <cmdsynopsis label="Usage" sepchar=" ">
985 <command>nslookup</command>
986 <arg rep="repeat" choice="opt">-option</arg>
987 <group choice="opt" rep="norepeat">
988 <arg choice="opt" rep="norepeat"><replaceable>host-to-find</replaceable></arg>
989 <arg choice="opt" rep="norepeat">- <arg choice="opt" rep="norepeat">server</arg></arg>
993 Interactive mode is entered when no arguments are given (the
994 default name server will be used) or when the first argument
996 hyphen (`-') and the second argument is the host name or
1001 Non-interactive mode is used when the name or Internet
1003 of the host to be looked up is given as the first argument.
1005 optional second argument specifies the host name or address
1009 Due to its arcane user interface and frequently inconsistent
1010 behavior, we do not recommend the use of <command>nslookup</command>.
1011 Use <command>dig</command> instead.
1019 <section xml:id="admin_tools"><info><title>Administrative Tools</title></info>
1021 Administrative tools play an integral part in the management
1025 <varlistentry xml:id="named-checkconf" xreflabel="Named Configuration Checking application">
1027 <term><command>named-checkconf</command></term>
1030 The <command>named-checkconf</command> program
1031 checks the syntax of a <filename>named.conf</filename> file.
1033 <cmdsynopsis label="Usage" sepchar=" ">
1034 <command>named-checkconf</command>
1035 <arg choice="opt" rep="norepeat">-jvz</arg>
1036 <arg choice="opt" rep="norepeat">-t <replaceable>directory</replaceable></arg>
1037 <arg choice="opt" rep="norepeat"><replaceable>filename</replaceable></arg>
1041 <varlistentry xml:id="named-checkzone" xreflabel="Zone Checking application">
1043 <term><command>named-checkzone</command></term>
1046 The <command>named-checkzone</command> program
1047 checks a master file for
1048 syntax and consistency.
1050 <cmdsynopsis label="Usage" sepchar=" ">
1051 <command>named-checkzone</command>
1052 <arg choice="opt" rep="norepeat">-djqvD</arg>
1053 <arg choice="opt" rep="norepeat">-c <replaceable>class</replaceable></arg>
1054 <arg choice="opt" rep="norepeat">-o <replaceable>output</replaceable></arg>
1055 <arg choice="opt" rep="norepeat">-t <replaceable>directory</replaceable></arg>
1056 <arg choice="opt" rep="norepeat">-w <replaceable>directory</replaceable></arg>
1057 <arg choice="opt" rep="norepeat">-k <replaceable>(ignore|warn|fail)</replaceable></arg>
1058 <arg choice="opt" rep="norepeat">-n <replaceable>(ignore|warn|fail)</replaceable></arg>
1059 <arg choice="opt" rep="norepeat">-W <replaceable>(ignore|warn)</replaceable></arg>
1060 <arg choice="plain" rep="norepeat"><replaceable>zone</replaceable></arg>
1061 <arg choice="opt" rep="norepeat"><replaceable>filename</replaceable></arg>
1065 <varlistentry xml:id="named-compilezone" xreflabel="Zone Compilation application">
1066 <term><command>named-compilezone</command></term>
1069 Similar to <command>named-checkzone,</command> but
1070 it always dumps the zone content to a specified file
1071 (typically in a different format).
1075 <varlistentry xml:id="rndc" xreflabel="Remote Name Daemon Control application">
1077 <term><command>rndc</command></term>
1080 The remote name daemon control
1081 (<command>rndc</command>) program allows the
1083 administrator to control the operation of a name server.
1084 Since <acronym>BIND</acronym> 9.2, <command>rndc</command>
1085 supports all the commands of the BIND 8 <command>ndc</command>
1086 utility except <command>ndc start</command> and
1087 <command>ndc restart</command>, which were also
1088 not supported in <command>ndc</command>'s
1090 If you run <command>rndc</command> without any
1092 it will display a usage message as follows:
1094 <cmdsynopsis label="Usage" sepchar=" ">
1095 <command>rndc</command>
1096 <arg choice="opt" rep="norepeat">-c <replaceable>config</replaceable></arg>
1097 <arg choice="opt" rep="norepeat">-s <replaceable>server</replaceable></arg>
1098 <arg choice="opt" rep="norepeat">-p <replaceable>port</replaceable></arg>
1099 <arg choice="opt" rep="norepeat">-y <replaceable>key</replaceable></arg>
1100 <arg choice="plain" rep="norepeat"><replaceable>command</replaceable></arg>
1101 <arg rep="repeat" choice="opt"><replaceable>command</replaceable></arg>
1104 <para>See <xref linkend="man.rndc"/> for details of
1105 the available <command>rndc</command> commands.
1109 <command>rndc</command> requires a configuration file,
1111 communication with the server is authenticated with
1112 digital signatures that rely on a shared secret, and
1113 there is no way to provide that secret other than with a
1114 configuration file. The default location for the
1115 <command>rndc</command> configuration file is
1116 <filename>/etc/rndc.conf</filename>, but an
1118 location can be specified with the <option>-c</option>
1119 option. If the configuration file is not found,
1120 <command>rndc</command> will also look in
1121 <filename>/etc/rndc.key</filename> (or whatever
1122 <varname>sysconfdir</varname> was defined when
1123 the <acronym>BIND</acronym> build was
1125 The <filename>rndc.key</filename> file is
1127 running <command>rndc-confgen -a</command> as
1129 <xref linkend="controls_statement_definition_and_usage"/>.
1133 The format of the configuration file is similar to
1134 that of <filename>named.conf</filename>, but
1136 only four statements, the <command>options</command>,
1137 <command>key</command>, <command>server</command> and
1138 <command>include</command>
1139 statements. These statements are what associate the
1140 secret keys to the servers with which they are meant to
1141 be shared. The order of statements is not
1146 The <command>options</command> statement has
1148 <command>default-server</command>, <command>default-key</command>,
1149 and <command>default-port</command>.
1150 <command>default-server</command> takes a
1151 host name or address argument and represents the server
1153 be contacted if no <option>-s</option>
1154 option is provided on the command line.
1155 <command>default-key</command> takes
1156 the name of a key as its argument, as defined by a <command>key</command> statement.
1157 <command>default-port</command> specifies the
1159 <command>rndc</command> should connect if no
1160 port is given on the command line or in a
1161 <command>server</command> statement.
1165 The <command>key</command> statement defines a
1167 by <command>rndc</command> when authenticating
1169 <command>named</command>. Its syntax is
1171 <command>key</command> statement in <filename>named.conf</filename>.
1172 The keyword <userinput>key</userinput> is
1173 followed by a key name, which must be a valid
1174 domain name, though it need not actually be hierarchical;
1176 a string like "<userinput>rndc_key</userinput>" is a valid
1178 The <command>key</command> statement has two
1180 <command>algorithm</command> and <command>secret</command>.
1181 While the configuration parser will accept any string as the
1183 to algorithm, currently only the string "<userinput>hmac-md5</userinput>"
1184 has any meaning. The secret is a base-64 encoded string
1185 as specified in RFC 3548.
1189 The <command>server</command> statement
1191 defined using the <command>key</command>
1192 statement with a server.
1193 The keyword <userinput>server</userinput> is followed by a
1194 host name or address. The <command>server</command> statement
1195 has two clauses: <command>key</command> and <command>port</command>.
1196 The <command>key</command> clause specifies the
1198 to be used when communicating with this server, and the
1199 <command>port</command> clause can be used to
1200 specify the port <command>rndc</command> should
1206 A sample minimal configuration file is as follows:
1211 algorithm "hmac-md5";
1213 "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
1216 default-server 127.0.0.1;
1217 default-key rndc_key;
1222 This file, if installed as <filename>/etc/rndc.conf</filename>,
1223 would allow the command:
1227 <prompt>$ </prompt><userinput>rndc reload</userinput>
1231 to connect to 127.0.0.1 port 953 and cause the name server
1232 to reload, if a name server on the local machine were
1234 following controls statements:
1240 allow { localhost; } keys { rndc_key; };
1245 and it had an identical key statement for
1246 <literal>rndc_key</literal>.
1250 Running the <command>rndc-confgen</command>
1252 conveniently create a <filename>rndc.conf</filename>
1253 file for you, and also display the
1254 corresponding <command>controls</command>
1255 statement that you need to
1256 add to <filename>named.conf</filename>.
1258 you can run <command>rndc-confgen -a</command>
1260 a <filename>rndc.key</filename> file and not
1262 <filename>named.conf</filename> at all.
1272 <section xml:id="signals"><info><title>Signals</title></info>
1274 Certain UNIX signals cause the name server to take specific
1275 actions, as described in the following table. These signals can
1276 be sent using the <command>kill</command> command.
1278 <informaltable frame="all">
1280 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
1281 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
1285 <para><command>SIGHUP</command></para>
1289 Causes the server to read <filename>named.conf</filename> and
1290 reload the database.
1296 <para><command>SIGTERM</command></para>
1300 Causes the server to clean up and exit.
1306 <para><command>SIGINT</command></para>
1310 Causes the server to clean up and exit.
1321 <chapter xml:id="Bv9ARM.ch04"><info><title>Advanced DNS Features</title></info>
1323 <section xml:id="notify"><info><title>Notify</title></info>
1325 <acronym>DNS</acronym> NOTIFY is a mechanism that allows master
1326 servers to notify their slave servers of changes to a zone's data. In
1327 response to a <command>NOTIFY</command> from a master server, the
1328 slave will check to see that its version of the zone is the
1329 current version and, if not, initiate a zone transfer.
1333 For more information about <acronym>DNS</acronym>
1334 <command>NOTIFY</command>, see the description of the
1335 <command>notify</command> option in <xref linkend="boolean_options"/> and
1336 the description of the zone option <command>also-notify</command> in
1337 <xref linkend="zone_transfers"/>. The <command>NOTIFY</command>
1338 protocol is specified in RFC 1996.
1342 As a slave zone can also be a master to other slaves, <command>named</command>,
1343 by default, sends <command>NOTIFY</command> messages for every zone
1344 it loads. Specifying <command>notify master-only;</command> will
1345 cause <command>named</command> to only send <command>NOTIFY</command> for master
1346 zones that it loads.
1351 <section xml:id="dynamic_update"><info><title>Dynamic Update</title></info>
1354 Dynamic Update is a method for adding, replacing or deleting
1355 records in a master server by sending it a special form of DNS
1356 messages. The format and meaning of these messages is specified
1361 Dynamic update is enabled by including an
1362 <command>allow-update</command> or an <command>update-policy</command>
1363 clause in the <command>zone</command> statement.
1367 If the zone's <command>update-policy</command> is set to
1368 <userinput>local</userinput>, updates to the zone
1369 will be permitted for the key <varname>local-ddns</varname>,
1370 which will be generated by <command>named</command> at startup.
1371 See <xref linkend="dynamic_update_policies"/> for more details.
1375 Dynamic updates using Kerberos signed requests can be made
1376 using the TKEY/GSS protocol by setting either the
1377 <command>tkey-gssapi-keytab</command> option, or alternatively
1378 by setting both the <command>tkey-gssapi-credential</command>
1379 and <command>tkey-domain</command> options. Once enabled,
1380 Kerberos signed requests will be matched against the update
1381 policies for the zone, using the Kerberos principal as the
1382 signer for the request.
1386 Updating of secure zones (zones using DNSSEC) follows RFC
1387 3007: RRSIG, NSEC and NSEC3 records affected by updates are
1388 automatically regenerated by the server using an online
1389 zone key. Update authorization is based on transaction
1390 signatures and an explicit server policy.
1393 <section xml:id="journal"><info><title>The journal file</title></info>
1396 All changes made to a zone using dynamic update are stored
1397 in the zone's journal file. This file is automatically created
1398 by the server when the first dynamic update takes place.
1399 The name of the journal file is formed by appending the extension
1400 <filename>.jnl</filename> to the name of the
1402 file unless specifically overridden. The journal file is in a
1403 binary format and should not be edited manually.
1407 The server will also occasionally write ("dump")
1408 the complete contents of the updated zone to its zone file.
1409 This is not done immediately after
1410 each dynamic update, because that would be too slow when a large
1411 zone is updated frequently. Instead, the dump is delayed by
1412 up to 15 minutes, allowing additional updates to take place.
1413 During the dump process, transient files will be created
1414 with the extensions <filename>.jnw</filename> and
1415 <filename>.jbk</filename>; under ordinary circumstances, these
1416 will be removed when the dump is complete, and can be safely
1421 When a server is restarted after a shutdown or crash, it will replay
1422 the journal file to incorporate into the zone any updates that
1424 place after the last zone dump.
1428 Changes that result from incoming incremental zone transfers are
1430 journalled in a similar way.
1434 The zone files of dynamic zones cannot normally be edited by
1435 hand because they are not guaranteed to contain the most recent
1436 dynamic changes — those are only in the journal file.
1437 The only way to ensure that the zone file of a dynamic zone
1438 is up to date is to run <command>rndc stop</command>.
1442 If you have to make changes to a dynamic zone
1443 manually, the following procedure will work:
1444 Disable dynamic updates to the zone using
1445 <command>rndc freeze <replaceable>zone</replaceable></command>.
1446 This will update the zone's master file with the changes
1447 stored in its <filename>.jnl</filename> file.
1448 Edit the zone file. Run
1449 <command>rndc thaw <replaceable>zone</replaceable></command>
1450 to reload the changed zone and re-enable dynamic updates.
1454 <command>rndc sync <replaceable>zone</replaceable></command>
1455 will update the zone file with changes from the journal file
1456 without stopping dynamic updates; this may be useful for viewing
1457 the current zone state. To remove the <filename>.jnl</filename>
1458 file after updating the zone file, use
1459 <command>rndc sync -clean</command>.
1466 <section xml:id="incremental_zone_transfers"><info><title>Incremental Zone Transfers (IXFR)</title></info>
1469 The incremental zone transfer (IXFR) protocol is a way for
1470 slave servers to transfer only changed data, instead of having to
1471 transfer the entire zone. The IXFR protocol is specified in RFC
1472 1995. See <xref linkend="proposed_standards"/>.
1476 When acting as a master, <acronym>BIND</acronym> 9
1477 supports IXFR for those zones
1478 where the necessary change history information is available. These
1479 include master zones maintained by dynamic update and slave zones
1480 whose data was obtained by IXFR. For manually maintained master
1481 zones, and for slave zones obtained by performing a full zone
1482 transfer (AXFR), IXFR is supported only if the option
1483 <command>ixfr-from-differences</command> is set
1484 to <userinput>yes</userinput>.
1488 When acting as a slave, <acronym>BIND</acronym> 9 will
1489 attempt to use IXFR unless
1490 it is explicitly disabled. For more information about disabling
1491 IXFR, see the description of the <command>request-ixfr</command> clause
1492 of the <command>server</command> statement.
1496 <section xml:id="split_dns"><info><title>Split DNS</title></info>
1499 Setting up different views, or visibility, of the DNS space to
1500 internal and external resolvers is usually referred to as a
1501 <emphasis>Split DNS</emphasis> setup. There are several
1502 reasons an organization would want to set up its DNS this way.
1505 One common reason for setting up a DNS system this way is
1506 to hide "internal" DNS information from "external" clients on the
1507 Internet. There is some debate as to whether or not this is actually
1509 Internal DNS information leaks out in many ways (via email headers,
1510 for example) and most savvy "attackers" can find the information
1511 they need using other means.
1512 However, since listing addresses of internal servers that
1513 external clients cannot possibly reach can result in
1514 connection delays and other annoyances, an organization may
1515 choose to use a Split DNS to present a consistent view of itself
1516 to the outside world.
1519 Another common reason for setting up a Split DNS system is
1520 to allow internal networks that are behind filters or in RFC 1918
1521 space (reserved IP space, as documented in RFC 1918) to resolve DNS
1522 on the Internet. Split DNS can also be used to allow mail from outside
1523 back in to the internal network.
1525 <section xml:id="split_dns_sample"><info><title>Example split DNS setup</title></info>
1527 Let's say a company named <emphasis>Example, Inc.</emphasis>
1528 (<literal>example.com</literal>)
1529 has several corporate sites that have an internal network with
1531 Internet Protocol (IP) space and an external demilitarized zone (DMZ),
1532 or "outside" section of a network, that is available to the public.
1535 <emphasis>Example, Inc.</emphasis> wants its internal clients
1536 to be able to resolve external hostnames and to exchange mail with
1537 people on the outside. The company also wants its internal resolvers
1538 to have access to certain internal-only zones that are not available
1539 at all outside of the internal network.
1542 In order to accomplish this, the company will set up two sets
1543 of name servers. One set will be on the inside network (in the
1545 IP space) and the other set will be on bastion hosts, which are
1547 hosts that can talk to both sides of its network, in the DMZ.
1550 The internal servers will be configured to forward all queries,
1551 except queries for <filename>site1.internal</filename>, <filename>site2.internal</filename>, <filename>site1.example.com</filename>,
1552 and <filename>site2.example.com</filename>, to the servers
1554 DMZ. These internal servers will have complete sets of information
1555 for <filename>site1.example.com</filename>, <filename>site2.example.com</filename>, <filename>site1.internal</filename>,
1556 and <filename>site2.internal</filename>.
1559 To protect the <filename>site1.internal</filename> and <filename>site2.internal</filename> domains,
1560 the internal name servers must be configured to disallow all queries
1561 to these domains from any external hosts, including the bastion
1565 The external servers, which are on the bastion hosts, will
1566 be configured to serve the "public" version of the <filename>site1</filename> and <filename>site2.example.com</filename> zones.
1567 This could include things such as the host records for public servers
1568 (<filename>www.example.com</filename> and <filename>ftp.example.com</filename>),
1569 and mail exchange (MX) records (<filename>a.mx.example.com</filename> and <filename>b.mx.example.com</filename>).
1572 In addition, the public <filename>site1</filename> and <filename>site2.example.com</filename> zones
1573 should have special MX records that contain wildcard (`*') records
1574 pointing to the bastion hosts. This is needed because external mail
1575 servers do not have any other way of looking up how to deliver mail
1576 to those internal hosts. With the wildcard records, the mail will
1577 be delivered to the bastion host, which can then forward it on to
1581 Here's an example of a wildcard MX record:
1583 <programlisting>* IN MX 10 external1.example.com.</programlisting>
1585 Now that they accept mail on behalf of anything in the internal
1586 network, the bastion hosts will need to know how to deliver mail
1587 to internal hosts. In order for this to work properly, the resolvers
1589 the bastion hosts will need to be configured to point to the internal
1590 name servers for DNS resolution.
1593 Queries for internal hostnames will be answered by the internal
1594 servers, and queries for external hostnames will be forwarded back
1595 out to the DNS servers on the bastion hosts.
1598 In order for all this to work properly, internal clients will
1599 need to be configured to query <emphasis>only</emphasis> the internal
1600 name servers for DNS queries. This could also be enforced via
1602 filtering on the network.
1605 If everything has been set properly, <emphasis>Example, Inc.</emphasis>'s
1606 internal clients will now be able to:
1611 Look up any hostnames in the <literal>site1</literal>
1613 <literal>site2.example.com</literal> zones.
1618 Look up any hostnames in the <literal>site1.internal</literal> and
1619 <literal>site2.internal</literal> domains.
1623 <simpara>Look up any hostnames on the Internet.</simpara>
1626 <simpara>Exchange mail with both internal and external people.</simpara>
1630 Hosts on the Internet will be able to:
1635 Look up any hostnames in the <literal>site1</literal>
1637 <literal>site2.example.com</literal> zones.
1642 Exchange mail with anyone in the <literal>site1</literal> and
1643 <literal>site2.example.com</literal> zones.
1649 Here is an example configuration for the setup we just
1650 described above. Note that this is only configuration information;
1651 for information on how to configure your zone files, see <xref linkend="sample_configuration"/>.
1655 Internal DNS server config:
1660 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
1662 acl externals { <varname>bastion-ips-go-here</varname>; };
1668 // forward to external servers
1670 <varname>bastion-ips-go-here</varname>;
1672 // sample allow-transfer (no one)
1673 allow-transfer { none; };
1674 // restrict query access
1675 allow-query { internals; externals; };
1676 // restrict recursion
1677 allow-recursion { internals; };
1682 // sample master zone
1683 zone "site1.example.com" {
1685 file "m/site1.example.com";
1686 // do normal iterative resolution (do not forward)
1688 allow-query { internals; externals; };
1689 allow-transfer { internals; };
1692 // sample slave zone
1693 zone "site2.example.com" {
1695 file "s/site2.example.com";
1696 masters { 172.16.72.3; };
1698 allow-query { internals; externals; };
1699 allow-transfer { internals; };
1702 zone "site1.internal" {
1704 file "m/site1.internal";
1706 allow-query { internals; };
1707 allow-transfer { internals; }
1710 zone "site2.internal" {
1712 file "s/site2.internal";
1713 masters { 172.16.72.3; };
1715 allow-query { internals };
1716 allow-transfer { internals; }
1721 External (bastion host) DNS server config:
1725 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
1727 acl externals { bastion-ips-go-here; };
1732 // sample allow-transfer (no one)
1733 allow-transfer { none; };
1734 // default query access
1735 allow-query { any; };
1736 // restrict cache access
1737 allow-query-cache { internals; externals; };
1738 // restrict recursion
1739 allow-recursion { internals; externals; };
1744 // sample slave zone
1745 zone "site1.example.com" {
1747 file "m/site1.foo.com";
1748 allow-transfer { internals; externals; };
1751 zone "site2.example.com" {
1753 file "s/site2.foo.com";
1754 masters { another_bastion_host_maybe; };
1755 allow-transfer { internals; externals; }
1760 In the <filename>resolv.conf</filename> (or equivalent) on
1761 the bastion host(s):
1766 nameserver 172.16.72.2
1767 nameserver 172.16.72.3
1768 nameserver 172.16.72.4
1773 <section xml:id="tsig"><info><title>TSIG</title></info>
1776 TSIG (Transaction SIGnatures) is a mechanism for authenticating DNS
1777 messages, originally specified in RFC 2845. It allows DNS messages
1778 to be cryptographically signed using a shared secret. TSIG can
1779 be used in any DNS transaction, as a way to restrict access to
1780 certain server functions (e.g., recursive queries) to authorized
1781 clients when IP-based access control is insufficient or needs to
1782 be overridden, or as a way to ensure message authenticity when it
1783 is critical to the integrity of the server, such as with dynamic
1784 UPDATE messages or zone transfers from a master to a slave server.
1787 This is a guide to setting up TSIG in <acronym>BIND</acronym>.
1788 It describes the configuration syntax and the process of creating
1792 <command>named</command> supports TSIG for server-to-server
1793 communication, and some of the tools included with
1794 <acronym>BIND</acronym> support it for sending messages to
1795 <command>named</command>:
1798 <xref linkend="man.nsupdate"/> supports TSIG via the
1799 <option>-k</option>, <option>-l</option> and
1800 <option>-y</option> command line options, or via
1801 the <command>key</command> command when running
1805 <xref linkend="man.dig"/> supports TSIG via the
1806 <option>-k</option> and <option>-y</option> command
1812 <section><info><title>Generating a Shared Key</title></info>
1814 TSIG keys can be generated using the <command>ddns-confgen</command>
1815 command; the output of the command is a <command>key</command> directive
1816 suitable for inclusion in <filename>named.conf</filename>. The
1817 key name and algorithm can be specified by command line parameters;
1818 the defaults are "ddns-key" and HMAC-SHA256, respectively. By
1819 default, the output of <command>ddns-confgen</command> also includes
1820 additional configuration text for setting up dynamic DNS in
1821 <command>named</command>; the <option>-q</option> suppresses
1822 this. See <xref linkend="man.ddns-confgen"/> for further details.
1825 Any string which is a valid DNS name can be used as a key name.
1826 For example, a key to be shared between servers called
1827 <emphasis>host1</emphasis> and <emphasis>host2</emphasis> could
1828 be called "host1-host2.", and this key could be generated using:
1831 $ ddns-confgen -q -k host1-host2. > host1-host2.key
1834 This key may then be copied to both hosts. The key name and secret
1835 must be identical on both hosts.
1836 (Note: copying a shared secret from one server to another is beyond
1837 the scope of the DNS. A secure transport mechanism should be used:
1838 secure FTP, SSL, ssh, telephone, encrypted email, etc.)
1842 <section><info><title>Loading A New Key</title></info>
1844 For a key shared between servers called
1845 <emphasis>host1</emphasis> and <emphasis>host2</emphasis>,
1846 the following could be added to each server's
1847 <filename>named.conf</filename> file:
1850 key "host1-host2." {
1851 algorithm hmac-sha256;
1852 secret "DAopyf1mhCbFVZw7pgmNPBoLUq8wEUT7UuPoLENP2HY=";
1856 (This is the same key generated above using
1857 <command>ddns-confgen</command>.)
1860 Since this text contains a secret, it
1861 is recommended that either <filename>named.conf</filename> not be
1862 world-readable, or that the <command>key</command> directive
1863 be stored in a file which is not world-readable, and which is
1864 included in <filename>named.conf</filename> via the
1865 <command>include</command> directive.
1868 Once a key has been added to <filename>named.conf</filename> and the
1869 server has been restarted or reconfigured, the server can recognize
1870 the key. If the server receives a message signed by the
1871 key, it will be able to verify the signature. If the signature
1872 is valid, the response will be signed using the same key.
1875 TSIG keys that are known to a server can be listed using the
1876 command <command>rndc tsig-list</command>.
1880 <section><info><title>Instructing the Server to Use a Key</title></info>
1882 A server sending a request to another server must be told whether
1883 to use a key, and if so, which key to use.
1886 For example, a key may be specified for each server in the
1887 <command>masters</command> statement in the definition of a
1888 slave zone; in this case, all SOA QUERY messages, NOTIFY
1889 messages, and zone transfer requests (AXFR or IXFR) will be
1890 signed using the specified key. Keys may also be specified
1891 in the <command>also-notify</command> statement of a master
1892 or slave zone, causing NOTIFY messages to be signed using
1896 Keys can also be specified in a <command>server</command>
1897 directive. Adding the following on <emphasis>host1</emphasis>,
1898 if the IP address of <emphasis>host2</emphasis> is 10.1.2.3, would
1899 cause <emphasis>all</emphasis> requests from <emphasis>host1</emphasis>
1900 to <emphasis>host2</emphasis>, including normal DNS queries, to be
1901 signed using the <command>host1-host2.</command> key:
1905 keys { host1-host2. ;};
1909 Multiple keys may be present in the <command>keys</command>
1910 statement, but only the first one is used. As this directive does
1911 not contain secrets, it can be used in a world-readable file.
1914 Requests sent by <emphasis>host2</emphasis> to <emphasis>host1</emphasis>
1915 would <emphasis>not</emphasis> be signed, unless a similar
1916 <command>server</command> directive were in <emphasis>host2</emphasis>'s
1920 Whenever any server sends a TSIG-signed DNS request, it will expect
1921 the response to be signed with the same key. If a response is not
1922 signed, or if the signature is not valid, the response will be
1927 <section><info><title>TSIG-Based Access Control</title></info>
1929 TSIG keys may be specified in ACL definitions and ACL directives
1930 such as <command>allow-query</command>, <command>allow-transfer</command>
1931 and <command>allow-update</command>.
1932 The above key would be denoted in an ACL element as
1933 <command>key host1-host2.</command>
1936 An example of an <command>allow-update</command> directive using
1940 allow-update { !{ !localnets; any; }; key host1-host2. ;};
1943 This allows dynamic updates to succeed only if the UPDATE
1944 request comes from an address in <command>localnets</command>,
1945 <emphasis>and</emphasis> if it is signed using the
1946 <command>host1-host2.</command> key.
1949 See <xref linkend="dynamic_update_policies"/> for a discussion of
1950 the more flexible <command>update-policy</command> statement.
1954 <section><info><title>Errors</title></info>
1956 Processing of TSIG-signed messages can result in several errors:
1959 If a TSIG-aware server receives a message signed by an
1960 unknown key, the response will be unsigned, with the TSIG
1961 extended error code set to BADKEY.
1964 If a TSIG-aware server receives a message from a known key
1965 but with an invalid signature, the response will be unsigned,
1966 with the TSIG extended error code set to BADSIG.
1969 If a TSIG-aware server receives a message with a time
1970 outside of the allowed range, the response will be signed, with
1971 the TSIG extended error code set to BADTIME, and the time values
1972 will be adjusted so that the response can be successfully
1976 In all of the above cases, the server will return a response code
1977 of NOTAUTH (not authenticated).
1982 <section xml:id="tkey"><info><title>TKEY</title></info>
1985 TKEY (Transaction KEY) is a mechanism for automatically negotiating
1986 a shared secret between two hosts, originally specified in RFC 2930.
1989 There are several TKEY "modes" that specify how a key is to be
1990 generated or assigned. <acronym>BIND</acronym> 9 implements only
1991 one of these modes: Diffie-Hellman key exchange. Both hosts are
1992 required to have a KEY record with algorithm DH (though this
1993 record is not required to be present in a zone).
1996 The TKEY process is initiated by a client or server by sending
1997 a query of type TKEY to a TKEY-aware server. The query must include
1998 an appropriate KEY record in the additional section, and
1999 must be signed using either TSIG or SIG(0) with a previously
2000 established key. The server's response, if successful, will
2001 contain a TKEY record in its answer section. After this transaction,
2002 both participants will have enough information to calculate a
2003 shared secret using Diffie-Hellman key exchange. The shared secret
2004 can then be used by to sign subsequent transactions between the
2008 TSIG keys known by the server, including TKEY-negotiated keys, can
2009 be listed using <command>rndc tsig-list</command>.
2012 TKEY-negotiated keys can be deleted from a server using
2013 <command>rndc tsig-delete</command>. This can also be done via
2014 the TKEY protocol itself, by sending an authenticated TKEY query
2015 specifying the "key deletion" mode.
2019 <section xml:id="sig0"><info><title>SIG(0)</title></info>
2022 <acronym>BIND</acronym> partially supports DNSSEC SIG(0)
2023 transaction signatures as specified in RFC 2535 and RFC 2931.
2024 SIG(0) uses public/private keys to authenticate messages. Access control
2025 is performed in the same manner as TSIG keys; privileges can be
2026 granted or denied in ACL directives based on the key name.
2029 When a SIG(0) signed message is received, it will only be
2030 verified if the key is known and trusted by the server. The
2031 server will not attempt to recursively fetch or validate the
2035 SIG(0) signing of multiple-message TCP streams is not supported.
2038 The only tool shipped with <acronym>BIND</acronym> 9 that
2039 generates SIG(0) signed messages is <command>nsupdate</command>.
2043 <section xml:id="DNSSEC"><info><title>DNSSEC</title></info>
2045 Cryptographic authentication of DNS information is possible
2046 through the DNS Security (<emphasis>DNSSEC-bis</emphasis>) extensions,
2047 defined in RFC 4033, RFC 4034, and RFC 4035.
2048 This section describes the creation and use of DNSSEC signed zones.
2052 In order to set up a DNSSEC secure zone, there are a series
2053 of steps which must be followed. <acronym>BIND</acronym>
2056 that are used in this process, which are explained in more detail
2057 below. In all cases, the <option>-h</option> option prints a
2058 full list of parameters. Note that the DNSSEC tools require the
2059 keyset files to be in the working directory or the
2060 directory specified by the <option>-d</option> option, and
2061 that the tools shipped with BIND 9.2.x and earlier are not compatible
2062 with the current ones.
2066 There must also be communication with the administrators of
2067 the parent and/or child zone to transmit keys. A zone's security
2068 status must be indicated by the parent zone for a DNSSEC capable
2069 resolver to trust its data. This is done through the presence
2070 or absence of a <literal>DS</literal> record at the
2076 For other servers to trust data in this zone, they must
2077 either be statically configured with this zone's zone key or the
2078 zone key of another zone above this one in the DNS tree.
2081 <section xml:id="dnssec_keys"><info><title>Generating Keys</title></info>
2084 The <command>dnssec-keygen</command> program is used to
2089 A secure zone must contain one or more zone keys. The
2090 zone keys will sign all other records in the zone, as well as
2091 the zone keys of any secure delegated zones. Zone keys must
2092 have the same name as the zone, a name type of
2093 <command>ZONE</command>, and must be usable for
2095 It is recommended that zone keys use a cryptographic algorithm
2096 designated as "mandatory to implement" by the IETF; currently
2097 the only one is RSASHA1.
2101 The following command will generate a 768-bit RSASHA1 key for
2102 the <filename>child.example</filename> zone:
2106 <userinput>dnssec-keygen -a RSASHA1 -b 768 -n ZONE child.example.</userinput>
2110 Two output files will be produced:
2111 <filename>Kchild.example.+005+12345.key</filename> and
2112 <filename>Kchild.example.+005+12345.private</filename>
2114 12345 is an example of a key tag). The key filenames contain
2115 the key name (<filename>child.example.</filename>),
2117 is DSA, 1 is RSAMD5, 5 is RSASHA1, etc.), and the key tag (12345 in
2119 The private key (in the <filename>.private</filename>
2121 used to generate signatures, and the public key (in the
2122 <filename>.key</filename> file) is used for signature
2127 To generate another key with the same properties (but with
2128 a different key tag), repeat the above command.
2132 The <command>dnssec-keyfromlabel</command> program is used
2133 to get a key pair from a crypto hardware and build the key
2134 files. Its usage is similar to <command>dnssec-keygen</command>.
2138 The public keys should be inserted into the zone file by
2139 including the <filename>.key</filename> files using
2140 <command>$INCLUDE</command> statements.
2144 <section xml:id="dnssec_signing"><info><title>Signing the Zone</title></info>
2147 The <command>dnssec-signzone</command> program is used
2152 Any <filename>keyset</filename> files corresponding to
2153 secure subzones should be present. The zone signer will
2154 generate <literal>NSEC</literal>, <literal>NSEC3</literal>
2155 and <literal>RRSIG</literal> records for the zone, as
2156 well as <literal>DS</literal> for the child zones if
2157 <literal>'-g'</literal> is specified. If <literal>'-g'</literal>
2158 is not specified, then DS RRsets for the secure child
2159 zones need to be added manually.
2163 The following command signs the zone, assuming it is in a
2164 file called <filename>zone.child.example</filename>. By
2165 default, all zone keys which have an available private key are
2166 used to generate signatures.
2170 <userinput>dnssec-signzone -o child.example zone.child.example</userinput>
2174 One output file is produced:
2175 <filename>zone.child.example.signed</filename>. This
2177 should be referenced by <filename>named.conf</filename>
2179 input file for the zone.
2182 <para><command>dnssec-signzone</command>
2183 will also produce a keyset and dsset files and optionally a
2184 dlvset file. These are used to provide the parent zone
2185 administrators with the <literal>DNSKEYs</literal> (or their
2186 corresponding <literal>DS</literal> records) that are the
2187 secure entry point to the zone.
2192 <section xml:id="dnssec_config"><info><title>Configuring Servers</title></info>
2195 To enable <command>named</command> to respond appropriately
2196 to DNS requests from DNSSEC aware clients,
2197 <command>dnssec-enable</command> must be set to yes.
2198 (This is the default setting.)
2202 To enable <command>named</command> to validate answers from
2203 other servers, the <command>dnssec-enable</command> option
2204 must be set to <userinput>yes</userinput>, and the
2205 <command>dnssec-validation</command> options must be set to
2206 <userinput>yes</userinput> or <userinput>auto</userinput>.
2210 If <command>dnssec-validation</command> is set to
2211 <userinput>auto</userinput>, then a default
2212 trust anchor for the DNS root zone will be used.
2213 If it is set to <userinput>yes</userinput>, however,
2214 then at least one trust anchor must be configured
2215 with a <command>trusted-keys</command> or
2216 <command>managed-keys</command> statement in
2217 <filename>named.conf</filename>, or DNSSEC validation
2218 will not occur. The default setting is
2219 <userinput>yes</userinput>.
2223 <command>trusted-keys</command> are copies of DNSKEY RRs
2224 for zones that are used to form the first link in the
2225 cryptographic chain of trust. All keys listed in
2226 <command>trusted-keys</command> (and corresponding zones)
2227 are deemed to exist and only the listed keys will be used
2228 to validated the DNSKEY RRset that they are from.
2232 <command>managed-keys</command> are trusted keys which are
2233 automatically kept up to date via RFC 5011 trust anchor
2238 <command>trusted-keys</command> and
2239 <command>managed-keys</command> are described in more detail
2240 later in this document.
2244 Unlike <acronym>BIND</acronym> 8, <acronym>BIND</acronym>
2245 9 does not verify signatures on load, so zone keys for
2246 authoritative zones do not need to be specified in the
2251 After DNSSEC gets established, a typical DNSSEC configuration
2252 will look something like the following. It has one or
2253 more public keys for the root. This allows answers from
2254 outside the organization to be validated. It will also
2255 have several keys for parts of the namespace the organization
2256 controls. These are here to ensure that <command>named</command>
2257 is immune to compromises in the DNSSEC components of the security
2264 "." initial-key 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS
2265 JxrGkxJWoZu6I7PzJu/E9gx4UC1zGAHlXKdE4zYIpRh
2266 aBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3zy2Xy
2267 4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYg
2268 hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp
2269 5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M/lUUVRbke
2270 g1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq
2271 66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ
2272 97S+LKUTpQcq27R7AT3/V5hRQxScINqwcz4jYqZD2fQ
2273 dgxbcDTClU0CRBdiieyLMNzXG3";
2277 /* Key for our organization's forward zone */
2278 example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6
2279 5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z
2280 GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb
2281 4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL
2282 kBOUKUf/mC7HvfwYH/Be22GnClrinKJp1O
2283 g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S
2284 TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq
2285 FxmAVZP20igTixin/1LcrgX/KMEGd/biuv
2286 F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm
2287 /oyWR8BW/hWdzOvnSCThlHf3xiYleDbt/o
2290 /* Key for our reverse zone. */
2291 2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwc
2292 xOdNax071L18QqZnQQQAVVr+i
2293 LhGTnNGp3HoWQLUIzKrJVZ3zg
2294 gy3WwNT6kZo6c0tszYqbtvchm
2295 gQC8CzKojM/W16i6MG/eafGU3
2296 siaOdS0yOI6BgPsw+YZdzlYMa
2297 IJGf4M4dyoKIhzdZyQ2bYQrjy
2298 Q4LB0lC7aOnsMyYKHHYeRvPxj
2299 IQXmdqgOJGq+vsevG06zW+1xg
2300 YJh9rCIfnm1GX/KMgxLPG2vXT
2301 D/RnLX+D3T3UL7HJYHJhAZD5L
2302 59VvjSPsZJHeDCUyWYrvPZesZ
2303 DIRvhDD52SKvbheeTJUm6Ehkz
2304 ytNN2SN96QRk8j/iI8ib";
2310 dnssec-validation yes;
2315 None of the keys listed in this example are valid. In particular,
2316 the root key is not valid.
2320 When DNSSEC validation is enabled and properly configured,
2321 the resolver will reject any answers from signed, secure zones
2322 which fail to validate, and will return SERVFAIL to the client.
2326 Responses may fail to validate for any of several reasons,
2327 including missing, expired, or invalid signatures, a key which
2328 does not match the DS RRset in the parent zone, or an insecure
2329 response from a zone which, according to its parent, should have
2335 When the validator receives a response from an unsigned zone
2336 that has a signed parent, it must confirm with the parent
2337 that the zone was intentionally left unsigned. It does
2338 this by verifying, via signed and validated NSEC/NSEC3 records,
2339 that the parent zone contains no DS records for the child.
2342 If the validator <emphasis>can</emphasis> prove that the zone
2343 is insecure, then the response is accepted. However, if it
2344 cannot, then it must assume an insecure response to be a
2345 forgery; it rejects the response and logs an error.
2348 The logged error reads "insecurity proof failed" and
2349 "got insecure response; parent indicates it should be secure".
2350 (Prior to BIND 9.7, the logged error was "not insecure".
2351 This referred to the zone, not the response.)
2358 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="dnssec.xml"/>
2360 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="managed-keys.xml"/>
2362 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="pkcs11.xml"/>
2364 <section xml:id="ipv6"><info><title>IPv6 Support in <acronym>BIND</acronym> 9</title></info>
2366 <acronym>BIND</acronym> 9 fully supports all currently
2367 defined forms of IPv6 name to address and address to name
2368 lookups. It will also use IPv6 addresses to make queries when
2369 running on an IPv6 capable system.
2373 For forward lookups, <acronym>BIND</acronym> 9 supports
2374 only AAAA records. RFC 3363 deprecated the use of A6 records,
2375 and client-side support for A6 records was accordingly removed
2376 from <acronym>BIND</acronym> 9.
2377 However, authoritative <acronym>BIND</acronym> 9 name servers still
2378 load zone files containing A6 records correctly, answer queries
2379 for A6 records, and accept zone transfer for a zone containing A6
2384 For IPv6 reverse lookups, <acronym>BIND</acronym> 9 supports
2385 the traditional "nibble" format used in the
2386 <emphasis>ip6.arpa</emphasis> domain, as well as the older, deprecated
2387 <emphasis>ip6.int</emphasis> domain.
2388 Older versions of <acronym>BIND</acronym> 9
2389 supported the "binary label" (also known as "bitstring") format,
2390 but support of binary labels has been completely removed per
2392 Many applications in <acronym>BIND</acronym> 9 do not understand
2393 the binary label format at all any more, and will return an
2395 In particular, an authoritative <acronym>BIND</acronym> 9
2396 name server will not load a zone file containing binary labels.
2400 For an overview of the format and structure of IPv6 addresses,
2401 see <xref linkend="ipv6addresses"/>.
2404 <section><info><title>Address Lookups Using AAAA Records</title></info>
2407 The IPv6 AAAA record is a parallel to the IPv4 A record,
2408 and, unlike the deprecated A6 record, specifies the entire
2409 IPv6 address in a single record. For example,
2413 $ORIGIN example.com.
2414 host 3600 IN AAAA 2001:db8::1
2418 Use of IPv4-in-IPv6 mapped addresses is not recommended.
2419 If a host has an IPv4 address, use an A record, not
2420 a AAAA, with <literal>::ffff:192.168.42.1</literal> as
2424 <section><info><title>Address to Name Lookups Using Nibble Format</title></info>
2427 When looking up an address in nibble format, the address
2428 components are simply reversed, just as in IPv4, and
2429 <literal>ip6.arpa.</literal> is appended to the
2431 For example, the following would provide reverse name lookup for
2433 <literal>2001:db8::1</literal>.
2437 $ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
2438 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR (
2446 <chapter xml:id="Bv9ARM.ch05"><info><title>The <acronym>BIND</acronym> 9 Lightweight Resolver</title></info>
2448 <section xml:id="lightweight_resolver"><info><title>The Lightweight Resolver Library</title></info>
2451 Traditionally applications have been linked with a stub resolver
2452 library that sends recursive DNS queries to a local caching name
2456 IPv6 once introduced new complexity into the resolution process,
2457 such as following A6 chains and DNAME records, and simultaneous
2458 lookup of IPv4 and IPv6 addresses. Though most of the complexity was
2459 then removed, these are hard or impossible
2460 to implement in a traditional stub resolver.
2463 <acronym>BIND</acronym> 9 therefore can also provide resolution
2464 services to local clients
2465 using a combination of a lightweight resolver library and a resolver
2466 daemon process running on the local host. These communicate using
2467 a simple UDP-based protocol, the "lightweight resolver protocol"
2468 that is distinct from and simpler than the full DNS protocol.
2471 <section xml:id="lwresd"><info><title>Running a Resolver Daemon</title></info>
2474 To use the lightweight resolver interface, the system must
2475 run the resolver daemon <command>lwresd</command> or a
2477 name server configured with a <command>lwres</command>
2482 By default, applications using the lightweight resolver library will
2484 UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
2486 address can be overridden by <command>lwserver</command>
2488 <filename>/etc/resolv.conf</filename>.
2492 The daemon currently only looks in the DNS, but in the future
2493 it may use other sources such as <filename>/etc/hosts</filename>,
2498 The <command>lwresd</command> daemon is essentially a
2499 caching-only name server that responds to requests using the
2501 resolver protocol rather than the DNS protocol. Because it needs
2502 to run on each host, it is designed to require no or minimal
2504 Unless configured otherwise, it uses the name servers listed on
2505 <command>nameserver</command> lines in <filename>/etc/resolv.conf</filename>
2506 as forwarders, but is also capable of doing the resolution
2511 The <command>lwresd</command> daemon may also be
2513 <filename>named.conf</filename> style configuration file,
2515 <filename>/etc/lwresd.conf</filename> by default. A name
2517 be configured to act as a lightweight resolver daemon using the
2518 <command>lwres</command> statement in <filename>named.conf</filename>.
2524 <chapter xml:id="Bv9ARM.ch06"><info><title><acronym>BIND</acronym> 9 Configuration Reference</title></info>
2527 <acronym>BIND</acronym> 9 configuration is broadly similar
2528 to <acronym>BIND</acronym> 8; however, there are a few new
2530 of configuration, such as views. <acronym>BIND</acronym>
2531 8 configuration files should work with few alterations in <acronym>BIND</acronym>
2532 9, although more complex configurations should be reviewed to check
2533 if they can be more efficiently implemented using the new features
2534 found in <acronym>BIND</acronym> 9.
2538 <acronym>BIND</acronym> 4 configuration files can be
2539 converted to the new format
2540 using the shell script
2541 <filename>contrib/named-bootconf/named-bootconf.sh</filename>.
2543 <section xml:id="configuration_file_elements"><info><title>Configuration File Elements</title></info>
2546 Following is a list of elements used throughout the <acronym>BIND</acronym> configuration
2549 <informaltable colsep="0" rowsep="0">
2550 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
2551 <colspec colname="1" colnum="1" colsep="0" colwidth="1.855in"/>
2552 <colspec colname="2" colnum="2" colsep="0" colwidth="3.770in"/>
2557 <varname>acl_name</varname>
2562 The name of an <varname>address_match_list</varname> as
2563 defined by the <command>acl</command> statement.
2570 <varname>address_match_list</varname>
2575 A list of one or more
2576 <varname>ip_addr</varname>,
2577 <varname>ip_prefix</varname>, <varname>key_id</varname>,
2578 or <varname>acl_name</varname> elements, see
2579 <xref linkend="address_match_lists"/>.
2586 <varname>masters_list</varname>
2591 A named list of one or more <varname>ip_addr</varname>
2592 with optional <varname>key_id</varname> and/or
2593 <varname>ip_port</varname>.
2594 A <varname>masters_list</varname> may include other
2595 <varname>masters_lists</varname>.
2602 <varname>domain_name</varname>
2607 A quoted string which will be used as
2608 a DNS name, for example "<literal>my.test.domain</literal>".
2615 <varname>namelist</varname>
2620 A list of one or more <varname>domain_name</varname>
2628 <varname>dotted_decimal</varname>
2633 One to four integers valued 0 through
2634 255 separated by dots (`.'), such as <command>123</command>,
2635 <command>45.67</command> or <command>89.123.45.67</command>.
2642 <varname>ip4_addr</varname>
2647 An IPv4 address with exactly four elements
2648 in <varname>dotted_decimal</varname> notation.
2655 <varname>ip6_addr</varname>
2660 An IPv6 address, such as <command>2001:db8::1234</command>.
2661 IPv6 scoped addresses that have ambiguity on their
2662 scope zones must be disambiguated by an appropriate
2663 zone ID with the percent character (`%') as
2664 delimiter. It is strongly recommended to use
2665 string zone names rather than numeric identifiers,
2666 in order to be robust against system configuration
2667 changes. However, since there is no standard
2668 mapping for such names and identifier values,
2669 currently only interface names as link identifiers
2670 are supported, assuming one-to-one mapping between
2671 interfaces and links. For example, a link-local
2672 address <command>fe80::1</command> on the link
2673 attached to the interface <command>ne0</command>
2674 can be specified as <command>fe80::1%ne0</command>.
2675 Note that on most systems link-local addresses
2676 always have the ambiguity, and need to be
2684 <varname>ip_addr</varname>
2689 An <varname>ip4_addr</varname> or <varname>ip6_addr</varname>.
2696 <varname>ip_port</varname>
2701 An IP port <varname>number</varname>.
2702 The <varname>number</varname> is limited to 0
2703 through 65535, with values
2704 below 1024 typically restricted to use by processes running
2706 In some cases, an asterisk (`*') character can be used as a
2708 select a random high-numbered port.
2715 <varname>ip_prefix</varname>
2720 An IP network specified as an <varname>ip_addr</varname>,
2721 followed by a slash (`/') and then the number of bits in the
2723 Trailing zeros in a <varname>ip_addr</varname>
2725 For example, <command>127/8</command> is the
2726 network <command>127.0.0.0</command> with
2727 netmask <command>255.0.0.0</command> and <command>1.2.3.0/28</command> is
2728 network <command>1.2.3.0</command> with netmask <command>255.255.255.240</command>.
2731 When specifying a prefix involving a IPv6 scoped address
2732 the scope may be omitted. In that case the prefix will
2733 match packets from any scope.
2740 <varname>key_id</varname>
2745 A <varname>domain_name</varname> representing
2746 the name of a shared key, to be used for transaction
2754 <varname>key_list</varname>
2759 A list of one or more
2760 <varname>key_id</varname>s,
2761 separated by semicolons and ending with a semicolon.
2768 <varname>number</varname>
2773 A non-negative 32-bit integer
2774 (i.e., a number between 0 and 4294967295, inclusive).
2775 Its acceptable value might further
2776 be limited by the context in which it is used.
2783 <varname>path_name</varname>
2788 A quoted string which will be used as
2789 a pathname, such as <filename>zones/master/my.test.domain</filename>.
2796 <varname>port_list</varname>
2801 A list of an <varname>ip_port</varname> or a port
2803 A port range is specified in the form of
2804 <userinput>range</userinput> followed by
2805 two <varname>ip_port</varname>s,
2806 <varname>port_low</varname> and
2807 <varname>port_high</varname>, which represents
2808 port numbers from <varname>port_low</varname> through
2809 <varname>port_high</varname>, inclusive.
2810 <varname>port_low</varname> must not be larger than
2811 <varname>port_high</varname>.
2813 <userinput>range 1024 65535</userinput> represents
2814 ports from 1024 through 65535.
2815 In either case an asterisk (`*') character is not
2816 allowed as a valid <varname>ip_port</varname>.
2823 <varname>size_spec</varname>
2828 A 64-bit unsigned integer, or the keywords
2829 <userinput>unlimited</userinput> or
2830 <userinput>default</userinput>.
2833 Integers may take values
2834 0 <= value <= 18446744073709551615, though
2836 (such as <command>max-journal-size</command>) may
2837 use a more limited range within these extremes.
2838 In most cases, setting a value to 0 does not
2839 literally mean zero; it means "undefined" or
2840 "as big as possible", depending on the context.
2841 See the explanations of particular parameters
2842 that use <varname>size_spec</varname>
2843 for details on how they interpret its use.
2846 Numeric values can optionally be followed by a
2848 <userinput>K</userinput> or <userinput>k</userinput>
2850 <userinput>M</userinput> or <userinput>m</userinput>
2852 <userinput>G</userinput> or <userinput>g</userinput>
2853 for gigabytes, which scale by 1024, 1024*1024, and
2854 1024*1024*1024 respectively.
2857 <varname>unlimited</varname> generally means
2858 "as big as possible", though in certain contexts,
2859 (including <option>max-cache-size</option>), it may
2860 mean the largest possible 32-bit unsigned integer
2861 (0xffffffff); this distinction can be important when
2862 dealing with larger quantities.
2863 <varname>unlimited</varname> is usually the best way
2864 to safely set a very large number.
2867 <varname>default</varname>
2868 uses the limit that was in force when the server was started.
2875 <varname>yes_or_no</varname>
2880 Either <userinput>yes</userinput> or <userinput>no</userinput>.
2881 The words <userinput>true</userinput> and <userinput>false</userinput> are
2882 also accepted, as are the numbers <userinput>1</userinput>
2883 and <userinput>0</userinput>.
2890 <varname>dialup_option</varname>
2895 One of <userinput>yes</userinput>,
2896 <userinput>no</userinput>, <userinput>notify</userinput>,
2897 <userinput>notify-passive</userinput>, <userinput>refresh</userinput> or
2898 <userinput>passive</userinput>.
2899 When used in a zone, <userinput>notify-passive</userinput>,
2900 <userinput>refresh</userinput>, and <userinput>passive</userinput>
2901 are restricted to slave and stub zones.
2908 <section xml:id="address_match_lists"><info><title>Address Match Lists</title></info>
2910 <section><info><title>Syntax</title></info>
2912 <programlisting><varname>address_match_list</varname> = address_match_list_element ;
2913 <optional> address_match_list_element; ... </optional>
2914 <varname>address_match_list_element</varname> = <optional> ! </optional> (ip_address <optional>/length</optional> |
2915 key key_id | acl_name | { address_match_list } )
2919 <section><info><title>Definition and Usage</title></info>
2922 Address match lists are primarily used to determine access
2923 control for various server operations. They are also used in
2924 the <command>listen-on</command> and <command>sortlist</command>
2925 statements. The elements which constitute an address match
2926 list can be any of the following:
2930 <simpara>an IP address (IPv4 or IPv6)</simpara>
2933 <simpara>an IP prefix (in `/' notation)</simpara>
2937 a key ID, as defined by the <command>key</command>
2942 <simpara>the name of an address match list defined with
2943 the <command>acl</command> statement
2947 <simpara>a nested address match list enclosed in braces</simpara>
2952 Elements can be negated with a leading exclamation mark (`!'),
2953 and the match list names "any", "none", "localhost", and
2954 "localnets" are predefined. More information on those names
2955 can be found in the description of the acl statement.
2959 The addition of the key clause made the name of this syntactic
2960 element something of a misnomer, since security keys can be used
2961 to validate access without regard to a host or network address.
2962 Nonetheless, the term "address match list" is still used
2963 throughout the documentation.
2967 When a given IP address or prefix is compared to an address
2968 match list, the comparison takes place in approximately O(1)
2969 time. However, key comparisons require that the list of keys
2970 be traversed until a matching key is found, and therefore may
2975 The interpretation of a match depends on whether the list is being
2976 used for access control, defining <command>listen-on</command> ports, or in a
2977 <command>sortlist</command>, and whether the element was negated.
2981 When used as an access control list, a non-negated match
2982 allows access and a negated match denies access. If
2983 there is no match, access is denied. The clauses
2984 <command>allow-notify</command>,
2985 <command>allow-recursion</command>,
2986 <command>allow-recursion-on</command>,
2987 <command>allow-query</command>,
2988 <command>allow-query-on</command>,
2989 <command>allow-query-cache</command>,
2990 <command>allow-query-cache-on</command>,
2991 <command>allow-transfer</command>,
2992 <command>allow-update</command>,
2993 <command>allow-update-forwarding</command>, and
2994 <command>blackhole</command> all use address match
2995 lists. Similarly, the <command>listen-on</command> option will cause the
2996 server to refuse queries on any of the machine's
2997 addresses which do not match the list.
3001 Order of insertion is significant. If more than one element
3002 in an ACL is found to match a given IP address or prefix,
3003 preference will be given to the one that came
3004 <emphasis>first</emphasis> in the ACL definition.
3005 Because of this first-match behavior, an element that
3006 defines a subset of another element in the list should
3007 come before the broader element, regardless of whether
3008 either is negated. For example, in
3009 <command>1.2.3/24; ! 1.2.3.13;</command>
3010 the 1.2.3.13 element is completely useless because the
3011 algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
3012 element. Using <command>! 1.2.3.13; 1.2.3/24</command> fixes
3013 that problem by having 1.2.3.13 blocked by the negation, but
3014 all other 1.2.3.* hosts fall through.
3019 <section xml:id="comment_syntax"><info><title>Comment Syntax</title></info>
3022 The <acronym>BIND</acronym> 9 comment syntax allows for
3024 anywhere that whitespace may appear in a <acronym>BIND</acronym> configuration
3025 file. To appeal to programmers of all kinds, they can be written
3026 in the C, C++, or shell/perl style.
3029 <section><info><title>Syntax</title></info>
3032 <programlisting>/* This is a <acronym>BIND</acronym> comment as in C */</programlisting>
3033 <programlisting>// This is a <acronym>BIND</acronym> comment as in C++</programlisting>
3034 <programlisting># This is a <acronym>BIND</acronym> comment as in common UNIX shells
3035 # and perl</programlisting>
3038 <section><info><title>Definition and Usage</title></info>
3041 Comments may appear anywhere that whitespace may appear in
3042 a <acronym>BIND</acronym> configuration file.
3045 C-style comments start with the two characters /* (slash,
3046 star) and end with */ (star, slash). Because they are completely
3047 delimited with these characters, they can be used to comment only
3048 a portion of a line or to span multiple lines.
3051 C-style comments cannot be nested. For example, the following
3052 is not valid because the entire comment ends with the first */:
3056 <programlisting>/* This is the start of a comment.
3057 This is still part of the comment.
3058 /* This is an incorrect attempt at nesting a comment. */
3059 This is no longer in any comment. */
3065 C++-style comments start with the two characters // (slash,
3066 slash) and continue to the end of the physical line. They cannot
3067 be continued across multiple physical lines; to have one logical
3068 comment span multiple lines, each line must use the // pair.
3073 <programlisting>// This is the start of a comment. The next line
3074 // is a new comment, even though it is logically
3075 // part of the previous comment.
3080 Shell-style (or perl-style, if you prefer) comments start
3081 with the character <literal>#</literal> (number sign)
3082 and continue to the end of the
3083 physical line, as in C++ comments.
3089 <programlisting># This is the start of a comment. The next line
3090 # is a new comment, even though it is logically
3091 # part of the previous comment.
3098 You cannot use the semicolon (`;') character
3099 to start a comment such as you would in a zone file. The
3100 semicolon indicates the end of a configuration
3108 <section xml:id="Configuration_File_Grammar"><info><title>Configuration File Grammar</title></info>
3111 A <acronym>BIND</acronym> 9 configuration consists of
3112 statements and comments.
3113 Statements end with a semicolon. Statements and comments are the
3114 only elements that can appear without enclosing braces. Many
3115 statements contain a block of sub-statements, which are also
3116 terminated with a semicolon.
3120 The following statements are supported:
3123 <informaltable colsep="0" rowsep="0">
3124 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
3125 <colspec colname="1" colnum="1" colsep="0" colwidth="1.336in"/>
3126 <colspec colname="2" colnum="2" colsep="0" colwidth="3.778in"/>
3130 <para><command>acl</command></para>
3134 defines a named IP address
3135 matching list, for access control and other uses.
3141 <para><command>controls</command></para>
3145 declares control channels to be used
3146 by the <command>rndc</command> utility.
3152 <para><command>include</command></para>
3162 <para><command>key</command></para>
3166 specifies key information for use in
3167 authentication and authorization using TSIG.
3173 <para><command>logging</command></para>
3177 specifies what the server logs, and where
3178 the log messages are sent.
3184 <para><command>lwres</command></para>
3188 configures <command>named</command> to
3189 also act as a light-weight resolver daemon (<command>lwresd</command>).
3195 <para><command>masters</command></para>
3199 defines a named masters list for
3200 inclusion in stub and slave zones'
3201 <command>masters</command> or
3202 <command>also-notify</command> lists.
3208 <para><command>options</command></para>
3212 controls global server configuration
3213 options and sets defaults for other statements.
3219 <para><command>server</command></para>
3223 sets certain configuration options on
3230 <para><command>statistics-channels</command></para>
3234 declares communication channels to get access to
3235 <command>named</command> statistics.
3241 <para><command>trusted-keys</command></para>
3245 defines trusted DNSSEC keys.
3251 <para><command>managed-keys</command></para>
3255 lists DNSSEC keys to be kept up to date
3256 using RFC 5011 trust anchor maintenance.
3262 <para><command>view</command></para>
3272 <para><command>zone</command></para>
3285 The <command>logging</command> and
3286 <command>options</command> statements may only occur once
3291 <section xml:id="acl_grammar"><info><title><command>acl</command> Statement Grammar</title></info>
3293 <programlisting><command>acl</command> acl-name {
3299 <section xml:id="acl"><info><title><command>acl</command> Statement Definition and
3300 Usage</title></info>
3303 The <command>acl</command> statement assigns a symbolic
3304 name to an address match list. It gets its name from a primary
3305 use of address match lists: Access Control Lists (ACLs).
3309 The following ACLs are built-in:
3312 <informaltable colsep="0" rowsep="0">
3313 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
3314 <colspec colname="1" colnum="1" colsep="0" colwidth="1.130in"/>
3315 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
3319 <para><command>any</command></para>
3329 <para><command>none</command></para>
3339 <para><command>localhost</command></para>
3343 Matches the IPv4 and IPv6 addresses of all network
3344 interfaces on the system. When addresses are
3345 added or removed, the <command>localhost</command>
3346 ACL element is updated to reflect the changes.
3352 <para><command>localnets</command></para>
3356 Matches any host on an IPv4 or IPv6 network
3357 for which the system has an interface.
3358 When addresses are added or removed,
3359 the <command>localnets</command>
3360 ACL element is updated to reflect the changes.
3361 Some systems do not provide a way to determine the prefix
3363 local IPv6 addresses.
3364 In such a case, <command>localnets</command>
3365 only matches the local
3366 IPv6 addresses, just like <command>localhost</command>.
3375 <section xml:id="controls_grammar"><info><title><command>controls</command> Statement Grammar</title></info>
3377 <programlisting><command>controls</command> {
3378 [ inet ( ip_addr | * ) [ port ip_port ]
3379 allow { <replaceable> address_match_list </replaceable> }
3380 keys { <replaceable>key_list</replaceable> }; ]
3382 [ unix <replaceable>path</replaceable> perm <replaceable>number</replaceable> owner <replaceable>number</replaceable> group <replaceable>number</replaceable>
3383 keys { <replaceable>key_list</replaceable> }; ]
3390 <section xml:id="controls_statement_definition_and_usage"><info><title><command>controls</command> Statement Definition and
3391 Usage</title></info>
3394 The <command>controls</command> statement declares control
3395 channels to be used by system administrators to control the
3396 operation of the name server. These control channels are
3397 used by the <command>rndc</command> utility to send
3398 commands to and retrieve non-DNS results from a name server.
3402 An <command>inet</command> control channel is a TCP socket
3403 listening at the specified <command>ip_port</command> on the
3404 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
3405 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
3406 interpreted as the IPv4 wildcard address; connections will be
3407 accepted on any of the system's IPv4 addresses.
3408 To listen on the IPv6 wildcard address,
3409 use an <command>ip_addr</command> of <literal>::</literal>.
3410 If you will only use <command>rndc</command> on the local host,
3411 using the loopback address (<literal>127.0.0.1</literal>
3412 or <literal>::1</literal>) is recommended for maximum security.
3416 If no port is specified, port 953 is used. The asterisk
3417 "<literal>*</literal>" cannot be used for <command>ip_port</command>.
3421 The ability to issue commands over the control channel is
3422 restricted by the <command>allow</command> and
3423 <command>keys</command> clauses.
3424 Connections to the control channel are permitted based on the
3425 <command>address_match_list</command>. This is for simple
3426 IP address based filtering only; any <command>key_id</command>
3427 elements of the <command>address_match_list</command>
3432 A <command>unix</command> control channel is a UNIX domain
3433 socket listening at the specified path in the file system.
3434 Access to the socket is specified by the <command>perm</command>,
3435 <command>owner</command> and <command>group</command> clauses.
3436 Note on some platforms (SunOS and Solaris) the permissions
3437 (<command>perm</command>) are applied to the parent directory
3438 as the permissions on the socket itself are ignored.
3442 The primary authorization mechanism of the command
3443 channel is the <command>key_list</command>, which
3444 contains a list of <command>key_id</command>s.
3445 Each <command>key_id</command> in the <command>key_list</command>
3446 is authorized to execute commands over the control channel.
3447 See <xref linkend="rndc"/> in <xref linkend="admin_tools"/>)
3448 for information about configuring keys in <command>rndc</command>.
3452 If no <command>controls</command> statement is present,
3453 <command>named</command> will set up a default
3454 control channel listening on the loopback address 127.0.0.1
3455 and its IPv6 counterpart ::1.
3456 In this case, and also when the <command>controls</command> statement
3457 is present but does not have a <command>keys</command> clause,
3458 <command>named</command> will attempt to load the command channel key
3459 from the file <filename>rndc.key</filename> in
3460 <filename>/etc</filename> (or whatever <varname>sysconfdir</varname>
3461 was specified as when <acronym>BIND</acronym> was built).
3462 To create a <filename>rndc.key</filename> file, run
3463 <userinput>rndc-confgen -a</userinput>.
3467 The <filename>rndc.key</filename> feature was created to
3468 ease the transition of systems from <acronym>BIND</acronym> 8,
3469 which did not have digital signatures on its command channel
3470 messages and thus did not have a <command>keys</command> clause.
3472 It makes it possible to use an existing <acronym>BIND</acronym> 8
3473 configuration file in <acronym>BIND</acronym> 9 unchanged,
3474 and still have <command>rndc</command> work the same way
3475 <command>ndc</command> worked in BIND 8, simply by executing the
3476 command <userinput>rndc-confgen -a</userinput> after BIND 9 is
3481 Since the <filename>rndc.key</filename> feature
3482 is only intended to allow the backward-compatible usage of
3483 <acronym>BIND</acronym> 8 configuration files, this
3485 have a high degree of configurability. You cannot easily change
3486 the key name or the size of the secret, so you should make a
3487 <filename>rndc.conf</filename> with your own key if you
3489 those things. The <filename>rndc.key</filename> file
3491 permissions set such that only the owner of the file (the user that
3492 <command>named</command> is running as) can access it.
3494 desire greater flexibility in allowing other users to access
3495 <command>rndc</command> commands, then you need to create
3497 <filename>rndc.conf</filename> file and make it group
3499 that contains the users who should have access.
3503 To disable the command channel, use an empty
3504 <command>controls</command> statement:
3505 <command>controls { };</command>.
3509 <section xml:id="include_grammar"><info><title><command>include</command> Statement Grammar</title></info>
3511 <programlisting><command>include</command> <replaceable>filename</replaceable>;</programlisting>
3513 <section xml:id="include_statement"><info><title><command>include</command> Statement Definition and Usage</title></info>
3516 The <command>include</command> statement inserts the
3517 specified file at the point where the <command>include</command>
3518 statement is encountered. The <command>include</command>
3519 statement facilitates the administration of configuration
3521 by permitting the reading or writing of some things but not
3522 others. For example, the statement could include private keys
3523 that are readable only by the name server.
3527 <section xml:id="key_grammar"><info><title><command>key</command> Statement Grammar</title></info>
3529 <programlisting><command>key</command> <replaceable>key_id</replaceable> {
3530 algorithm <replaceable>algorithm_id</replaceable>;
3531 secret <replaceable>secret_string</replaceable>;
3537 <section xml:id="key_statement"><info><title><command>key</command> Statement Definition and Usage</title></info>
3540 The <command>key</command> statement defines a shared
3541 secret key for use with TSIG (see <xref linkend="tsig"/>)
3542 or the command channel
3543 (see <xref linkend="controls_statement_definition_and_usage"/>).
3547 The <command>key</command> statement can occur at the
3549 of the configuration file or inside a <command>view</command>
3550 statement. Keys defined in top-level <command>key</command>
3551 statements can be used in all views. Keys intended for use in
3552 a <command>controls</command> statement
3553 (see <xref linkend="controls_statement_definition_and_usage"/>)
3554 must be defined at the top level.
3558 The <replaceable>key_id</replaceable>, also known as the
3559 key name, is a domain name uniquely identifying the key. It can
3560 be used in a <command>server</command>
3561 statement to cause requests sent to that
3562 server to be signed with this key, or in address match lists to
3563 verify that incoming requests have been signed with a key
3564 matching this name, algorithm, and secret.
3568 The <replaceable>algorithm_id</replaceable> is a string
3569 that specifies a security/authentication algorithm. Named
3570 supports <literal>hmac-md5</literal>,
3571 <literal>hmac-sha1</literal>, <literal>hmac-sha224</literal>,
3572 <literal>hmac-sha256</literal>, <literal>hmac-sha384</literal>
3573 and <literal>hmac-sha512</literal> TSIG authentication.
3574 Truncated hashes are supported by appending the minimum
3575 number of required bits preceded by a dash, e.g.
3576 <literal>hmac-sha1-80</literal>. The
3577 <replaceable>secret_string</replaceable> is the secret
3578 to be used by the algorithm, and is treated as a base-64
3583 <section xml:id="logging_grammar"><info><title><command>logging</command> Statement Grammar</title></info>
3585 <programlisting><command>logging</command> {
3586 [ <command>channel</command> <replaceable>channel_name</replaceable> {
3587 ( <command>file</command> <replaceable>path_name</replaceable>
3588 [ <command>versions</command> ( <replaceable>number</replaceable> | <command>unlimited</command> ) ]
3589 [ <command>size</command> <replaceable>size_spec</replaceable> ]
3590 | <command>syslog</command> <replaceable>syslog_facility</replaceable>
3591 | <command>stderr</command>
3592 | <command>null</command> );
3593 [ <command>severity</command> (<option>critical</option> | <option>error</option> | <option>warning</option> | <option>notice</option> |
3594 <option>info</option> | <option>debug</option> [ <replaceable>level</replaceable> ] | <option>dynamic</option> ); ]
3595 [ <command>print-category</command> <option>yes</option> or <option>no</option>; ]
3596 [ <command>print-severity</command> <option>yes</option> or <option>no</option>; ]
3597 [ <command>print-time</command> <option>yes</option> or <option>no</option>; ]
3599 [ <command>category</command> <replaceable>category_name</replaceable> {
3600 <replaceable>channel_name</replaceable> ; [ <replaceable>channel_name</replaceable> ; ... ]
3608 <section xml:id="logging_statement"><info><title><command>logging</command> Statement Definition and Usage</title></info>
3611 The <command>logging</command> statement configures a
3613 variety of logging options for the name server. Its <command>channel</command> phrase
3614 associates output methods, format options and severity levels with
3615 a name that can then be used with the <command>category</command> phrase
3616 to select how various classes of messages are logged.
3619 Only one <command>logging</command> statement is used to
3621 as many channels and categories as are wanted. If there is no <command>logging</command> statement,
3622 the logging configuration will be:
3625 <programlisting>logging {
3626 category default { default_syslog; default_debug; };
3627 category unmatched { null; };
3632 In <acronym>BIND</acronym> 9, the logging configuration
3633 is only established when
3634 the entire configuration file has been parsed. In <acronym>BIND</acronym> 8, it was
3635 established as soon as the <command>logging</command>
3637 was parsed. When the server is starting up, all logging messages
3638 regarding syntax errors in the configuration file go to the default
3639 channels, or to standard error if the "<option>-g</option>" option
3643 <section xml:id="channel"><info><title>The <command>channel</command> Phrase</title></info>
3646 All log output goes to one or more <emphasis>channels</emphasis>;
3647 you can make as many of them as you want.
3651 Every channel definition must include a destination clause that
3652 says whether messages selected for the channel go to a file, to a
3653 particular syslog facility, to the standard error stream, or are
3654 discarded. It can optionally also limit the message severity level
3655 that will be accepted by the channel (the default is
3656 <command>info</command>), and whether to include a
3657 <command>named</command>-generated time stamp, the
3659 and/or severity level (the default is not to include any).
3663 The <command>null</command> destination clause
3664 causes all messages sent to the channel to be discarded;
3665 in that case, other options for the channel are meaningless.
3669 The <command>file</command> destination clause directs
3671 to a disk file. It can include limitations
3672 both on how large the file is allowed to become, and how many
3674 of the file will be saved each time the file is opened.
3678 If you use the <command>versions</command> log file
3680 <command>named</command> will retain that many backup
3681 versions of the file by
3682 renaming them when opening. For example, if you choose to keep
3684 of the file <filename>lamers.log</filename>, then just
3686 <filename>lamers.log.1</filename> is renamed to
3687 <filename>lamers.log.2</filename>, <filename>lamers.log.0</filename> is renamed
3688 to <filename>lamers.log.1</filename>, and <filename>lamers.log</filename> is
3689 renamed to <filename>lamers.log.0</filename>.
3690 You can say <command>versions unlimited</command> to
3692 the number of versions.
3693 If a <command>size</command> option is associated with
3695 then renaming is only done when the file being opened exceeds the
3696 indicated size. No backup versions are kept by default; any
3698 log file is simply appended.
3702 The <command>size</command> option for files is used
3704 growth. If the file ever exceeds the size, then <command>named</command> will
3705 stop writing to the file unless it has a <command>versions</command> option
3706 associated with it. If backup versions are kept, the files are
3708 described above and a new one begun. If there is no
3709 <command>versions</command> option, no more data will
3710 be written to the log
3711 until some out-of-band mechanism removes or truncates the log to
3713 maximum size. The default behavior is not to limit the size of
3719 Example usage of the <command>size</command> and
3720 <command>versions</command> options:
3723 <programlisting>channel an_example_channel {
3724 file "example.log" versions 3 size 20m;
3731 The <command>syslog</command> destination clause
3733 channel to the system log. Its argument is a
3734 syslog facility as described in the <command>syslog</command> man
3735 page. Known facilities are <command>kern</command>, <command>user</command>,
3736 <command>mail</command>, <command>daemon</command>, <command>auth</command>,
3737 <command>syslog</command>, <command>lpr</command>, <command>news</command>,
3738 <command>uucp</command>, <command>cron</command>, <command>authpriv</command>,
3739 <command>ftp</command>, <command>local0</command>, <command>local1</command>,
3740 <command>local2</command>, <command>local3</command>, <command>local4</command>,
3741 <command>local5</command>, <command>local6</command> and
3742 <command>local7</command>, however not all facilities
3744 all operating systems.
3745 How <command>syslog</command> will handle messages
3747 this facility is described in the <command>syslog.conf</command> man
3748 page. If you have a system which uses a very old version of <command>syslog</command> that
3749 only uses two arguments to the <command>openlog()</command> function,
3750 then this clause is silently ignored.
3753 On Windows machines syslog messages are directed to the EventViewer.
3756 The <command>severity</command> clause works like <command>syslog</command>'s
3757 "priorities", except that they can also be used if you are writing
3758 straight to a file rather than using <command>syslog</command>.
3759 Messages which are not at least of the severity level given will
3760 not be selected for the channel; messages of higher severity
3765 If you are using <command>syslog</command>, then the <command>syslog.conf</command> priorities
3766 will also determine what eventually passes through. For example,
3767 defining a channel facility and severity as <command>daemon</command> and <command>debug</command> but
3768 only logging <command>daemon.warning</command> via <command>syslog.conf</command> will
3769 cause messages of severity <command>info</command> and
3770 <command>notice</command> to
3771 be dropped. If the situation were reversed, with <command>named</command> writing
3772 messages of only <command>warning</command> or higher,
3773 then <command>syslogd</command> would
3774 print all messages it received from the channel.
3778 The <command>stderr</command> destination clause
3780 channel to the server's standard error stream. This is intended
3782 use when the server is running as a foreground process, for
3784 when debugging a configuration.
3788 The server can supply extensive debugging information when
3789 it is in debugging mode. If the server's global debug level is
3791 than zero, then debugging mode will be active. The global debug
3792 level is set either by starting the <command>named</command> server
3793 with the <option>-d</option> flag followed by a positive integer,
3794 or by running <command>rndc trace</command>.
3795 The global debug level
3796 can be set to zero, and debugging mode turned off, by running <command>rndc
3797 notrace</command>. All debugging messages in the server have a debug
3798 level, and higher debug levels give more detailed output. Channels
3799 that specify a specific debug severity, for example:
3802 <programlisting>channel specific_debug_level {
3809 will get debugging output of level 3 or less any time the
3810 server is in debugging mode, regardless of the global debugging
3811 level. Channels with <command>dynamic</command>
3813 server's global debug level to determine what messages to print.
3816 If <command>print-time</command> has been turned on,
3818 the date and time will be logged. <command>print-time</command> may
3819 be specified for a <command>syslog</command> channel,
3821 pointless since <command>syslog</command> also logs
3823 time. If <command>print-category</command> is
3825 category of the message will be logged as well. Finally, if <command>print-severity</command> is
3826 on, then the severity level of the message will be logged. The <command>print-</command> options may
3827 be used in any combination, and will always be printed in the
3829 order: time, category, severity. Here is an example where all
3830 three <command>print-</command> options
3835 <computeroutput>28-Feb-2000 15:05:32.863 general: notice: running</computeroutput>
3839 There are four predefined channels that are used for
3840 <command>named</command>'s default logging as follows.
3842 used is described in <xref linkend="the_category_phrase"/>.
3845 <programlisting>channel default_syslog {
3846 // send to syslog's daemon facility
3848 // only send priority info and higher
3851 channel default_debug {
3852 // write to named.run in the working directory
3853 // Note: stderr is used instead of "named.run" if
3854 // the server is started with the '-f' option.
3856 // log at the server's current debug level
3860 channel default_stderr {
3863 // only send priority info and higher
3868 // toss anything sent to this channel
3874 The <command>default_debug</command> channel has the
3876 property that it only produces output when the server's debug
3878 nonzero. It normally writes to a file called <filename>named.run</filename>
3879 in the server's working directory.
3883 For security reasons, when the "<option>-u</option>"
3884 command line option is used, the <filename>named.run</filename> file
3885 is created only after <command>named</command> has
3887 new UID, and any debug output generated while <command>named</command> is
3888 starting up and still running as root is discarded. If you need
3889 to capture this output, you must run the server with the "<option>-g</option>"
3890 option and redirect standard error to a file.
3894 Once a channel is defined, it cannot be redefined. Thus you
3895 cannot alter the built-in channels directly, but you can modify
3896 the default logging by pointing categories at channels you have
3901 <section xml:id="the_category_phrase"><info><title>The <command>category</command> Phrase</title></info>
3904 There are many categories, so you can send the logs you want
3905 to see wherever you want, without seeing logs you don't want. If
3906 you don't specify a list of channels for a category, then log
3908 in that category will be sent to the <command>default</command> category
3909 instead. If you don't specify a default category, the following
3910 "default default" is used:
3913 <programlisting>category default { default_syslog; default_debug; };
3917 As an example, let's say you want to log security events to
3918 a file, but you also want keep the default logging behavior. You'd
3919 specify the following:
3922 <programlisting>channel my_security_channel {
3923 file "my_security_file";
3927 my_security_channel;
3933 To discard all messages in a category, specify the <command>null</command> channel:
3936 <programlisting>category xfer-out { null; };
3937 category notify { null; };
3941 Following are the available categories and brief descriptions
3942 of the types of log information they contain. More
3943 categories may be added in future <acronym>BIND</acronym> releases.
3945 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="logging-categories.xml"/>
3947 <section xml:id="query_errors"><info><title>The <command>query-errors</command> Category</title></info>
3950 The <command>query-errors</command> category is
3951 specifically intended for debugging purposes: To identify
3952 why and how specific queries result in responses which
3954 Messages of this category are therefore only logged
3955 with <command>debug</command> levels.
3959 At the debug levels of 1 or higher, each response with the
3960 rcode of SERVFAIL is logged as follows:
3963 <computeroutput>client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</computeroutput>
3966 This means an error resulting in SERVFAIL was
3967 detected at line 3880 of source file
3968 <filename>query.c</filename>.
3969 Log messages of this level will particularly
3970 help identify the cause of SERVFAIL for an
3971 authoritative server.
3974 At the debug levels of 2 or higher, detailed context
3975 information of recursive resolutions that resulted in
3977 The log message will look like as follows:
3980 <!-- NOTE: newlines and some spaces added so this would fit on page -->
3982 fetch completed at resolver.c:2970 for www.example.com/A
3983 in 30.000183: timed out/success [domain:example.com,
3984 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
3985 badresp:1,adberr:0,findfail:0,valfail:0]
3989 The first part before the colon shows that a recursive
3990 resolution for AAAA records of www.example.com completed
3991 in 30.000183 seconds and the final result that led to the
3992 SERVFAIL was determined at line 2970 of source file
3993 <filename>resolver.c</filename>.
3996 The following part shows the detected final result and the
3997 latest result of DNSSEC validation.
3998 The latter is always success when no validation attempt
4000 In this example, this query resulted in SERVFAIL probably
4001 because all name servers are down or unreachable, leading
4002 to a timeout in 30 seconds.
4003 DNSSEC validation was probably not attempted.
4006 The last part enclosed in square brackets shows statistics
4007 information collected for this particular resolution
4009 The <varname>domain</varname> field shows the deepest zone
4010 that the resolver reached;
4011 it is the zone where the error was finally detected.
4012 The meaning of the other fields is summarized in the
4016 <informaltable colsep="0" rowsep="0">
4017 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4018 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4019 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4023 <para><varname>referral</varname></para>
4027 The number of referrals the resolver received
4028 throughout the resolution process.
4029 In the above example this is 2, which are most
4030 likely com and example.com.
4036 <para><varname>restart</varname></para>
4040 The number of cycles that the resolver tried
4041 remote servers at the <varname>domain</varname>
4043 In each cycle the resolver sends one query
4044 (possibly resending it, depending on the response)
4045 to each known name server of
4046 the <varname>domain</varname> zone.
4052 <para><varname>qrysent</varname></para>
4056 The number of queries the resolver sent at the
4057 <varname>domain</varname> zone.
4063 <para><varname>timeout</varname></para>
4067 The number of timeouts since the resolver
4068 received the last response.
4074 <para><varname>lame</varname></para>
4078 The number of lame servers the resolver detected
4079 at the <varname>domain</varname> zone.
4080 A server is detected to be lame either by an
4081 invalid response or as a result of lookup in
4082 BIND9's address database (ADB), where lame
4089 <para><varname>neterr</varname></para>
4093 The number of erroneous results that the
4094 resolver encountered in sending queries
4095 at the <varname>domain</varname> zone.
4096 One common case is the remote server is
4097 unreachable and the resolver receives an ICMP
4098 unreachable error message.
4104 <para><varname>badresp</varname></para>
4108 The number of unexpected responses (other than
4109 <varname>lame</varname>) to queries sent by the
4110 resolver at the <varname>domain</varname> zone.
4116 <para><varname>adberr</varname></para>
4120 Failures in finding remote server addresses
4121 of the <varname>domain</varname> zone in the ADB.
4122 One common case of this is that the remote
4123 server's name does not have any address records.
4129 <para><varname>findfail</varname></para>
4133 Failures of resolving remote server addresses.
4134 This is a total number of failures throughout
4135 the resolution process.
4141 <para><varname>valfail</varname></para>
4145 Failures of DNSSEC validation.
4146 Validation failures are counted throughout
4147 the resolution process (not limited to
4148 the <varname>domain</varname> zone), but should
4149 only happen in <varname>domain</varname>.
4157 At the debug levels of 3 or higher, the same messages
4158 as those at the debug 1 level are logged for other errors
4160 Note that negative responses such as NXDOMAIN are not
4161 regarded as errors here.
4164 At the debug levels of 4 or higher, the same messages
4165 as those at the debug 2 level are logged for other errors
4167 Unlike the above case of level 3, messages are logged for
4169 This is because any unexpected results can be difficult to
4170 debug in the recursion case.
4175 <section xml:id="lwres_grammar"><info><title><command>lwres</command> Statement Grammar</title></info>
4178 This is the grammar of the <command>lwres</command>
4179 statement in the <filename>named.conf</filename> file:
4182 <programlisting><command>lwres</command> {
4183 <optional> listen-on { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
4184 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
4185 <optional> view <replaceable>view_name</replaceable>; </optional>
4186 <optional> search { <replaceable>domain_name</replaceable> ; <optional> <replaceable>domain_name</replaceable> ; ... </optional> }; </optional>
4187 <optional> ndots <replaceable>number</replaceable>; </optional>
4192 <section xml:id="lwres_statement"><info><title><command>lwres</command> Statement Definition and Usage</title></info>
4195 The <command>lwres</command> statement configures the
4197 server to also act as a lightweight resolver server. (See
4198 <xref linkend="lwresd"/>.) There may be multiple
4199 <command>lwres</command> statements configuring
4200 lightweight resolver servers with different properties.
4204 The <command>listen-on</command> statement specifies a
4206 IPv4 addresses (and ports) that this instance of a lightweight
4208 should accept requests on. If no port is specified, port 921 is
4210 If this statement is omitted, requests will be accepted on
4216 The <command>view</command> statement binds this
4218 lightweight resolver daemon to a view in the DNS namespace, so that
4220 response will be constructed in the same manner as a normal DNS
4222 matching this view. If this statement is omitted, the default view
4224 used, and if there is no default view, an error is triggered.
4228 The <command>search</command> statement is equivalent to
4230 <command>search</command> statement in
4231 <filename>/etc/resolv.conf</filename>. It provides a
4233 which are appended to relative names in queries.
4237 The <command>ndots</command> statement is equivalent to
4239 <command>ndots</command> statement in
4240 <filename>/etc/resolv.conf</filename>. It indicates the
4242 number of dots in a relative domain name that should result in an
4243 exact match lookup before search path elements are appended.
4246 <section xml:id="masters_grammar"><info><title><command>masters</command> Statement Grammar</title></info>
4249 <command>masters</command> <replaceable>name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> |
4250 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> };
4255 <section xml:id="masters_statement"><info><title><command>masters</command> Statement Definition and
4256 Usage</title></info>
4258 <para><command>masters</command>
4259 lists allow for a common set of masters to be easily used by
4260 multiple stub and slave zones in their <command>masters</command>
4261 or <command>also-notify</command> lists.
4265 <section xml:id="options_grammar"><info><title><command>options</command> Statement Grammar</title></info>
4268 This is the grammar of the <command>options</command>
4269 statement in the <filename>named.conf</filename> file:
4272 <programlisting><command>options</command> {
4273 <optional> attach-cache <replaceable>cache_name</replaceable>; </optional>
4274 <optional> version <replaceable>version_string</replaceable>; </optional>
4275 <optional> hostname <replaceable>hostname_string</replaceable>; </optional>
4276 <optional> server-id <replaceable>server_id_string</replaceable>; </optional>
4277 <optional> directory <replaceable>path_name</replaceable>; </optional>
4278 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
4279 <optional> managed-keys-directory <replaceable>path_name</replaceable>; </optional>
4280 <optional> named-xfer <replaceable>path_name</replaceable>; </optional>
4281 <optional> tkey-gssapi-keytab <replaceable>path_name</replaceable>; </optional>
4282 <optional> tkey-gssapi-credential <replaceable>principal</replaceable>; </optional>
4283 <optional> tkey-domain <replaceable>domainname</replaceable>; </optional>
4284 <optional> tkey-dhkey <replaceable>key_name</replaceable> <replaceable>key_tag</replaceable>; </optional>
4285 <optional> cache-file <replaceable>path_name</replaceable>; </optional>
4286 <optional> dump-file <replaceable>path_name</replaceable>; </optional>
4287 <optional> bindkeys-file <replaceable>path_name</replaceable>; </optional>
4288 <optional> secroots-file <replaceable>path_name</replaceable>; </optional>
4289 <optional> session-keyfile <replaceable>path_name</replaceable>; </optional>
4290 <optional> session-keyname <replaceable>key_name</replaceable>; </optional>
4291 <optional> session-keyalg <replaceable>algorithm_id</replaceable>; </optional>
4292 <optional> memstatistics <replaceable>yes_or_no</replaceable>; </optional>
4293 <optional> memstatistics-file <replaceable>path_name</replaceable>; </optional>
4294 <optional> pid-file <replaceable>path_name</replaceable>; </optional>
4295 <optional> recursing-file <replaceable>path_name</replaceable>; </optional>
4296 <optional> statistics-file <replaceable>path_name</replaceable>; </optional>
4297 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
4298 <optional> auth-nxdomain <replaceable>yes_or_no</replaceable>; </optional>
4299 <optional> deallocate-on-exit <replaceable>yes_or_no</replaceable>; </optional>
4300 <optional> dialup <replaceable>dialup_option</replaceable>; </optional>
4301 <optional> fake-iquery <replaceable>yes_or_no</replaceable>; </optional>
4302 <optional> fetch-glue <replaceable>yes_or_no</replaceable>; </optional>
4303 <optional> flush-zones-on-shutdown <replaceable>yes_or_no</replaceable>; </optional>
4304 <optional> has-old-clients <replaceable>yes_or_no</replaceable>; </optional>
4305 <optional> host-statistics <replaceable>yes_or_no</replaceable>; </optional>
4306 <optional> host-statistics-max <replaceable>number</replaceable>; </optional>
4307 <optional> minimal-responses <replaceable>yes_or_no</replaceable>; </optional>
4308 <optional> multiple-cnames <replaceable>yes_or_no</replaceable>; </optional>
4309 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable>; </optional>
4310 <optional> recursion <replaceable>yes_or_no</replaceable>; </optional>
4311 <optional> request-nsid <replaceable>yes_or_no</replaceable>; </optional>
4312 <optional> rfc2308-type1 <replaceable>yes_or_no</replaceable>; </optional>
4313 <optional> use-id-pool <replaceable>yes_or_no</replaceable>; </optional>
4314 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable>; </optional>
4315 <optional> ixfr-from-differences (<replaceable>yes_or_no</replaceable> | <constant>master</constant> | <constant>slave</constant>); </optional>
4316 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>off</constant>; </optional>
4317 <optional> dnssec-enable <replaceable>yes_or_no</replaceable>; </optional>
4318 <optional> dnssec-validation (<replaceable>yes_or_no</replaceable> | <constant>auto</constant>); </optional>
4319 <optional> dnssec-lookaside ( <replaceable>auto</replaceable> |
4320 <replaceable>no</replaceable> |
4321 <replaceable>domain</replaceable> trust-anchor <replaceable>domain</replaceable> ); </optional>
4322 <optional> dnssec-must-be-secure <replaceable>domain yes_or_no</replaceable>; </optional>
4323 <optional> dnssec-accept-expired <replaceable>yes_or_no</replaceable>; </optional>
4324 <optional> forward ( <replaceable>only</replaceable> | <replaceable>first</replaceable> ); </optional>
4325 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
4326 <optional> dual-stack-servers <optional>port <replaceable>ip_port</replaceable></optional> {
4327 ( <replaceable>domain_name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> |
4328 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ) ;
4330 <optional> check-names ( <replaceable>master</replaceable> | <replaceable>slave</replaceable> | <replaceable>response</replaceable> )
4331 ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4332 <optional> check-dup-records ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4333 <optional> check-mx ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4334 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
4335 <optional> check-integrity <replaceable>yes_or_no</replaceable>; </optional>
4336 <optional> check-mx-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4337 <optional> check-srv-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4338 <optional> check-sibling <replaceable>yes_or_no</replaceable>; </optional>
4339 <optional> check-spf ( <replaceable>warn</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4340 <optional> allow-new-zones { <replaceable>yes_or_no</replaceable> }; </optional>
4341 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
4342 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
4343 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
4344 <optional> allow-query-cache { <replaceable>address_match_list</replaceable> }; </optional>
4345 <optional> allow-query-cache-on { <replaceable>address_match_list</replaceable> }; </optional>
4346 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
4347 <optional> allow-recursion { <replaceable>address_match_list</replaceable> }; </optional>
4348 <optional> allow-recursion-on { <replaceable>address_match_list</replaceable> }; </optional>
4349 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
4350 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
4351 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
4352 <optional> dnssec-update-mode ( <replaceable>maintain</replaceable> | <replaceable>no-resign</replaceable> ); </optional>
4353 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
4354 <optional> dnssec-loadkeys-interval <replaceable>number</replaceable>; </optional>
4355 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ;</optional>
4356 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
4357 <optional> allow-v6-synthesis { <replaceable>address_match_list</replaceable> }; </optional>
4358 <optional> blackhole { <replaceable>address_match_list</replaceable> }; </optional>
4359 <optional> no-case-compress { <replaceable>address_match_list</replaceable> }; </optional>
4360 <optional> use-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4361 <optional> avoid-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4362 <optional> use-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4363 <optional> avoid-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4364 <optional> listen-on <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
4365 <optional> listen-on-v6 <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
4366 <optional> query-source ( ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> )
4367 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
4368 <optional> address ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
4369 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
4370 <optional> query-source-v6 ( ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> )
4371 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
4372 <optional> address ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
4373 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
4374 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
4375 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
4376 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
4377 <optional> max-transfer-time-in <replaceable>number</replaceable>; </optional>
4378 <optional> max-transfer-time-out <replaceable>number</replaceable>; </optional>
4379 <optional> max-transfer-idle-in <replaceable>number</replaceable>; </optional>
4380 <optional> max-transfer-idle-out <replaceable>number</replaceable>; </optional>
4381 <optional> reserved-sockets <replaceable>number</replaceable>; </optional>
4382 <optional> recursive-clients <replaceable>number</replaceable>; </optional>
4383 <optional> tcp-clients <replaceable>number</replaceable>; </optional>
4384 <optional> clients-per-query <replaceable>number</replaceable> ; </optional>
4385 <optional> max-clients-per-query <replaceable>number</replaceable> ; </optional>
4386 <optional> fetches-per-server <replaceable>number</replaceable> <optional><replaceable>(drop | fail)</replaceable></optional>; </optional>
4387 <optional> fetch-quota-params <replaceable>number fixedpoint fixedpoint fixedpoint</replaceable> ; </optional>
4388 <optional> fetches-per-zone <replaceable>number</replaceable> <optional><replaceable>(drop | fail)</replaceable></optional>; </optional>
4389 <optional> serial-query-rate <replaceable>number</replaceable>; </optional>
4390 <optional> serial-queries <replaceable>number</replaceable>; </optional>
4391 <optional> tcp-listen-queue <replaceable>number</replaceable>; </optional>
4392 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable>; </optional>
4393 <optional> transfers-in <replaceable>number</replaceable>; </optional>
4394 <optional> transfers-out <replaceable>number</replaceable>; </optional>
4395 <optional> transfers-per-ns <replaceable>number</replaceable>; </optional>
4396 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4397 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4398 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4399 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
4400 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4401 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
4402 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
4403 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4404 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4405 <optional> notify-to-soa <replaceable>yes_or_no</replaceable> ; </optional>
4406 <optional> also-notify <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
4407 <optional>port <replaceable>ip_port</replaceable></optional>
4408 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
4409 <optional> max-ixfr-log-size <replaceable>number</replaceable>; </optional>
4410 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
4411 <optional> coresize <replaceable>size_spec</replaceable> ; </optional>
4412 <optional> datasize <replaceable>size_spec</replaceable> ; </optional>
4413 <optional> files <replaceable>size_spec</replaceable> ; </optional>
4414 <optional> stacksize <replaceable>size_spec</replaceable> ; </optional>
4415 <optional> cleaning-interval <replaceable>number</replaceable>; </optional>
4416 <optional> heartbeat-interval <replaceable>number</replaceable>; </optional>
4417 <optional> interface-interval <replaceable>number</replaceable>; </optional>
4418 <optional> statistics-interval <replaceable>number</replaceable>; </optional>
4419 <optional> topology { <replaceable>address_match_list</replaceable> }</optional>;
4420 <optional> sortlist { <replaceable>address_match_list</replaceable> }</optional>;
4421 <optional> rrset-order { <replaceable>order_spec</replaceable> ; <optional> <replaceable>order_spec</replaceable> ; ... </optional> </optional> };
4422 <optional> lame-ttl <replaceable>number</replaceable>; </optional>
4423 <optional> max-ncache-ttl <replaceable>number</replaceable>; </optional>
4424 <optional> max-cache-ttl <replaceable>number</replaceable>; </optional>
4425 <optional> serial-update-method <constant>increment</constant>|<constant>unixtime</constant>|<constant>date</constant>; </optional>
4426 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
4427 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
4428 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
4429 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
4430 <optional> min-roots <replaceable>number</replaceable>; </optional>
4431 <optional> use-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
4432 <optional> provide-ixfr <replaceable>yes_or_no</replaceable>; </optional>
4433 <optional> request-ixfr <replaceable>yes_or_no</replaceable>; </optional>
4434 <optional> treat-cr-as-space <replaceable>yes_or_no</replaceable> ; </optional>
4435 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
4436 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
4437 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
4438 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
4439 <optional> port <replaceable>ip_port</replaceable>; </optional>
4440 <optional> additional-from-auth <replaceable>yes_or_no</replaceable> ; </optional>
4441 <optional> additional-from-cache <replaceable>yes_or_no</replaceable> ; </optional>
4442 <optional> random-device <replaceable>path_name</replaceable> ; </optional>
4443 <optional> max-cache-size <replaceable>size_spec</replaceable> ; </optional>
4444 <optional> match-mapped-addresses <replaceable>yes_or_no</replaceable>; </optional>
4445 <optional> filter-aaaa-on-v4 ( <replaceable>yes_or_no</replaceable> | <replaceable>break-dnssec</replaceable> ); </optional>
4446 <optional> filter-aaaa { <replaceable>address_match_list</replaceable> }; </optional>
4447 <optional> dns64 <replaceable>ipv6-prefix</replaceable> {
4448 <optional> clients { <replaceable>address_match_list</replaceable> }; </optional>
4449 <optional> mapped { <replaceable>address_match_list</replaceable> }; </optional>
4450 <optional> exclude { <replaceable>address_match_list</replaceable> }; </optional>
4451 <optional> suffix <replaceable>IPv6-address</replaceable>; </optional>
4452 <optional> recursive-only <replaceable>yes_or_no</replaceable>; </optional>
4453 <optional> break-dnssec <replaceable>yes_or_no</replaceable>; </optional>
4455 <optional> dns64-server <replaceable>name</replaceable> </optional>
4456 <optional> dns64-contact <replaceable>name</replaceable> </optional>
4457 <optional> preferred-glue ( <replaceable>A</replaceable> | <replaceable>AAAA</replaceable> | <replaceable>NONE</replaceable> ); </optional>
4458 <optional> edns-udp-size <replaceable>number</replaceable>; </optional>
4459 <optional> max-udp-size <replaceable>number</replaceable>; </optional>
4460 <optional> max-rsa-exponent-size <replaceable>number</replaceable>; </optional>
4461 <optional> root-delegation-only <optional> exclude { <replaceable>namelist</replaceable> } </optional> ; </optional>
4462 <optional> querylog <replaceable>yes_or_no</replaceable> ; </optional>
4463 <optional> disable-algorithms <replaceable>domain</replaceable> { <replaceable>algorithm</replaceable>;
4464 <optional> <replaceable>algorithm</replaceable>; </optional> }; </optional>
4465 <optional> acache-enable <replaceable>yes_or_no</replaceable> ; </optional>
4466 <optional> acache-cleaning-interval <replaceable>number</replaceable>; </optional>
4467 <optional> max-acache-size <replaceable>size_spec</replaceable> ; </optional>
4468 <optional> max-recursion-depth <replaceable>number</replaceable> ; </optional>
4469 <optional> max-recursion-queries <replaceable>number</replaceable> ; </optional>
4470 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
4471 <optional> empty-server <replaceable>name</replaceable> ; </optional>
4472 <optional> empty-contact <replaceable>name</replaceable> ; </optional>
4473 <optional> empty-zones-enable <replaceable>yes_or_no</replaceable> ; </optional>
4474 <optional> disable-empty-zone <replaceable>zone_name</replaceable> ; </optional>
4475 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
4476 <optional> zero-no-soa-ttl-cache <replaceable>yes_or_no</replaceable> ; </optional>
4477 <optional> resolver-query-timeout <replaceable>number</replaceable> ; </optional>
4478 <optional> deny-answer-addresses { <replaceable>address_match_list</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
4479 <optional> deny-answer-aliases { <replaceable>namelist</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
4480 <optional> rate-limit {
4481 <optional> responses-per-second <replaceable>number</replaceable> ; </optional>
4482 <optional> referrals-per-second <replaceable>number</replaceable> ; </optional>
4483 <optional> nodata-per-second <replaceable>number</replaceable> ; </optional>
4484 <optional> nxdomains-per-second <replaceable>number</replaceable> ; </optional>
4485 <optional> errors-per-second <replaceable>number</replaceable> ; </optional>
4486 <optional> all-per-second <replaceable>number</replaceable> ; </optional>
4487 <optional> window <replaceable>number</replaceable> ; </optional>
4488 <optional> log-only <replaceable>yes_or_no</replaceable> ; </optional>
4489 <optional> qps-scale <replaceable>number</replaceable> ; </optional>
4490 <optional> ipv4-prefix-length <replaceable>number</replaceable> ; </optional>
4491 <optional> ipv6-prefix-length <replaceable>number</replaceable> ; </optional>
4492 <optional> slip <replaceable>number</replaceable> ; </optional>
4493 <optional> exempt-clients { <replaceable>address_match_list</replaceable> } ; </optional>
4494 <optional> max-table-size <replaceable>number</replaceable> ; </optional>
4495 <optional> min-table-size <replaceable>number</replaceable> ; </optional>
4497 <optional> response-policy {
4498 zone <replaceable>zone_name</replaceable>
4499 <optional> policy <replaceable>(given | disabled | passthru |
4500 nxdomain | nodata | cname domain</replaceable>) </optional>
4501 ; <optional>...</optional>
4502 } <optional> recursive-only <replaceable>yes_or_no</replaceable> </optional>
4503 <optional> max-policy-ttl <replaceable>number</replaceable> </optional>
4504 <optional> break-dnssec <replaceable>yes_or_no</replaceable> </optional>
4505 <optional> min-ns-dots <replaceable>number</replaceable> </optional>
4512 <section xml:id="options"><info><title><command>options</command> Statement Definition and
4513 Usage</title></info>
4516 The <command>options</command> statement sets up global
4518 to be used by <acronym>BIND</acronym>. This statement
4520 once in a configuration file. If there is no <command>options</command>
4521 statement, an options block with each option set to its default will
4528 <term><command>attach-cache</command></term>
4531 Allows multiple views to share a single cache
4533 Each view has its own cache database by default, but
4534 if multiple views have the same operational policy
4535 for name resolution and caching, those views can
4536 share a single cache to save memory and possibly
4537 improve resolution efficiency by using this option.
4541 The <command>attach-cache</command> option
4542 may also be specified in <command>view</command>
4543 statements, in which case it overrides the
4544 global <command>attach-cache</command> option.
4548 The <replaceable>cache_name</replaceable> specifies
4549 the cache to be shared.
4550 When the <command>named</command> server configures
4551 views which are supposed to share a cache, it
4552 creates a cache with the specified name for the
4553 first view of these sharing views.
4554 The rest of the views will simply refer to the
4555 already created cache.
4559 One common configuration to share a cache would be to
4560 allow all views to share a single cache.
4561 This can be done by specifying
4562 the <command>attach-cache</command> as a global
4563 option with an arbitrary name.
4567 Another possible operation is to allow a subset of
4568 all views to share a cache while the others to
4569 retain their own caches.
4570 For example, if there are three views A, B, and C,
4571 and only A and B should share a cache, specify the
4572 <command>attach-cache</command> option as a view A (or
4573 B)'s option, referring to the other view name:
4578 // this view has its own cache
4582 // this view refers to A's cache
4586 // this view has its own cache
4592 Views that share a cache must have the same policy
4593 on configurable parameters that may affect caching.
4594 The current implementation requires the following
4595 configurable options be consistent among these
4597 <command>check-names</command>,
4598 <command>cleaning-interval</command>,
4599 <command>dnssec-accept-expired</command>,
4600 <command>dnssec-validation</command>,
4601 <command>max-cache-ttl</command>,
4602 <command>max-ncache-ttl</command>,
4603 <command>max-cache-size</command>, and
4604 <command>zero-no-soa-ttl</command>.
4608 Note that there may be other parameters that may
4609 cause confusion if they are inconsistent for
4610 different views that share a single cache.
4611 For example, if these views define different sets of
4612 forwarders that can return different answers for the
4613 same question, sharing the answer does not make
4614 sense or could even be harmful.
4615 It is administrator's responsibility to ensure
4616 configuration differences in different views do
4617 not cause disruption with a shared cache.
4624 <term><command>directory</command></term>
4627 The working directory of the server.
4628 Any non-absolute pathnames in the configuration file will be
4630 as relative to this directory. The default location for most
4632 output files (e.g. <filename>named.run</filename>)
4634 If a directory is not specified, the working directory
4635 defaults to `<filename>.</filename>', the directory from
4637 was started. The directory specified should be an absolute
4644 <term><command>key-directory</command></term>
4647 When performing dynamic update of secure zones, the
4648 directory where the public and private DNSSEC key files
4649 should be found, if different than the current working
4650 directory. (Note that this option has no effect on the
4651 paths for files containing non-DNSSEC keys such as
4652 <filename>bind.keys</filename>,
4653 <filename>rndc.key</filename> or
4654 <filename>session.key</filename>.)
4660 <term><command>managed-keys-directory</command></term>
4663 Specifies the directory in which to store the files that
4664 track managed DNSSEC keys. By default, this is the working
4668 If <command>named</command> is not configured to use views,
4669 then managed keys for the server will be tracked in a single
4670 file called <filename>managed-keys.bind</filename>.
4671 Otherwise, managed keys will be tracked in separate files,
4672 one file per view; each file name will be the SHA256 hash
4673 of the view name, followed by the extension
4674 <filename>.mkeys</filename>.
4680 <term><command>named-xfer</command></term>
4683 <emphasis>This option is obsolete.</emphasis> It
4684 was used in <acronym>BIND</acronym> 8 to specify
4685 the pathname to the <command>named-xfer</command>
4686 program. In <acronym>BIND</acronym> 9, no separate
4687 <command>named-xfer</command> program is needed;
4688 its functionality is built into the name server.
4694 <term><command>tkey-gssapi-keytab</command></term>
4697 The KRB5 keytab file to use for GSS-TSIG updates. If
4698 this option is set and tkey-gssapi-credential is not
4699 set, then updates will be allowed with any key
4700 matching a principal in the specified keytab.
4706 <term><command>tkey-gssapi-credential</command></term>
4709 The security credential with which the server should
4710 authenticate keys requested by the GSS-TSIG protocol.
4711 Currently only Kerberos 5 authentication is available
4712 and the credential is a Kerberos principal which the
4713 server can acquire through the default system key
4714 file, normally <filename>/etc/krb5.keytab</filename>.
4715 The location keytab file can be overridden using the
4716 tkey-gssapi-keytab option. Normally this principal is
4717 of the form "<userinput>DNS/</userinput><varname>server.domain</varname>".
4718 To use GSS-TSIG, <command>tkey-domain</command> must
4719 also be set if a specific keytab is not set with
4726 <term><command>tkey-domain</command></term>
4729 The domain appended to the names of all shared keys
4730 generated with <command>TKEY</command>. When a
4731 client requests a <command>TKEY</command> exchange,
4732 it may or may not specify the desired name for the
4733 key. If present, the name of the shared key will
4734 be <varname>client specified part</varname> +
4735 <varname>tkey-domain</varname>. Otherwise, the
4736 name of the shared key will be <varname>random hex
4737 digits</varname> + <varname>tkey-domain</varname>.
4738 In most cases, the <command>domainname</command>
4739 should be the server's domain name, or an otherwise
4740 non-existent subdomain like
4741 "_tkey.<varname>domainname</varname>". If you are
4742 using GSS-TSIG, this variable must be defined, unless
4743 you specify a specific keytab using tkey-gssapi-keytab.
4749 <term><command>tkey-dhkey</command></term>
4752 The Diffie-Hellman key used by the server
4753 to generate shared keys with clients using the Diffie-Hellman
4755 of <command>TKEY</command>. The server must be
4757 public and private keys from files in the working directory.
4759 most cases, the keyname should be the server's host name.
4765 <term><command>cache-file</command></term>
4768 This is for testing only. Do not use.
4774 <term><command>dump-file</command></term>
4777 The pathname of the file the server dumps
4778 the database to when instructed to do so with
4779 <command>rndc dumpdb</command>.
4780 If not specified, the default is <filename>named_dump.db</filename>.
4786 <term><command>memstatistics-file</command></term>
4789 The pathname of the file the server writes memory
4790 usage statistics to on exit. If not specified,
4791 the default is <filename>named.memstats</filename>.
4797 <term><command>pid-file</command></term>
4800 The pathname of the file the server writes its process ID
4801 in. If not specified, the default is
4802 <filename>/var/run/named/named.pid</filename>.
4803 The PID file is used by programs that want to send signals to
4805 name server. Specifying <command>pid-file none</command> disables the
4806 use of a PID file — no file will be written and any
4807 existing one will be removed. Note that <command>none</command>
4808 is a keyword, not a filename, and therefore is not enclosed
4816 <term><command>recursing-file</command></term>
4819 The pathname of the file the server dumps
4820 the queries that are currently recursing when instructed
4821 to do so with <command>rndc recursing</command>.
4822 If not specified, the default is <filename>named.recursing</filename>.
4828 <term><command>statistics-file</command></term>
4831 The pathname of the file the server appends statistics
4832 to when instructed to do so using <command>rndc stats</command>.
4833 If not specified, the default is <filename>named.stats</filename> in the
4834 server's current directory. The format of the file is
4836 in <xref linkend="statsfile"/>.
4842 <term><command>bindkeys-file</command></term>
4845 The pathname of a file to override the built-in trusted
4846 keys provided by <command>named</command>.
4847 See the discussion of <command>dnssec-lookaside</command>
4848 and <command>dnssec-validation</command> for details.
4849 If not specified, the default is
4850 <filename>/etc/bind.keys</filename>.
4856 <term><command>secroots-file</command></term>
4859 The pathname of the file the server dumps
4860 security roots to when instructed to do so with
4861 <command>rndc secroots</command>.
4862 If not specified, the default is
4863 <filename>named.secroots</filename>.
4869 <term><command>session-keyfile</command></term>
4872 The pathname of the file into which to write a TSIG
4873 session key generated by <command>named</command> for use by
4874 <command>nsupdate -l</command>. If not specified, the
4875 default is <filename>/var/run/named/session.key</filename>.
4876 (See <xref linkend="dynamic_update_policies"/>, and in
4877 particular the discussion of the
4878 <command>update-policy</command> statement's
4879 <userinput>local</userinput> option for more
4880 information about this feature.)
4886 <term><command>session-keyname</command></term>
4889 The key name to use for the TSIG session key.
4890 If not specified, the default is "local-ddns".
4896 <term><command>session-keyalg</command></term>
4899 The algorithm to use for the TSIG session key.
4900 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
4901 hmac-sha384, hmac-sha512 and hmac-md5. If not
4902 specified, the default is hmac-sha256.
4908 <term><command>port</command></term>
4911 The UDP/TCP port number the server uses for
4912 receiving and sending DNS protocol traffic.
4913 The default is 53. This option is mainly intended for server
4915 a server using a port other than 53 will not be able to
4923 <term><command>random-device</command></term>
4926 The source of entropy to be used by the server. Entropy is
4928 for DNSSEC operations, such as TKEY transactions and dynamic
4930 zones. This options specifies the device (or file) from which
4932 entropy. If this is a file, operations requiring entropy will
4934 file has been exhausted. If not specified, the default value
4936 <filename>/dev/random</filename>
4937 (or equivalent) when present, and none otherwise. The
4938 <command>random-device</command> option takes
4940 the initial configuration load at server startup time and
4941 is ignored on subsequent reloads.
4947 <term><command>preferred-glue</command></term>
4950 If specified, the listed type (A or AAAA) will be emitted
4952 in the additional section of a query response.
4953 The default is to prefer A records when responding
4954 to queries that arrived via IPv4 and AAAA when
4955 responding to queries that arrived via IPv6.
4960 <varlistentry xml:id="root_delegation_only">
4961 <term><command>root-delegation-only</command></term>
4964 Turn on enforcement of delegation-only in TLDs
4965 (top level domains) and root zones with an optional
4969 DS queries are expected to be made to and be answered by
4970 delegation only zones. Such queries and responses are
4971 treated as an exception to delegation-only processing
4972 and are not converted to NXDOMAIN responses provided
4973 a CNAME is not discovered at the query name.
4976 If a delegation only zone server also serves a child
4977 zone it is not always possible to determine whether
4978 an answer comes from the delegation only zone or the
4979 child zone. SOA NS and DNSKEY records are apex
4980 only records and a matching response that contains
4981 these records or DS is treated as coming from a
4982 child zone. RRSIG records are also examined to see
4983 if they are signed by a child zone or not. The
4984 authority section is also examined to see if there
4985 is evidence that the answer is from the child zone.
4986 Answers that are determined to be from a child zone
4987 are not converted to NXDOMAIN responses. Despite
4988 all these checks there is still a possibility of
4989 false negatives when a child zone is being served.
4992 Similarly false positives can arise from empty nodes
4993 (no records at the name) in the delegation only zone
4994 when the query type is not ANY.
4997 Note some TLDs are not delegation only (e.g. "DE", "LV",
4998 "US" and "MUSEUM"). This list is not exhaustive.
5003 root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
5011 <term><command>disable-algorithms</command></term>
5014 Disable the specified DNSSEC algorithms at and below the
5016 Multiple <command>disable-algorithms</command>
5017 statements are allowed.
5018 Only the most specific will be applied.
5024 <term><command>dnssec-lookaside</command></term>
5027 When set, <command>dnssec-lookaside</command> provides the
5028 validator with an alternate method to validate DNSKEY
5029 records at the top of a zone. When a DNSKEY is at or
5030 below a domain specified by the deepest
5031 <command>dnssec-lookaside</command>, and the normal DNSSEC
5032 validation has left the key untrusted, the trust-anchor
5033 will be appended to the key name and a DLV record will be
5034 looked up to see if it can validate the key. If the DLV
5035 record validates a DNSKEY (similarly to the way a DS
5036 record does) the DNSKEY RRset is deemed to be trusted.
5039 If <command>dnssec-lookaside</command> is set to
5040 <userinput>auto</userinput>, then built-in default
5041 values for the DLV domain and trust anchor will be
5042 used, along with a built-in key for validation.
5045 If <command>dnssec-lookaside</command> is set to
5046 <userinput>no</userinput>, then dnssec-lookaside
5050 The default DLV key is stored in the file
5051 <filename>bind.keys</filename>;
5052 <command>named</command> will load that key at
5053 startup if <command>dnssec-lookaside</command> is set to
5054 <constant>auto</constant>. A copy of the file is
5055 installed along with <acronym>BIND</acronym> 9, and is
5056 current as of the release date. If the DLV key expires, a
5057 new copy of <filename>bind.keys</filename> can be downloaded
5058 from <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.isc.org/solutions/dlv/">https://www.isc.org/solutions/dlv/</link>.
5061 (To prevent problems if <filename>bind.keys</filename> is
5062 not found, the current key is also compiled in to
5063 <command>named</command>. Relying on this is not
5064 recommended, however, as it requires <command>named</command>
5065 to be recompiled with a new key when the DLV key expires.)
5068 NOTE: <command>named</command> only loads certain specific
5069 keys from <filename>bind.keys</filename>: those for the
5070 DLV zone and for the DNS root zone. The file cannot be
5071 used to store keys for other zones.
5077 <term><command>dnssec-must-be-secure</command></term>
5080 Specify hierarchies which must be or may not be secure
5081 (signed and validated). If <userinput>yes</userinput>,
5082 then <command>named</command> will only accept answers if
5083 they are secure. If <userinput>no</userinput>, then normal
5084 DNSSEC validation applies allowing for insecure answers to
5085 be accepted. The specified domain must be under a
5086 <command>trusted-keys</command> or
5087 <command>managed-keys</command> statement, or
5088 <command>dnssec-lookaside</command> must be active.
5094 <term><command>dns64</command></term>
5097 This directive instructs <command>named</command> to
5098 return mapped IPv4 addresses to AAAA queries when
5099 there are no AAAA records. It is intended to be
5100 used in conjunction with a NAT64. Each
5101 <command>dns64</command> defines one DNS64 prefix.
5102 Multiple DNS64 prefixes can be defined.
5105 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
5106 64 and 96 as per RFC 6052.
5109 Additionally a reverse IP6.ARPA zone will be created for
5110 the prefix to provide a mapping from the IP6.ARPA names
5111 to the corresponding IN-ADDR.ARPA names using synthesized
5112 CNAMEs. <command>dns64-server</command> and
5113 <command>dns64-contact</command> can be used to specify
5114 the name of the server and contact for the zones. These
5115 are settable at the view / options level. These are
5116 not settable on a per-prefix basis.
5119 Each <command>dns64</command> supports an optional
5120 <command>clients</command> ACL that determines which
5121 clients are affected by this directive. If not defined,
5122 it defaults to <userinput>any;</userinput>.
5125 Each <command>dns64</command> supports an optional
5126 <command>mapped</command> ACL that selects which
5127 IPv4 addresses are to be mapped in the corresponding
5128 A RRset. If not defined it defaults to
5129 <userinput>any;</userinput>.
5132 Normally, DNS64 won't apply to a domain name that
5133 owns one or more AAAA records; these records will
5134 simply be returned. The optional
5135 <command>exclude</command> ACL allows specification
5136 of a list of IPv6 addresses that will be ignored
5137 if they appear in a domain name's AAAA records, and
5138 DNS64 will be applied to any A records the domain
5139 name owns. If not defined, <command>exclude</command>
5143 A optional <command>suffix</command> can also
5144 be defined to set the bits trailing the mapped
5145 IPv4 address bits. By default these bits are
5146 set to <userinput>::</userinput>. The bits
5147 matching the prefix and mapped IPv4 address
5151 If <command>recursive-only</command> is set to
5152 <command>yes</command> the DNS64 synthesis will
5153 only happen for recursive queries. The default
5154 is <command>no</command>.
5157 If <command>break-dnssec</command> is set to
5158 <command>yes</command> the DNS64 synthesis will
5159 happen even if the result, if validated, would
5160 cause a DNSSEC validation failure. If this option
5161 is set to <command>no</command> (the default), the DO
5162 is set on the incoming query, and there are RRSIGs on
5163 the applicable records, then synthesis will not happen.
5166 acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
5168 dns64 64:FF9B::/96 {
5170 mapped { !rfc1918; any; };
5171 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
5179 <term><command>dnssec-loadkeys-interval</command></term>
5182 When a zone is configured with <command>auto-dnssec
5183 maintain;</command> its key repository must be checked
5184 periodically to see if any new keys have been added
5185 or any existing keys' timing metadata has been updated
5186 (see <xref linkend="man.dnssec-keygen"/> and
5187 <xref linkend="man.dnssec-settime"/>). The
5188 <command>dnssec-loadkeys-interval</command> option
5189 sets the frequency of automatic repository checks, in
5190 minutes. The default is <literal>60</literal> (1 hour),
5191 the minimum is <literal>1</literal> (1 minute), and the
5192 maximum is <literal>1440</literal> (24 hours); any higher
5193 value is silently reduced.
5199 <term><command>dnssec-update-mode</command></term>
5202 If this option is set to its default value of
5203 <literal>maintain</literal> in a zone of type
5204 <literal>master</literal> which is DNSSEC-signed
5205 and configured to allow dynamic updates (see
5206 <xref linkend="dynamic_update_policies"/>), and
5207 if <command>named</command> has access to the
5208 private signing key(s) for the zone, then
5209 <command>named</command> will automatically sign all new
5210 or changed records and maintain signatures for the zone
5211 by regenerating RRSIG records whenever they approach
5212 their expiration date.
5215 If the option is changed to <literal>no-resign</literal>,
5216 then <command>named</command> will sign all new or
5217 changed records, but scheduled maintenance of
5218 signatures is disabled.
5221 With either of these settings, <command>named</command>
5222 will reject updates to a DNSSEC-signed zone when the
5223 signing keys are inactive or unavailable to
5224 <command>named</command>. (A planned third option,
5225 <literal>external</literal>, will disable all automatic
5226 signing and allow DNSSEC data to be submitted into a zone
5227 via dynamic update; this is not yet implemented.)
5233 <term><command>serial-update-method</command></term>
5236 Zones configured for dynamic DNS may use this
5237 option to set the update method that will be used for
5238 the zone serial number in the SOA record.
5241 With the default setting of
5242 <command>serial-update-method increment;</command>, the
5243 SOA serial number will be incremented by one each time
5244 the zone is updated.
5248 <command>serial-update-method unixtime;</command>, the
5249 SOA serial number will be set to the number of seconds
5250 since the UNIX epoch, unless the serial number is
5251 already greater than or equal to that value, in which
5252 case it is simply incremented by one.
5258 <term><command>zone-statistics</command></term>
5261 If <userinput>full</userinput>, the server will collect
5262 statistical data on all zones (unless specifically
5263 turned off on a per-zone basis by specifying
5264 <command>zone-statistics terse</command> or
5265 <command>zone-statistics none</command>
5266 in the <command>zone</command> statement).
5267 The default is <userinput>terse</userinput>, providing
5268 minimal statistics on zones (including name and
5269 current serial number, but not query type
5273 These statistics may be accessed via the
5274 <command>statistics-channel</command> or
5275 using <command>rndc stats</command>, which
5276 will dump them to the file listed
5277 in the <command>statistics-file</command>. See
5278 also <xref linkend="statsfile"/>.
5281 For backward compatibility with earlier versions
5282 of BIND 9, the <command>zone-statistics</command>
5283 option can also accept <userinput>yes</userinput>
5284 or <userinput>no</userinput>, which have the same
5285 effect as <userinput>full</userinput> and
5286 <userinput>terse</userinput>, respectively.
5292 <section xml:id="boolean_options"><info><title>Boolean Options</title></info>
5297 <term><command>allow-new-zones</command></term>
5300 If <userinput>yes</userinput>, then zones can be
5301 added at runtime via <command>rndc addzone</command>
5302 or deleted via <command>rndc delzone</command>.
5303 The default is <userinput>no</userinput>.
5309 <term><command>auth-nxdomain</command></term>
5312 If <userinput>yes</userinput>, then the <command>AA</command> bit
5313 is always set on NXDOMAIN responses, even if the server is
5315 authoritative. The default is <userinput>no</userinput>;
5317 a change from <acronym>BIND</acronym> 8. If you
5318 are using very old DNS software, you
5319 may need to set it to <userinput>yes</userinput>.
5325 <term><command>deallocate-on-exit</command></term>
5328 This option was used in <acronym>BIND</acronym>
5329 8 to enable checking
5330 for memory leaks on exit. <acronym>BIND</acronym> 9 ignores the option and always performs
5337 <term><command>memstatistics</command></term>
5340 Write memory statistics to the file specified by
5341 <command>memstatistics-file</command> at exit.
5342 The default is <userinput>no</userinput> unless
5343 '-m record' is specified on the command line in
5344 which case it is <userinput>yes</userinput>.
5350 <term><command>dialup</command></term>
5353 If <userinput>yes</userinput>, then the
5354 server treats all zones as if they are doing zone transfers
5356 a dial-on-demand dialup link, which can be brought up by
5358 originating from this server. This has different effects
5360 to zone type and concentrates the zone maintenance so that
5362 happens in a short interval, once every <command>heartbeat-interval</command> and
5363 hopefully during the one call. It also suppresses some of
5365 zone maintenance traffic. The default is <userinput>no</userinput>.
5368 The <command>dialup</command> option
5369 may also be specified in the <command>view</command> and
5370 <command>zone</command> statements,
5371 in which case it overrides the global <command>dialup</command>
5375 If the zone is a master zone, then the server will send out a
5377 request to all the slaves (default). This should trigger the
5379 number check in the slave (providing it supports NOTIFY)
5381 to verify the zone while the connection is active.
5382 The set of servers to which NOTIFY is sent can be controlled
5384 <command>notify</command> and <command>also-notify</command>.
5388 zone is a slave or stub zone, then the server will suppress
5390 "zone up to date" (refresh) queries and only perform them
5392 <command>heartbeat-interval</command> expires in
5397 Finer control can be achieved by using
5398 <userinput>notify</userinput> which only sends NOTIFY
5400 <userinput>notify-passive</userinput> which sends NOTIFY
5402 suppresses the normal refresh queries, <userinput>refresh</userinput>
5403 which suppresses normal refresh processing and sends refresh
5405 when the <command>heartbeat-interval</command>
5407 <userinput>passive</userinput> which just disables normal
5412 <informaltable colsep="0" rowsep="0">
5413 <tgroup cols="4" colsep="0" rowsep="0" tgroupstyle="4Level-table">
5414 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
5415 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
5416 <colspec colname="3" colnum="3" colsep="0" colwidth="1.150in"/>
5417 <colspec colname="4" colnum="4" colsep="0" colwidth="1.150in"/>
5443 <para><command>no</command> (default)</para>
5463 <para><command>yes</command></para>
5483 <para><command>notify</command></para>
5503 <para><command>refresh</command></para>
5523 <para><command>passive</command></para>
5543 <para><command>notify-passive</command></para>
5566 Note that normal NOTIFY processing is not affected by
5567 <command>dialup</command>.
5574 <term><command>fake-iquery</command></term>
5577 In <acronym>BIND</acronym> 8, this option
5578 enabled simulating the obsolete DNS query type
5579 IQUERY. <acronym>BIND</acronym> 9 never does
5586 <term><command>fetch-glue</command></term>
5589 This option is obsolete.
5590 In BIND 8, <userinput>fetch-glue yes</userinput>
5591 caused the server to attempt to fetch glue resource records
5593 didn't have when constructing the additional
5594 data section of a response. This is now considered a bad
5596 and BIND 9 never does it.
5602 <term><command>flush-zones-on-shutdown</command></term>
5605 When the nameserver exits due receiving SIGTERM,
5606 flush or do not flush any pending zone writes. The default
5608 <command>flush-zones-on-shutdown</command> <userinput>no</userinput>.
5614 <term><command>has-old-clients</command></term>
5617 This option was incorrectly implemented
5618 in <acronym>BIND</acronym> 8, and is ignored by <acronym>BIND</acronym> 9.
5619 To achieve the intended effect
5621 <command>has-old-clients</command> <userinput>yes</userinput>, specify
5622 the two separate options <command>auth-nxdomain</command> <userinput>yes</userinput>
5623 and <command>rfc2308-type1</command> <userinput>no</userinput> instead.
5629 <term><command>host-statistics</command></term>
5632 In BIND 8, this enables keeping of
5633 statistics for every host that the name server interacts
5635 Not implemented in BIND 9.
5641 <term><command>maintain-ixfr-base</command></term>
5644 <emphasis>This option is obsolete</emphasis>.
5645 It was used in <acronym>BIND</acronym> 8 to
5646 determine whether a transaction log was
5647 kept for Incremental Zone Transfer. <acronym>BIND</acronym> 9 maintains a transaction
5648 log whenever possible. If you need to disable outgoing
5650 transfers, use <command>provide-ixfr</command> <userinput>no</userinput>.
5656 <term><command>minimal-responses</command></term>
5659 If <userinput>yes</userinput>, then when generating
5660 responses the server will only add records to the authority
5661 and additional data sections when they are required (e.g.
5662 delegations, negative responses). This may improve the
5663 performance of the server.
5664 The default is <userinput>no</userinput>.
5670 <term><command>multiple-cnames</command></term>
5673 This option was used in <acronym>BIND</acronym> 8 to allow
5674 a domain name to have multiple CNAME records in violation of
5675 the DNS standards. <acronym>BIND</acronym> 9.2 onwards
5676 always strictly enforces the CNAME rules both in master
5677 files and dynamic updates.
5683 <term><command>notify</command></term>
5686 If <userinput>yes</userinput> (the default),
5687 DNS NOTIFY messages are sent when a zone the server is
5689 changes, see <xref linkend="notify"/>. The messages are
5691 servers listed in the zone's NS records (except the master
5693 in the SOA MNAME field), and to any servers listed in the
5694 <command>also-notify</command> option.
5697 If <userinput>master-only</userinput>, notifies are only
5700 If <userinput>explicit</userinput>, notifies are sent only
5702 servers explicitly listed using <command>also-notify</command>.
5703 If <userinput>no</userinput>, no notifies are sent.
5706 The <command>notify</command> option may also be
5707 specified in the <command>zone</command>
5709 in which case it overrides the <command>options notify</command> statement.
5710 It would only be necessary to turn off this option if it
5718 <term><command>notify-to-soa</command></term>
5721 If <userinput>yes</userinput> do not check the nameservers
5722 in the NS RRset against the SOA MNAME. Normally a NOTIFY
5723 message is not sent to the SOA MNAME (SOA ORIGIN) as it is
5724 supposed to contain the name of the ultimate master.
5725 Sometimes, however, a slave is listed as the SOA MNAME in
5726 hidden master configurations and in that case you would
5727 want the ultimate master to still send NOTIFY messages to
5728 all the nameservers listed in the NS RRset.
5734 <term><command>recursion</command></term>
5737 If <userinput>yes</userinput>, and a
5738 DNS query requests recursion, then the server will attempt
5740 all the work required to answer the query. If recursion is
5742 and the server does not already know the answer, it will
5744 referral response. The default is
5745 <userinput>yes</userinput>.
5746 Note that setting <command>recursion no</command> does not prevent
5747 clients from getting data from the server's cache; it only
5748 prevents new data from being cached as an effect of client
5750 Caching may still occur as an effect the server's internal
5751 operation, such as NOTIFY address lookups.
5757 <term><command>request-nsid</command></term>
5760 If <userinput>yes</userinput>, then an empty EDNS(0)
5761 NSID (Name Server Identifier) option is sent with all
5762 queries to authoritative name servers during iterative
5763 resolution. If the authoritative server returns an NSID
5764 option in its response, then its contents are logged in
5765 the <command>resolver</command> category at level
5766 <command>info</command>.
5767 The default is <userinput>no</userinput>.
5773 <term><command>rfc2308-type1</command></term>
5776 Setting this to <userinput>yes</userinput> will
5777 cause the server to send NS records along with the SOA
5779 answers. The default is <userinput>no</userinput>.
5783 Not yet implemented in <acronym>BIND</acronym>
5791 <term><command>use-id-pool</command></term>
5794 <emphasis>This option is obsolete</emphasis>.
5795 <acronym>BIND</acronym> 9 always allocates query
5802 <term><command>use-ixfr</command></term>
5805 <emphasis>This option is obsolete</emphasis>.
5806 If you need to disable IXFR to a particular server or
5808 the information on the <command>provide-ixfr</command> option
5809 in <xref linkend="server_statement_definition_and_usage"/>.
5811 <xref linkend="incremental_zone_transfers"/>.
5817 <term><command>provide-ixfr</command></term>
5820 See the description of
5821 <command>provide-ixfr</command> in
5822 <xref linkend="server_statement_definition_and_usage"/>.
5828 <term><command>request-ixfr</command></term>
5831 See the description of
5832 <command>request-ixfr</command> in
5833 <xref linkend="server_statement_definition_and_usage"/>.
5839 <term><command>treat-cr-as-space</command></term>
5842 This option was used in <acronym>BIND</acronym>
5844 the server treat carriage return ("<command>\r</command>") characters the same way
5845 as a space or tab character,
5846 to facilitate loading of zone files on a UNIX system that
5848 on an NT or DOS machine. In <acronym>BIND</acronym> 9, both UNIX "<command>\n</command>"
5849 and NT/DOS "<command>\r\n</command>" newlines
5850 are always accepted,
5851 and the option is ignored.
5857 <term><command>additional-from-auth</command></term>
5858 <term><command>additional-from-cache</command></term>
5862 These options control the behavior of an authoritative
5864 answering queries which have additional data, or when
5870 When both of these options are set to <userinput>yes</userinput>
5872 query is being answered from authoritative data (a zone
5873 configured into the server), the additional data section of
5875 reply will be filled in using data from other authoritative
5877 and from the cache. In some situations this is undesirable,
5879 as when there is concern over the correctness of the cache,
5881 in servers where slave zones may be added and modified by
5882 untrusted third parties. Also, avoiding
5883 the search for this additional data will speed up server
5885 at the possible expense of additional queries to resolve
5887 otherwise be provided in the additional section.
5891 For example, if a query asks for an MX record for host <literal>foo.example.com</literal>,
5892 and the record found is "<literal>MX 10 mail.example.net</literal>", normally the address
5893 records (A and AAAA) for <literal>mail.example.net</literal> will be provided as well,
5894 if known, even though they are not in the example.com zone.
5895 Setting these options to <command>no</command>
5896 disables this behavior and makes
5897 the server only search for additional data in the zone it
5902 These options are intended for use in authoritative-only
5903 servers, or in authoritative-only views. Attempts to set
5904 them to <command>no</command> without also
5906 <command>recursion no</command> will cause the
5908 ignore the options and log a warning message.
5912 Specifying <command>additional-from-cache no</command> actually
5913 disables the use of the cache not only for additional data
5915 but also when looking up the answer. This is usually the
5917 behavior in an authoritative-only server where the
5919 the cached data is an issue.
5923 When a name server is non-recursively queried for a name
5925 below the apex of any served zone, it normally answers with
5927 "upwards referral" to the root servers or the servers of
5929 known parent of the query name. Since the data in an
5931 comes from the cache, the server will not be able to provide
5933 referrals when <command>additional-from-cache no</command>
5934 has been specified. Instead, it will respond to such
5936 with REFUSED. This should not cause any problems since
5937 upwards referrals are not required for the resolution
5945 <term><command>match-mapped-addresses</command></term>
5948 If <userinput>yes</userinput>, then an
5949 IPv4-mapped IPv6 address will match any address match
5950 list entries that match the corresponding IPv4 address.
5953 This option was introduced to work around a kernel quirk
5954 in some operating systems that causes IPv4 TCP
5955 connections, such as zone transfers, to be accepted on an
5956 IPv6 socket using mapped addresses. This caused address
5957 match lists designed for IPv4 to fail to match. However,
5958 <command>named</command> now solves this problem
5959 internally. The use of this option is discouraged.
5965 <term><command>filter-aaaa-on-v4</command></term>
5968 This option is only available when
5969 <acronym>BIND</acronym> 9 is compiled with the
5970 <userinput>--enable-filter-aaaa</userinput> option on the
5971 "configure" command line. It is intended to help the
5972 transition from IPv4 to IPv6 by not giving IPv6 addresses
5973 to DNS clients unless they have connections to the IPv6
5974 Internet. This is not recommended unless absolutely
5975 necessary. The default is <userinput>no</userinput>.
5976 The <command>filter-aaaa-on-v4</command> option
5977 may also be specified in <command>view</command> statements
5978 to override the global <command>filter-aaaa-on-v4</command>
5982 If <userinput>yes</userinput>,
5983 the DNS client is at an IPv4 address, in <command>filter-aaaa</command>,
5984 and if the response does not include DNSSEC signatures,
5985 then all AAAA records are deleted from the response.
5986 This filtering applies to all responses and not only
5987 authoritative responses.
5990 If <userinput>break-dnssec</userinput>,
5991 then AAAA records are deleted even when dnssec is enabled.
5992 As suggested by the name, this makes the response not verify,
5993 because the DNSSEC protocol is designed detect deletions.
5996 This mechanism can erroneously cause other servers to
5997 not give AAAA records to their clients.
5998 A recursing server with both IPv6 and IPv4 network connections
5999 that queries an authoritative server using this mechanism
6000 via IPv4 will be denied AAAA records even if its client is
6004 This mechanism is applied to authoritative as well as
6005 non-authoritative records.
6006 A client using IPv4 that is not allowed recursion can
6007 erroneously be given AAAA records because the server is not
6008 allowed to check for A records.
6011 Some AAAA records are given to IPv4 clients in glue records.
6012 IPv4 clients that are servers can then erroneously
6013 answer requests for AAAA records received via IPv4.
6019 <term><command>ixfr-from-differences</command></term>
6022 When <userinput>yes</userinput> and the server loads a new
6023 version of a master zone from its zone file or receives a
6024 new version of a slave file via zone transfer, it will
6025 compare the new version to the previous one and calculate
6026 a set of differences. The differences are then logged in
6027 the zone's journal file such that the changes can be
6028 transmitted to downstream slaves as an incremental zone
6032 By allowing incremental zone transfers to be used for
6033 non-dynamic zones, this option saves bandwidth at the
6034 expense of increased CPU and memory consumption at the
6036 In particular, if the new version of a zone is completely
6037 different from the previous one, the set of differences
6038 will be of a size comparable to the combined size of the
6039 old and new zone version, and the server will need to
6040 temporarily allocate memory to hold this complete
6043 <para><command>ixfr-from-differences</command>
6044 also accepts <command>master</command> and
6045 <command>slave</command> at the view and options
6047 <command>ixfr-from-differences</command> to be enabled for
6048 all <command>master</command> or
6049 <command>slave</command> zones respectively.
6050 It is off by default.
6056 <term><command>multi-master</command></term>
6059 This should be set when you have multiple masters for a zone
6061 addresses refer to different machines. If <userinput>yes</userinput>, <command>named</command> will
6063 when the serial number on the master is less than what <command>named</command>
6065 has. The default is <userinput>no</userinput>.
6071 <term><command>auto-dnssec</command></term>
6074 Zones configured for dynamic DNS may use this
6075 option to allow varying levels of automatic DNSSEC key
6076 management. There are three possible settings:
6079 <command>auto-dnssec allow;</command> permits
6080 keys to be updated and the zone fully re-signed
6081 whenever the user issues the command <command>rndc sign
6082 <replaceable>zonename</replaceable></command>.
6085 <command>auto-dnssec maintain;</command> includes the
6086 above, but also automatically adjusts the zone's DNSSEC
6087 keys on schedule, according to the keys' timing metadata
6088 (see <xref linkend="man.dnssec-keygen"/> and
6089 <xref linkend="man.dnssec-settime"/>). The command
6091 <replaceable>zonename</replaceable></command> causes
6092 <command>named</command> to load keys from the key
6093 repository and sign the zone with all keys that are
6095 <command>rndc loadkeys
6096 <replaceable>zonename</replaceable></command> causes
6097 <command>named</command> to load keys from the key
6098 repository and schedule key maintenance events to occur
6099 in the future, but it does not sign the full zone
6100 immediately. Note: once keys have been loaded for a
6101 zone the first time, the repository will be searched
6102 for changes periodically, regardless of whether
6103 <command>rndc loadkeys</command> is used. The recheck
6104 interval is defined by
6105 <command>dnssec-loadkeys-interval</command>.)
6108 The default setting is <command>auto-dnssec off</command>.
6114 <term><command>dnssec-enable</command></term>
6117 This indicates whether DNSSEC-related resource
6118 records are to be returned by <command>named</command>.
6119 If set to <userinput>no</userinput>,
6120 <command>named</command> will not return DNSSEC-related
6121 resource records unless specifically queried for.
6122 The default is <userinput>yes</userinput>.
6128 <term><command>dnssec-validation</command></term>
6131 Enable DNSSEC validation in <command>named</command>.
6132 Note <command>dnssec-enable</command> also needs to be
6133 set to <userinput>yes</userinput> to be effective.
6134 If set to <userinput>no</userinput>, DNSSEC validation
6135 is disabled. If set to <userinput>auto</userinput>,
6136 DNSSEC validation is enabled, and a default
6137 trust-anchor for the DNS root zone is used. If set to
6138 <userinput>yes</userinput>, DNSSEC validation is enabled,
6139 but a trust anchor must be manually configured using
6140 a <command>trusted-keys</command> or
6141 <command>managed-keys</command> statement. The default
6142 is <userinput>yes</userinput>.
6146 Whenever the resolver sends out queries to an
6147 EDNS-compliant server, it always sets the DO bit
6148 indicating it can support DNSSEC responses even if
6149 <command>dnssec-validation</command> is off.
6156 <term><command>dnssec-accept-expired</command></term>
6159 Accept expired signatures when verifying DNSSEC signatures.
6160 The default is <userinput>no</userinput>.
6161 Setting this option to <userinput>yes</userinput>
6162 leaves <command>named</command> vulnerable to
6169 <term><command>querylog</command></term>
6172 Specify whether query logging should be started when <command>named</command>
6174 If <command>querylog</command> is not specified,
6175 then the query logging
6176 is determined by the presence of the logging category <command>queries</command>.
6182 <term><command>check-names</command></term>
6185 This option is used to restrict the character set and syntax
6187 certain domain names in master files and/or DNS responses
6189 from the network. The default varies according to usage
6191 <command>master</command> zones the default is <command>fail</command>.
6192 For <command>slave</command> zones the default
6193 is <command>warn</command>.
6194 For answers received from the network (<command>response</command>)
6195 the default is <command>ignore</command>.
6198 The rules for legal hostnames and mail domains are derived
6199 from RFC 952 and RFC 821 as modified by RFC 1123.
6201 <para><command>check-names</command>
6202 applies to the owner names of A, AAAA and MX records.
6203 It also applies to the domain names in the RDATA of NS, SOA,
6204 MX, and SRV records.
6205 It also applies to the RDATA of PTR records where the owner
6206 name indicated that it is a reverse lookup of a hostname
6207 (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
6213 <term><command>check-dup-records</command></term>
6216 Check master zones for records that are treated as different
6217 by DNSSEC but are semantically equal in plain DNS. The
6218 default is to <command>warn</command>. Other possible
6219 values are <command>fail</command> and
6220 <command>ignore</command>.
6226 <term><command>check-mx</command></term>
6229 Check whether the MX record appears to refer to a IP address.
6230 The default is to <command>warn</command>. Other possible
6231 values are <command>fail</command> and
6232 <command>ignore</command>.
6238 <term><command>check-wildcard</command></term>
6241 This option is used to check for non-terminal wildcards.
6242 The use of non-terminal wildcards is almost always as a
6244 to understand the wildcard matching algorithm (RFC 1034).
6246 affects master zones. The default (<command>yes</command>) is to check
6247 for non-terminal wildcards and issue a warning.
6253 <term><command>check-integrity</command></term>
6256 Perform post load zone integrity checks on master
6257 zones. This checks that MX and SRV records refer
6258 to address (A or AAAA) records and that glue
6259 address records exist for delegated zones. For
6260 MX and SRV records only in-zone hostnames are
6261 checked (for out-of-zone hostnames use
6262 <command>named-checkzone</command>).
6263 For NS records only names below top of zone are
6264 checked (for out-of-zone names and glue consistency
6265 checks use <command>named-checkzone</command>).
6266 The default is <command>yes</command>.
6269 The use of the SPF record for publishing Sender
6270 Policy Framework is deprecated as the migration
6271 from using TXT records to SPF records was abandoned.
6272 Enabling this option also checks that a TXT Sender
6273 Policy Framework record exists (starts with "v=spf1")
6274 if there is an SPF record. Warnings are emitted if the
6275 TXT record does not exist and can be suppressed with
6276 <command>check-spf</command>.
6282 <term><command>check-mx-cname</command></term>
6285 If <command>check-integrity</command> is set then
6286 fail, warn or ignore MX records that refer
6287 to CNAMES. The default is to <command>warn</command>.
6293 <term><command>check-srv-cname</command></term>
6296 If <command>check-integrity</command> is set then
6297 fail, warn or ignore SRV records that refer
6298 to CNAMES. The default is to <command>warn</command>.
6304 <term><command>check-sibling</command></term>
6307 When performing integrity checks, also check that
6308 sibling glue exists. The default is <command>yes</command>.
6314 <term><command>check-spf</command></term>
6317 If <command>check-integrity</command> is set then
6318 check that there is a TXT Sender Policy Framework
6319 record present (starts with "v=spf1") if there is an
6320 SPF record present. The default is
6321 <command>warn</command>.
6327 <term><command>zero-no-soa-ttl</command></term>
6330 When returning authoritative negative responses to
6331 SOA queries set the TTL of the SOA record returned in
6332 the authority section to zero.
6333 The default is <command>yes</command>.
6339 <term><command>zero-no-soa-ttl-cache</command></term>
6342 When caching a negative response to a SOA query
6343 set the TTL to zero.
6344 The default is <command>no</command>.
6350 <term><command>update-check-ksk</command></term>
6353 When set to the default value of <literal>yes</literal>,
6354 check the KSK bit in each key to determine how the key
6355 should be used when generating RRSIGs for a secure zone.
6358 Ordinarily, zone-signing keys (that is, keys without the
6359 KSK bit set) are used to sign the entire zone, while
6360 key-signing keys (keys with the KSK bit set) are only
6361 used to sign the DNSKEY RRset at the zone apex.
6362 However, if this option is set to <literal>no</literal>,
6363 then the KSK bit is ignored; KSKs are treated as if they
6364 were ZSKs and are used to sign the entire zone. This is
6365 similar to the <command>dnssec-signzone -z</command>
6366 command line option.
6369 When this option is set to <literal>yes</literal>, there
6370 must be at least two active keys for every algorithm
6371 represented in the DNSKEY RRset: at least one KSK and one
6372 ZSK per algorithm. If there is any algorithm for which
6373 this requirement is not met, this option will be ignored
6380 <term><command>dnssec-dnskey-kskonly</command></term>
6383 When this option and <command>update-check-ksk</command>
6384 are both set to <literal>yes</literal>, only key-signing
6385 keys (that is, keys with the KSK bit set) will be used
6386 to sign the DNSKEY RRset at the zone apex. Zone-signing
6387 keys (keys without the KSK bit set) will be used to sign
6388 the remainder of the zone, but not the DNSKEY RRset.
6389 This is similar to the
6390 <command>dnssec-signzone -x</command> command line option.
6393 The default is <command>no</command>. If
6394 <command>update-check-ksk</command> is set to
6395 <literal>no</literal>, this option is ignored.
6401 <term><command>try-tcp-refresh</command></term>
6404 Try to refresh the zone using TCP if UDP queries fail.
6405 For BIND 8 compatibility, the default is
6406 <command>yes</command>.
6412 <term><command>dnssec-secure-to-insecure</command></term>
6415 Allow a dynamic zone to transition from secure to
6416 insecure (i.e., signed to unsigned) by deleting all
6417 of the DNSKEY records. The default is <command>no</command>.
6418 If set to <command>yes</command>, and if the DNSKEY RRset
6419 at the zone apex is deleted, all RRSIG and NSEC records
6420 will be removed from the zone as well.
6423 If the zone uses NSEC3, then it is also necessary to
6424 delete the NSEC3PARAM RRset from the zone apex; this will
6425 cause the removal of all corresponding NSEC3 records.
6426 (It is expected that this requirement will be eliminated
6427 in a future release.)
6430 Note that if a zone has been configured with
6431 <command>auto-dnssec maintain</command> and the
6432 private keys remain accessible in the key repository,
6433 then the zone will be automatically signed again the
6434 next time <command>named</command> is started.
6443 <section xml:id="forwarding"><info><title>Forwarding</title></info>
6446 The forwarding facility can be used to create a large site-wide
6447 cache on a few servers, reducing traffic over links to external
6448 name servers. It can also be used to allow queries by servers that
6449 do not have direct access to the Internet, but wish to look up
6451 names anyway. Forwarding occurs only on those queries for which
6452 the server is not authoritative and does not have the answer in
6458 <term><command>forward</command></term>
6461 This option is only meaningful if the
6462 forwarders list is not empty. A value of <varname>first</varname>,
6463 the default, causes the server to query the forwarders
6465 if that doesn't answer the question, the server will then
6467 the answer itself. If <varname>only</varname> is
6469 server will only query the forwarders.
6475 <term><command>forwarders</command></term>
6478 Specifies the IP addresses to be used
6479 for forwarding. The default is the empty list (no
6488 Forwarding can also be configured on a per-domain basis, allowing
6489 for the global forwarding options to be overridden in a variety
6490 of ways. You can set particular domains to use different
6492 or have a different <command>forward only/first</command> behavior,
6493 or not forward at all, see <xref linkend="zone_statement_grammar"/>.
6497 <section xml:id="dual_stack"><info><title>Dual-stack Servers</title></info>
6500 Dual-stack servers are used as servers of last resort to work
6502 problems in reachability due the lack of support for either IPv4
6504 on the host machine.
6509 <term><command>dual-stack-servers</command></term>
6512 Specifies host names or addresses of machines with access to
6513 both IPv4 and IPv6 transports. If a hostname is used, the
6515 to resolve the name using only the transport it has. If the
6517 stacked, then the <command>dual-stack-servers</command> have no effect unless
6518 access to a transport has been disabled on the command line
6519 (e.g. <command>named -4</command>).
6526 <section xml:id="access_control"><info><title>Access Control</title></info>
6530 Access to the server can be restricted based on the IP address
6531 of the requesting system. See <xref linkend="address_match_lists"/> for
6532 details on how to specify IP address lists.
6538 <term><command>allow-notify</command></term>
6541 Specifies which hosts are allowed to
6542 notify this server, a slave, of zone changes in addition
6543 to the zone masters.
6544 <command>allow-notify</command> may also be
6546 <command>zone</command> statement, in which case
6548 <command>options allow-notify</command>
6549 statement. It is only meaningful
6550 for a slave zone. If not specified, the default is to
6551 process notify messages
6552 only from a zone's master.
6558 <term><command>allow-query</command></term>
6561 Specifies which hosts are allowed to ask ordinary
6562 DNS questions. <command>allow-query</command> may
6563 also be specified in the <command>zone</command>
6564 statement, in which case it overrides the
6565 <command>options allow-query</command> statement.
6566 If not specified, the default is to allow queries
6571 <command>allow-query-cache</command> is now
6572 used to specify access to the cache.
6579 <term><command>allow-query-on</command></term>
6582 Specifies which local addresses can accept ordinary
6583 DNS questions. This makes it possible, for instance,
6584 to allow queries on internal-facing interfaces but
6585 disallow them on external-facing ones, without
6586 necessarily knowing the internal network's addresses.
6589 Note that <command>allow-query-on</command> is only
6590 checked for queries that are permitted by
6591 <command>allow-query</command>. A query must be
6592 allowed by both ACLs, or it will be refused.
6595 <command>allow-query-on</command> may
6596 also be specified in the <command>zone</command>
6597 statement, in which case it overrides the
6598 <command>options allow-query-on</command> statement.
6601 If not specified, the default is to allow queries
6606 <command>allow-query-cache</command> is
6607 used to specify access to the cache.
6614 <term><command>allow-query-cache</command></term>
6617 Specifies which hosts are allowed to get answers
6618 from the cache. If <command>allow-query-cache</command>
6619 is not set then <command>allow-recursion</command>
6620 is used if set, otherwise <command>allow-query</command>
6621 is used if set unless <command>recursion no;</command> is
6622 set in which case <command>none;</command> is used,
6623 otherwise the default (<command>localnets;</command>
6624 <command>localhost;</command>) is used.
6630 <term><command>allow-query-cache-on</command></term>
6633 Specifies which local addresses can give answers
6634 from the cache. If not specified, the default is
6635 to allow cache queries on any address,
6636 <command>localnets</command> and
6637 <command>localhost</command>.
6643 <term><command>allow-recursion</command></term>
6646 Specifies which hosts are allowed to make recursive
6647 queries through this server. If
6648 <command>allow-recursion</command> is not set
6649 then <command>allow-query-cache</command> is
6650 used if set, otherwise <command>allow-query</command>
6651 is used if set, otherwise the default
6652 (<command>localnets;</command>
6653 <command>localhost;</command>) is used.
6659 <term><command>allow-recursion-on</command></term>
6662 Specifies which local addresses can accept recursive
6663 queries. If not specified, the default is to allow
6664 recursive queries on all addresses.
6670 <term><command>allow-update</command></term>
6673 Specifies which hosts are allowed to
6674 submit Dynamic DNS updates for master zones. The default is
6676 updates from all hosts. Note that allowing updates based
6677 on the requestor's IP address is insecure; see
6678 <xref linkend="dynamic_update_security"/> for details.
6684 <term><command>allow-update-forwarding</command></term>
6687 Specifies which hosts are allowed to
6688 submit Dynamic DNS updates to slave zones to be forwarded to
6690 master. The default is <userinput>{ none; }</userinput>,
6692 means that no update forwarding will be performed. To
6694 update forwarding, specify
6695 <userinput>allow-update-forwarding { any; };</userinput>.
6696 Specifying values other than <userinput>{ none; }</userinput> or
6697 <userinput>{ any; }</userinput> is usually
6698 counterproductive, since
6699 the responsibility for update access control should rest
6701 master server, not the slaves.
6704 Note that enabling the update forwarding feature on a slave
6706 may expose master servers relying on insecure IP address
6708 access control to attacks; see <xref linkend="dynamic_update_security"/>
6715 <term><command>allow-v6-synthesis</command></term>
6718 This option was introduced for the smooth transition from
6720 to A6 and from "nibble labels" to binary labels.
6721 However, since both A6 and binary labels were then
6723 this option was also deprecated.
6724 It is now ignored with some warning messages.
6730 <term><command>allow-transfer</command></term>
6733 Specifies which hosts are allowed to
6734 receive zone transfers from the server. <command>allow-transfer</command> may
6735 also be specified in the <command>zone</command>
6737 case it overrides the <command>options allow-transfer</command> statement.
6738 If not specified, the default is to allow transfers to all
6745 <term><command>blackhole</command></term>
6748 Specifies a list of addresses that the
6749 server will not accept queries from or use to resolve a
6751 from these addresses will not be responded to. The default
6752 is <userinput>none</userinput>.
6758 <term><command>filter-aaaa</command></term>
6761 Specifies a list of addresses to which
6762 <command>filter-aaaa-on-v4</command>
6763 is applies. The default is <userinput>any</userinput>.
6769 <term><command>no-case-compress</command></term> <listitem>
6771 Specifies a list of addresses which require responses
6772 to use case-insensitive compression. This ACL can be
6773 used when <command>named</command> needs to work with
6774 clients that do not comply with the requirement in RFC
6775 1034 to use case-insensitive name comparisons when
6776 checking for matching domain names.
6779 If left undefined, the ACL defaults to
6780 <command>none</command>: case-insensitive compression
6781 will be used for all clients. If the ACL is defined and
6782 matches a client, then case will be ignored when
6783 compressing domain names in DNS responses sent to that
6787 This can result in slightly smaller responses: if
6788 a response contains the names "example.com" and
6789 "example.COM", case-insensitive compression would treat
6790 the second one as a duplicate. It also ensures
6791 that the case of the query name exactly matches the
6792 case of the owner names of returned records, rather
6793 than matching the case of the records entered in
6794 the zone file. This allows responses to exactly
6795 match the query, which is required by some clients
6796 due to incorrect use of case-sensitive comparisons.
6799 Case-insensitive compression is <emphasis>always</emphasis>
6800 used in AXFR and IXFR responses, regardless of whether
6801 the client matches this ACL.
6804 There are circumstances in which <command>named</command>
6805 will not preserve the case of owner names of records:
6806 if a zone file defines records of different types with
6807 the same name, but the capitalization of the name is
6808 different (e.g., "www.example.com/A" and
6809 "WWW.EXAMPLE.COM/AAAA"), then all responses for that
6810 name will use the <emphasis>first</emphasis> version
6811 of the name that was used in the zone file. This
6812 limitation may be addressed in a future release. However,
6813 domain names specified in the rdata of resource records
6814 (i.e., records of type NS, MX, CNAME, etc) will always
6815 have their case preserved unless the client matches this
6822 <term><command>resolver-query-timeout</command></term>
6825 The amount of time the resolver will spend attempting
6826 to resolve a recursive query before failing. The default
6827 and minimum is <literal>10</literal> and the maximum is
6828 <literal>30</literal>. Setting it to <literal>0</literal>
6829 will result in the default being used.
6837 <section xml:id="interfaces"><info><title>Interfaces</title></info>
6840 The interfaces and ports that the server will answer queries
6841 from may be specified using the <command>listen-on</command> option. <command>listen-on</command> takes
6842 an optional port and an <varname>address_match_list</varname>
6843 of IPv4 addresses. (IPv6 addresses are ignored, with a
6845 The server will listen on all interfaces allowed by the address
6846 match list. If a port is not specified, port 53 will be used.
6849 Multiple <command>listen-on</command> statements are
6854 <programlisting>listen-on { 5.6.7.8; };
6855 listen-on port 1234 { !1.2.3.4; 1.2/16; };
6859 will enable the name server on port 53 for the IP address
6860 5.6.7.8, and on port 1234 of an address on the machine in net
6861 1.2 that is not 1.2.3.4.
6865 If no <command>listen-on</command> is specified, the
6866 server will listen on port 53 on all IPv4 interfaces.
6870 The <command>listen-on-v6</command> option is used to
6871 specify the interfaces and the ports on which the server will
6873 for incoming queries sent using IPv6.
6877 When <programlisting>{ any; }</programlisting> is
6879 as the <varname>address_match_list</varname> for the
6880 <command>listen-on-v6</command> option,
6881 the server does not bind a separate socket to each IPv6 interface
6882 address as it does for IPv4 if the operating system has enough API
6883 support for IPv6 (specifically if it conforms to RFC 3493 and RFC
6885 Instead, it listens on the IPv6 wildcard address.
6886 If the system only has incomplete API support for IPv6, however,
6887 the behavior is the same as that for IPv4.
6891 A list of particular IPv6 addresses can also be specified, in
6893 the server listens on a separate socket for each specified
6895 regardless of whether the desired API is supported by the system.
6896 IPv4 addresses specified in <command>listen-on-v6</command>
6897 will be ignored, with a logged warning.
6901 Multiple <command>listen-on-v6</command> options can
6906 <programlisting>listen-on-v6 { any; };
6907 listen-on-v6 port 1234 { !2001:db8::/32; any; };
6911 will enable the name server on port 53 for any IPv6 addresses
6912 (with a single wildcard socket),
6913 and on port 1234 of IPv6 addresses that is not in the prefix
6914 2001:db8::/32 (with separate sockets for each matched address.)
6918 To make the server not listen on any IPv6 address, use
6921 <programlisting>listen-on-v6 { none; };
6925 If no <command>listen-on-v6</command> option is
6926 specified, the server will not listen on any IPv6 address
6927 unless <command>-6</command> is specified when <command>named</command> is
6928 invoked. If <command>-6</command> is specified then
6929 <command>named</command> will listen on port 53 on all IPv6 interfaces by default.
6933 <section xml:id="query_address"><info><title>Query Address</title></info>
6936 If the server doesn't know the answer to a question, it will
6937 query other name servers. <command>query-source</command> specifies
6938 the address and port used for such queries. For queries sent over
6939 IPv6, there is a separate <command>query-source-v6</command> option.
6940 If <command>address</command> is <command>*</command> (asterisk) or is omitted,
6941 a wildcard IP address (<command>INADDR_ANY</command>)
6946 If <command>port</command> is <command>*</command> or is omitted,
6947 a random port number from a pre-configured
6948 range is picked up and will be used for each query.
6949 The port range(s) is that specified in
6950 the <command>use-v4-udp-ports</command> (for IPv4)
6951 and <command>use-v6-udp-ports</command> (for IPv6)
6952 options, excluding the ranges specified in
6953 the <command>avoid-v4-udp-ports</command>
6954 and <command>avoid-v6-udp-ports</command> options, respectively.
6958 The defaults of the <command>query-source</command> and
6959 <command>query-source-v6</command> options
6963 <programlisting>query-source address * port *;
6964 query-source-v6 address * port *;
6968 If <command>use-v4-udp-ports</command> or
6969 <command>use-v6-udp-ports</command> is unspecified,
6970 <command>named</command> will check if the operating
6971 system provides a programming interface to retrieve the
6972 system's default range for ephemeral ports.
6973 If such an interface is available,
6974 <command>named</command> will use the corresponding system
6975 default range; otherwise, it will use its own defaults:
6978 <programlisting>use-v4-udp-ports { range 1024 65535; };
6979 use-v6-udp-ports { range 1024 65535; };
6983 Note: make sure the ranges be sufficiently large for
6984 security. A desirable size depends on various parameters,
6985 but we generally recommend it contain at least 16384 ports
6986 (14 bits of entropy).
6987 Note also that the system's default range when used may be
6988 too small for this purpose, and that the range may even be
6989 changed while <command>named</command> is running; the new
6990 range will automatically be applied when <command>named</command>
6993 configure <command>use-v4-udp-ports</command> and
6994 <command>use-v6-udp-ports</command> explicitly so that the
6995 ranges are sufficiently large and are reasonably
6996 independent from the ranges used by other applications.
7000 Note: the operational configuration
7001 where <command>named</command> runs may prohibit the use
7002 of some ports. For example, UNIX systems will not allow
7003 <command>named</command> running without a root privilege
7004 to use ports less than 1024.
7005 If such ports are included in the specified (or detected)
7006 set of query ports, the corresponding query attempts will
7007 fail, resulting in resolution failures or delay.
7008 It is therefore important to configure the set of ports
7009 that can be safely used in the expected operational environment.
7013 The defaults of the <command>avoid-v4-udp-ports</command> and
7014 <command>avoid-v6-udp-ports</command> options
7018 <programlisting>avoid-v4-udp-ports {};
7019 avoid-v6-udp-ports {};
7023 Note: BIND 9.5.0 introduced
7024 the <command>use-queryport-pool</command>
7025 option to support a pool of such random ports, but this
7026 option is now obsolete because reusing the same ports in
7027 the pool may not be sufficiently secure.
7028 For the same reason, it is generally strongly discouraged to
7029 specify a particular port for the
7030 <command>query-source</command> or
7031 <command>query-source-v6</command> options;
7032 it implicitly disables the use of randomized port numbers.
7037 <term><command>use-queryport-pool</command></term>
7040 This option is obsolete.
7046 <term><command>queryport-pool-ports</command></term>
7049 This option is obsolete.
7055 <term><command>queryport-pool-updateinterval</command></term>
7058 This option is obsolete.
7066 The address specified in the <command>query-source</command> option
7067 is used for both UDP and TCP queries, but the port applies only
7068 to UDP queries. TCP queries always use a random
7074 Solaris 2.5.1 and earlier does not support setting the source
7075 address for TCP sockets.
7080 See also <command>transfer-source</command> and
7081 <command>notify-source</command>.
7086 <section xml:id="zone_transfers"><info><title>Zone Transfers</title></info>
7089 <acronym>BIND</acronym> has mechanisms in place to
7090 facilitate zone transfers
7091 and set limits on the amount of load that transfers place on the
7092 system. The following options apply to zone transfers.
7098 <term><command>also-notify</command></term>
7101 Defines a global list of IP addresses of name servers
7102 that are also sent NOTIFY messages whenever a fresh copy of
7104 zone is loaded, in addition to the servers listed in the
7106 This helps to ensure that copies of the zones will
7107 quickly converge on stealth servers.
7108 Optionally, a port may be specified with each
7109 <command>also-notify</command> address to send
7110 the notify messages to a port other than the
7112 An optional TSIG key can also be specified with each
7113 address to cause the notify messages to be signed; this
7114 can be useful when sending notifies to multiple views.
7115 In place of explicit addresses, one or more named
7116 <command>masters</command> lists can be used.
7119 If an <command>also-notify</command> list
7120 is given in a <command>zone</command> statement,
7122 the <command>options also-notify</command>
7123 statement. When a <command>zone notify</command>
7125 is set to <command>no</command>, the IP
7126 addresses in the global <command>also-notify</command> list will
7127 not be sent NOTIFY messages for that zone. The default is
7129 list (no global notification list).
7135 <term><command>max-transfer-time-in</command></term>
7138 Inbound zone transfers running longer than
7139 this many minutes will be terminated. The default is 120
7141 (2 hours). The maximum value is 28 days (40320 minutes).
7147 <term><command>max-transfer-idle-in</command></term>
7150 Inbound zone transfers making no progress
7151 in this many minutes will be terminated. The default is 60
7153 (1 hour). The maximum value is 28 days (40320 minutes).
7159 <term><command>max-transfer-time-out</command></term>
7162 Outbound zone transfers running longer than
7163 this many minutes will be terminated. The default is 120
7165 (2 hours). The maximum value is 28 days (40320 minutes).
7171 <term><command>max-transfer-idle-out</command></term>
7174 Outbound zone transfers making no progress
7175 in this many minutes will be terminated. The default is 60
7177 hour). The maximum value is 28 days (40320 minutes).
7183 <term><command>serial-query-rate</command></term>
7186 Slave servers will periodically query master
7187 servers to find out if zone serial numbers have
7188 changed. Each such query uses a minute amount of
7189 the slave server's network bandwidth. To limit
7190 the amount of bandwidth used, BIND 9 limits the
7191 rate at which queries are sent. The value of the
7192 <command>serial-query-rate</command> option, an
7193 integer, is the maximum number of queries sent
7194 per second. The default is 20 per second.
7195 The lowest possible rate is one per second; when set
7196 to zero, it will be silently raised to one.
7199 In addition to controlling the rate SOA refresh
7200 queries are issued at,
7201 <command>serial-query-rate</command> also controls
7202 the rate at which NOTIFY messages are sent from
7203 both master and slave zones.
7209 <term><command>serial-queries</command></term>
7212 In BIND 8, the <command>serial-queries</command>
7214 set the maximum number of concurrent serial number queries
7215 allowed to be outstanding at any given time.
7216 BIND 9 does not limit the number of outstanding
7217 serial queries and ignores the <command>serial-queries</command> option.
7218 Instead, it limits the rate at which the queries are sent
7219 as defined using the <command>serial-query-rate</command> option.
7225 <term><command>transfer-format</command></term>
7229 Zone transfers can be sent using two different formats,
7230 <command>one-answer</command> and
7231 <command>many-answers</command>.
7232 The <command>transfer-format</command> option is used
7233 on the master server to determine which format it sends.
7234 <command>one-answer</command> uses one DNS message per
7235 resource record transferred.
7236 <command>many-answers</command> packs as many resource
7237 records as possible into a message.
7238 <command>many-answers</command> is more efficient, but is
7239 only supported by relatively new slave servers,
7240 such as <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
7241 8.x and <acronym>BIND</acronym> 4.9.5 onwards.
7242 The <command>many-answers</command> format is also supported by
7243 recent Microsoft Windows nameservers.
7244 The default is <command>many-answers</command>.
7245 <command>transfer-format</command> may be overridden on a
7246 per-server basis by using the <command>server</command>
7254 <term><command>transfers-in</command></term>
7257 The maximum number of inbound zone transfers
7258 that can be running concurrently. The default value is <literal>10</literal>.
7259 Increasing <command>transfers-in</command> may
7260 speed up the convergence
7261 of slave zones, but it also may increase the load on the
7268 <term><command>transfers-out</command></term>
7271 The maximum number of outbound zone transfers
7272 that can be running concurrently. Zone transfer requests in
7274 of the limit will be refused. The default value is <literal>10</literal>.
7280 <term><command>transfers-per-ns</command></term>
7283 The maximum number of inbound zone transfers
7284 that can be concurrently transferring from a given remote
7286 The default value is <literal>2</literal>.
7287 Increasing <command>transfers-per-ns</command>
7289 speed up the convergence of slave zones, but it also may
7291 the load on the remote name server. <command>transfers-per-ns</command> may
7292 be overridden on a per-server basis by using the <command>transfers</command> phrase
7293 of the <command>server</command> statement.
7299 <term><command>transfer-source</command></term>
7301 <para><command>transfer-source</command>
7302 determines which local address will be bound to IPv4
7303 TCP connections used to fetch zones transferred
7304 inbound by the server. It also determines the
7305 source IPv4 address, and optionally the UDP port,
7306 used for the refresh queries and forwarded dynamic
7307 updates. If not set, it defaults to a system
7308 controlled value which will usually be the address
7309 of the interface "closest to" the remote end. This
7310 address must appear in the remote end's
7311 <command>allow-transfer</command> option for the
7312 zone being transferred, if one is specified. This
7314 <command>transfer-source</command> for all zones,
7315 but can be overridden on a per-view or per-zone
7316 basis by including a
7317 <command>transfer-source</command> statement within
7318 the <command>view</command> or
7319 <command>zone</command> block in the configuration
7324 Solaris 2.5.1 and earlier does not support setting the
7325 source address for TCP sockets.
7332 <term><command>transfer-source-v6</command></term>
7335 The same as <command>transfer-source</command>,
7336 except zone transfers are performed using IPv6.
7342 <term><command>alt-transfer-source</command></term>
7345 An alternate transfer source if the one listed in
7346 <command>transfer-source</command> fails and
7347 <command>use-alt-transfer-source</command> is
7351 If you do not wish the alternate transfer source
7352 to be used, you should set
7353 <command>use-alt-transfer-source</command>
7354 appropriately and you should not depend upon
7355 getting an answer back to the first refresh
7362 <term><command>alt-transfer-source-v6</command></term>
7365 An alternate transfer source if the one listed in
7366 <command>transfer-source-v6</command> fails and
7367 <command>use-alt-transfer-source</command> is
7374 <term><command>use-alt-transfer-source</command></term>
7377 Use the alternate transfer sources or not. If views are
7378 specified this defaults to <command>no</command>
7379 otherwise it defaults to
7380 <command>yes</command> (for BIND 8
7387 <term><command>notify-source</command></term>
7389 <para><command>notify-source</command>
7390 determines which local source address, and
7391 optionally UDP port, will be used to send NOTIFY
7392 messages. This address must appear in the slave
7393 server's <command>masters</command> zone clause or
7394 in an <command>allow-notify</command> clause. This
7395 statement sets the <command>notify-source</command>
7396 for all zones, but can be overridden on a per-zone or
7397 per-view basis by including a
7398 <command>notify-source</command> statement within
7399 the <command>zone</command> or
7400 <command>view</command> block in the configuration
7405 Solaris 2.5.1 and earlier does not support setting the
7406 source address for TCP sockets.
7413 <term><command>notify-source-v6</command></term>
7416 Like <command>notify-source</command>,
7417 but applies to notify messages sent to IPv6 addresses.
7426 <section xml:id="port_lists"><info><title>UDP Port Lists</title></info>
7429 <command>use-v4-udp-ports</command>,
7430 <command>avoid-v4-udp-ports</command>,
7431 <command>use-v6-udp-ports</command>, and
7432 <command>avoid-v6-udp-ports</command>
7433 specify a list of IPv4 and IPv6 UDP ports that will be
7434 used or not used as source ports for UDP messages.
7435 See <xref linkend="query_address"/> about how the
7436 available ports are determined.
7437 For example, with the following configuration
7441 use-v6-udp-ports { range 32768 65535; };
7442 avoid-v6-udp-ports { 40000; range 50000 60000; };
7446 UDP ports of IPv6 messages sent
7447 from <command>named</command> will be in one
7448 of the following ranges: 32768 to 39999, 40001 to 49999,
7453 <command>avoid-v4-udp-ports</command> and
7454 <command>avoid-v6-udp-ports</command> can be used
7455 to prevent <command>named</command> from choosing as its random source port a
7456 port that is blocked by your firewall or a port that is
7457 used by other applications;
7458 if a query went out with a source port blocked by a
7460 answer would not get by the firewall and the name server would
7461 have to query again.
7462 Note: the desired range can also be represented only with
7463 <command>use-v4-udp-ports</command> and
7464 <command>use-v6-udp-ports</command>, and the
7465 <command>avoid-</command> options are redundant in that
7466 sense; they are provided for backward compatibility and
7467 to possibly simplify the port specification.
7471 <section xml:id="resource_limits"><info><title>Operating System Resource Limits</title></info>
7474 The server's usage of many system resources can be limited.
7475 Scaled values are allowed when specifying resource limits. For
7476 example, <command>1G</command> can be used instead of
7477 <command>1073741824</command> to specify a limit of
7479 gigabyte. <command>unlimited</command> requests
7480 unlimited use, or the
7481 maximum available amount. <command>default</command>
7483 that was in force when the server was started. See the description
7484 of <command>size_spec</command> in <xref linkend="configuration_file_elements"/>.
7488 The following options set operating system resource limits for
7489 the name server process. Some operating systems don't support
7491 any of the limits. On such systems, a warning will be issued if
7493 unsupported limit is used.
7499 <term><command>coresize</command></term>
7502 The maximum size of a core dump. The default
7503 is <literal>default</literal>.
7509 <term><command>datasize</command></term>
7512 The maximum amount of data memory the server
7513 may use. The default is <literal>default</literal>.
7514 This is a hard limit on server memory usage.
7515 If the server attempts to allocate memory in excess of this
7516 limit, the allocation will fail, which may in turn leave
7517 the server unable to perform DNS service. Therefore,
7518 this option is rarely useful as a way of limiting the
7519 amount of memory used by the server, but it can be used
7520 to raise an operating system data size limit that is
7521 too small by default. If you wish to limit the amount
7522 of memory used by the server, use the
7523 <command>max-cache-size</command> and
7524 <command>recursive-clients</command>
7531 <term><command>files</command></term>
7534 The maximum number of files the server
7535 may have open concurrently. The default is <literal>unlimited</literal>.
7541 <term><command>stacksize</command></term>
7544 The maximum amount of stack memory the server
7545 may use. The default is <literal>default</literal>.
7554 <section xml:id="server_resource_limits"><info><title>Server Resource Limits</title></info>
7557 The following options set limits on the server's
7558 resource consumption that are enforced internally by the
7559 server rather than the operating system.
7565 <term><command>max-ixfr-log-size</command></term>
7568 This option is obsolete; it is accepted
7569 and ignored for BIND 8 compatibility. The option
7570 <command>max-journal-size</command> performs a
7571 similar function in BIND 9.
7577 <term><command>max-journal-size</command></term>
7580 Sets a maximum size for each journal file
7581 (see <xref linkend="journal"/>). When the journal file
7583 the specified size, some of the oldest transactions in the
7585 will be automatically removed. The largest permitted
7586 value is 2 gigabytes. The default is
7587 <literal>unlimited</literal>, which also
7589 This may also be set on a per-zone basis.
7595 <term><command>host-statistics-max</command></term>
7598 In BIND 8, specifies the maximum number of host statistics
7600 Not implemented in BIND 9.
7606 <term><command>recursive-clients</command></term>
7609 The maximum number ("hard quota") of simultaneous
7610 recursive lookups the server will perform on behalf
7611 of clients. The default is
7612 <literal>1000</literal>. Because each recursing
7614 bit of memory (on the order of 20 kilobytes), the
7616 <command>recursive-clients</command> option may
7617 have to be decreased on hosts with limited memory.
7620 <option>recursive-clients</option> defines a "hard
7621 quota" limit for pending recursive clients: when more
7622 clients than this are pending, new incoming requests
7623 will not be accepted, and for each incoming request
7624 a previous pending request will also be dropped.
7627 A "soft quota" is also set. When this lower
7628 quota is exceeded, incoming requests are accepted, but
7629 for each one, a pending request will be dropped.
7630 If <option>recursive-clients</option> is greater than
7631 1000, the soft quota is set to
7632 <option>recursive-clients</option> minus 100;
7633 otherwise it is set to 90% of
7634 <option>recursive-clients</option>.
7640 <term><command>tcp-clients</command></term>
7643 The maximum number of simultaneous client TCP
7644 connections that the server will accept.
7645 The default is <literal>100</literal>.
7650 <varlistentry xml:id="clients-per-query">
7651 <term xml:id="cpq_term"><command>clients-per-query</command></term>
7652 <term><command>max-clients-per-query</command></term>
7655 initial value (minimum) and maximum number of recursive
7656 simultaneous clients for any given query
7657 (<qname,qtype,qclass>) that the server will accept
7658 before dropping additional clients. <command>named</command> will attempt to
7659 self tune this value and changes will be logged. The
7660 default values are 10 and 100.
7663 This value should reflect how many queries come in for
7664 a given name in the time it takes to resolve that name.
7665 If the number of queries exceed this value, <command>named</command> will
7666 assume that it is dealing with a non-responsive zone
7667 and will drop additional queries. If it gets a response
7668 after dropping queries, it will raise the estimate. The
7669 estimate will then be lowered in 20 minutes if it has
7673 If <command>clients-per-query</command> is set to zero,
7674 then there is no limit on the number of clients per query
7675 and no queries will be dropped.
7678 If <command>max-clients-per-query</command> is set to zero,
7679 then there is no upper bound other than imposed by
7680 <command>recursive-clients</command>.
7685 <varlistentry xml:id="fetches-per-zone">
7686 <term><command>fetches-per-zone</command></term>
7689 The maximum number of simultaneous iterative
7690 queries to any one domain that the server will
7691 permit before blocking new queries for data
7692 in or beneath that zone.
7693 This value should reflect how many fetches would
7694 normally be sent to any one zone in the time it
7695 would take to resolve them. It should be smaller
7696 than <option>recursive-clients</option>.
7699 When many clients simultaneously query for the
7700 same name and type, the clients will all be attached
7701 to the same fetch, up to the
7702 <option>max-clients-per-query</option> limit,
7703 and only one iterative query will be sent.
7704 However, when clients are simultaneously
7705 querying for <emphasis>different</emphasis> names
7706 or types, multiple queries will be sent and
7707 <option>max-clients-per-query</option> is not
7708 effective as a limit.
7711 Optionally, this value may be followed by the keyword
7712 <literal>drop</literal> or <literal>fail</literal>,
7713 indicating whether queries which exceed the fetch
7714 quota for a zone will be dropped with no response,
7715 or answered with SERVFAIL. The default is
7716 <literal>drop</literal>.
7719 If <command>fetches-per-zone</command> is set to zero,
7720 then there is no limit on the number of fetches per query
7721 and no queries will be dropped. The default is zero.
7724 The current list of active fetches can be dumped by
7725 running <command>rndc recursing</command>. The list
7726 includes the number of active fetches for each
7727 domain and the number of queries that have been
7728 passed or dropped as a result of the
7729 <option>fetches-per-zone</option> limit. (Note:
7730 these counters are not cumulative over time; whenever
7731 the number of active fetches for a domain drops to
7732 zero, the counter for that domain is deleted, and the
7733 next time a fetch is sent to that domain, it is
7734 recreated with the counters set to zero.)
7737 (Note: This option is only available when BIND is
7738 built with <command>configure --enable-fetchlimit</command>.)
7743 <varlistentry xml:id="fetches-per-server">
7744 <term><command>fetches-per-server</command></term>
7747 The maximum number of simultaneous iterative
7748 queries that the server will allow to be sent to
7749 a single upstream name server before blocking
7751 This value should reflect how many fetches would
7752 normally be sent to any one server in the time it
7753 would take to resolve them. It should be smaller
7754 than <option>recursive-clients</option>.
7757 Optionally, this value may be followed by the keyword
7758 <literal>drop</literal> or <literal>fail</literal>,
7759 indicating whether queries will be dropped with no
7760 response, or answered with SERVFAIL, when all of the
7761 servers authoritative for a zone are found to have
7762 exceeded the per-server quota. The default is
7763 <literal>fail</literal>.
7766 If <command>fetches-per-server</command> is set to zero,
7767 then there is no limit on the number of fetches per query
7768 and no queries will be dropped. The default is zero.
7771 The <command>fetches-per-server</command> quota is
7772 dynamically adjusted in response to detected
7773 congestion. As queries are sent to a server
7774 and are either answered or time out, an
7775 exponentially weighted moving average is calculated
7776 of the ratio of timeouts to responses. If the
7777 current average timeout ratio rises above a "high"
7778 threshold, then <command>fetches-per-server</command>
7779 is reduced for that server. If the timeout ratio
7780 drops below a "low" threshold, then
7781 <command>fetches-per-server</command> is increased.
7782 The <command>fetch-quota-params</command> options
7783 can be used to adjust the parameters for this
7787 (Note: This option is only available when BIND is
7788 built with <command>configure --enable-fetchlimit</command>.)
7794 <term><command>fetch-quota-params</command></term>
7797 Sets the parameters to use for dynamic resizing of
7798 the <option>fetches-per-server</option> quota in
7799 response to detected congestion.
7802 The first argument is an integer value indicating
7803 how frequently to recalculate the moving average
7804 of the ratio of timeouts to responses for each
7805 server. The default is 100, meaning we recalculate
7806 the average ratio after every 100 queries have either
7807 been answered or timed out.
7810 The remaining three arguments represent the "low"
7811 threshold (defaulting to a timeout ratio of 0.1),
7812 the "high" threshold (defaulting to a timeout
7813 ratio of 0.3), and the discount rate for
7814 the moving average (defaulting to 0.7).
7815 A higher discount rate causes recent events to
7816 weigh more heavily when calculating the moving
7817 average; a lower discount rate causes past
7818 events to weigh more heavily, smoothing out
7819 short-term blips in the timeout ratio.
7820 These arguments are all fixed-point numbers with
7821 precision of 1/100: at most two places after
7822 the decimal point are significant.
7825 (Note: This option is only available when BIND is
7826 built with <command>configure --enable-fetchlimit</command>.)
7832 <term><command>reserved-sockets</command></term>
7835 The number of file descriptors reserved for TCP, stdio,
7836 etc. This needs to be big enough to cover the number of
7837 interfaces <command>named</command> listens on, <command>tcp-clients</command> as well as
7838 to provide room for outgoing TCP queries and incoming zone
7839 transfers. The default is <literal>512</literal>.
7840 The minimum value is <literal>128</literal> and the
7841 maximum value is <literal>128</literal> less than
7842 maxsockets (-S). This option may be removed in the future.
7845 This option has little effect on Windows.
7851 <term><command>max-cache-size</command></term>
7854 The maximum amount of memory to use for the
7855 server's cache, in bytes.
7856 When the amount of data in the cache
7857 reaches this limit, the server will cause records to expire
7858 prematurely based on an LRU based strategy so that
7859 the limit is not exceeded.
7860 A value of 0 is special, meaning that
7861 records are purged from the cache only when their
7863 Another special keyword <userinput>unlimited</userinput>
7864 means the maximum value of 32-bit unsigned integers
7865 (0xffffffff), which may not have the same effect as
7866 0 on machines that support more than 32 bits of
7868 Any positive values less than 2MB will be ignored reset
7870 In a server with multiple views, the limit applies
7871 separately to the cache of each view.
7878 <term><command>tcp-listen-queue</command></term>
7881 The listen queue depth. The default and minimum is 10.
7882 If the kernel supports the accept filter "dataready" this
7884 many TCP connections that will be queued in kernel space
7886 some data before being passed to accept. Nonzero values
7887 less than 10 will be silently raised. A value of 0 may also
7888 be used; on most platforms this sets the listen queue
7889 length to a system-defined default value.
7898 <section xml:id="intervals"><info><title>Periodic Task Intervals</title></info>
7903 <term><command>cleaning-interval</command></term>
7906 This interval is effectively obsolete. Previously,
7907 the server would remove expired resource records
7908 from the cache every <command>cleaning-interval</command> minutes.
7909 <acronym>BIND</acronym> 9 now manages cache
7910 memory in a more sophisticated manner and does not
7911 rely on the periodic cleaning any more.
7912 Specifying this option therefore has no effect on
7913 the server's behavior.
7919 <term><command>heartbeat-interval</command></term>
7922 The server will perform zone maintenance tasks
7923 for all zones marked as <command>dialup</command> whenever this
7924 interval expires. The default is 60 minutes. Reasonable
7926 to 1 day (1440 minutes). The maximum value is 28 days
7928 If set to 0, no zone maintenance for these zones will occur.
7934 <term><command>interface-interval</command></term>
7937 The server will scan the network interface list
7938 every <command>interface-interval</command>
7939 minutes. The default
7940 is 60 minutes. The maximum value is 28 days (40320 minutes).
7941 If set to 0, interface scanning will only occur when
7942 the configuration file is loaded. After the scan, the
7944 begin listening for queries on any newly discovered
7945 interfaces (provided they are allowed by the
7946 <command>listen-on</command> configuration), and
7948 stop listening on interfaces that have gone away.
7954 <term><command>statistics-interval</command></term>
7957 Name server statistics will be logged
7958 every <command>statistics-interval</command>
7959 minutes. The default is
7960 60. The maximum value is 28 days (40320 minutes).
7961 If set to 0, no statistics will be logged.
7964 Not yet implemented in
7965 <acronym>BIND</acronym> 9.
7975 <section xml:id="topology"><info><title>Topology</title></info>
7978 All other things being equal, when the server chooses a name
7980 to query from a list of name servers, it prefers the one that is
7981 topologically closest to itself. The <command>topology</command> statement
7982 takes an <command>address_match_list</command> and
7984 in a special way. Each top-level list element is assigned a
7986 Non-negated elements get a distance based on their position in the
7987 list, where the closer the match is to the start of the list, the
7988 shorter the distance is between it and the server. A negated match
7989 will be assigned the maximum distance from the server. If there
7990 is no match, the address will get a distance which is further than
7991 any non-negated list element, and closer than any negated element.
7995 <programlisting>topology {
8002 will prefer servers on network 10 the most, followed by hosts
8003 on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
8004 exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
8005 is preferred least of all.
8008 The default topology is
8011 <programlisting> topology { localhost; localnets; };
8016 The <command>topology</command> option
8017 is not implemented in <acronym>BIND</acronym> 9.
8022 <section xml:id="the_sortlist_statement"><info><title>The <command>sortlist</command> Statement</title></info>
8025 The response to a DNS query may consist of multiple resource
8026 records (RRs) forming a resource records set (RRset).
8027 The name server will normally return the
8028 RRs within the RRset in an indeterminate order
8029 (but see the <command>rrset-order</command>
8030 statement in <xref linkend="rrset_ordering"/>).
8031 The client resolver code should rearrange the RRs as appropriate,
8032 that is, using any addresses on the local net in preference to
8034 However, not all resolvers can do this or are correctly
8036 When a client is using a local server, the sorting can be performed
8037 in the server, based on the client's address. This only requires
8038 configuring the name servers, not all the clients.
8042 The <command>sortlist</command> statement (see below)
8044 an <command>address_match_list</command> and
8046 more specifically than the <command>topology</command>
8048 does (<xref linkend="topology"/>).
8049 Each top level statement in the <command>sortlist</command> must
8050 itself be an explicit <command>address_match_list</command> with
8051 one or two elements. The first element (which may be an IP
8053 an IP prefix, an ACL name or a nested <command>address_match_list</command>)
8054 of each top level list is checked against the source address of
8055 the query until a match is found.
8058 Once the source address of the query has been matched, if
8059 the top level statement contains only one element, the actual
8061 element that matched the source address is used to select the
8063 in the response to move to the beginning of the response. If the
8064 statement is a list of two elements, then the second element is
8065 treated the same as the <command>address_match_list</command> in
8066 a <command>topology</command> statement. Each top
8068 is assigned a distance and the address in the response with the
8070 distance is moved to the beginning of the response.
8073 In the following example, any queries received from any of
8074 the addresses of the host itself will get responses preferring
8076 on any of the locally connected networks. Next most preferred are
8078 on the 192.168.1/24 network, and after that either the
8081 192.168.3/24 network with no preference shown between these two
8082 networks. Queries received from a host on the 192.168.1/24 network
8083 will prefer other addresses on that network to the 192.168.2/24
8085 192.168.3/24 networks. Queries received from a host on the
8087 or the 192.168.5/24 network will only prefer other addresses on
8088 their directly connected networks.
8091 <programlisting>sortlist {
8092 // IF the local host
8093 // THEN first fit on the following nets
8097 { 192.168.2/24; 192.168.3/24; }; }; };
8098 // IF on class C 192.168.1 THEN use .1, or .2 or .3
8101 { 192.168.2/24; 192.168.3/24; }; }; };
8102 // IF on class C 192.168.2 THEN use .2, or .1 or .3
8105 { 192.168.1/24; 192.168.3/24; }; }; };
8106 // IF on class C 192.168.3 THEN use .3, or .1 or .2
8109 { 192.168.1/24; 192.168.2/24; }; }; };
8110 // IF .4 or .5 THEN prefer that net
8111 { { 192.168.4/24; 192.168.5/24; };
8116 The following example will give reasonable behavior for the
8117 local host and hosts on directly connected networks. It is similar
8118 to the behavior of the address sort in <acronym>BIND</acronym> 4.9.x. Responses sent
8119 to queries from the local host will favor any of the directly
8121 networks. Responses sent to queries from any other hosts on a
8123 connected network will prefer addresses on that same network.
8125 to other queries will not be sorted.
8128 <programlisting>sortlist {
8129 { localhost; localnets; };
8135 <section xml:id="rrset_ordering"><info><title xml:id="rrset_ordering_title">RRset Ordering</title></info>
8138 When multiple records are returned in an answer it may be
8139 useful to configure the order of the records placed into the
8141 The <command>rrset-order</command> statement permits
8143 of the ordering of the records in a multiple record response.
8144 See also the <command>sortlist</command> statement,
8145 <xref linkend="the_sortlist_statement"/>.
8149 An <command>order_spec</command> is defined as
8153 <optional>class <replaceable>class_name</replaceable></optional>
8154 <optional>type <replaceable>type_name</replaceable></optional>
8155 <optional>name <replaceable>"domain_name"</replaceable></optional>
8156 order <replaceable>ordering</replaceable>
8159 If no class is specified, the default is <command>ANY</command>.
8160 If no type is specified, the default is <command>ANY</command>.
8161 If no name is specified, the default is "<command>*</command>" (asterisk).
8164 The legal values for <command>ordering</command> are:
8166 <informaltable colsep="0" rowsep="0">
8167 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
8168 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
8169 <colspec colname="2" colnum="2" colsep="0" colwidth="3.750in"/>
8173 <para><command>fixed</command></para>
8177 Records are returned in the order they
8178 are defined in the zone file.
8184 <para><command>random</command></para>
8188 Records are returned in some random order.
8194 <para><command>cyclic</command></para>
8198 Records are returned in a cyclic round-robin order.
8201 If <acronym>BIND</acronym> is configured with the
8202 "--enable-fixed-rrset" option at compile time, then
8203 the initial ordering of the RRset will match the
8204 one specified in the zone file.
8215 <programlisting>rrset-order {
8216 class IN type A name "host.example.com" order random;
8222 will cause any responses for type A records in class IN that
8223 have "<literal>host.example.com</literal>" as a
8224 suffix, to always be returned
8225 in random order. All other records are returned in cyclic order.
8228 If multiple <command>rrset-order</command> statements
8229 appear, they are not combined — the last one applies.
8232 By default, all records are returned in random order.
8237 In this release of <acronym>BIND</acronym> 9, the
8238 <command>rrset-order</command> statement does not support
8239 "fixed" ordering by default. Fixed ordering can be enabled
8240 at compile time by specifying "--enable-fixed-rrset" on
8241 the "configure" command line.
8246 <section xml:id="tuning"><info><title>Tuning</title></info>
8251 <term><command>lame-ttl</command></term>
8254 Sets the number of seconds to cache a
8255 lame server indication. 0 disables caching. (This is
8256 <emphasis role="bold">NOT</emphasis> recommended.)
8257 The default is <literal>600</literal> (10 minutes) and the
8259 <literal>1800</literal> (30 minutes).
8263 Lame-ttl also controls the amount of time DNSSEC
8264 validation failures are cached. There is a minimum
8265 of 30 seconds applied to bad cache entries if the
8266 lame-ttl is set to less than 30 seconds.
8273 <term><command>max-ncache-ttl</command></term>
8276 To reduce network traffic and increase performance,
8277 the server stores negative answers. <command>max-ncache-ttl</command> is
8278 used to set a maximum retention time for these answers in
8280 in seconds. The default
8281 <command>max-ncache-ttl</command> is <literal>10800</literal> seconds (3 hours).
8282 <command>max-ncache-ttl</command> cannot exceed
8284 be silently truncated to 7 days if set to a greater value.
8290 <term><command>max-cache-ttl</command></term>
8293 Sets the maximum time for which the server will
8294 cache ordinary (positive) answers. The default is
8296 A value of zero may cause all queries to return
8297 SERVFAIL, because of lost caches of intermediate
8298 RRsets (such as NS and glue AAAA/A records) in the
8305 <term><command>min-roots</command></term>
8308 The minimum number of root servers that
8309 is required for a request for the root servers to be
8310 accepted. The default
8311 is <userinput>2</userinput>.
8315 Not implemented in <acronym>BIND</acronym> 9.
8322 <term><command>sig-validity-interval</command></term>
8325 Specifies the number of days into the future when
8326 DNSSEC signatures automatically generated as a
8327 result of dynamic updates (<xref linkend="dynamic_update"/>) will expire. There
8328 is an optional second field which specifies how
8329 long before expiry that the signatures will be
8330 regenerated. If not specified, the signatures will
8331 be regenerated at 1/4 of base interval. The second
8332 field is specified in days if the base interval is
8333 greater than 7 days otherwise it is specified in hours.
8334 The default base interval is <literal>30</literal> days
8335 giving a re-signing interval of 7 1/2 days. The maximum
8336 values are 10 years (3660 days).
8339 The signature inception time is unconditionally
8340 set to one hour before the current time to allow
8341 for a limited amount of clock skew.
8344 The <command>sig-validity-interval</command>
8345 should be, at least, several multiples of the SOA
8346 expire interval to allow for reasonable interaction
8347 between the various timer and expiry dates.
8353 <term><command>sig-signing-nodes</command></term>
8356 Specify the maximum number of nodes to be
8357 examined in each quantum when signing a zone with
8358 a new DNSKEY. The default is
8359 <literal>100</literal>.
8365 <term><command>sig-signing-signatures</command></term>
8368 Specify a threshold number of signatures that
8369 will terminate processing a quantum when signing
8370 a zone with a new DNSKEY. The default is
8371 <literal>10</literal>.
8377 <term><command>sig-signing-type</command></term>
8380 Specify a private RDATA type to be used when generating
8381 signing state records. The default is
8382 <literal>65534</literal>.
8385 It is expected that this parameter may be removed
8386 in a future version once there is a standard type.
8389 Signing state records are used to internally by
8390 <command>named</command> to track the current state of
8391 a zone-signing process, i.e., whether it is still active
8392 or has been completed. The records can be inspected
8394 <command>rndc signing -list <replaceable>zone</replaceable></command>.
8395 Once <command>named</command> has finished signing
8396 a zone with a particular key, the signing state
8397 record associated with that key can be removed from
8399 <command>rndc signing -clear <replaceable>keyid/algorithm</replaceable> <replaceable>zone</replaceable></command>.
8400 To clear all of the completed signing state
8401 records for a zone, use
8402 <command>rndc signing -clear all <replaceable>zone</replaceable></command>.
8408 <term><command>min-refresh-time</command></term>
8409 <term><command>max-refresh-time</command></term>
8410 <term><command>min-retry-time</command></term>
8411 <term><command>max-retry-time</command></term>
8414 These options control the server's behavior on refreshing a
8416 (querying for SOA changes) or retrying failed transfers.
8417 Usually the SOA values for the zone are used, but these
8419 are set by the master, giving slave server administrators
8421 control over their contents.
8424 These options allow the administrator to set a minimum and
8426 refresh and retry time either per-zone, per-view, or
8428 These options are valid for slave and stub zones,
8429 and clamp the SOA refresh and retry times to the specified
8433 The following defaults apply.
8434 <command>min-refresh-time</command> 300 seconds,
8435 <command>max-refresh-time</command> 2419200 seconds
8436 (4 weeks), <command>min-retry-time</command> 500 seconds,
8437 and <command>max-retry-time</command> 1209600 seconds
8444 <term><command>edns-udp-size</command></term>
8447 Sets the advertised EDNS UDP buffer size in bytes
8448 to control the size of packets received.
8449 Valid values are 512 to 4096 (values outside this range
8450 will be silently adjusted). The default value
8451 is 4096. The usual reason for setting
8452 <command>edns-udp-size</command> to a non-default
8453 value is to get UDP answers to pass through broken
8454 firewalls that block fragmented packets and/or
8455 block UDP packets that are greater than 512 bytes.
8458 <command>named</command> will fallback to using 512 bytes
8459 if it get a series of timeout at the initial value. 512
8460 bytes is not being offered to encourage sites to fix their
8461 firewalls. Small EDNS UDP sizes will result in the
8462 excessive use of TCP.
8468 <term><command>max-udp-size</command></term>
8471 Sets the maximum EDNS UDP message size
8472 <command>named</command> will send in bytes.
8473 Valid values are 512 to 4096 (values outside this
8474 range will be silently adjusted). The default
8475 value is 4096. The usual reason for setting
8476 <command>max-udp-size</command> to a non-default
8477 value is to get UDP answers to pass through broken
8478 firewalls that block fragmented packets and/or
8479 block UDP packets that are greater than 512 bytes.
8480 This is independent of the advertised receive
8481 buffer (<command>edns-udp-size</command>).
8484 Setting this to a low value will encourage additional
8485 TCP traffic to the nameserver.
8491 <term><command>masterfile-format</command></term>
8494 the file format of zone files (see
8495 <xref linkend="zonefile_format"/>).
8496 The default value is <constant>text</constant>, which is the
8497 standard textual representation, except for slave zones,
8498 in which the default value is <constant>raw</constant>.
8499 Files in other formats than <constant>text</constant> are
8500 typically expected to be generated by the
8501 <command>named-compilezone</command> tool, or dumped by
8502 <command>named</command>.
8505 Note that when a zone file in a different format than
8506 <constant>text</constant> is loaded, <command>named</command>
8507 may omit some of the checks which would be performed for a
8508 file in the <constant>text</constant> format. In particular,
8509 <command>check-names</command> checks do not apply
8510 for the <constant>raw</constant> format. This means
8511 a zone file in the <constant>raw</constant> format
8512 must be generated with the same check level as that
8513 specified in the <command>named</command> configuration
8514 file. This statement sets the
8515 <command>masterfile-format</command> for all zones,
8516 but can be overridden on a per-zone or per-view basis
8517 by including a <command>masterfile-format</command>
8518 statement within the <command>zone</command> or
8519 <command>view</command> block in the configuration
8525 <varlistentry xml:id="max-recursion-depth">
8526 <term><command>max-recursion-depth</command></term>
8529 Sets the maximum number of levels of recursion
8530 that are permitted at any one time while servicing
8531 a recursive query. Resolving a name may require
8532 looking up a name server address, which in turn
8533 requires resolving another name, etc; if the number
8534 of indirections exceeds this value, the recursive
8535 query is terminated and returns SERVFAIL. The
8541 <varlistentry xml:id="max-recursion-queries">
8542 <term><command>max-recursion-queries</command></term>
8545 Sets the maximum number of iterative queries that
8546 may be sent while servicing a recursive query.
8547 If more queries are sent, the recursive query
8548 is terminated and returns SERVFAIL. Queries to
8549 look up top level comains such as "com" and "net"
8550 and the DNS root zone are exempt from this limitation.
8557 <term><command>notify-delay</command></term>
8560 The delay, in seconds, between sending sets of notify
8561 messages for a zone. The default is five (5) seconds.
8564 The overall rate that NOTIFY messages are sent for all
8565 zones is controlled by <command>serial-query-rate</command>.
8571 <term><command>max-rsa-exponent-size</command></term>
8574 The maximum RSA exponent size, in bits, that will
8575 be accepted when validating. Valid values are 35
8576 to 4096 bits. The default zero (0) is also accepted
8577 and is equivalent to 4096.
8585 <section xml:id="builtin"><info><title>Built-in server information zones</title></info>
8588 The server provides some helpful diagnostic information
8589 through a number of built-in zones under the
8590 pseudo-top-level-domain <literal>bind</literal> in the
8591 <command>CHAOS</command> class. These zones are part
8593 built-in view (see <xref linkend="view_statement_grammar"/>) of
8595 <command>CHAOS</command> which is separate from the
8596 default view of class <command>IN</command>. Most global
8597 configuration options (<command>allow-query</command>,
8598 etc) will apply to this view, but some are locally
8599 overridden: <command>notify</command>,
8600 <command>recursion</command> and
8601 <command>allow-new-zones</command> are
8602 always set to <userinput>no</userinput>.
8605 If you need to disable these zones, use the options
8606 below, or hide the built-in <command>CHAOS</command>
8608 defining an explicit view of class <command>CHAOS</command>
8609 that matches all clients.
8615 <term><command>version</command></term>
8618 The version the server should report
8619 via a query of the name <literal>version.bind</literal>
8620 with type <command>TXT</command>, class <command>CHAOS</command>.
8621 The default is the real version number of this server.
8622 Specifying <command>version none</command>
8623 disables processing of the queries.
8629 <term><command>hostname</command></term>
8632 The hostname the server should report via a query of
8633 the name <filename>hostname.bind</filename>
8634 with type <command>TXT</command>, class <command>CHAOS</command>.
8635 This defaults to the hostname of the machine hosting the
8637 found by the gethostname() function. The primary purpose of such queries
8639 identify which of a group of anycast servers is actually
8640 answering your queries. Specifying <command>hostname none;</command>
8641 disables processing of the queries.
8647 <term><command>server-id</command></term>
8650 The ID the server should report when receiving a Name
8651 Server Identifier (NSID) query, or a query of the name
8652 <filename>ID.SERVER</filename> with type
8653 <command>TXT</command>, class <command>CHAOS</command>.
8654 The primary purpose of such queries is to
8655 identify which of a group of anycast servers is actually
8656 answering your queries. Specifying <command>server-id none;</command>
8657 disables processing of the queries.
8658 Specifying <command>server-id hostname;</command> will cause <command>named</command> to
8659 use the hostname as found by the gethostname() function.
8660 The default <command>server-id</command> is <command>none</command>.
8669 <section xml:id="empty"><info><title>Built-in Empty Zones</title></info>
8672 Named has some built-in empty zones (SOA and NS records only).
8673 These are for zones that should normally be answered locally
8674 and which queries should not be sent to the Internet's root
8675 servers. The official servers which cover these namespaces
8676 return NXDOMAIN responses to these queries. In particular,
8677 these cover the reverse namespaces for addresses from
8678 RFC 1918, RFC 4193, RFC 5737 and RFC 6598. They also include the
8679 reverse namespace for IPv6 local address (locally assigned),
8680 IPv6 link local addresses, the IPv6 loopback address and the
8681 IPv6 unknown address.
8684 Named will attempt to determine if a built-in zone already exists
8685 or is active (covered by a forward-only forwarding declaration)
8686 and will not create an empty zone in that case.
8689 The current list of empty zones is:
8691 <listitem>10.IN-ADDR.ARPA</listitem>
8692 <listitem>16.172.IN-ADDR.ARPA</listitem>
8693 <listitem>17.172.IN-ADDR.ARPA</listitem>
8694 <listitem>18.172.IN-ADDR.ARPA</listitem>
8695 <listitem>19.172.IN-ADDR.ARPA</listitem>
8696 <listitem>20.172.IN-ADDR.ARPA</listitem>
8697 <listitem>21.172.IN-ADDR.ARPA</listitem>
8698 <listitem>22.172.IN-ADDR.ARPA</listitem>
8699 <listitem>23.172.IN-ADDR.ARPA</listitem>
8700 <listitem>24.172.IN-ADDR.ARPA</listitem>
8701 <listitem>25.172.IN-ADDR.ARPA</listitem>
8702 <listitem>26.172.IN-ADDR.ARPA</listitem>
8703 <listitem>27.172.IN-ADDR.ARPA</listitem>
8704 <listitem>28.172.IN-ADDR.ARPA</listitem>
8705 <listitem>29.172.IN-ADDR.ARPA</listitem>
8706 <listitem>30.172.IN-ADDR.ARPA</listitem>
8707 <listitem>31.172.IN-ADDR.ARPA</listitem>
8708 <listitem>168.192.IN-ADDR.ARPA</listitem>
8709 <listitem>64.100.IN-ADDR.ARPA</listitem>
8710 <listitem>65.100.IN-ADDR.ARPA</listitem>
8711 <listitem>66.100.IN-ADDR.ARPA</listitem>
8712 <listitem>67.100.IN-ADDR.ARPA</listitem>
8713 <listitem>68.100.IN-ADDR.ARPA</listitem>
8714 <listitem>69.100.IN-ADDR.ARPA</listitem>
8715 <listitem>70.100.IN-ADDR.ARPA</listitem>
8716 <listitem>71.100.IN-ADDR.ARPA</listitem>
8717 <listitem>72.100.IN-ADDR.ARPA</listitem>
8718 <listitem>73.100.IN-ADDR.ARPA</listitem>
8719 <listitem>74.100.IN-ADDR.ARPA</listitem>
8720 <listitem>75.100.IN-ADDR.ARPA</listitem>
8721 <listitem>76.100.IN-ADDR.ARPA</listitem>
8722 <listitem>77.100.IN-ADDR.ARPA</listitem>
8723 <listitem>78.100.IN-ADDR.ARPA</listitem>
8724 <listitem>79.100.IN-ADDR.ARPA</listitem>
8725 <listitem>80.100.IN-ADDR.ARPA</listitem>
8726 <listitem>81.100.IN-ADDR.ARPA</listitem>
8727 <listitem>82.100.IN-ADDR.ARPA</listitem>
8728 <listitem>83.100.IN-ADDR.ARPA</listitem>
8729 <listitem>84.100.IN-ADDR.ARPA</listitem>
8730 <listitem>85.100.IN-ADDR.ARPA</listitem>
8731 <listitem>86.100.IN-ADDR.ARPA</listitem>
8732 <listitem>87.100.IN-ADDR.ARPA</listitem>
8733 <listitem>88.100.IN-ADDR.ARPA</listitem>
8734 <listitem>89.100.IN-ADDR.ARPA</listitem>
8735 <listitem>90.100.IN-ADDR.ARPA</listitem>
8736 <listitem>91.100.IN-ADDR.ARPA</listitem>
8737 <listitem>92.100.IN-ADDR.ARPA</listitem>
8738 <listitem>93.100.IN-ADDR.ARPA</listitem>
8739 <listitem>94.100.IN-ADDR.ARPA</listitem>
8740 <listitem>95.100.IN-ADDR.ARPA</listitem>
8741 <listitem>96.100.IN-ADDR.ARPA</listitem>
8742 <listitem>97.100.IN-ADDR.ARPA</listitem>
8743 <listitem>98.100.IN-ADDR.ARPA</listitem>
8744 <listitem>99.100.IN-ADDR.ARPA</listitem>
8745 <listitem>100.100.IN-ADDR.ARPA</listitem>
8746 <listitem>101.100.IN-ADDR.ARPA</listitem>
8747 <listitem>102.100.IN-ADDR.ARPA</listitem>
8748 <listitem>103.100.IN-ADDR.ARPA</listitem>
8749 <listitem>104.100.IN-ADDR.ARPA</listitem>
8750 <listitem>105.100.IN-ADDR.ARPA</listitem>
8751 <listitem>106.100.IN-ADDR.ARPA</listitem>
8752 <listitem>107.100.IN-ADDR.ARPA</listitem>
8753 <listitem>108.100.IN-ADDR.ARPA</listitem>
8754 <listitem>109.100.IN-ADDR.ARPA</listitem>
8755 <listitem>110.100.IN-ADDR.ARPA</listitem>
8756 <listitem>111.100.IN-ADDR.ARPA</listitem>
8757 <listitem>112.100.IN-ADDR.ARPA</listitem>
8758 <listitem>113.100.IN-ADDR.ARPA</listitem>
8759 <listitem>114.100.IN-ADDR.ARPA</listitem>
8760 <listitem>115.100.IN-ADDR.ARPA</listitem>
8761 <listitem>116.100.IN-ADDR.ARPA</listitem>
8762 <listitem>117.100.IN-ADDR.ARPA</listitem>
8763 <listitem>118.100.IN-ADDR.ARPA</listitem>
8764 <listitem>119.100.IN-ADDR.ARPA</listitem>
8765 <listitem>120.100.IN-ADDR.ARPA</listitem>
8766 <listitem>121.100.IN-ADDR.ARPA</listitem>
8767 <listitem>122.100.IN-ADDR.ARPA</listitem>
8768 <listitem>123.100.IN-ADDR.ARPA</listitem>
8769 <listitem>124.100.IN-ADDR.ARPA</listitem>
8770 <listitem>125.100.IN-ADDR.ARPA</listitem>
8771 <listitem>126.100.IN-ADDR.ARPA</listitem>
8772 <listitem>127.100.IN-ADDR.ARPA</listitem>
8773 <listitem>0.IN-ADDR.ARPA</listitem>
8774 <listitem>127.IN-ADDR.ARPA</listitem>
8775 <listitem>254.169.IN-ADDR.ARPA</listitem>
8776 <listitem>2.0.192.IN-ADDR.ARPA</listitem>
8777 <listitem>100.51.198.IN-ADDR.ARPA</listitem>
8778 <listitem>113.0.203.IN-ADDR.ARPA</listitem>
8779 <listitem>255.255.255.255.IN-ADDR.ARPA</listitem>
8780 <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>
8781 <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>
8782 <listitem>8.B.D.0.1.0.0.2.IP6.ARPA</listitem>
8783 <listitem>D.F.IP6.ARPA</listitem>
8784 <listitem>8.E.F.IP6.ARPA</listitem>
8785 <listitem>9.E.F.IP6.ARPA</listitem>
8786 <listitem>A.E.F.IP6.ARPA</listitem>
8787 <listitem>B.E.F.IP6.ARPA</listitem>
8791 Empty zones are settable at the view level and only apply to
8792 views of class IN. Disabled empty zones are only inherited
8793 from options if there are no disabled empty zones specified
8794 at the view level. To override the options list of disabled
8795 zones, you can disable the root zone at the view level, for example:
8797 disable-empty-zone ".";
8801 If you are using the address ranges covered here, you should
8802 already have reverse zones covering the addresses you use.
8803 In practice this appears to not be the case with many queries
8804 being made to the infrastructure servers for names in these
8805 spaces. So many in fact that sacrificial servers were needed
8806 to be deployed to channel the query load away from the
8807 infrastructure servers.
8810 The real parent servers for these zones should disable all
8811 empty zone under the parent zone they serve. For the real
8812 root servers, this is all built-in empty zones. This will
8813 enable them to return referrals to deeper in the tree.
8817 <term><command>empty-server</command></term>
8820 Specify what server name will appear in the returned
8821 SOA record for empty zones. If none is specified, then
8822 the zone's name will be used.
8828 <term><command>empty-contact</command></term>
8831 Specify what contact name will appear in the returned
8832 SOA record for empty zones. If none is specified, then
8839 <term><command>empty-zones-enable</command></term>
8842 Enable or disable all empty zones. By default, they
8849 <term><command>disable-empty-zone</command></term>
8852 Disable individual empty zones. By default, none are
8853 disabled. This option can be specified multiple times.
8860 <section xml:id="acache"><info><title>Additional Section Caching</title></info>
8864 The additional section cache, also called <command>acache</command>,
8865 is an internal cache to improve the response performance of BIND 9.
8866 When additional section caching is enabled, BIND 9 will
8867 cache an internal short-cut to the additional section content for
8869 Note that <command>acache</command> is an internal caching
8870 mechanism of BIND 9, and is not related to the DNS caching
8875 Additional section caching does not change the
8876 response content (except the RRsets ordering of the additional
8877 section, see below), but can improve the response performance
8879 It is particularly effective when BIND 9 acts as an authoritative
8880 server for a zone that has many delegations with many glue RRs.
8884 In order to obtain the maximum performance improvement
8885 from additional section caching, setting
8886 <command>additional-from-cache</command>
8887 to <command>no</command> is recommended, since the current
8888 implementation of <command>acache</command>
8889 does not short-cut of additional section information from the
8894 One obvious disadvantage of <command>acache</command> is
8895 that it requires much more
8896 memory for the internal cached data.
8897 Thus, if the response performance does not matter and memory
8898 consumption is much more critical, the
8899 <command>acache</command> mechanism can be
8900 disabled by setting <command>acache-enable</command> to
8901 <command>no</command>.
8902 It is also possible to specify the upper limit of memory
8904 for acache by using <command>max-acache-size</command>.
8908 Additional section caching also has a minor effect on the
8909 RRset ordering in the additional section.
8910 Without <command>acache</command>,
8911 <command>cyclic</command> order is effective for the additional
8912 section as well as the answer and authority sections.
8913 However, additional section caching fixes the ordering when it
8914 first caches an RRset for the additional section, and the same
8915 ordering will be kept in succeeding responses, regardless of the
8916 setting of <command>rrset-order</command>.
8917 The effect of this should be minor, however, since an
8918 RRset in the additional section
8919 typically only contains a small number of RRs (and in many cases
8920 it only contains a single RR), in which case the
8921 ordering does not matter much.
8925 The following is a summary of options related to
8926 <command>acache</command>.
8932 <term><command>acache-enable</command></term>
8935 If <command>yes</command>, additional section caching is
8936 enabled. The default value is <command>no</command>.
8942 <term><command>acache-cleaning-interval</command></term>
8945 The server will remove stale cache entries, based on an LRU
8947 algorithm, every <command>acache-cleaning-interval</command> minutes.
8948 The default is 60 minutes.
8949 If set to 0, no periodic cleaning will occur.
8955 <term><command>max-acache-size</command></term>
8958 The maximum amount of memory in bytes to use for the server's acache.
8959 When the amount of data in the acache reaches this limit,
8961 will clean more aggressively so that the limit is not
8963 In a server with multiple views, the limit applies
8965 acache of each view.
8966 The default is <literal>16M</literal>.
8975 <section xml:id="content_filtering"><info><title>Content Filtering</title></info>
8978 <acronym>BIND</acronym> 9 provides the ability to filter
8979 out DNS responses from external DNS servers containing
8980 certain types of data in the answer section.
8981 Specifically, it can reject address (A or AAAA) records if
8982 the corresponding IPv4 or IPv6 addresses match the given
8983 <varname>address_match_list</varname> of the
8984 <command>deny-answer-addresses</command> option.
8985 It can also reject CNAME or DNAME records if the "alias"
8986 name (i.e., the CNAME alias or the substituted query name
8987 due to DNAME) matches the
8988 given <varname>namelist</varname> of the
8989 <command>deny-answer-aliases</command> option, where
8990 "match" means the alias name is a subdomain of one of
8991 the <varname>name_list</varname> elements.
8992 If the optional <varname>namelist</varname> is specified
8993 with <command>except-from</command>, records whose query name
8994 matches the list will be accepted regardless of the filter
8996 Likewise, if the alias name is a subdomain of the
8997 corresponding zone, the <command>deny-answer-aliases</command>
8998 filter will not apply;
8999 for example, even if "example.com" is specified for
9000 <command>deny-answer-aliases</command>,
9002 <programlisting>www.example.com. CNAME xxx.example.com.</programlisting>
9005 returned by an "example.com" server will be accepted.
9009 In the <varname>address_match_list</varname> of the
9010 <command>deny-answer-addresses</command> option, only
9011 <varname>ip_addr</varname>
9012 and <varname>ip_prefix</varname>
9014 any <varname>key_id</varname> will be silently ignored.
9018 If a response message is rejected due to the filtering,
9019 the entire message is discarded without being cached, and
9020 a SERVFAIL error will be returned to the client.
9024 This filtering is intended to prevent "DNS rebinding attacks," in
9025 which an attacker, in response to a query for a domain name the
9026 attacker controls, returns an IP address within your own network or
9027 an alias name within your own domain.
9028 A naive web browser or script could then serve as an
9029 unintended proxy, allowing the attacker
9030 to get access to an internal node of your local network
9031 that couldn't be externally accessed otherwise.
9032 See the paper available at
9033 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://portal.acm.org/citation.cfm?id=1315245.1315298">
9034 http://portal.acm.org/citation.cfm?id=1315245.1315298
9036 for more details about the attacks.
9040 For example, if you own a domain named "example.net" and
9041 your internal network uses an IPv4 prefix 192.0.2.0/24,
9042 you might specify the following rules:
9045 <programlisting>deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
9046 deny-answer-aliases { "example.net"; };
9050 If an external attacker lets a web browser in your local
9051 network look up an IPv4 address of "attacker.example.com",
9052 the attacker's DNS server would return a response like this:
9055 <programlisting>attacker.example.com. A 192.0.2.1</programlisting>
9058 in the answer section.
9059 Since the rdata of this record (the IPv4 address) matches
9060 the specified prefix 192.0.2.0/24, this response will be
9065 On the other hand, if the browser looks up a legitimate
9066 internal web server "www.example.net" and the
9067 following response is returned to
9068 the <acronym>BIND</acronym> 9 server
9071 <programlisting>www.example.net. A 192.0.2.2</programlisting>
9074 it will be accepted since the owner name "www.example.net"
9075 matches the <command>except-from</command> element,
9080 Note that this is not really an attack on the DNS per se.
9081 In fact, there is nothing wrong for an "external" name to
9082 be mapped to your "internal" IP address or domain name
9083 from the DNS point of view.
9084 It might actually be provided for a legitimate purpose,
9085 such as for debugging.
9086 As long as the mapping is provided by the correct owner,
9087 it is not possible or does not make sense to detect
9088 whether the intent of the mapping is legitimate or not
9090 The "rebinding" attack must primarily be protected at the
9091 application that uses the DNS.
9092 For a large site, however, it may be difficult to protect
9093 all possible applications at once.
9094 This filtering feature is provided only to help such an
9095 operational environment;
9096 it is generally discouraged to turn it on unless you are
9097 very sure you have no other choice and the attack is a
9098 real threat for your applications.
9102 Care should be particularly taken if you want to use this
9103 option for addresses within 127.0.0.0/8.
9104 These addresses are obviously "internal", but many
9105 applications conventionally rely on a DNS mapping from
9106 some name to such an address.
9107 Filtering out DNS records containing this address
9108 spuriously can break such applications.
9112 <section xml:id="rpz"><info><title>Response Policy Zone (RPZ) Rewriting</title></info>
9115 <acronym>BIND</acronym> 9 includes a limited
9116 mechanism to modify DNS responses for requests
9117 analogous to email anti-spam DNS blacklists.
9118 Responses can be changed to deny the existence of domains (NXDOMAIN),
9119 deny the existence of IP addresses for domains (NODATA),
9120 or contain other IP addresses or data.
9124 Response policy zones are named in the
9125 <command>response-policy</command> option for the view or among the
9126 global options if there is no response-policy option for the view.
9127 RPZs are ordinary DNS zones containing RRsets
9128 that can be queried normally if allowed.
9129 It is usually best to restrict those queries with something like
9130 <command>allow-query { localhost; };</command>.
9134 Four policy triggers are encoded in RPZ records, QNAME, IP, NSIP,
9136 QNAME RPZ records triggered by query names of requests and targets
9137 of CNAME records resolved to generate the response.
9138 The owner name of a QNAME RPZ record is the query name relativized
9143 The second kind of RPZ trigger is an IP address in an A and AAAA
9144 record in the ANSWER section of a response.
9145 IP address triggers are encoded in records that have owner names
9146 that are subdomains of <userinput>rpz-ip</userinput> relativized
9147 to the RPZ origin name and encode an IP address or address block.
9148 IPv4 trigger addresses are represented as
9149 <userinput>prefixlength.B4.B3.B2.B1.rpz-ip</userinput>.
9150 The prefix length must be between 1 and 32.
9151 All four bytes, B4, B3, B2, and B1, must be present.
9152 B4 is the decimal value of the least significant byte of the
9153 IPv4 address as in IN-ADDR.ARPA.
9154 IPv6 addresses are encoded in a format similar to the standard
9155 IPv6 text representation,
9156 <userinput>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</userinput>.
9157 Each of W8,...,W1 is a one to four digit hexadecimal number
9158 representing 16 bits of the IPv6 address as in the standard text
9159 representation of IPv6 addresses, but reversed as in IN-ADDR.ARPA.
9160 All 8 words must be present except when consecutive
9161 zero words are replaced with <userinput>.zz.</userinput>
9162 analogous to double colons (::) in standard IPv6 text encodings.
9163 The prefix length must be between 1 and 128.
9167 NSDNAME triggers match names of authoritative servers
9168 for the query name, a parent of the query name, a CNAME for
9169 query name, or a parent of a CNAME.
9170 They are encoded as subdomains of
9171 <userinput>rpz-nsdomain</userinput> relativized
9172 to the RPZ origin name.
9173 NSIP triggers match IP addresses in A and
9174 AAAA RRsets for domains that can be checked against NSDNAME
9176 NSIP triggers are encoded like IP triggers except as subdomains of
9177 <userinput>rpz-nsip</userinput>.
9178 NSDNAME and NSIP triggers are checked only for names with at
9179 least <command>min-ns-dots</command> dots.
9180 The default value of <command>min-ns-dots</command> is 1 to
9181 exclude top level domains.
9185 The query response is checked against all RPZs, so
9186 two or more policy records can be triggered by a response.
9187 Because DNS responses can be rewritten according to at most one
9188 policy record, a single record encoding an action (other than
9189 <command>DISABLED</command> actions) must be chosen.
9190 Triggers or the records that encode them are chosen in
9191 the following order:
9193 <listitem>Choose the triggered record in the zone that appears
9194 first in the response-policy option.
9196 <listitem>Prefer QNAME to IP to NSDNAME to NSIP triggers
9199 <listitem>Among NSDNAME triggers, prefer the
9200 trigger that matches the smallest name under the DNSSEC ordering.
9202 <listitem>Among IP or NSIP triggers, prefer the trigger
9203 with the longest prefix.
9205 <listitem>Among triggers with the same prefix length,
9206 prefer the IP or NSIP trigger that matches
9207 the smallest IP address.
9213 When the processing of a response is restarted to resolve
9214 DNAME or CNAME records and a policy record set has
9216 all RPZs are again consulted for the DNAME or CNAME names
9221 RPZ record sets are sets of any types of DNS record except
9222 DNAME or DNSSEC that encode actions or responses to queries.
9224 <listitem>The <command>NXDOMAIN</command> response is encoded
9225 by a CNAME whose target is the root domain (.)
9227 <listitem>A CNAME whose target is the wildcard top-level
9228 domain (*.) specifies the <command>NODATA</command> action,
9229 which rewrites the response to NODATA or ANCOUNT=1.
9231 <listitem>The <command>Local Data</command> action is
9232 represented by a set ordinary DNS records that are used
9233 to answer queries. Queries for record types not the
9234 set are answered with NODATA.
9236 A special form of local data is a CNAME whose target is a
9237 wildcard such as *.example.com.
9238 It is used as if were an ordinary CNAME after the astrisk (*)
9239 has been replaced with the query name.
9240 The purpose for this special form is query logging in the
9241 walled garden's authority DNS server.
9243 <listitem>The <command>PASSTHRU</command> policy is specified
9244 by a CNAME whose target is <command>rpz-passthru.</command>
9245 It causes the response to not be rewritten
9246 and is most often used to "poke holes" in policies for
9248 (A CNAME whose target is the variable part of its owner name
9249 is an obsolete specification of the PASSTHRU policy.)
9255 The actions specified in an RPZ can be overridden with a
9256 <command>policy</command> clause in the
9257 <command>response-policy</command> option.
9258 An organization using an RPZ provided by another organization might
9259 use this mechanism to redirect domains to its own walled garden.
9261 <listitem><command>GIVEN</command> says "do not override but
9262 perform the action specified in the zone."
9264 <listitem><command>DISABLED</command> causes policy records to do
9265 nothing but log what they might have done.
9266 The response to the DNS query will be written according to
9267 any triggered policy records that are not disabled.
9268 Disabled policy zones should appear first,
9269 because they will often not be logged
9270 if a higher precedence trigger is found first.
9272 <listitem><command>PASSTHRU</command> causes all policy records
9273 to act as if they were CNAME records with targets the variable
9274 part of their owner name. They protect the response from
9277 <listitem><command>NXDOMAIN</command> causes all RPZ records
9278 to specify NXDOMAIN policies.
9280 <listitem><command>NODATA</command> overrides with the
9283 <listitem><command>CNAME domain</command> causes all RPZ
9284 policy records to act as if they were "cname domain" records.
9290 By default, the actions encoded in an RPZ are applied
9291 only to queries that ask for recursion (RD=1).
9292 That default can be changed for a single RPZ or all RPZs in a view
9293 with a <command>recursive-only no</command> clause.
9294 This feature is useful for serving the same zone files
9295 both inside and outside an RFC 1918 cloud and using RPZ to
9296 delete answers that would otherwise contain RFC 1918 values
9297 on the externally visible name server or view.
9301 Also by default, RPZ actions are applied only to DNS requests that
9302 either do not request DNSSEC metadata (DO=0) or when no DNSSEC
9303 records are available for request name in the original zone (not
9304 the response policy zone).
9305 This default can be changed for all RPZs in a view with a
9306 <command>break-dnssec yes</command> clause.
9307 In that case, RPZ actions are applied regardless of DNSSEC.
9308 The name of the clause option reflects the fact that results
9309 rewritten by RPZ actions cannot verify.
9313 The TTL of a record modified by RPZ policies is set from the
9314 TTL of the relevant record in policy zone. It is then limited
9316 The <command>max-policy-ttl</command> clause changes that
9317 maximum from its default of 5.
9321 For example, you might use this option statement
9323 <programlisting> response-policy { zone "badlist"; };</programlisting>
9325 and this zone statement
9327 <programlisting> zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</programlisting>
9331 <programlisting>$TTL 1H
9332 @ SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
9335 ; QNAME policy records. There are no periods (.) after the owner names.
9336 nxdomain.domain.com CNAME . ; NXDOMAIN policy
9337 nodata.domain.com CNAME *. ; NODATA policy
9338 bad.domain.com A 10.0.0.1 ; redirect to a walled garden
9341 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
9342 ok.domain.com CNAME rpz-passthru.
9344 bzone.domain.com CNAME garden.example.com.
9346 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
9347 *.bzone.domain.com CNAME *.garden.example.com.
9350 ; IP policy records that rewrite all answers for 127/8 except 127.0.0.1
9351 8.0.0.0.127.rpz-ip CNAME .
9352 32.1.0.0.127.rpz-ip CNAME rpz-passthru.
9354 ; NSDNAME and NSIP policy records
9355 ns.domain.com.rpz-nsdname CNAME .
9356 48.zz.2.2001.rpz-nsip CNAME .
9359 RPZ can affect server performance.
9360 Each configured response policy zone requires the server to
9361 perform one to four additional database lookups before a
9362 query can be answered.
9363 For example, a DNS server with four policy zones, each with all
9364 four kinds of response triggers, QNAME, IP, NSIP, and
9365 NSDNAME, requires a total of 17 times as many database
9366 lookups as a similar DNS server with no response policy zones.
9367 A <acronym>BIND9</acronym> server with adequate memory and one
9368 response policy zone with QNAME and IP triggers might achieve a
9369 maximum queries-per-second rate about 20% lower.
9370 A server with four response policy zones with QNAME and IP
9371 triggers might have a maximum QPS rate about 50% lower.
9375 Responses rewritten by RPZ are counted in the
9376 <command>RPZRewrites</command> statistics.
9380 <section xml:id="rrl"><info><title>Response Rate Limiting</title></info>
9383 This feature is only available when <acronym>BIND</acronym> 9
9384 is compiled with the <userinput>--enable-rrl</userinput>
9385 option on the "configure" command line.
9388 Excessive almost identical UDP <emphasis>responses</emphasis>
9389 can be controlled by configuring a
9390 <command>rate-limit</command> clause in an
9391 <command>options</command> or <command>view</command> statement.
9392 This mechanism keeps authoritative BIND 9 from being used
9393 in amplifying reflection denial of service (DoS) attacks.
9394 Short truncated (TC=1) responses can be sent to provide
9395 rate-limited responses to legitimate clients within
9396 a range of forged, attacked IP addresses.
9397 Legitimate clients react to dropped or truncated response
9398 by retrying with UDP or with TCP respectively.
9402 This mechanism is intended for authoritative DNS servers.
9403 It can be used on recursive servers but can slow
9404 applications such as SMTP servers (mail receivers) and
9405 HTTP clients (web browsers) that repeatedly request the
9407 When possible, closing "open" recursive servers is better.
9411 Response rate limiting uses a "credit" or "token bucket" scheme.
9412 Each combination of identical response and client
9413 has a conceptual account that earns a specified number
9414 of credits every second.
9415 A prospective response debits its account by one.
9416 Responses are dropped or truncated
9417 while the account is negative.
9418 Responses are tracked within a rolling window of time
9419 which defaults to 15 seconds, but can be configured with
9420 the <command>window</command> option to any value from
9421 1 to 3600 seconds (1 hour).
9422 The account cannot become more positive than
9423 the per-second limit
9424 or more negative than <command>window</command>
9425 times the per-second limit.
9426 When the specified number of credits for a class of
9427 responses is set to 0, those responses are not rate limited.
9431 The notions of "identical response" and "DNS client"
9432 for rate limiting are not simplistic.
9433 All responses to an address block are counted as if to a
9435 The prefix lengths of addresses blocks are
9436 specified with <command>ipv4-prefix-length</command> (default 24)
9437 and <command>ipv6-prefix-length</command> (default 56).
9441 All non-empty responses for a valid domain name (qname)
9442 and record type (qtype) are identical and have a limit specified
9443 with <command>responses-per-second</command>
9444 (default 0 or no limit).
9445 All empty (NODATA) responses for a valid domain,
9446 regardless of query type, are identical.
9447 Responses in the NODATA class are limited by
9448 <command>nodata-per-second</command>
9449 (default <command>responses-per-second</command>).
9450 Requests for any and all undefined subdomains of a given
9451 valid domain result in NXDOMAIN errors, and are identical
9452 regardless of query type.
9453 They are limited by <command>nxdomain-per-second</command>
9454 (default <command>responses-per-second</command>).
9455 This controls some attacks using random names, but
9456 can be relaxed or turned off (set to 0)
9457 on servers that expect many legitimate
9458 NXDOMAIN responses, such as from anti-spam blacklists.
9459 Referrals or delegations to the server of a given
9460 domain are identical and are limited by
9461 <command>referrals-per-second</command>
9462 (default <command>responses-per-second</command>).
9466 Responses generated from local wildcards are counted and limited
9467 as if they were for the parent domain name.
9468 This controls flooding using random.wild.example.com.
9472 All requests that result in DNS errors other
9473 than NXDOMAIN, such as SERVFAIL and FORMERR, are identical
9474 regardless of requested name (qname) or record type (qtype).
9475 This controls attacks using invalid requests or distant,
9476 broken authoritative servers.
9477 By default the limit on errors is the same as the
9478 <command>responses-per-second</command> value,
9479 but it can be set separately with
9480 <command>errors-per-second</command>.
9484 Many attacks using DNS involve UDP requests with forged source
9486 Rate limiting prevents the use of BIND 9 to flood a network
9487 with responses to requests with forged source addresses,
9488 but could let a third party block responses to legitimate requests.
9489 There is a mechanism that can answer some legitimate
9490 requests from a client whose address is being forged in a flood.
9491 Setting <command>slip</command> to 2 (its default) causes every
9492 other UDP request to be answered with a small truncated (TC=1)
9494 The small size and reduced frequency, and so lack of
9495 amplification, of "slipped" responses make them unattractive
9496 for reflection DoS attacks.
9497 <command>slip</command> must be between 0 and 10.
9498 A value of 0 does not "slip":
9499 no truncated responses are sent due to rate limiting,
9500 all responses are dropped.
9501 A value of 1 causes every response to slip;
9502 values between 2 and 10 cause every n'th response to slip.
9503 Some error responses including REFUSED and SERVFAIL
9504 cannot be replaced with truncated responses and are instead
9505 leaked at the <command>slip</command> rate.
9509 (NOTE: Dropped responses from an authoritative server may
9510 reduce the difficulty of a third party successfully forging
9511 a response to a recursive resolver. The best security
9512 against forged responses is for authoritative operators
9513 to sign their zones using DNSSEC and for resolver operators
9514 to validate the responses. When this is not an option,
9515 operators who are more concerned with response integrity
9516 than with flood mitigation may consider setting
9517 <command>slip</command> to 1, causing all rate-limited
9518 responses to be truncated rather than dropped. This reduces
9519 the effectiveness of rate-limiting against reflection attacks.)
9523 When the approximate query per second rate exceeds
9524 the <command>qps-scale</command> value,
9525 then the <command>responses-per-second</command>,
9526 <command>errors-per-second</command>,
9527 <command>nxdomains-per-second</command> and
9528 <command>all-per-second</command> values are reduced by the
9529 ratio of the current rate to the <command>qps-scale</command> value.
9530 This feature can tighten defenses during attacks.
9532 <command>qps-scale 250; responses-per-second 20;</command> and
9533 a total query rate of 1000 queries/second for all queries from
9534 all DNS clients including via TCP,
9535 then the effective responses/second limit changes to
9537 Responses sent via TCP are not limited
9538 but are counted to compute the query per second rate.
9542 Communities of DNS clients can be given their own parameters or no
9543 rate limiting by putting
9544 <command>rate-limit</command> statements in <command>view</command>
9545 statements instead of the global <command>option</command>
9547 A <command>rate-limit</command> statement in a view replaces,
9548 rather than supplementing, a <command>rate-limit</command>
9549 statement among the main options.
9550 DNS clients within a view can be exempted from rate limits
9551 with the <command>exempt-clients</command> clause.
9555 UDP responses of all kinds can be limited with the
9556 <command>all-per-second</command> phrase.
9557 This rate limiting is unlike the rate limiting provided by
9558 <command>responses-per-second</command>,
9559 <command>errors-per-second</command>, and
9560 <command>nxdomains-per-second</command> on a DNS server
9561 which are often invisible to the victim of a DNS reflection attack.
9562 Unless the forged requests of the attack are the same as the
9563 legitimate requests of the victim, the victim's requests are
9565 Responses affected by an <command>all-per-second</command> limit
9566 are always dropped; the <command>slip</command> value has no
9568 An <command>all-per-second</command> limit should be
9569 at least 4 times as large as the other limits,
9570 because single DNS clients often send bursts of legitimate
9572 For example, the receipt of a single mail message can prompt
9573 requests from an SMTP server for NS, PTR, A, and AAAA records
9574 as the incoming SMTP/TCP/IP connection is considered.
9575 The SMTP server can need additional NS, A, AAAA, MX, TXT, and SPF
9576 records as it considers the STMP <command>Mail From</command>
9578 Web browsers often repeatedly resolve the same names that
9579 are repeated in HTML <IMG> tags in a page.
9580 <command>All-per-second</command> is similar to the
9581 rate limiting offered by firewalls but often inferior.
9582 Attacks that justify ignoring the
9583 contents of DNS responses are likely to be attacks on the
9585 They usually should be discarded before the DNS server
9586 spends resources making TCP connections or parsing DNS requests,
9587 but that rate limiting must be done before the
9588 DNS server sees the requests.
9592 The maximum size of the table used to track requests and
9593 rate limit responses is set with <command>max-table-size</command>.
9594 Each entry in the table is between 40 and 80 bytes.
9595 The table needs approximately as many entries as the number
9596 of requests received per second.
9597 The default is 20,000.
9598 To reduce the cold start of growing the table,
9599 <command>min-table-size</command> (default 500)
9600 can set the minimum table size.
9601 Enable <command>rate-limit</command> category logging to monitor
9602 expansions of the table and inform
9603 choices for the initial and maximum table size.
9607 Use <command>log-only yes</command> to test rate limiting parameters
9608 without actually dropping any requests.
9612 Responses dropped by rate limits are included in the
9613 <command>RateDropped</command> and <command>QryDropped</command>
9615 Responses that truncated by rate limits are included in
9616 <command>RateSlipped</command> and <command>RespTruncated</command>.
9621 <section xml:id="server_statement_grammar"><info><title><command>server</command> Statement Grammar</title></info>
9623 <programlisting><command>server</command> <replaceable>ip_addr[/prefixlen]</replaceable> {
9624 <optional> bogus <replaceable>yes_or_no</replaceable> ; </optional>
9625 <optional> provide-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9626 <optional> request-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9627 <optional> request-nsid <replaceable>yes_or_no</replaceable> ; </optional>
9628 <optional> edns <replaceable>yes_or_no</replaceable> ; </optional>
9629 <optional> edns-udp-size <replaceable>number</replaceable> ; </optional>
9630 <optional> max-udp-size <replaceable>number</replaceable> ; </optional>
9631 <optional> transfers <replaceable>number</replaceable> ; </optional>
9632 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable> ; ]</optional>
9633 <optional> keys { <replaceable>key_id</replaceable> }; </optional>
9634 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9635 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9636 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9637 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9638 <optional> query-source <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9639 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9640 <optional> query-source-v6 <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9641 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9642 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
9643 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
9644 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
9650 <section xml:id="server_statement_definition_and_usage"><info><title><command>server</command> Statement Definition and
9651 Usage</title></info>
9654 The <command>server</command> statement defines
9656 to be associated with a remote name server. If a prefix length is
9657 specified, then a range of servers is covered. Only the most
9659 server clause applies regardless of the order in
9660 <filename>named.conf</filename>.
9664 The <command>server</command> statement can occur at
9665 the top level of the
9666 configuration file or inside a <command>view</command>
9668 If a <command>view</command> statement contains
9669 one or more <command>server</command> statements, only
9671 apply to the view and any top-level ones are ignored.
9672 If a view contains no <command>server</command>
9674 any top-level <command>server</command> statements are
9680 If you discover that a remote server is giving out bad data,
9681 marking it as bogus will prevent further queries to it. The
9683 value of <command>bogus</command> is <command>no</command>.
9686 The <command>provide-ixfr</command> clause determines
9688 the local server, acting as master, will respond with an
9690 zone transfer when the given remote server, a slave, requests it.
9691 If set to <command>yes</command>, incremental transfer
9693 whenever possible. If set to <command>no</command>,
9695 to the remote server will be non-incremental. If not set, the
9697 of the <command>provide-ixfr</command> option in the
9699 global options block is used as a default.
9703 The <command>request-ixfr</command> clause determines
9705 the local server, acting as a slave, will request incremental zone
9706 transfers from the given remote server, a master. If not set, the
9707 value of the <command>request-ixfr</command> option in
9708 the view or global options block is used as a default. It may
9709 also be set in the zone block and, if set there, it will
9710 override the global or view setting for that zone.
9714 IXFR requests to servers that do not support IXFR will
9716 fall back to AXFR. Therefore, there is no need to manually list
9717 which servers support IXFR and which ones do not; the global
9719 of <command>yes</command> should always work.
9720 The purpose of the <command>provide-ixfr</command> and
9721 <command>request-ixfr</command> clauses is
9722 to make it possible to disable the use of IXFR even when both
9724 and slave claim to support it, for example if one of the servers
9725 is buggy and crashes or corrupts data when IXFR is used.
9729 The <command>edns</command> clause determines whether
9730 the local server will attempt to use EDNS when communicating
9731 with the remote server. The default is <command>yes</command>.
9735 The <command>edns-udp-size</command> option sets the EDNS UDP size
9736 that is advertised by <command>named</command> when querying the remote server.
9737 Valid values are 512 to 4096 bytes (values outside this range will be
9738 silently adjusted). This option is useful when you wish to
9739 advertises a different value to this server than the value you
9740 advertise globally, for example, when there is a firewall at the
9741 remote site that is blocking large replies.
9745 The <command>max-udp-size</command> option sets the
9746 maximum EDNS UDP message size <command>named</command> will send. Valid
9747 values are 512 to 4096 bytes (values outside this range will
9748 be silently adjusted). This option is useful when you
9749 know that there is a firewall that is blocking large
9750 replies from <command>named</command>.
9754 The server supports two zone transfer methods. The first, <command>one-answer</command>,
9755 uses one DNS message per resource record transferred. <command>many-answers</command> packs
9756 as many resource records as possible into a message. <command>many-answers</command> is
9757 more efficient, but is only known to be understood by <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
9758 8.x, and patched versions of <acronym>BIND</acronym>
9759 4.9.5. You can specify which method
9760 to use for a server with the <command>transfer-format</command> option.
9761 If <command>transfer-format</command> is not
9762 specified, the <command>transfer-format</command>
9764 by the <command>options</command> statement will be
9768 <para><command>transfers</command>
9769 is used to limit the number of concurrent inbound zone
9770 transfers from the specified server. If no
9771 <command>transfers</command> clause is specified, the
9772 limit is set according to the
9773 <command>transfers-per-ns</command> option.
9777 The <command>keys</command> clause identifies a
9778 <command>key_id</command> defined by the <command>key</command> statement,
9779 to be used for transaction security (TSIG, <xref linkend="tsig"/>)
9780 when talking to the remote server.
9781 When a request is sent to the remote server, a request signature
9782 will be generated using the key specified here and appended to the
9783 message. A request originating from the remote server is not
9785 to be signed by this key.
9789 Only a single key per server is currently supported.
9793 The <command>transfer-source</command> and
9794 <command>transfer-source-v6</command> clauses specify
9795 the IPv4 and IPv6 source
9796 address to be used for zone transfer with the remote server,
9798 For an IPv4 remote server, only <command>transfer-source</command> can
9800 Similarly, for an IPv6 remote server, only
9801 <command>transfer-source-v6</command> can be
9803 For more details, see the description of
9804 <command>transfer-source</command> and
9805 <command>transfer-source-v6</command> in
9806 <xref linkend="zone_transfers"/>.
9810 The <command>notify-source</command> and
9811 <command>notify-source-v6</command> clauses specify the
9812 IPv4 and IPv6 source address to be used for notify
9813 messages sent to remote servers, respectively. For an
9814 IPv4 remote server, only <command>notify-source</command>
9815 can be specified. Similarly, for an IPv6 remote server,
9816 only <command>notify-source-v6</command> can be specified.
9820 The <command>query-source</command> and
9821 <command>query-source-v6</command> clauses specify the
9822 IPv4 and IPv6 source address to be used for queries
9823 sent to remote servers, respectively. For an IPv4
9824 remote server, only <command>query-source</command> can
9825 be specified. Similarly, for an IPv6 remote server,
9826 only <command>query-source-v6</command> can be specified.
9830 The <command>request-nsid</command> clause determines
9831 whether the local server will add a NSID EDNS option
9832 to requests sent to the server. This overrides
9833 <command>request-nsid</command> set at the view or
9838 <section xml:id="statschannels"><info><title><command>statistics-channels</command> Statement Grammar</title></info>
9840 <programlisting><command>statistics-channels</command> {
9841 [ inet ( ip_addr | * ) [ port ip_port ]
9842 [ allow { <replaceable> address_match_list </replaceable> } ]; ]
9848 <section xml:id="statistics_channels"><info><title><command>statistics-channels</command> Statement Definition and
9849 Usage</title></info>
9852 The <command>statistics-channels</command> statement
9853 declares communication channels to be used by system
9854 administrators to get access to statistics information of
9859 This statement intends to be flexible to support multiple
9860 communication protocols in the future, but currently only
9861 HTTP access is supported.
9862 It requires that BIND 9 be compiled with libxml2;
9863 the <command>statistics-channels</command> statement is
9864 still accepted even if it is built without the library,
9865 but any HTTP access will fail with an error.
9869 An <command>inet</command> control channel is a TCP socket
9870 listening at the specified <command>ip_port</command> on the
9871 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
9872 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
9873 interpreted as the IPv4 wildcard address; connections will be
9874 accepted on any of the system's IPv4 addresses.
9875 To listen on the IPv6 wildcard address,
9876 use an <command>ip_addr</command> of <literal>::</literal>.
9880 If no port is specified, port 80 is used for HTTP channels.
9881 The asterisk "<literal>*</literal>" cannot be used for
9882 <command>ip_port</command>.
9886 The attempt of opening a statistics channel is
9887 restricted by the optional <command>allow</command> clause.
9888 Connections to the statistics channel are permitted based on the
9889 <command>address_match_list</command>.
9890 If no <command>allow</command> clause is present,
9891 <command>named</command> accepts connection
9892 attempts from any address; since the statistics may
9893 contain sensitive internal information, it is highly
9894 recommended to restrict the source of connection requests
9899 If no <command>statistics-channels</command> statement is present,
9900 <command>named</command> will not open any communication channels.
9904 If the statistics channel is configured to listen on 127.0.0.1
9905 port 8888, then the statistics are accessible in XML format at
9906 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/">http://127.0.0.1:8888/</link> or
9907 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml">http://127.0.0.1:8888/xml</link>. A CSS file is
9908 included which can format the XML statistics into tables
9909 when viewed with a stylesheet-capable browser. When
9910 <acronym>BIND</acronym> 9 is configured with --enable-newstats,
9911 a new XML schema is used (version 3) which adds additional
9912 zone statistics and uses a flatter tree for more efficient
9913 parsing. The stylesheet included uses the Google Charts API
9914 to render data into into charts and graphs when using a
9915 javascript-capable browser.
9919 Applications that depend on a particular XML schema
9921 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v2">http://127.0.0.1:8888/xml/v2</link> for version 2
9922 of the statistics XML schema or
9923 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://127.0.0.1:8888/xml/v3">http://127.0.0.1:8888/xml/v3</link> for version 3.
9924 If the requested schema is supported by the server, then
9925 it will respond; if not, it will return a "page not found"
9930 <section xml:id="trusted-keys"><info><title><command>trusted-keys</command> Statement Grammar</title></info>
9932 <programlisting><command>trusted-keys</command> {
9933 <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9934 <optional> <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9939 <section xml:id="trusted_keys"><info><title><command>trusted-keys</command> Statement Definition
9940 and Usage</title></info>
9943 The <command>trusted-keys</command> statement defines
9944 DNSSEC security roots. DNSSEC is described in <xref linkend="DNSSEC"/>. A security root is defined when the
9945 public key for a non-authoritative zone is known, but
9946 cannot be securely obtained through DNS, either because
9947 it is the DNS root zone or because its parent zone is
9948 unsigned. Once a key has been configured as a trusted
9949 key, it is treated as if it had been validated and
9950 proven secure. The resolver attempts DNSSEC validation
9951 on all DNS data in subdomains of a security root.
9954 All keys (and corresponding zones) listed in
9955 <command>trusted-keys</command> are deemed to exist regardless
9956 of what parent zones say. Similarly for all keys listed in
9957 <command>trusted-keys</command> only those keys are
9958 used to validate the DNSKEY RRset. The parent's DS RRset
9962 The <command>trusted-keys</command> statement can contain
9963 multiple key entries, each consisting of the key's
9964 domain name, flags, protocol, algorithm, and the Base-64
9965 representation of the key data.
9966 Spaces, tabs, newlines and carriage returns are ignored
9967 in the key data, so the configuration may be split up into
9971 <command>trusted-keys</command> may be set at the top level
9972 of <filename>named.conf</filename> or within a view. If it is
9973 set in both places, they are additive: keys defined at the top
9974 level are inherited by all views, but keys defined in a view
9975 are only used within that view.
9979 <section xml:id="managed_keys"><info><title><command>managed-keys</command> Statement Grammar</title></info>
9981 <programlisting><command>managed-keys</command> {
9982 <replaceable>name</replaceable> initial-key <replaceable>flags</replaceable> <replaceable>protocol</replaceable> <replaceable>algorithm</replaceable> <replaceable>key-data</replaceable> ;
9983 <optional> <replaceable>name</replaceable> initial-key <replaceable>flags</replaceable> <replaceable>protocol</replaceable> <replaceable>algorithm</replaceable> <replaceable>key-data</replaceable> ; <optional>...</optional></optional>
9988 <section xml:id="managed-keys"><info><title><command>managed-keys</command> Statement Definition
9989 and Usage</title></info>
9992 The <command>managed-keys</command> statement, like
9993 <command>trusted-keys</command>, defines DNSSEC
9994 security roots. The difference is that
9995 <command>managed-keys</command> can be kept up to date
9996 automatically, without intervention from the resolver
10000 Suppose, for example, that a zone's key-signing
10001 key was compromised, and the zone owner had to revoke and
10002 replace the key. A resolver which had the old key in a
10003 <command>trusted-keys</command> statement would be
10004 unable to validate this zone any longer; it would
10005 reply with a SERVFAIL response code. This would
10006 continue until the resolver operator had updated the
10007 <command>trusted-keys</command> statement with the new key.
10010 If, however, the zone were listed in a
10011 <command>managed-keys</command> statement instead, then the
10012 zone owner could add a "stand-by" key to the zone in advance.
10013 <command>named</command> would store the stand-by key, and
10014 when the original key was revoked, <command>named</command>
10015 would be able to transition smoothly to the new key. It would
10016 also recognize that the old key had been revoked, and cease
10017 using that key to validate answers, minimizing the damage that
10018 the compromised key could do.
10021 A <command>managed-keys</command> statement contains a list of
10022 the keys to be managed, along with information about how the
10023 keys are to be initialized for the first time. The only
10024 initialization method currently supported (as of
10025 <acronym>BIND</acronym> 9.7.0) is <literal>initial-key</literal>.
10026 This means the <command>managed-keys</command> statement must
10027 contain a copy of the initializing key. (Future releases may
10028 allow keys to be initialized by other methods, eliminating this
10032 Consequently, a <command>managed-keys</command> statement
10033 appears similar to a <command>trusted-keys</command>, differing
10034 in the presence of the second field, containing the keyword
10035 <literal>initial-key</literal>. The difference is, whereas the
10036 keys listed in a <command>trusted-keys</command> continue to be
10037 trusted until they are removed from
10038 <filename>named.conf</filename>, an initializing key listed
10039 in a <command>managed-keys</command> statement is only trusted
10040 <emphasis>once</emphasis>: for as long as it takes to load the
10041 managed key database and start the RFC 5011 key maintenance
10045 The first time <command>named</command> runs with a managed key
10046 configured in <filename>named.conf</filename>, it fetches the
10047 DNSKEY RRset directly from the zone apex, and validates it
10048 using the key specified in the <command>managed-keys</command>
10049 statement. If the DNSKEY RRset is validly signed, then it is
10050 used as the basis for a new managed keys database.
10053 From that point on, whenever <command>named</command> runs, it
10054 sees the <command>managed-keys</command> statement, checks to
10055 make sure RFC 5011 key maintenance has already been initialized
10056 for the specified domain, and if so, it simply moves on. The
10057 key specified in the <command>managed-keys</command> is not
10058 used to validate answers; it has been superseded by the key or
10059 keys stored in the managed keys database.
10062 The next time <command>named</command> runs after a name
10063 has been <emphasis>removed</emphasis> from the
10064 <command>managed-keys</command> statement, the corresponding
10065 zone will be removed from the managed keys database,
10066 and RFC 5011 key maintenance will no longer be used for that
10070 <command>named</command> only maintains a single managed keys
10071 database; consequently, unlike <command>trusted-keys</command>,
10072 <command>managed-keys</command> may only be set at the top
10073 level of <filename>named.conf</filename>, not within a view.
10076 In the current implementation, the managed keys database is
10077 stored as a master-format zone file called
10078 <filename>managed-keys.bind</filename>. When the key database
10079 is changed, the zone is updated. As with any other dynamic
10080 zone, changes will be written into a journal file,
10081 <filename>managed-keys.bind.jnl</filename>. They are committed
10082 to the master file as soon as possible afterward; in the case
10083 of the managed key database, this will usually occur within 30
10084 seconds. So, whenever <command>named</command> is using
10085 automatic key maintenance, those two files can be expected to
10086 exist in the working directory. (For this reason among others,
10087 the working directory should be always be writable by
10088 <command>named</command>.)
10091 If the <command>dnssec-validation</command> option is
10092 set to <userinput>auto</userinput>, <command>named</command>
10093 will automatically initialize a managed key for the
10094 root zone. Similarly, if the <command>dnssec-lookaside</command>
10095 option is set to <userinput>auto</userinput>,
10096 <command>named</command> will automatically initialize
10097 a managed key for the zone <literal>dlv.isc.org</literal>.
10098 In both cases, the key that is used to initialize the key
10099 maintenance process is built into <command>named</command>,
10100 and can be overridden from <command>bindkeys-file</command>.
10104 <section xml:id="view_statement_grammar"><info><title><command>view</command> Statement Grammar</title></info>
10106 <programlisting><command>view</command> <replaceable>view_name</replaceable>
10107 <optional><replaceable>class</replaceable></optional> {
10108 match-clients { <replaceable>address_match_list</replaceable> };
10109 match-destinations { <replaceable>address_match_list</replaceable> };
10110 match-recursive-only <replaceable>yes_or_no</replaceable> ;
10111 <optional> <replaceable>view_option</replaceable>; ...</optional>
10112 <optional> <replaceable>zone_statement</replaceable>; ...</optional>
10117 <section xml:id="view_statement"><info><title><command>view</command> Statement Definition and Usage</title></info>
10120 The <command>view</command> statement is a powerful
10122 of <acronym>BIND</acronym> 9 that lets a name server
10123 answer a DNS query differently
10124 depending on who is asking. It is particularly useful for
10126 split DNS setups without having to run multiple servers.
10130 Each <command>view</command> statement defines a view
10132 DNS namespace that will be seen by a subset of clients. A client
10134 a view if its source IP address matches the
10135 <varname>address_match_list</varname> of the view's
10136 <command>match-clients</command> clause and its
10137 destination IP address matches
10138 the <varname>address_match_list</varname> of the
10140 <command>match-destinations</command> clause. If not
10142 <command>match-clients</command> and <command>match-destinations</command>
10143 default to matching all addresses. In addition to checking IP
10145 <command>match-clients</command> and <command>match-destinations</command>
10146 can also take <command>keys</command> which provide an
10148 client to select the view. A view can also be specified
10149 as <command>match-recursive-only</command>, which
10150 means that only recursive
10151 requests from matching clients will match that view.
10152 The order of the <command>view</command> statements is
10154 a client request will be resolved in the context of the first
10155 <command>view</command> that it matches.
10159 Zones defined within a <command>view</command>
10161 only be accessible to clients that match the <command>view</command>.
10162 By defining a zone of the same name in multiple views, different
10163 zone data can be given to different clients, for example,
10165 and "external" clients in a split DNS setup.
10169 Many of the options given in the <command>options</command> statement
10170 can also be used within a <command>view</command>
10171 statement, and then
10172 apply only when resolving queries with that view. When no
10174 value is given, the value in the <command>options</command> statement
10175 is used as a default. Also, zone options can have default values
10177 in the <command>view</command> statement; these
10178 view-specific defaults
10179 take precedence over those in the <command>options</command> statement.
10183 Views are class specific. If no class is given, class IN
10184 is assumed. Note that all non-IN views must contain a hint zone,
10185 since only the IN class has compiled-in default hints.
10189 If there are no <command>view</command> statements in
10191 file, a default view that matches any client is automatically
10193 in class IN. Any <command>zone</command> statements
10195 the top level of the configuration file are considered to be part
10197 this default view, and the <command>options</command>
10199 apply to the default view. If any explicit <command>view</command>
10200 statements are present, all <command>zone</command>
10202 occur inside <command>view</command> statements.
10206 Here is an example of a typical split DNS setup implemented
10207 using <command>view</command> statements:
10210 <programlisting>view "internal" {
10211 // This should match our internal networks.
10212 match-clients { 10.0.0.0/8; };
10214 // Provide recursive service to internal
10218 // Provide a complete view of the example.com
10219 // zone including addresses of internal hosts.
10220 zone "example.com" {
10222 file "example-internal.db";
10227 // Match all clients not matched by the
10229 match-clients { any; };
10231 // Refuse recursive service to external clients.
10234 // Provide a restricted view of the example.com
10235 // zone containing only publicly accessible hosts.
10236 zone "example.com" {
10238 file "example-external.db";
10244 <section xml:id="zone_statement_grammar"><info><title><command>zone</command>
10245 Statement Grammar</title></info>
10247 <programlisting><command>zone</command> <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10249 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10250 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10251 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
10252 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
10253 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
10254 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
10255 <optional> dnssec-loadkeys-interval <replaceable>number</replaceable>; </optional>
10256 <optional> update-policy <replaceable>local</replaceable> | { <replaceable>update_policy_rule</replaceable> <optional>...</optional> }; </optional>
10257 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10258 <optional> check-mx (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10259 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
10260 <optional> check-spf ( <replaceable>warn</replaceable> | <replaceable>ignore</replaceable> ); </optional>
10261 <optional> check-integrity <replaceable>yes_or_no</replaceable> ; </optional>
10262 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10263 <optional> file <replaceable>string</replaceable> ; </optional>
10264 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10265 <optional> journal <replaceable>string</replaceable> ; </optional>
10266 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
10267 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10268 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10269 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
10270 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
10271 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
10272 <optional> request-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
10273 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
10274 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
10275 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
10276 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
10277 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
10278 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
10279 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
10280 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10281 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10282 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10283 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
10284 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
10285 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
10286 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
10287 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
10288 <optional> database <replaceable>string</replaceable> ; </optional>
10289 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10290 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10291 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10292 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10293 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
10294 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>off</constant>; </optional>
10295 <optional> inline-signing <replaceable>yes_or_no</replaceable>; </optional>
10296 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
10297 <optional> serial-update-method <constant>increment</constant>|<constant>unixtime</constant>; </optional>
10300 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10302 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
10303 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10304 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10305 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
10306 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
10307 <optional> dnssec-update-mode ( <replaceable>maintain</replaceable> | <replaceable>no-resign</replaceable> ); </optional>
10308 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
10309 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
10310 <optional> dnssec-loadkeys-interval <replaceable>number</replaceable>; </optional>
10311 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ; </optional>
10312 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
10313 <optional> also-notify <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10314 <optional>port <replaceable>ip_port</replaceable></optional>
10315 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10316 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10317 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10318 <optional> file <replaceable>string</replaceable> ; </optional>
10319 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10320 <optional> journal <replaceable>string</replaceable> ; </optional>
10321 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
10322 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10323 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10324 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
10325 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
10326 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
10327 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
10328 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10329 <optional>port <replaceable>ip_port</replaceable></optional>
10330 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10331 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
10332 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10333 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
10334 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10335 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
10336 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
10337 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
10338 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
10339 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10340 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10341 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10342 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10343 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10344 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10345 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10346 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10347 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10348 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
10349 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
10350 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
10351 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
10352 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
10353 <optional> database <replaceable>string</replaceable> ; </optional>
10354 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10355 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10356 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10357 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10358 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
10359 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>off</constant>; </optional>
10360 <optional> inline-signing <replaceable>yes_or_no</replaceable>; </optional>
10361 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10362 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
10365 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10367 file <replaceable>string</replaceable> ;
10368 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10369 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional> // Not Implemented.
10372 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10374 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10375 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10376 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10377 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10378 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10379 <optional> file <replaceable>string</replaceable> ; </optional>
10380 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10381 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10382 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10383 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10384 <optional>port <replaceable>ip_port</replaceable></optional>
10385 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10386 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10387 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10388 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10389 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10390 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10391 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10392 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10393 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10394 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10395 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10396 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
10397 <optional> database <replaceable>string</replaceable> ; </optional>
10398 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10399 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10400 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10401 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10402 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10405 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10407 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10408 <optional> server-addresses { <optional> <replaceable>ip_addr</replaceable> ; ... </optional> }; </optional>
10409 <optional> server-names { <optional> <replaceable>namelist</replaceable> </optional> }; </optional>
10410 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
10413 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10415 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10416 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10417 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10420 zone <replaceable>"."</replaceable> <optional><replaceable>class</replaceable></optional> {
10422 file <replaceable>string</replaceable> ;
10423 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10424 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10427 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10428 type delegation-only;
10434 <section xml:id="zone_statement"><info><title><command>zone</command> Statement Definition and Usage</title></info>
10436 <section xml:id="zone_types"><info><title>Zone Types</title></info>
10439 The <command>type</command> keyword is required
10440 for the <command>zone</command> configuration. Its
10441 acceptable values include: <varname>delegation-only</varname>,
10442 <varname>forward</varname>, <varname>hint</varname>,
10443 <varname>master</varname>, <varname>redirect</varname>,
10444 <varname>slave</varname>, <varname>static-stub</varname>,
10445 and <varname>stub</varname>.
10448 <informaltable colsep="0" rowsep="0">
10449 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
10450 <!--colspec colname="1" colnum="1" colsep="0" colwidth="1.108in"/-->
10451 <!--colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/-->
10452 <colspec colname="1" colnum="1" colsep="0"/>
10453 <colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/>
10456 <entry colname="1">
10458 <varname>master</varname>
10461 <entry colname="2">
10463 The server has a master copy of the data
10464 for the zone and will be able to provide authoritative
10471 <entry colname="1">
10473 <varname>slave</varname>
10476 <entry colname="2">
10478 A slave zone is a replica of a master
10479 zone. The <command>masters</command> list
10480 specifies one or more IP addresses
10481 of master servers that the slave contacts to update
10482 its copy of the zone.
10483 Masters list elements can also be names of other
10485 By default, transfers are made from port 53 on the
10487 be changed for all servers by specifying a port number
10489 list of IP addresses, or on a per-server basis after
10491 Authentication to the master can also be done with
10492 per-server TSIG keys.
10493 If a file is specified, then the
10494 replica will be written to this file whenever the zone
10496 and reloaded from this file on a server restart. Use
10498 recommended, since it often speeds server startup and
10500 a needless waste of bandwidth. Note that for large
10502 tens or hundreds of thousands) of zones per server, it
10504 use a two-level naming scheme for zone filenames. For
10506 a slave server for the zone <literal>example.com</literal> might place
10507 the zone contents into a file called
10508 <filename>ex/example.com</filename> where <filename>ex/</filename> is
10509 just the first two letters of the zone name. (Most
10511 behave very slowly if you put 100000 files into
10512 a single directory.)
10517 <entry colname="1">
10519 <varname>stub</varname>
10522 <entry colname="2">
10524 A stub zone is similar to a slave zone,
10525 except that it replicates only the NS records of a
10526 master zone instead
10527 of the entire zone. Stub zones are not a standard part
10529 they are a feature specific to the <acronym>BIND</acronym> implementation.
10533 Stub zones can be used to eliminate the need for glue
10535 in a parent zone at the expense of maintaining a stub
10537 a set of name server addresses in <filename>named.conf</filename>.
10538 This usage is not recommended for new configurations,
10540 supports it only in a limited way.
10541 In <acronym>BIND</acronym> 4/8, zone
10542 transfers of a parent zone
10543 included the NS records from stub children of that
10545 that, in some cases, users could get away with
10546 configuring child stubs
10547 only in the master server for the parent zone. <acronym>BIND</acronym>
10548 9 never mixes together zone data from different zones
10550 way. Therefore, if a <acronym>BIND</acronym> 9 master serving a parent
10551 zone has child stub zones configured, all the slave
10553 parent zone also need to have the same child stub
10559 Stub zones can also be used as a way of forcing the
10561 of a given domain to use a particular set of
10562 authoritative servers.
10563 For example, the caching name servers on a private
10565 RFC1918 addressing may be configured with stub zones
10567 <literal>10.in-addr.arpa</literal>
10568 to use a set of internal name servers as the
10570 servers for that domain.
10575 <entry colname="1">
10577 <varname>static-stub</varname>
10580 <entry colname="2">
10582 A static-stub zone is similar to a stub zone
10583 with the following exceptions:
10584 the zone data is statically configured, rather
10585 than transferred from a master server;
10586 when recursion is necessary for a query that
10587 matches a static-stub zone, the locally
10588 configured data (nameserver names and glue addresses)
10589 is always used even if different authoritative
10590 information is cached.
10593 Zone data is configured via the
10594 <command>server-addresses</command> and
10595 <command>server-names</command> zone options.
10598 The zone data is maintained in the form of NS
10599 and (if necessary) glue A or AAAA RRs
10600 internally, which can be seen by dumping zone
10601 databases by <command>rndc dumpdb -all</command>.
10602 The configured RRs are considered local configuration
10603 parameters rather than public data.
10604 Non recursive queries (i.e., those with the RD
10605 bit off) to a static-stub zone are therefore
10606 prohibited and will be responded with REFUSED.
10609 Since the data is statically configured, no
10610 zone maintenance action takes place for a static-stub
10612 For example, there is no periodic refresh
10613 attempt, and an incoming notify message
10614 will be rejected with an rcode of NOTAUTH.
10617 Each static-stub zone is configured with
10618 internally generated NS and (if necessary)
10624 <entry colname="1">
10626 <varname>forward</varname>
10629 <entry colname="2">
10631 A "forward zone" is a way to configure
10632 forwarding on a per-domain basis. A <command>zone</command> statement
10633 of type <command>forward</command> can
10634 contain a <command>forward</command>
10635 and/or <command>forwarders</command>
10637 which will apply to queries within the domain given by
10639 name. If no <command>forwarders</command>
10640 statement is present or
10641 an empty list for <command>forwarders</command> is given, then no
10642 forwarding will be done for the domain, canceling the
10644 any forwarders in the <command>options</command> statement. Thus
10645 if you want to use this type of zone to change the
10647 global <command>forward</command> option
10648 (that is, "forward first"
10649 to, then "forward only", or vice versa, but want to
10651 servers as set globally) you need to re-specify the
10657 <entry colname="1">
10659 <varname>hint</varname>
10662 <entry colname="2">
10664 The initial set of root name servers is
10665 specified using a "hint zone". When the server starts
10667 the root hints to find a root name server and get the
10669 list of root name servers. If no hint zone is
10670 specified for class
10671 IN, the server uses a compiled-in default set of root
10673 Classes other than IN have no built-in defaults hints.
10678 <entry colname="1">
10680 <varname>redirect</varname>
10683 <entry colname="2">
10685 Redirect zones are used to provide answers to
10686 queries when normal resolution would result in
10687 NXDOMAIN being returned.
10688 Only one redirect zone is supported
10689 per view. <command>allow-query</command> can be
10690 used to restrict which clients see these answers.
10693 If the client has requested DNSSEC records (DO=1) and
10694 the NXDOMAIN response is signed then no substitution
10698 To redirect all NXDOMAIN responses to
10700 2001:ffff:ffff::100.100.100.2, one would
10701 configure a type redirect zone named ".",
10702 with the zone file containing wildcard records
10703 that point to the desired addresses:
10704 <literal>"*. IN A 100.100.100.2"</literal>
10706 <literal>"*. IN AAAA 2001:ffff:ffff::100.100.100.2"</literal>.
10709 To redirect all Spanish names (under .ES) one
10710 would use similar entries but with the names
10711 "*.ES." instead of "*.". To redirect all
10712 commercial Spanish names (under COM.ES) one
10713 would use wildcard entries called "*.COM.ES.".
10716 Note that the redirect zone supports all
10717 possible types; it is not limited to A and
10721 Because redirect zones are not referenced
10722 directly by name, they are not kept in the
10723 zone lookup table with normal master and slave
10724 zones. Consequently, it is not currently possible
10726 <command>rndc reload
10727 <replaceable>zonename</replaceable></command>
10728 to reload a redirect zone. However, when using
10729 <command>rndc reload</command> without specifying
10730 a zone name, redirect zones will be reloaded along
10736 <entry colname="1">
10738 <varname>delegation-only</varname>
10741 <entry colname="2">
10743 This is used to enforce the delegation-only
10744 status of infrastructure zones (e.g. COM,
10745 NET, ORG). Any answer that is received
10746 without an explicit or implicit delegation
10747 in the authority section will be treated
10748 as NXDOMAIN. This does not apply to the
10749 zone apex. This should not be applied to
10753 <varname>delegation-only</varname> has no
10754 effect on answers received from forwarders.
10757 See caveats in <xref linkend="root_delegation_only"/>.
10766 <section xml:id="class"><info><title>Class</title></info>
10769 The zone's name may optionally be followed by a class. If
10770 a class is not specified, class <literal>IN</literal> (for <varname>Internet</varname>),
10771 is assumed. This is correct for the vast majority of cases.
10774 The <literal>hesiod</literal> class is
10775 named for an information service from MIT's Project Athena. It
10777 used to share information about various systems databases, such
10778 as users, groups, printers and so on. The keyword
10779 <literal>HS</literal> is
10780 a synonym for hesiod.
10783 Another MIT development is Chaosnet, a LAN protocol created
10784 in the mid-1970s. Zone data for it can be specified with the <literal>CHAOS</literal> class.
10788 <section xml:id="zone_options"><info><title>Zone Options</title></info>
10793 <term><command>allow-notify</command></term>
10796 See the description of
10797 <command>allow-notify</command> in <xref linkend="access_control"/>.
10803 <term><command>allow-query</command></term>
10806 See the description of
10807 <command>allow-query</command> in <xref linkend="access_control"/>.
10813 <term><command>allow-query-on</command></term>
10816 See the description of
10817 <command>allow-query-on</command> in <xref linkend="access_control"/>.
10823 <term><command>allow-transfer</command></term>
10826 See the description of <command>allow-transfer</command>
10827 in <xref linkend="access_control"/>.
10833 <term><command>allow-update</command></term>
10836 See the description of <command>allow-update</command>
10837 in <xref linkend="access_control"/>.
10843 <term><command>update-policy</command></term>
10846 Specifies a "Simple Secure Update" policy. See
10847 <xref linkend="dynamic_update_policies"/>.
10853 <term><command>allow-update-forwarding</command></term>
10856 See the description of <command>allow-update-forwarding</command>
10857 in <xref linkend="access_control"/>.
10863 <term><command>also-notify</command></term>
10866 Only meaningful if <command>notify</command>
10868 active for this zone. The set of machines that will
10870 <literal>DNS NOTIFY</literal> message
10871 for this zone is made up of all the listed name servers
10873 the primary master) for the zone plus any IP addresses
10875 with <command>also-notify</command>. A port
10877 with each <command>also-notify</command>
10878 address to send the notify
10879 messages to a port other than the default of 53.
10880 A TSIG key may also be specified to cause the
10881 <literal>NOTIFY</literal> to be signed by the
10883 <command>also-notify</command> is not
10884 meaningful for stub zones.
10885 The default is the empty list.
10891 <term><command>check-names</command></term>
10894 This option is used to restrict the character set and
10896 certain domain names in master files and/or DNS responses
10898 network. The default varies according to zone type. For <command>master</command> zones the default is <command>fail</command>. For <command>slave</command>
10899 zones the default is <command>warn</command>.
10900 It is not implemented for <command>hint</command> zones.
10906 <term><command>check-mx</command></term>
10909 See the description of
10910 <command>check-mx</command> in <xref linkend="boolean_options"/>.
10916 <term><command>check-spf</command></term>
10919 See the description of
10920 <command>check-spf</command> in <xref linkend="boolean_options"/>.
10926 <term><command>check-wildcard</command></term>
10929 See the description of
10930 <command>check-wildcard</command> in <xref linkend="boolean_options"/>.
10936 <term><command>check-integrity</command></term>
10939 See the description of
10940 <command>check-integrity</command> in <xref linkend="boolean_options"/>.
10946 <term><command>check-sibling</command></term>
10949 See the description of
10950 <command>check-sibling</command> in <xref linkend="boolean_options"/>.
10956 <term><command>zero-no-soa-ttl</command></term>
10959 See the description of
10960 <command>zero-no-soa-ttl</command> in <xref linkend="boolean_options"/>.
10966 <term><command>update-check-ksk</command></term>
10969 See the description of
10970 <command>update-check-ksk</command> in <xref linkend="boolean_options"/>.
10976 <term><command>dnssec-loadkeys-interval</command></term>
10979 See the description of
10980 <command>dnssec-loadkeys-interval</command> in <xref linkend="options"/>.
10986 <term><command>dnssec-update-mode</command></term>
10989 See the description of
10990 <command>dnssec-update-mode</command> in <xref linkend="options"/>.
10996 <term><command>dnssec-dnskey-kskonly</command></term>
10999 See the description of
11000 <command>dnssec-dnskey-kskonly</command> in <xref linkend="boolean_options"/>.
11006 <term><command>try-tcp-refresh</command></term>
11009 See the description of
11010 <command>try-tcp-refresh</command> in <xref linkend="boolean_options"/>.
11016 <term><command>database</command></term>
11019 Specify the type of database to be used for storing the
11020 zone data. The string following the <command>database</command> keyword
11021 is interpreted as a list of whitespace-delimited words.
11023 identifies the database type, and any subsequent words are
11025 as arguments to the database to be interpreted in a way
11027 to the database type.
11030 The default is <userinput>"rbt"</userinput>, BIND 9's
11032 red-black-tree database. This database does not take
11036 Other values are possible if additional database drivers
11037 have been linked into the server. Some sample drivers are
11039 with the distribution but none are linked in by default.
11045 <term><command>dialup</command></term>
11048 See the description of
11049 <command>dialup</command> in <xref linkend="boolean_options"/>.
11055 <term><command>delegation-only</command></term>
11058 The flag only applies to forward, hint and stub
11059 zones. If set to <userinput>yes</userinput>,
11060 then the zone will also be treated as if it is
11061 also a delegation-only type zone.
11064 See caveats in <xref linkend="root_delegation_only"/>.
11070 <term><command>forward</command></term>
11073 Only meaningful if the zone has a forwarders
11074 list. The <command>only</command> value causes
11076 after trying the forwarders and getting no answer, while <command>first</command> would
11077 allow a normal lookup to be tried.
11083 <term><command>forwarders</command></term>
11086 Used to override the list of global forwarders.
11087 If it is not specified in a zone of type <command>forward</command>,
11088 no forwarding is done for the zone and the global options are
11095 <term><command>ixfr-base</command></term>
11098 Was used in <acronym>BIND</acronym> 8 to
11100 of the transaction log (journal) file for dynamic update
11102 <acronym>BIND</acronym> 9 ignores the option
11103 and constructs the name of the journal
11104 file by appending "<filename>.jnl</filename>"
11112 <term><command>ixfr-tmp-file</command></term>
11115 Was an undocumented option in <acronym>BIND</acronym> 8.
11116 Ignored in <acronym>BIND</acronym> 9.
11122 <term><command>journal</command></term>
11125 Allow the default journal's filename to be overridden.
11126 The default is the zone's filename with "<filename>.jnl</filename>" appended.
11127 This is applicable to <command>master</command> and <command>slave</command> zones.
11133 <term><command>max-journal-size</command></term>
11136 See the description of
11137 <command>max-journal-size</command> in <xref linkend="server_resource_limits"/>.
11143 <term><command>max-transfer-time-in</command></term>
11146 See the description of
11147 <command>max-transfer-time-in</command> in <xref linkend="zone_transfers"/>.
11153 <term><command>max-transfer-idle-in</command></term>
11156 See the description of
11157 <command>max-transfer-idle-in</command> in <xref linkend="zone_transfers"/>.
11163 <term><command>max-transfer-time-out</command></term>
11166 See the description of
11167 <command>max-transfer-time-out</command> in <xref linkend="zone_transfers"/>.
11173 <term><command>max-transfer-idle-out</command></term>
11176 See the description of
11177 <command>max-transfer-idle-out</command> in <xref linkend="zone_transfers"/>.
11183 <term><command>notify</command></term>
11186 See the description of
11187 <command>notify</command> in <xref linkend="boolean_options"/>.
11193 <term><command>notify-delay</command></term>
11196 See the description of
11197 <command>notify-delay</command> in <xref linkend="tuning"/>.
11203 <term><command>notify-to-soa</command></term>
11206 See the description of
11207 <command>notify-to-soa</command> in
11208 <xref linkend="boolean_options"/>.
11214 <term><command>pubkey</command></term>
11217 In <acronym>BIND</acronym> 8, this option was
11218 intended for specifying
11219 a public zone key for verification of signatures in DNSSEC
11221 zones when they are loaded from disk. <acronym>BIND</acronym> 9 does not verify signatures
11222 on load and ignores the option.
11228 <term><command>zone-statistics</command></term>
11231 See the description of
11232 <command>zone-statistics</command> in
11233 <xref linkend="options"/>.
11239 <term><command>server-addresses</command></term>
11242 Only meaningful for static-stub zones.
11243 This is a list of IP addresses to which queries
11244 should be sent in recursive resolution for the
11246 A non empty list for this option will internally
11247 configure the apex NS RR with associated glue A or
11251 For example, if "example.com" is configured as a
11252 static-stub zone with 192.0.2.1 and 2001:db8::1234
11253 in a <command>server-addresses</command> option,
11254 the following RRs will be internally configured.
11256 <programlisting>example.com. NS example.com.
11257 example.com. A 192.0.2.1
11258 example.com. AAAA 2001:db8::1234</programlisting>
11260 These records are internally used to resolve
11261 names under the static-stub zone.
11262 For instance, if the server receives a query for
11263 "www.example.com" with the RD bit on, the server
11264 will initiate recursive resolution and send
11265 queries to 192.0.2.1 and/or 2001:db8::1234.
11271 <term><command>server-names</command></term>
11274 Only meaningful for static-stub zones.
11275 This is a list of domain names of nameservers that
11276 act as authoritative servers of the static-stub
11278 These names will be resolved to IP addresses when
11279 <command>named</command> needs to send queries to
11281 To make this supplemental resolution successful,
11282 these names must not be a subdomain of the origin
11283 name of static-stub zone.
11284 That is, when "example.net" is the origin of a
11285 static-stub zone, "ns.example" and
11286 "master.example.com" can be specified in the
11287 <command>server-names</command> option, but
11288 "ns.example.net" cannot, and will be rejected by
11289 the configuration parser.
11292 A non empty list for this option will internally
11293 configure the apex NS RR with the specified names.
11294 For example, if "example.com" is configured as a
11295 static-stub zone with "ns1.example.net" and
11297 in a <command>server-names</command> option,
11298 the following RRs will be internally configured.
11300 <programlisting>example.com. NS ns1.example.net.
11301 example.com. NS ns2.example.net.
11304 These records are internally used to resolve
11305 names under the static-stub zone.
11306 For instance, if the server receives a query for
11307 "www.example.com" with the RD bit on, the server
11308 initiate recursive resolution,
11309 resolve "ns1.example.net" and/or
11310 "ns2.example.net" to IP addresses, and then send
11311 queries to (one or more of) these addresses.
11317 <term><command>sig-validity-interval</command></term>
11320 See the description of
11321 <command>sig-validity-interval</command> in <xref linkend="tuning"/>.
11327 <term><command>sig-signing-nodes</command></term>
11330 See the description of
11331 <command>sig-signing-nodes</command> in <xref linkend="tuning"/>.
11337 <term><command>sig-signing-signatures</command></term>
11340 See the description of
11341 <command>sig-signing-signatures</command> in <xref linkend="tuning"/>.
11347 <term><command>sig-signing-type</command></term>
11350 See the description of
11351 <command>sig-signing-type</command> in <xref linkend="tuning"/>.
11357 <term><command>transfer-source</command></term>
11360 See the description of
11361 <command>transfer-source</command> in <xref linkend="zone_transfers"/>.
11367 <term><command>transfer-source-v6</command></term>
11370 See the description of
11371 <command>transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
11377 <term><command>alt-transfer-source</command></term>
11380 See the description of
11381 <command>alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
11387 <term><command>alt-transfer-source-v6</command></term>
11390 See the description of
11391 <command>alt-transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
11397 <term><command>use-alt-transfer-source</command></term>
11400 See the description of
11401 <command>use-alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
11408 <term><command>notify-source</command></term>
11411 See the description of
11412 <command>notify-source</command> in <xref linkend="zone_transfers"/>.
11418 <term><command>notify-source-v6</command></term>
11421 See the description of
11422 <command>notify-source-v6</command> in <xref linkend="zone_transfers"/>.
11428 <term><command>min-refresh-time</command></term>
11429 <term><command>max-refresh-time</command></term>
11430 <term><command>min-retry-time</command></term>
11431 <term><command>max-retry-time</command></term>
11434 See the description in <xref linkend="tuning"/>.
11440 <term><command>ixfr-from-differences</command></term>
11443 See the description of
11444 <command>ixfr-from-differences</command> in <xref linkend="boolean_options"/>.
11445 (Note that the <command>ixfr-from-differences</command>
11446 <userinput>master</userinput> and
11447 <userinput>slave</userinput> choices are not
11448 available at the zone level.)
11454 <term><command>key-directory</command></term>
11457 See the description of
11458 <command>key-directory</command> in <xref linkend="options"/>.
11464 <term><command>auto-dnssec</command></term>
11467 See the description of
11468 <command>auto-dnssec</command> in
11469 <xref linkend="options"/>.
11475 <term><command>serial-update-method</command></term>
11478 See the description of
11479 <command>serial-update-method</command> in
11480 <xref linkend="options"/>.
11486 <term><command>inline-signing</command></term>
11489 If <literal>yes</literal>, this enables
11490 "bump in the wire" signing of a zone, where a
11491 unsigned zone is transferred in or loaded from
11492 disk and a signed version of the zone is served,
11493 with possibly, a different serial number. This
11494 behaviour is disabled by default.
11500 <term><command>multi-master</command></term>
11503 See the description of <command>multi-master</command> in
11504 <xref linkend="boolean_options"/>.
11510 <term><command>masterfile-format</command></term>
11513 See the description of <command>masterfile-format</command>
11514 in <xref linkend="tuning"/>.
11520 <term><command>dnssec-secure-to-insecure</command></term>
11523 See the description of
11524 <command>dnssec-secure-to-insecure</command> in <xref linkend="boolean_options"/>.
11532 <section xml:id="dynamic_update_policies"><info><title>Dynamic Update Policies</title></info>
11534 <para><acronym>BIND</acronym> 9 supports two alternative
11535 methods of granting clients the right to perform
11536 dynamic updates to a zone, configured by the
11537 <command>allow-update</command> and
11538 <command>update-policy</command> option, respectively.
11541 The <command>allow-update</command> clause works the
11542 same way as in previous versions of <acronym>BIND</acronym>.
11543 It grants given clients the permission to update any
11544 record of any name in the zone.
11547 The <command>update-policy</command> clause
11548 allows more fine-grained control over what updates are
11549 allowed. A set of rules is specified, where each rule
11550 either grants or denies permissions for one or more
11551 names to be updated by one or more identities. If
11552 the dynamic update request message is signed (that is,
11553 it includes either a TSIG or SIG(0) record), the
11554 identity of the signer can be determined.
11557 Rules are specified in the <command>update-policy</command>
11558 zone option, and are only meaningful for master zones.
11559 When the <command>update-policy</command> statement
11560 is present, it is a configuration error for the
11561 <command>allow-update</command> statement to be
11562 present. The <command>update-policy</command> statement
11563 only examines the signer of a message; the source
11564 address is not relevant.
11567 There is a pre-defined <command>update-policy</command>
11568 rule which can be switched on with the command
11569 <command>update-policy local;</command>.
11570 Switching on this rule in a zone causes
11571 <command>named</command> to generate a TSIG session
11572 key and place it in a file, and to allow that key
11573 to update the zone. (By default, the file is
11574 <filename>/var/run/named/session.key</filename>, the key
11575 name is "local-ddns" and the key algorithm is HMAC-SHA256,
11576 but these values are configurable with the
11577 <command>session-keyfile</command>,
11578 <command>session-keyname</command> and
11579 <command>session-keyalg</command> options, respectively).
11582 A client running on the local system, and with appropriate
11583 permissions, may read that file and use the key to sign update
11584 requests. The zone's update policy will be set to allow that
11585 key to change any record within the zone. Assuming the
11586 key name is "local-ddns", this policy is equivalent to:
11589 <programlisting>update-policy { grant local-ddns zonesub any; };
11593 The command <command>nsupdate -l</command> sends update
11594 requests to localhost, and signs them using the session key.
11598 Other rule definitions look like this:
11602 ( <command>grant</command> | <command>deny</command> ) <replaceable>identity</replaceable> <replaceable>nametype</replaceable> <optional> <replaceable>name</replaceable> </optional> <optional> <replaceable>types</replaceable> </optional>
11606 Each rule grants or denies privileges. Once a message has
11607 successfully matched a rule, the operation is immediately
11608 granted or denied and no further rules are examined. A rule
11609 is matched when the signer matches the identity field, the
11610 name matches the name field in accordance with the nametype
11611 field, and the type matches the types specified in the type
11615 No signer is required for <replaceable>tcp-self</replaceable>
11616 or <replaceable>6to4-self</replaceable> however the standard
11617 reverse mapping / prefix conversion must match the identity
11621 The identity field specifies a name or a wildcard
11622 name. Normally, this is the name of the TSIG or
11623 SIG(0) key used to sign the update request. When a
11624 TKEY exchange has been used to create a shared secret,
11625 the identity of the shared secret is the same as the
11626 identity of the key used to authenticate the TKEY
11627 exchange. TKEY is also the negotiation method used
11628 by GSS-TSIG, which establishes an identity that is
11629 the Kerberos principal of the client, such as
11630 <userinput>"user@host.domain"</userinput>. When the
11631 <replaceable>identity</replaceable> field specifies
11632 a wildcard name, it is subject to DNS wildcard
11633 expansion, so the rule will apply to multiple identities.
11634 The <replaceable>identity</replaceable> field must
11635 contain a fully-qualified domain name.
11638 For nametypes <varname>krb5-self</varname>,
11639 <varname>ms-self</varname>, <varname>krb5-subdomain</varname>,
11640 and <varname>ms-subdomain</varname> the
11641 <replaceable>identity</replaceable> field specifies
11642 the Windows or Kerberos realm of the machine belongs to.
11645 The <replaceable>nametype</replaceable> field has 13
11647 <varname>name</varname>, <varname>subdomain</varname>,
11648 <varname>wildcard</varname>, <varname>self</varname>,
11649 <varname>selfsub</varname>, <varname>selfwild</varname>,
11650 <varname>krb5-self</varname>, <varname>ms-self</varname>,
11651 <varname>krb5-subdomain</varname>,
11652 <varname>ms-subdomain</varname>,
11653 <varname>tcp-self</varname>, <varname>6to4-self</varname>,
11654 <varname>zonesub</varname>, and <varname>external</varname>.
11657 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11658 <colspec colname="1" colnum="1" colsep="0" colwidth="0.819in"/>
11659 <colspec colname="2" colnum="2" colsep="0" colwidth="3.681in"/>
11662 <entry colname="1">
11664 <varname>name</varname>
11666 </entry> <entry colname="2">
11668 Exact-match semantics. This rule matches
11669 when the name being updated is identical
11670 to the contents of the
11671 <replaceable>name</replaceable> field.
11676 <entry colname="1">
11678 <varname>subdomain</varname>
11680 </entry> <entry colname="2">
11682 This rule matches when the name being updated
11683 is a subdomain of, or identical to, the
11684 contents of the <replaceable>name</replaceable>
11690 <entry colname="1">
11692 <varname>zonesub</varname>
11694 </entry> <entry colname="2">
11696 This rule is similar to subdomain, except that
11697 it matches when the name being updated is a
11698 subdomain of the zone in which the
11699 <command>update-policy</command> statement
11700 appears. This obviates the need to type the zone
11701 name twice, and enables the use of a standard
11702 <command>update-policy</command> statement in
11703 multiple zones without modification.
11706 When this rule is used, the
11707 <replaceable>name</replaceable> field is omitted.
11712 <entry colname="1">
11714 <varname>wildcard</varname>
11716 </entry> <entry colname="2">
11718 The <replaceable>name</replaceable> field
11719 is subject to DNS wildcard expansion, and
11720 this rule matches when the name being updated
11721 is a valid expansion of the wildcard.
11726 <entry colname="1">
11728 <varname>self</varname>
11731 <entry colname="2">
11733 This rule matches when the name being updated
11734 matches the contents of the
11735 <replaceable>identity</replaceable> field.
11736 The <replaceable>name</replaceable> field
11737 is ignored, but should be the same as the
11738 <replaceable>identity</replaceable> field.
11739 The <varname>self</varname> nametype is
11740 most useful when allowing using one key per
11741 name to update, where the key has the same
11742 name as the name to be updated. The
11743 <replaceable>identity</replaceable> would
11744 be specified as <constant>*</constant> (an asterisk) in
11750 <entry colname="1">
11752 <varname>selfsub</varname>
11754 </entry> <entry colname="2">
11756 This rule is similar to <varname>self</varname>
11757 except that subdomains of <varname>self</varname>
11758 can also be updated.
11763 <entry colname="1">
11765 <varname>selfwild</varname>
11767 </entry> <entry colname="2">
11769 This rule is similar to <varname>self</varname>
11770 except that only subdomains of
11771 <varname>self</varname> can be updated.
11776 <entry colname="1">
11778 <varname>ms-self</varname>
11780 </entry> <entry colname="2">
11782 This rule takes a Windows machine principal
11783 (machine$@REALM) for machine in REALM and
11784 and converts it machine.realm allowing the machine
11785 to update machine.realm. The REALM to be matched
11786 is specified in the <replaceable>identity</replaceable>
11792 <entry colname="1">
11794 <varname>ms-subdomain</varname>
11796 </entry> <entry colname="2">
11798 This rule takes a Windows machine principal
11799 (machine$@REALM) for machine in REALM and
11800 converts it to machine.realm allowing the machine
11801 to update subdomains of machine.realm. The REALM
11802 to be matched is specified in the
11803 <replaceable>identity</replaceable> field.
11808 <entry colname="1">
11810 <varname>krb5-self</varname>
11812 </entry> <entry colname="2">
11814 This rule takes a Kerberos machine principal
11815 (host/machine@REALM) for machine in REALM and
11816 and converts it machine.realm allowing the machine
11817 to update machine.realm. The REALM to be matched
11818 is specified in the <replaceable>identity</replaceable>
11824 <entry colname="1">
11826 <varname>krb5-subdomain</varname>
11828 </entry> <entry colname="2">
11830 This rule takes a Kerberos machine principal
11831 (host/machine@REALM) for machine in REALM and
11832 converts it to machine.realm allowing the machine
11833 to update subdomains of machine.realm. The REALM
11834 to be matched is specified in the
11835 <replaceable>identity</replaceable> field.
11840 <entry colname="1">
11842 <varname>tcp-self</varname>
11844 </entry> <entry colname="2">
11846 Allow updates that have been sent via TCP and
11847 for which the standard mapping from the initiating
11848 IP address into the IN-ADDR.ARPA and IP6.ARPA
11849 namespaces match the name to be updated.
11852 It is theoretically possible to spoof these TCP
11858 <entry colname="1">
11860 <varname>6to4-self</varname>
11862 </entry> <entry colname="2">
11864 Allow the 6to4 prefix to be update by any TCP
11865 connection from the 6to4 network or from the
11866 corresponding IPv4 address. This is intended
11867 to allow NS or DNAME RRsets to be added to the
11871 It is theoretically possible to spoof these TCP
11877 <entry colname="1">
11879 <varname>external</varname>
11881 </entry> <entry colname="2">
11883 This rule allows <command>named</command>
11884 to defer the decision of whether to allow a
11885 given update to an external daemon.
11888 The method of communicating with the daemon is
11889 specified in the <replaceable>identity</replaceable>
11890 field, the format of which is
11891 "<constant>local:</constant><replaceable>path</replaceable>",
11892 where <replaceable>path</replaceable> is the location
11893 of a UNIX-domain socket. (Currently, "local" is the
11894 only supported mechanism.)
11897 Requests to the external daemon are sent over the
11898 UNIX-domain socket as datagrams with the following
11902 Protocol version number (4 bytes, network byte order, currently 1)
11903 Request length (4 bytes, network byte order)
11904 Signer (null-terminated string)
11905 Name (null-terminated string)
11906 TCP source address (null-terminated string)
11907 Rdata type (null-terminated string)
11908 Key (null-terminated string)
11909 TKEY token length (4 bytes, network byte order)
11910 TKEY token (remainder of packet)</programlisting>
11912 The daemon replies with a four-byte value in
11913 network byte order, containing either 0 or 1; 0
11914 indicates that the specified update is not
11915 permitted, and 1 indicates that it is.
11924 In all cases, the <replaceable>name</replaceable>
11925 field must specify a fully-qualified domain name.
11929 If no types are explicitly specified, this rule matches
11930 all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
11931 may be specified by name, including "ANY" (ANY matches
11932 all types except NSEC and NSEC3, which can never be
11933 updated). Note that when an attempt is made to delete
11934 all records associated with a name, the rules are
11935 checked for each existing record type.
11940 <section xml:id="zone_file"><info><title>Zone File</title></info>
11942 <section xml:id="types_of_resource_records_and_when_to_use_them"><info><title>Types of Resource Records and When to Use Them</title></info>
11945 This section, largely borrowed from RFC 1034, describes the
11946 concept of a Resource Record (RR) and explains when each is used.
11947 Since the publication of RFC 1034, several new RRs have been
11949 and implemented in the DNS. These are also included.
11951 <section><info><title>Resource Records</title></info>
11954 A domain name identifies a node. Each node has a set of
11955 resource information, which may be empty. The set of resource
11956 information associated with a particular name is composed of
11957 separate RRs. The order of RRs in a set is not significant and
11958 need not be preserved by name servers, resolvers, or other
11959 parts of the DNS. However, sorting of multiple RRs is
11960 permitted for optimization purposes, for example, to specify
11961 that a particular nearby server be tried first. See <xref linkend="the_sortlist_statement"/> and <xref linkend="rrset_ordering"/>.
11965 The components of a Resource Record are:
11967 <informaltable colsep="0" rowsep="0">
11968 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11969 <colspec colname="1" colnum="1" colsep="0" colwidth="1.000in"/>
11970 <colspec colname="2" colnum="2" colsep="0" colwidth="3.500in"/>
11973 <entry colname="1">
11978 <entry colname="2">
11980 The domain name where the RR is found.
11985 <entry colname="1">
11990 <entry colname="2">
11992 An encoded 16-bit value that specifies
11993 the type of the resource record.
11998 <entry colname="1">
12003 <entry colname="2">
12005 The time-to-live of the RR. This field
12006 is a 32-bit integer in units of seconds, and is
12008 resolvers when they cache RRs. The TTL describes how
12010 be cached before it should be discarded.
12015 <entry colname="1">
12020 <entry colname="2">
12022 An encoded 16-bit value that identifies
12023 a protocol family or instance of a protocol.
12028 <entry colname="1">
12033 <entry colname="2">
12035 The resource data. The format of the
12036 data is type (and sometimes class) specific.
12044 The following are <emphasis>types</emphasis> of valid RRs:
12046 <informaltable colsep="0" rowsep="0">
12047 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12048 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
12049 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
12052 <entry colname="1">
12057 <entry colname="2">
12059 A host address. In the IN class, this is a
12060 32-bit IP address. Described in RFC 1035.
12065 <entry colname="1">
12070 <entry colname="2">
12072 IPv6 address. Described in RFC 1886.
12077 <entry colname="1">
12082 <entry colname="2">
12084 IPv6 address. This can be a partial
12085 address (a suffix) and an indirection to the name
12086 where the rest of the
12087 address (the prefix) can be found. Experimental.
12088 Described in RFC 2874.
12093 <entry colname="1">
12098 <entry colname="2">
12100 Location of AFS database servers.
12101 Experimental. Described in RFC 1183.
12106 <entry colname="1">
12111 <entry colname="2">
12113 Address prefix list. Experimental.
12114 Described in RFC 3123.
12119 <entry colname="1">
12124 <entry colname="2">
12131 <entry colname="1">
12136 <entry colname="2">
12138 Application Visibility and Control record.
12143 <entry colname="1">
12148 <entry colname="2">
12150 Identifies which Certificate Authorities can issue
12151 certificates for this domain and what rules they
12152 need to follow when doing so. Defined in RFC 6844.
12157 <entry colname="1">
12162 <entry colname="2">
12164 Identifies which DNSKEY records should be published
12165 as DS records in the parent zone.
12170 <entry colname="1">
12175 <entry colname="2">
12177 Contains the set of DS records that should be published
12178 by the parent zone.
12183 <entry colname="1">
12188 <entry colname="2">
12190 Holds a digital certificate.
12191 Described in RFC 2538.
12196 <entry colname="1">
12201 <entry colname="2">
12203 Identifies the canonical name of an alias.
12204 Described in RFC 1035.
12209 <entry colname="1">
12214 <entry colname="2">
12216 Child-to-Parent Synchronization in DNS as described
12222 <entry colname="1">
12227 <entry colname="2">
12229 Is used for identifying which DHCP client is
12230 associated with this name. Described in RFC 4701.
12235 <entry colname="1">
12240 <entry colname="2">
12242 A DNS Look-aside Validation record which contains
12243 the records that are used as trust anchors for
12244 zones in a DLV namespace. Described in RFC 4431.
12249 <entry colname="1">
12254 <entry colname="2">
12256 Replaces the domain name specified with
12257 another name to be looked up, effectively aliasing an
12259 subtree of the domain name space rather than a single
12261 as in the case of the CNAME RR.
12262 Described in RFC 2672.
12267 <entry colname="1">
12272 <entry colname="2">
12274 Stores a public key associated with a signed
12275 DNS zone. Described in RFC 4034.
12280 <entry colname="1">
12285 <entry colname="2">
12287 Stores the hash of a public key associated with a
12288 signed DNS zone. Described in RFC 4034.
12293 <entry colname="1">
12298 <entry colname="2">
12300 End Point Identifier.
12305 <entry colname="1">
12310 <entry colname="2">
12312 A 48-bit EUI address. Described in RFC 7043.
12317 <entry colname="1">
12322 <entry colname="2">
12324 A 64-bit EUI address. Described in RFC 7043.
12329 <entry colname="1">
12334 <entry colname="2">
12341 <entry colname="1">
12346 <entry colname="2">
12348 Specifies the global position. Superseded by LOC.
12353 <entry colname="1">
12358 <entry colname="2">
12360 Identifies the CPU and OS used by a host.
12361 Described in RFC 1035.
12366 <entry colname="1">
12371 <entry colname="2">
12373 Host Identity Protocol Address.
12374 Described in RFC 5205.
12379 <entry colname="1">
12384 <entry colname="2">
12386 Provides a method for storing IPsec keying material in
12387 DNS. Described in RFC 4025.
12392 <entry colname="1">
12397 <entry colname="2">
12399 Representation of ISDN addresses.
12400 Experimental. Described in RFC 1183.
12405 <entry colname="1">
12410 <entry colname="2">
12412 Stores a public key associated with a
12413 DNS name. Used in original DNSSEC; replaced
12414 by DNSKEY in DNSSECbis, but still used with
12415 SIG(0). Described in RFCs 2535 and 2931.
12420 <entry colname="1">
12425 <entry colname="2">
12427 Identifies a key exchanger for this
12428 DNS name. Described in RFC 2230.
12433 <entry colname="1">
12438 <entry colname="2">
12440 Holds 32-bit Locator values for
12441 Identifier-Locator Network Protocol. Described
12447 <entry colname="1">
12452 <entry colname="2">
12454 Holds 64-bit Locator values for
12455 Identifier-Locator Network Protocol. Described
12461 <entry colname="1">
12466 <entry colname="2">
12468 For storing GPS info. Described in RFC 1876.
12474 <entry colname="1">
12479 <entry colname="2">
12481 Identifier-Locator Network Protocol.
12482 Described in RFC 6742.
12487 <entry colname="1">
12492 <entry colname="2">
12494 Mail Box. Historical.
12499 <entry colname="1">
12504 <entry colname="2">
12506 Mail Destination. Historical.
12511 <entry colname="1">
12516 <entry colname="2">
12518 Mail Forwarder. Historical.
12523 <entry colname="1">
12528 <entry colname="2">
12530 Mail Group. Historical.
12535 <entry colname="1">
12540 <entry colname="2">
12547 <entry colname="1">
12552 <entry colname="2">
12554 Mail Rename. Historical.
12559 <entry colname="1">
12564 <entry colname="2">
12566 Identifies a mail exchange for the domain with
12567 a 16-bit preference value (lower is better)
12568 followed by the host name of the mail exchange.
12569 Described in RFC 974, RFC 1035.
12574 <entry colname="1">
12579 <entry colname="2">
12581 Name authority pointer. Described in RFC 2915.
12586 <entry colname="1">
12591 <entry colname="2">
12593 Holds values for Node Identifiers in
12594 Identifier-Locator Network Protocol. Described
12600 <entry colname="1">
12605 <entry colname="2">
12607 Contains zone status information.
12612 <entry colname="1">
12617 <entry colname="2">
12624 <entry colname="1">
12629 <entry colname="2">
12631 A network service access point.
12632 Described in RFC 1706.
12637 <entry colname="1">
12642 <entry colname="2">
12649 <entry colname="1">
12654 <entry colname="2">
12656 The authoritative name server for the
12657 domain. Described in RFC 1035.
12662 <entry colname="1">
12667 <entry colname="2">
12669 Used in DNSSECbis to securely indicate that
12670 RRs with an owner name in a certain name interval do
12672 a zone and indicate what RR types are present for an
12674 Described in RFC 4034.
12679 <entry colname="1">
12684 <entry colname="2">
12686 Used in DNSSECbis to securely indicate that
12687 RRs with an owner name in a certain name
12688 interval do not exist in a zone and indicate
12689 what RR types are present for an existing
12690 name. NSEC3 differs from NSEC in that it
12691 prevents zone enumeration but is more
12692 computationally expensive on both the server
12693 and the client than NSEC. Described in RFC
12699 <entry colname="1">
12704 <entry colname="2">
12706 Used in DNSSECbis to tell the authoritative
12707 server which NSEC3 chains are available to use.
12708 Described in RFC 5155.
12713 <entry colname="1">
12718 <entry colname="2">
12720 This is an opaque container.
12725 <entry colname="1">
12730 <entry colname="2">
12732 Used in DNSSEC to securely indicate that
12733 RRs with an owner name in a certain name interval do
12735 a zone and indicate what RR types are present for an
12737 Used in original DNSSEC; replaced by NSEC in
12739 Described in RFC 2535.
12744 <entry colname="1">
12749 <entry colname="2">
12751 Used to hold an OPENPGPKEY.
12756 <entry colname="1">
12761 <entry colname="2">
12763 A pointer to another part of the domain
12764 name space. Described in RFC 1035.
12769 <entry colname="1">
12774 <entry colname="2">
12776 Provides mappings between RFC 822 and X.400
12777 addresses. Described in RFC 2163.
12782 <entry colname="1">
12787 <entry colname="2">
12794 <entry colname="1">
12799 <entry colname="2">
12801 Information on persons responsible
12802 for the domain. Experimental. Described in RFC 1183.
12807 <entry colname="1">
12812 <entry colname="2">
12814 Contains DNSSECbis signature data. Described
12820 <entry colname="1">
12825 <entry colname="2">
12827 Route-through binding for hosts that
12828 do not have their own direct wide area network
12830 Experimental. Described in RFC 1183.
12835 <entry colname="1">
12840 <entry colname="2">
12842 Contains DNSSEC signature data. Used in
12843 original DNSSEC; replaced by RRSIG in
12844 DNSSECbis, but still used for SIG(0).
12845 Described in RFCs 2535 and 2931.
12850 <entry colname="1">
12855 <entry colname="2">
12857 The kitchen sink record.
12862 <entry colname="1">
12867 <entry colname="2">
12869 The S/MIME Security Certificate Association.
12874 <entry colname="1">
12879 <entry colname="2">
12881 Identifies the start of a zone of authority.
12882 Described in RFC 1035.
12887 <entry colname="1">
12892 <entry colname="2">
12894 Contains the Sender Policy Framework information
12895 for a given email domain. Described in RFC 4408.
12900 <entry colname="1">
12905 <entry colname="2">
12907 Information about well known network
12908 services (replaces WKS). Described in RFC 2782.
12913 <entry colname="1">
12918 <entry colname="2">
12920 Provides a way to securely publish a secure shell key's
12921 fingerprint. Described in RFC 4255.
12926 <entry colname="1">
12931 <entry colname="2">
12933 Trust Anchor. Experimental.
12938 <entry colname="1">
12943 <entry colname="2">
12945 Trust Anchor Link. Experimental.
12950 <entry colname="1">
12955 <entry colname="2">
12957 Transport Layer Security Certificate Association.
12958 Described in RFC 6698.
12963 <entry colname="1">
12968 <entry colname="2">
12970 Text records. Described in RFC 1035.
12975 <entry colname="1">
12980 <entry colname="2">
12987 <entry colname="1">
12992 <entry colname="2">
12999 <entry colname="1">
13004 <entry colname="2">
13006 Reserved. Historical.
13011 <entry colname="1">
13016 <entry colname="2">
13018 Holds a URI. Described in RFC 7553.
13023 <entry colname="1">
13028 <entry colname="2">
13030 Information about which well known
13031 network services, such as SMTP, that a domain
13032 supports. Historical.
13037 <entry colname="1">
13042 <entry colname="2">
13044 Representation of X.25 network addresses.
13045 Experimental. Described in RFC 1183.
13053 The following <emphasis>classes</emphasis> of resource records
13054 are currently valid in the DNS:
13056 <informaltable colsep="0" rowsep="0"><tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13057 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
13058 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
13062 <entry colname="1">
13067 <entry colname="2">
13075 <entry colname="1">
13080 <entry colname="2">
13082 Chaosnet, a LAN protocol created at MIT in the
13084 Rarely used for its historical purpose, but reused for
13086 built-in server information zones, e.g.,
13087 <literal>version.bind</literal>.
13093 <entry colname="1">
13098 <entry colname="2">
13100 Hesiod, an information service
13101 developed by MIT's Project Athena. It is used to share
13103 about various systems databases, such as users,
13115 The owner name is often implicit, rather than forming an
13117 part of the RR. For example, many name servers internally form
13119 or hash structures for the name space, and chain RRs off nodes.
13120 The remaining RR parts are the fixed header (type, class, TTL)
13121 which is consistent for all RRs, and a variable part (RDATA)
13123 fits the needs of the resource being described.
13126 The meaning of the TTL field is a time limit on how long an
13127 RR can be kept in a cache. This limit does not apply to
13129 data in zones; it is also timed out, but by the refreshing
13131 for the zone. The TTL is assigned by the administrator for the
13132 zone where the data originates. While short TTLs can be used to
13133 minimize caching, and a zero TTL prohibits caching, the
13135 of Internet performance suggest that these times should be on
13137 order of days for the typical host. If a change can be
13139 the TTL can be reduced prior to the change to minimize
13141 during the change, and then increased back to its former value
13146 The data in the RDATA section of RRs is carried as a combination
13147 of binary strings and domain names. The domain names are
13149 used as "pointers" to other data in the DNS.
13152 <section xml:id="rr_text"><info><title>Textual expression of RRs</title></info>
13155 RRs are represented in binary form in the packets of the DNS
13156 protocol, and are usually represented in highly encoded form
13158 stored in a name server or resolver. In the examples provided
13160 RFC 1034, a style similar to that used in master files was
13162 in order to show the contents of RRs. In this format, most RRs
13163 are shown on a single line, although continuation lines are
13168 The start of the line gives the owner of the RR. If a line
13169 begins with a blank, then the owner is assumed to be the same as
13170 that of the previous RR. Blank lines are often included for
13174 Following the owner, we list the TTL, type, and class of the
13175 RR. Class and type use the mnemonics defined above, and TTL is
13176 an integer before the type field. In order to avoid ambiguity
13178 parsing, type and class mnemonics are disjoint, TTLs are
13180 and the type mnemonic is always last. The IN class and TTL
13182 are often omitted from examples in the interests of clarity.
13185 The resource data or RDATA section of the RR are given using
13186 knowledge of the typical representation for the data.
13189 For example, we might show the RRs carried in a message as:
13191 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13192 <colspec colname="1" colnum="1" colsep="0" colwidth="1.381in"/>
13193 <colspec colname="2" colnum="2" colsep="0" colwidth="1.020in"/>
13194 <colspec colname="3" colnum="3" colsep="0" colwidth="2.099in"/>
13197 <entry colname="1">
13199 <literal>ISI.EDU.</literal>
13202 <entry colname="2">
13204 <literal>MX</literal>
13207 <entry colname="3">
13209 <literal>10 VENERA.ISI.EDU.</literal>
13214 <entry colname="1">
13217 <entry colname="2">
13219 <literal>MX</literal>
13222 <entry colname="3">
13224 <literal>10 VAXA.ISI.EDU</literal>
13229 <entry colname="1">
13231 <literal>VENERA.ISI.EDU</literal>
13234 <entry colname="2">
13236 <literal>A</literal>
13239 <entry colname="3">
13241 <literal>128.9.0.32</literal>
13246 <entry colname="1">
13249 <entry colname="2">
13251 <literal>A</literal>
13254 <entry colname="3">
13256 <literal>10.1.0.52</literal>
13261 <entry colname="1">
13263 <literal>VAXA.ISI.EDU</literal>
13266 <entry colname="2">
13268 <literal>A</literal>
13271 <entry colname="3">
13273 <literal>10.2.0.27</literal>
13278 <entry colname="1">
13281 <entry colname="2">
13283 <literal>A</literal>
13286 <entry colname="3">
13288 <literal>128.9.0.33</literal>
13296 The MX RRs have an RDATA section which consists of a 16-bit
13297 number followed by a domain name. The address RRs use a
13299 IP address format to contain a 32-bit internet address.
13302 The above example shows six RRs, with two RRs at each of three
13306 Similarly we might see:
13308 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13309 <colspec colname="1" colnum="1" colsep="0" colwidth="1.491in"/>
13310 <colspec colname="2" colnum="2" colsep="0" colwidth="1.067in"/>
13311 <colspec colname="3" colnum="3" colsep="0" colwidth="2.067in"/>
13314 <entry colname="1">
13316 <literal>XX.LCS.MIT.EDU.</literal>
13319 <entry colname="2">
13321 <literal>IN A</literal>
13324 <entry colname="3">
13326 <literal>10.0.0.44</literal>
13331 <entry colname="1"/>
13332 <entry colname="2">
13334 <literal>CH A</literal>
13337 <entry colname="3">
13339 <literal>MIT.EDU. 2420</literal>
13347 This example shows two addresses for
13348 <literal>XX.LCS.MIT.EDU</literal>, each of a different class.
13353 <section xml:id="mx_records"><info><title>Discussion of MX Records</title></info>
13356 As described above, domain servers store information as a
13357 series of resource records, each of which contains a particular
13358 piece of information about a given domain name (which is usually,
13359 but not always, a host). The simplest way to think of a RR is as
13360 a typed pair of data, a domain name matched with a relevant datum,
13361 and stored with some additional type information to help systems
13362 determine when the RR is relevant.
13366 MX records are used to control delivery of email. The data
13367 specified in the record is a priority and a domain name. The
13369 controls the order in which email delivery is attempted, with the
13370 lowest number first. If two priorities are the same, a server is
13371 chosen randomly. If no servers at a given priority are responding,
13372 the mail transport agent will fall back to the next largest
13374 Priority numbers do not have any absolute meaning — they are
13376 only respective to other MX records for that domain name. The
13378 name given is the machine to which the mail will be delivered.
13379 It <emphasis>must</emphasis> have an associated address record
13380 (A or AAAA) — CNAME is not sufficient.
13383 For a given domain, if there is both a CNAME record and an
13384 MX record, the MX record is in error, and will be ignored.
13386 the mail will be delivered to the server specified in the MX
13388 pointed to by the CNAME.
13391 <informaltable colsep="0" rowsep="0">
13392 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13393 <colspec colname="1" colnum="1" colsep="0" colwidth="1.708in"/>
13394 <colspec colname="2" colnum="2" colsep="0" colwidth="0.444in"/>
13395 <colspec colname="3" colnum="3" colsep="0" colwidth="0.444in"/>
13396 <colspec colname="4" colnum="4" colsep="0" colwidth="0.976in"/>
13397 <colspec colname="5" colnum="5" colsep="0" colwidth="1.553in"/>
13400 <entry colname="1">
13402 <literal>example.com.</literal>
13405 <entry colname="2">
13407 <literal>IN</literal>
13410 <entry colname="3">
13412 <literal>MX</literal>
13415 <entry colname="4">
13417 <literal>10</literal>
13420 <entry colname="5">
13422 <literal>mail.example.com.</literal>
13427 <entry colname="1">
13430 <entry colname="2">
13432 <literal>IN</literal>
13435 <entry colname="3">
13437 <literal>MX</literal>
13440 <entry colname="4">
13442 <literal>10</literal>
13445 <entry colname="5">
13447 <literal>mail2.example.com.</literal>
13452 <entry colname="1">
13455 <entry colname="2">
13457 <literal>IN</literal>
13460 <entry colname="3">
13462 <literal>MX</literal>
13465 <entry colname="4">
13467 <literal>20</literal>
13470 <entry colname="5">
13472 <literal>mail.backup.org.</literal>
13477 <entry colname="1">
13479 <literal>mail.example.com.</literal>
13482 <entry colname="2">
13484 <literal>IN</literal>
13487 <entry colname="3">
13489 <literal>A</literal>
13492 <entry colname="4">
13494 <literal>10.0.0.1</literal>
13497 <entry colname="5">
13502 <entry colname="1">
13504 <literal>mail2.example.com.</literal>
13507 <entry colname="2">
13509 <literal>IN</literal>
13512 <entry colname="3">
13514 <literal>A</literal>
13517 <entry colname="4">
13519 <literal>10.0.0.2</literal>
13522 <entry colname="5">
13528 </informaltable><para>
13529 Mail delivery will be attempted to <literal>mail.example.com</literal> and
13530 <literal>mail2.example.com</literal> (in
13531 any order), and if neither of those succeed, delivery to <literal>mail.backup.org</literal> will
13535 <section xml:id="Setting_TTLs"><info><title>Setting TTLs</title></info>
13538 The time-to-live of the RR field is a 32-bit integer represented
13539 in units of seconds, and is primarily used by resolvers when they
13540 cache RRs. The TTL describes how long a RR can be cached before it
13541 should be discarded. The following three types of TTL are
13543 used in a zone file.
13545 <informaltable colsep="0" rowsep="0">
13546 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13547 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
13548 <colspec colname="2" colnum="2" colsep="0" colwidth="4.375in"/>
13551 <entry colname="1">
13556 <entry colname="2">
13558 The last field in the SOA is the negative
13559 caching TTL. This controls how long other servers will
13560 cache no-such-domain
13561 (NXDOMAIN) responses from you.
13564 The maximum time for
13565 negative caching is 3 hours (3h).
13570 <entry colname="1">
13575 <entry colname="2">
13577 The $TTL directive at the top of the
13578 zone file (before the SOA) gives a default TTL for every
13580 a specific TTL set.
13585 <entry colname="1">
13590 <entry colname="2">
13592 Each RR can have a TTL as the second
13593 field in the RR, which will control how long other
13594 servers can cache it.
13602 All of these TTLs default to units of seconds, though units
13603 can be explicitly specified, for example, <literal>1h30m</literal>.
13606 <section xml:id="ipv4_reverse"><info><title>Inverse Mapping in IPv4</title></info>
13609 Reverse name resolution (that is, translation from IP address
13610 to name) is achieved by means of the <emphasis>in-addr.arpa</emphasis> domain
13611 and PTR records. Entries in the in-addr.arpa domain are made in
13612 least-to-most significant order, read left to right. This is the
13613 opposite order to the way IP addresses are usually written. Thus,
13614 a machine with an IP address of 10.1.2.3 would have a
13616 in-addr.arpa name of
13617 3.2.1.10.in-addr.arpa. This name should have a PTR resource record
13618 whose data field is the name of the machine or, optionally,
13620 PTR records if the machine has more than one name. For example,
13621 in the <optional>example.com</optional> domain:
13623 <informaltable colsep="0" rowsep="0">
13624 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13625 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
13626 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
13629 <entry colname="1">
13631 <literal>$ORIGIN</literal>
13634 <entry colname="2">
13636 <literal>2.1.10.in-addr.arpa</literal>
13641 <entry colname="1">
13643 <literal>3</literal>
13646 <entry colname="2">
13648 <literal>IN PTR foo.example.com.</literal>
13657 The <command>$ORIGIN</command> lines in the examples
13658 are for providing context to the examples only — they do not
13660 appear in the actual usage. They are only used here to indicate
13661 that the example is relative to the listed origin.
13665 <section xml:id="zone_directives"><info><title>Other Zone File Directives</title></info>
13668 The Master File Format was initially defined in RFC 1035 and
13669 has subsequently been extended. While the Master File Format
13671 is class independent all records in a Master File must be of the
13676 Master File Directives include <command>$ORIGIN</command>, <command>$INCLUDE</command>,
13677 and <command>$TTL.</command>
13679 <section xml:id="atsign"><info><title>The <command>@</command> (at-sign)</title></info>
13682 When used in the label (or name) field, the asperand or
13683 at-sign (@) symbol represents the current origin.
13684 At the start of the zone file, it is the
13685 <<varname>zone_name</varname>> (followed by
13689 <section xml:id="origin_directive"><info><title>The <command>$ORIGIN</command> Directive</title></info>
13692 Syntax: <command>$ORIGIN</command>
13693 <replaceable>domain-name</replaceable>
13694 <optional><replaceable>comment</replaceable></optional>
13696 <para><command>$ORIGIN</command>
13697 sets the domain name that will be appended to any
13698 unqualified records. When a zone is first read in there
13699 is an implicit <command>$ORIGIN</command>
13700 <<varname>zone_name</varname>><command>.</command>
13701 (followed by trailing dot).
13702 The current <command>$ORIGIN</command> is appended to
13703 the domain specified in the <command>$ORIGIN</command>
13704 argument if it is not absolute.
13708 $ORIGIN example.com.
13709 WWW CNAME MAIN-SERVER
13717 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
13721 <section xml:id="include_directive"><info><title>The <command>$INCLUDE</command> Directive</title></info>
13724 Syntax: <command>$INCLUDE</command>
13725 <replaceable>filename</replaceable>
13727 <replaceable>origin</replaceable> </optional>
13728 <optional> <replaceable>comment</replaceable> </optional>
13731 Read and process the file <filename>filename</filename> as
13732 if it were included into the file at this point. If <command>origin</command> is
13733 specified the file is processed with <command>$ORIGIN</command> set
13734 to that value, otherwise the current <command>$ORIGIN</command> is
13738 The origin and the current domain name
13739 revert to the values they had prior to the <command>$INCLUDE</command> once
13740 the file has been read.
13744 RFC 1035 specifies that the current origin should be restored
13746 an <command>$INCLUDE</command>, but it is silent
13747 on whether the current
13748 domain name should also be restored. BIND 9 restores both of
13750 This could be construed as a deviation from RFC 1035, a
13755 <section xml:id="ttl_directive"><info><title>The <command>$TTL</command> Directive</title></info>
13758 Syntax: <command>$TTL</command>
13759 <replaceable>default-ttl</replaceable>
13761 <replaceable>comment</replaceable> </optional>
13764 Set the default Time To Live (TTL) for subsequent records
13765 with undefined TTLs. Valid TTLs are of the range 0-2147483647
13768 <para><command>$TTL</command>
13769 is defined in RFC 2308.
13773 <section xml:id="generate_directive"><info><title><acronym>BIND</acronym> Master File Extension: the <command>$GENERATE</command> Directive</title></info>
13776 Syntax: <command>$GENERATE</command>
13777 <replaceable>range</replaceable>
13778 <replaceable>lhs</replaceable>
13779 <optional><replaceable>ttl</replaceable></optional>
13780 <optional><replaceable>class</replaceable></optional>
13781 <replaceable>type</replaceable>
13782 <replaceable>rhs</replaceable>
13783 <optional><replaceable>comment</replaceable></optional>
13785 <para><command>$GENERATE</command>
13786 is used to create a series of resource records that only
13787 differ from each other by an
13788 iterator. <command>$GENERATE</command> can be used to
13789 easily generate the sets of records required to support
13790 sub /24 reverse delegations described in RFC 2317:
13791 Classless IN-ADDR.ARPA delegation.
13794 <programlisting>$ORIGIN 0.0.192.IN-ADDR.ARPA.
13795 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
13796 $GENERATE 1-127 $ CNAME $.0</programlisting>
13802 <programlisting>0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
13803 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
13804 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
13805 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
13807 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
13811 Generate a set of A and MX records. Note the MX's right hand
13812 side is a quoted string. The quotes will be stripped when the
13813 right hand side is processed.
13818 $GENERATE 1-127 HOST-$ A 1.2.3.$
13819 $GENERATE 1-127 HOST-$ MX "0 ."</programlisting>
13825 <programlisting>HOST-1.EXAMPLE. A 1.2.3.1
13826 HOST-1.EXAMPLE. MX 0 .
13827 HOST-2.EXAMPLE. A 1.2.3.2
13828 HOST-2.EXAMPLE. MX 0 .
13829 HOST-3.EXAMPLE. A 1.2.3.3
13830 HOST-3.EXAMPLE. MX 0 .
13832 HOST-127.EXAMPLE. A 1.2.3.127
13833 HOST-127.EXAMPLE. MX 0 .
13836 <informaltable colsep="0" rowsep="0">
13837 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13838 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
13839 <colspec colname="2" colnum="2" colsep="0" colwidth="4.250in"/>
13842 <entry colname="1">
13843 <para><command>range</command></para>
13845 <entry colname="2">
13847 This can be one of two forms: start-stop
13848 or start-stop/step. If the first form is used, then step
13849 is set to 1. start, stop and step must be positive
13850 integers between 0 and (2^31)-1. start must not be
13856 <entry colname="1">
13857 <para><command>lhs</command></para>
13859 <entry colname="2">
13861 describes the owner name of the resource records
13862 to be created. Any single <command>$</command>
13864 symbols within the <command>lhs</command> string
13865 are replaced by the iterator value.
13867 To get a $ in the output, you need to escape the
13868 <command>$</command> using a backslash
13869 <command>\</command>,
13870 e.g. <command>\$</command>. The
13871 <command>$</command> may optionally be followed
13872 by modifiers which change the offset from the
13873 iterator, field width and base.
13875 Modifiers are introduced by a
13876 <command>{</command> (left brace) immediately following the
13877 <command>$</command> as
13878 <command>${offset[,width[,base]]}</command>.
13879 For example, <command>${-20,3,d}</command>
13880 subtracts 20 from the current value, prints the
13881 result as a decimal in a zero-padded field of
13884 Available output forms are decimal
13885 (<command>d</command>), octal
13886 (<command>o</command>), hexadecimal
13887 (<command>x</command> or <command>X</command>
13888 for uppercase) and nibble
13889 (<command>n</command> or <command>N</command>\
13890 for uppercase). The default modifier is
13891 <command>${0,0,d}</command>. If the
13892 <command>lhs</command> is not absolute, the
13893 current <command>$ORIGIN</command> is appended
13897 In nibble mode the value will be treated as
13898 if it was a reversed hexadecimal string
13899 with each hexadecimal digit as a separate
13900 label. The width field includes the label
13904 For compatibility with earlier versions,
13905 <command>$$</command> is still recognized as
13906 indicating a literal $ in the output.
13911 <entry colname="1">
13912 <para><command>ttl</command></para>
13914 <entry colname="2">
13916 Specifies the time-to-live of the generated records. If
13917 not specified this will be inherited using the
13918 normal TTL inheritance rules.
13920 <para><command>class</command>
13921 and <command>ttl</command> can be
13922 entered in either order.
13927 <entry colname="1">
13928 <para><command>class</command></para>
13930 <entry colname="2">
13932 Specifies the class of the generated records.
13933 This must match the zone class if it is
13936 <para><command>class</command>
13937 and <command>ttl</command> can be
13938 entered in either order.
13943 <entry colname="1">
13944 <para><command>type</command></para>
13946 <entry colname="2">
13953 <entry colname="1">
13954 <para><command>rhs</command></para>
13956 <entry colname="2">
13958 <command>rhs</command>, optionally, quoted string.
13966 The <command>$GENERATE</command> directive is a <acronym>BIND</acronym> extension
13967 and not part of the standard zone file format.
13970 BIND 8 does not support the optional TTL and CLASS fields.
13974 <section xml:id="zonefile_format"><info><title>Additional File Formats</title></info>
13977 In addition to the standard textual format, BIND 9
13978 supports the ability to read or dump to zone files in
13979 other formats. The <constant>raw</constant> format is
13980 currently available as an additional format. It is a
13981 binary format representing BIND 9's internal data
13982 structure directly, thereby remarkably improving the
13986 For a primary server, a zone file in the
13987 <constant>raw</constant> format is expected to be
13988 generated from a textual zone file by the
13989 <command>named-compilezone</command> command. For a
13990 secondary server or for a dynamic zone, it is automatically
13991 generated (if this format is specified by the
13992 <command>masterfile-format</command> option) when
13993 <command>named</command> dumps the zone contents after
13994 zone transfer or when applying prior updates.
13997 If a zone file in a binary format needs manual modification,
13998 it first must be converted to a textual form by the
13999 <command>named-compilezone</command> command. All
14000 necessary modification should go to the text file, which
14001 should then be converted to the binary form by the
14002 <command>named-compilezone</command> command again.
14005 Although the <constant>raw</constant> format uses the
14006 network byte order and avoids architecture-dependent
14007 data alignment so that it is as much portable as
14008 possible, it is primarily expected to be used inside
14009 the same single system. In order to export a zone
14010 file in the <constant>raw</constant> format or make a
14011 portable backup of the file, it is recommended to
14012 convert the file to the standard textual representation.
14017 <section xml:id="statistics"><info><title>BIND9 Statistics</title></info>
14020 <acronym>BIND</acronym> 9 maintains lots of statistics
14021 information and provides several interfaces for users to
14022 get access to the statistics.
14023 The available statistics include all statistics counters
14024 that were available in <acronym>BIND</acronym> 8 and
14025 are meaningful in <acronym>BIND</acronym> 9,
14026 and other information that is considered useful.
14030 The statistics information is categorized into the following
14034 <informaltable frame="all">
14036 <colspec colname="1" colnum="1" colsep="0" colwidth="3.300in"/>
14037 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
14041 <entry colname="1">
14042 <para>Incoming Requests</para>
14044 <entry colname="2">
14046 The number of incoming DNS requests for each OPCODE.
14052 <entry colname="1">
14053 <para>Incoming Queries</para>
14055 <entry colname="2">
14057 The number of incoming queries for each RR type.
14063 <entry colname="1">
14064 <para>Outgoing Queries</para>
14066 <entry colname="2">
14068 The number of outgoing queries for each RR
14069 type sent from the internal resolver.
14070 Maintained per view.
14076 <entry colname="1">
14077 <para>Name Server Statistics</para>
14079 <entry colname="2">
14081 Statistics counters about incoming request processing.
14087 <entry colname="1">
14088 <para>Zone Maintenance Statistics</para>
14090 <entry colname="2">
14092 Statistics counters regarding zone maintenance
14093 operations such as zone transfers.
14099 <entry colname="1">
14100 <para>Resolver Statistics</para>
14102 <entry colname="2">
14104 Statistics counters about name resolution
14105 performed in the internal resolver.
14106 Maintained per view.
14112 <entry colname="1">
14113 <para>Cache DB RRsets</para>
14115 <entry colname="2">
14117 The number of RRsets per RR type and nonexistent
14118 names stored in the cache database.
14119 If the exclamation mark (!) is printed for a RR
14120 type, it means that particular type of RRset is
14121 known to be nonexistent (this is also known as
14123 Maintained per view.
14129 <entry colname="1">
14130 <para>Socket I/O Statistics</para>
14132 <entry colname="2">
14134 Statistics counters about network related events.
14144 A subset of Name Server Statistics is collected and shown
14145 per zone for which the server has the authority when
14146 <command>zone-statistics</command> is set to
14147 <userinput>full</userinput> (or <userinput>yes</userinput>
14148 for backward compatibility. See the description of
14149 <command>zone-statistics</command> in <xref linkend="options"/>
14150 for further details.
14154 These statistics counters are shown with their zone and
14155 view names. The view name is omitted when the server is
14156 not configured with explicit views.</para>
14159 There are currently two user interfaces to get access to the
14161 One is in the plain text format dumped to the file specified
14162 by the <command>statistics-file</command> configuration option.
14163 The other is remotely accessible via a statistics channel
14164 when the <command>statistics-channels</command> statement
14165 is specified in the configuration file
14166 (see <xref linkend="statschannels"/>.)
14169 <section xml:id="statsfile"><info><title>The Statistics File</title></info>
14172 The text format statistics dump begins with a line, like:
14175 <command>+++ Statistics Dump +++ (973798949)</command>
14178 The number in parentheses is a standard
14179 Unix-style timestamp, measured as seconds since January 1, 1970.
14182 that line is a set of statistics information, which is categorized
14183 as described above.
14184 Each section begins with a line, like:
14188 <command>++ Name Server Statistics ++</command>
14192 Each section consists of lines, each containing the statistics
14193 counter value followed by its textual description.
14194 See below for available counters.
14195 For brevity, counters that have a value of 0 are not shown
14196 in the statistics file.
14200 The statistics dump ends with the line where the
14201 number is identical to the number in the beginning line; for example:
14204 <command>--- Statistics Dump --- (973798949)</command>
14208 <section xml:id="statistics_counters"><info><title>Statistics Counters</title></info>
14211 The following tables summarize statistics counters that
14212 <acronym>BIND</acronym> 9 provides.
14213 For each row of the tables, the leftmost column is the
14214 abbreviated symbol name of that counter.
14215 These symbols are shown in the statistics information
14216 accessed via an HTTP statistics channel.
14217 The rightmost column gives the description of the counter,
14218 which is also shown in the statistics file
14219 (but, in this document, possibly with slight modification
14220 for better readability).
14221 Additional notes may also be provided in this column.
14222 When a middle column exists between these two columns,
14223 it gives the corresponding counter name of the
14224 <acronym>BIND</acronym> 8 statistics, if applicable.
14227 <section xml:id="stats_counters"><info><title>Name Server Statistics Counters</title></info>
14229 <informaltable colsep="0" rowsep="0">
14230 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14231 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14232 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
14233 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
14236 <entry colname="1">
14238 <emphasis>Symbol</emphasis>
14241 <entry colname="2">
14243 <emphasis>BIND8 Symbol</emphasis>
14246 <entry colname="3">
14248 <emphasis>Description</emphasis>
14254 <entry colname="1">
14255 <para><command>Requestv4</command></para>
14257 <entry colname="2">
14258 <para><command>RQ</command></para>
14260 <entry colname="3">
14262 IPv4 requests received.
14263 Note: this also counts non query requests.
14268 <entry colname="1">
14269 <para><command>Requestv6</command></para>
14271 <entry colname="2">
14272 <para><command>RQ</command></para>
14274 <entry colname="3">
14276 IPv6 requests received.
14277 Note: this also counts non query requests.
14282 <entry colname="1">
14283 <para><command>ReqEdns0</command></para>
14285 <entry colname="2">
14286 <para><command/></para>
14288 <entry colname="3">
14290 Requests with EDNS(0) received.
14295 <entry colname="1">
14296 <para><command>ReqBadEDNSVer</command></para>
14298 <entry colname="2">
14299 <para><command/></para>
14301 <entry colname="3">
14303 Requests with unsupported EDNS version received.
14308 <entry colname="1">
14309 <para><command>ReqTSIG</command></para>
14311 <entry colname="2">
14312 <para><command/></para>
14314 <entry colname="3">
14316 Requests with TSIG received.
14321 <entry colname="1">
14322 <para><command>ReqSIG0</command></para>
14324 <entry colname="2">
14325 <para><command/></para>
14327 <entry colname="3">
14329 Requests with SIG(0) received.
14334 <entry colname="1">
14335 <para><command>ReqBadSIG</command></para>
14337 <entry colname="2">
14338 <para><command/></para>
14340 <entry colname="3">
14342 Requests with invalid (TSIG or SIG(0)) signature.
14347 <entry colname="1">
14348 <para><command>ReqTCP</command></para>
14350 <entry colname="2">
14351 <para><command>RTCP</command></para>
14353 <entry colname="3">
14355 TCP requests received.
14360 <entry colname="1">
14361 <para><command>AuthQryRej</command></para>
14363 <entry colname="2">
14364 <para><command>RUQ</command></para>
14366 <entry colname="3">
14368 Authoritative (non recursive) queries rejected.
14373 <entry colname="1">
14374 <para><command>RecQryRej</command></para>
14376 <entry colname="2">
14377 <para><command>RURQ</command></para>
14379 <entry colname="3">
14381 Recursive queries rejected.
14386 <entry colname="1">
14387 <para><command>XfrRej</command></para>
14389 <entry colname="2">
14390 <para><command>RUXFR</command></para>
14392 <entry colname="3">
14394 Zone transfer requests rejected.
14399 <entry colname="1">
14400 <para><command>UpdateRej</command></para>
14402 <entry colname="2">
14403 <para><command>RUUpd</command></para>
14405 <entry colname="3">
14407 Dynamic update requests rejected.
14412 <entry colname="1">
14413 <para><command>Response</command></para>
14415 <entry colname="2">
14416 <para><command>SAns</command></para>
14418 <entry colname="3">
14425 <entry colname="1">
14426 <para><command>RespTruncated</command></para>
14428 <entry colname="2">
14429 <para><command/></para>
14431 <entry colname="3">
14433 Truncated responses sent.
14438 <entry colname="1">
14439 <para><command>RespEDNS0</command></para>
14441 <entry colname="2">
14442 <para><command/></para>
14444 <entry colname="3">
14446 Responses with EDNS(0) sent.
14451 <entry colname="1">
14452 <para><command>RespTSIG</command></para>
14454 <entry colname="2">
14455 <para><command/></para>
14457 <entry colname="3">
14459 Responses with TSIG sent.
14464 <entry colname="1">
14465 <para><command>RespSIG0</command></para>
14467 <entry colname="2">
14468 <para><command/></para>
14470 <entry colname="3">
14472 Responses with SIG(0) sent.
14477 <entry colname="1">
14478 <para><command>QrySuccess</command></para>
14480 <entry colname="2">
14481 <para><command/></para>
14483 <entry colname="3">
14485 Queries resulted in a successful answer.
14486 This means the query which returns a NOERROR response
14487 with at least one answer RR.
14488 This corresponds to the
14489 <command>success</command> counter
14490 of previous versions of
14491 <acronym>BIND</acronym> 9.
14496 <entry colname="1">
14497 <para><command>QryAuthAns</command></para>
14499 <entry colname="2">
14500 <para><command/></para>
14502 <entry colname="3">
14504 Queries resulted in authoritative answer.
14509 <entry colname="1">
14510 <para><command>QryNoauthAns</command></para>
14512 <entry colname="2">
14513 <para><command>SNaAns</command></para>
14515 <entry colname="3">
14517 Queries resulted in non authoritative answer.
14522 <entry colname="1">
14523 <para><command>QryReferral</command></para>
14525 <entry colname="2">
14526 <para><command/></para>
14528 <entry colname="3">
14530 Queries resulted in referral answer.
14531 This corresponds to the
14532 <command>referral</command> counter
14533 of previous versions of
14534 <acronym>BIND</acronym> 9.
14539 <entry colname="1">
14540 <para><command>QryNxrrset</command></para>
14542 <entry colname="2">
14543 <para><command/></para>
14545 <entry colname="3">
14547 Queries resulted in NOERROR responses with no data.
14548 This corresponds to the
14549 <command>nxrrset</command> counter
14550 of previous versions of
14551 <acronym>BIND</acronym> 9.
14556 <entry colname="1">
14557 <para><command>QrySERVFAIL</command></para>
14559 <entry colname="2">
14560 <para><command>SFail</command></para>
14562 <entry colname="3">
14564 Queries resulted in SERVFAIL.
14569 <entry colname="1">
14570 <para><command>QryFORMERR</command></para>
14572 <entry colname="2">
14573 <para><command>SFErr</command></para>
14575 <entry colname="3">
14577 Queries resulted in FORMERR.
14582 <entry colname="1">
14583 <para><command>QryNXDOMAIN</command></para>
14585 <entry colname="2">
14586 <para><command>SNXD</command></para>
14588 <entry colname="3">
14590 Queries resulted in NXDOMAIN.
14591 This corresponds to the
14592 <command>nxdomain</command> counter
14593 of previous versions of
14594 <acronym>BIND</acronym> 9.
14599 <entry colname="1">
14600 <para><command>QryRecursion</command></para>
14602 <entry colname="2">
14603 <para><command>RFwdQ</command></para>
14605 <entry colname="3">
14607 Queries which caused the server
14608 to perform recursion in order to find the final answer.
14609 This corresponds to the
14610 <command>recursion</command> counter
14611 of previous versions of
14612 <acronym>BIND</acronym> 9.
14617 <entry colname="1">
14618 <para><command>QryDuplicate</command></para>
14620 <entry colname="2">
14621 <para><command>RDupQ</command></para>
14623 <entry colname="3">
14625 Queries which the server attempted to
14626 recurse but discovered an existing query with the same
14627 IP address, port, query ID, name, type and class
14628 already being processed.
14629 This corresponds to the
14630 <command>duplicate</command> counter
14631 of previous versions of
14632 <acronym>BIND</acronym> 9.
14637 <entry colname="1">
14638 <para><command>QryDropped</command></para>
14640 <entry colname="2">
14641 <para><command/></para>
14643 <entry colname="3">
14645 Recursive queries for which the server
14646 discovered an excessive number of existing
14647 recursive queries for the same name, type and
14648 class and were subsequently dropped.
14649 This is the number of dropped queries due to
14650 the reason explained with the
14651 <command>clients-per-query</command>
14653 <command>max-clients-per-query</command>
14655 (see the description about
14656 <xref endterm="cpq_term" linkend="clients-per-query"/>.)
14657 This corresponds to the
14658 <command>dropped</command> counter
14659 of previous versions of
14660 <acronym>BIND</acronym> 9.
14665 <entry colname="1">
14666 <para><command>QryFailure</command></para>
14668 <entry colname="2">
14669 <para><command/></para>
14671 <entry colname="3">
14673 Other query failures.
14674 This corresponds to the
14675 <command>failure</command> counter
14676 of previous versions of
14677 <acronym>BIND</acronym> 9.
14678 Note: this counter is provided mainly for
14679 backward compatibility with the previous versions.
14680 Normally a more fine-grained counters such as
14681 <command>AuthQryRej</command> and
14682 <command>RecQryRej</command>
14683 that would also fall into this counter are provided,
14684 and so this counter would not be of much
14685 interest in practice.
14690 <entry colname="1">
14691 <para><command>XfrReqDone</command></para>
14693 <entry colname="2">
14694 <para><command/></para>
14696 <entry colname="3">
14698 Requested zone transfers completed.
14703 <entry colname="1">
14704 <para><command>UpdateReqFwd</command></para>
14706 <entry colname="2">
14707 <para><command/></para>
14709 <entry colname="3">
14711 Update requests forwarded.
14716 <entry colname="1">
14717 <para><command>UpdateRespFwd</command></para>
14719 <entry colname="2">
14720 <para><command/></para>
14722 <entry colname="3">
14724 Update responses forwarded.
14729 <entry colname="1">
14730 <para><command>UpdateFwdFail</command></para>
14732 <entry colname="2">
14733 <para><command/></para>
14735 <entry colname="3">
14737 Dynamic update forward failed.
14742 <entry colname="1">
14743 <para><command>UpdateDone</command></para>
14745 <entry colname="2">
14746 <para><command/></para>
14748 <entry colname="3">
14750 Dynamic updates completed.
14755 <entry colname="1">
14756 <para><command>UpdateFail</command></para>
14758 <entry colname="2">
14759 <para><command/></para>
14761 <entry colname="3">
14763 Dynamic updates failed.
14768 <entry colname="1">
14769 <para><command>UpdateBadPrereq</command></para>
14771 <entry colname="2">
14772 <para><command/></para>
14774 <entry colname="3">
14776 Dynamic updates rejected due to prerequisite failure.
14781 <entry colname="1">
14782 <para><command>RPZRewrites</command></para>
14784 <entry colname="2">
14785 <para><command/></para>
14787 <entry colname="3">
14789 Response policy zone rewrites.
14794 <entry colname="1">
14795 <para><command>RateDropped</command></para>
14797 <entry colname="2">
14798 <para><command/></para>
14800 <entry colname="3">
14802 Responses dropped by rate limits.
14807 <entry colname="1">
14808 <para><command>RateSlipped</command></para>
14810 <entry colname="2">
14811 <para><command/></para>
14813 <entry colname="3">
14815 Responses truncated by rate limits.
14824 <section xml:id="zone_stats"><info><title>Zone Maintenance Statistics Counters</title></info>
14826 <informaltable colsep="0" rowsep="0">
14827 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14828 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14829 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
14832 <entry colname="1">
14834 <emphasis>Symbol</emphasis>
14837 <entry colname="2">
14839 <emphasis>Description</emphasis>
14845 <entry colname="1">
14846 <para><command>NotifyOutv4</command></para>
14848 <entry colname="2">
14850 IPv4 notifies sent.
14855 <entry colname="1">
14856 <para><command>NotifyOutv6</command></para>
14858 <entry colname="2">
14860 IPv6 notifies sent.
14865 <entry colname="1">
14866 <para><command>NotifyInv4</command></para>
14868 <entry colname="2">
14870 IPv4 notifies received.
14875 <entry colname="1">
14876 <para><command>NotifyInv6</command></para>
14878 <entry colname="2">
14880 IPv6 notifies received.
14885 <entry colname="1">
14886 <para><command>NotifyRej</command></para>
14888 <entry colname="2">
14890 Incoming notifies rejected.
14895 <entry colname="1">
14896 <para><command>SOAOutv4</command></para>
14898 <entry colname="2">
14900 IPv4 SOA queries sent.
14905 <entry colname="1">
14906 <para><command>SOAOutv6</command></para>
14908 <entry colname="2">
14910 IPv6 SOA queries sent.
14915 <entry colname="1">
14916 <para><command>AXFRReqv4</command></para>
14918 <entry colname="2">
14920 IPv4 AXFR requested.
14925 <entry colname="1">
14926 <para><command>AXFRReqv6</command></para>
14928 <entry colname="2">
14930 IPv6 AXFR requested.
14935 <entry colname="1">
14936 <para><command>IXFRReqv4</command></para>
14938 <entry colname="2">
14940 IPv4 IXFR requested.
14945 <entry colname="1">
14946 <para><command>IXFRReqv6</command></para>
14948 <entry colname="2">
14950 IPv6 IXFR requested.
14955 <entry colname="1">
14956 <para><command>XfrSuccess</command></para>
14958 <entry colname="2">
14960 Zone transfer requests succeeded.
14965 <entry colname="1">
14966 <para><command>XfrFail</command></para>
14968 <entry colname="2">
14970 Zone transfer requests failed.
14979 <section xml:id="resolver_stats"><info><title>Resolver Statistics Counters</title></info>
14981 <informaltable colsep="0" rowsep="0">
14982 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14983 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14984 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
14985 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
14988 <entry colname="1">
14990 <emphasis>Symbol</emphasis>
14993 <entry colname="2">
14995 <emphasis>BIND8 Symbol</emphasis>
14998 <entry colname="3">
15000 <emphasis>Description</emphasis>
15006 <entry colname="1">
15007 <para><command>Queryv4</command></para>
15009 <entry colname="2">
15010 <para><command>SFwdQ</command></para>
15012 <entry colname="3">
15019 <entry colname="1">
15020 <para><command>Queryv6</command></para>
15022 <entry colname="2">
15023 <para><command>SFwdQ</command></para>
15025 <entry colname="3">
15032 <entry colname="1">
15033 <para><command>Responsev4</command></para>
15035 <entry colname="2">
15036 <para><command>RR</command></para>
15038 <entry colname="3">
15040 IPv4 responses received.
15045 <entry colname="1">
15046 <para><command>Responsev6</command></para>
15048 <entry colname="2">
15049 <para><command>RR</command></para>
15051 <entry colname="3">
15053 IPv6 responses received.
15058 <entry colname="1">
15059 <para><command>NXDOMAIN</command></para>
15061 <entry colname="2">
15062 <para><command>RNXD</command></para>
15064 <entry colname="3">
15071 <entry colname="1">
15072 <para><command>SERVFAIL</command></para>
15074 <entry colname="2">
15075 <para><command>RFail</command></para>
15077 <entry colname="3">
15084 <entry colname="1">
15085 <para><command>FORMERR</command></para>
15087 <entry colname="2">
15088 <para><command>RFErr</command></para>
15090 <entry colname="3">
15097 <entry colname="1">
15098 <para><command>OtherError</command></para>
15100 <entry colname="2">
15101 <para><command>RErr</command></para>
15103 <entry colname="3">
15105 Other errors received.
15110 <entry colname="1">
15111 <para><command>EDNS0Fail</command></para>
15113 <entry colname="2">
15114 <para><command/></para>
15116 <entry colname="3">
15118 EDNS(0) query failures.
15123 <entry colname="1">
15124 <para><command>Mismatch</command></para>
15126 <entry colname="2">
15127 <para><command>RDupR</command></para>
15129 <entry colname="3">
15131 Mismatch responses received.
15132 The DNS ID, response's source address,
15133 and/or the response's source port does not
15134 match what was expected.
15135 (The port must be 53 or as defined by
15136 the <command>port</command> option.)
15137 This may be an indication of a cache
15143 <entry colname="1">
15144 <para><command>Truncated</command></para>
15146 <entry colname="2">
15147 <para><command/></para>
15149 <entry colname="3">
15151 Truncated responses received.
15156 <entry colname="1">
15157 <para><command>Lame</command></para>
15159 <entry colname="2">
15160 <para><command>RLame</command></para>
15162 <entry colname="3">
15164 Lame delegations received.
15169 <entry colname="1">
15170 <para><command>Retry</command></para>
15172 <entry colname="2">
15173 <para><command>SDupQ</command></para>
15175 <entry colname="3">
15177 Query retries performed.
15182 <entry colname="1">
15183 <para><command>QueryAbort</command></para>
15185 <entry colname="2">
15186 <para><command/></para>
15188 <entry colname="3">
15190 Queries aborted due to quota control.
15195 <entry colname="1">
15196 <para><command>QuerySockFail</command></para>
15198 <entry colname="2">
15199 <para><command/></para>
15201 <entry colname="3">
15203 Failures in opening query sockets.
15204 One common reason for such failures is a
15205 failure of opening a new socket due to a
15206 limitation on file descriptors.
15211 <entry colname="1">
15212 <para><command>QueryTimeout</command></para>
15214 <entry colname="2">
15215 <para><command/></para>
15217 <entry colname="3">
15224 <entry colname="1">
15225 <para><command>GlueFetchv4</command></para>
15227 <entry colname="2">
15228 <para><command>SSysQ</command></para>
15230 <entry colname="3">
15232 IPv4 NS address fetches invoked.
15237 <entry colname="1">
15238 <para><command>GlueFetchv6</command></para>
15240 <entry colname="2">
15241 <para><command>SSysQ</command></para>
15243 <entry colname="3">
15245 IPv6 NS address fetches invoked.
15250 <entry colname="1">
15251 <para><command>GlueFetchv4Fail</command></para>
15253 <entry colname="2">
15254 <para><command/></para>
15256 <entry colname="3">
15258 IPv4 NS address fetch failed.
15263 <entry colname="1">
15264 <para><command>GlueFetchv6Fail</command></para>
15266 <entry colname="2">
15267 <para><command/></para>
15269 <entry colname="3">
15271 IPv6 NS address fetch failed.
15276 <entry colname="1">
15277 <para><command>ValAttempt</command></para>
15279 <entry colname="2">
15280 <para><command/></para>
15282 <entry colname="3">
15284 DNSSEC validation attempted.
15289 <entry colname="1">
15290 <para><command>ValOk</command></para>
15292 <entry colname="2">
15293 <para><command/></para>
15295 <entry colname="3">
15297 DNSSEC validation succeeded.
15302 <entry colname="1">
15303 <para><command>ValNegOk</command></para>
15305 <entry colname="2">
15306 <para><command/></para>
15308 <entry colname="3">
15310 DNSSEC validation on negative information succeeded.
15315 <entry colname="1">
15316 <para><command>ValFail</command></para>
15318 <entry colname="2">
15319 <para><command/></para>
15321 <entry colname="3">
15323 DNSSEC validation failed.
15328 <entry colname="1">
15329 <para><command>QryRTTnn</command></para>
15331 <entry colname="2">
15332 <para><command/></para>
15334 <entry colname="3">
15336 Frequency table on round trip times (RTTs) of
15338 Each <command>nn</command> specifies the corresponding
15341 <command>nn_1</command>,
15342 <command>nn_2</command>,
15344 <command>nn_m</command>,
15345 the value of <command>nn_i</command> is the
15346 number of queries whose RTTs are between
15347 <command>nn_(i-1)</command> (inclusive) and
15348 <command>nn_i</command> (exclusive) milliseconds.
15349 For the sake of convenience we define
15350 <command>nn_0</command> to be 0.
15351 The last entry should be represented as
15352 <command>nn_m+</command>, which means the
15353 number of queries whose RTTs are equal to or over
15354 <command>nn_m</command> milliseconds.
15364 <section xml:id="socket_stats"><info><title>Socket I/O Statistics Counters</title></info>
15367 Socket I/O statistics counters are defined per socket
15369 <command>UDP4</command> (UDP/IPv4),
15370 <command>UDP6</command> (UDP/IPv6),
15371 <command>TCP4</command> (TCP/IPv4),
15372 <command>TCP6</command> (TCP/IPv6),
15373 <command>Unix</command> (Unix Domain), and
15374 <command>FDwatch</command> (sockets opened outside the
15376 In the following table <command><TYPE></command>
15377 represents a socket type.
15378 Not all counters are available for all socket types;
15379 exceptions are noted in the description field.
15382 <informaltable colsep="0" rowsep="0">
15383 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
15384 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
15385 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
15388 <entry colname="1">
15390 <emphasis>Symbol</emphasis>
15393 <entry colname="2">
15395 <emphasis>Description</emphasis>
15401 <entry colname="1">
15402 <para><command><TYPE>Open</command></para>
15404 <entry colname="2">
15406 Sockets opened successfully.
15407 This counter is not applicable to the
15408 <command>FDwatch</command> type.
15413 <entry colname="1">
15414 <para><command><TYPE>OpenFail</command></para>
15416 <entry colname="2">
15418 Failures of opening sockets.
15419 This counter is not applicable to the
15420 <command>FDwatch</command> type.
15425 <entry colname="1">
15426 <para><command><TYPE>Close</command></para>
15428 <entry colname="2">
15435 <entry colname="1">
15436 <para><command><TYPE>BindFail</command></para>
15438 <entry colname="2">
15440 Failures of binding sockets.
15445 <entry colname="1">
15446 <para><command><TYPE>ConnFail</command></para>
15448 <entry colname="2">
15450 Failures of connecting sockets.
15455 <entry colname="1">
15456 <para><command><TYPE>Conn</command></para>
15458 <entry colname="2">
15460 Connections established successfully.
15465 <entry colname="1">
15466 <para><command><TYPE>AcceptFail</command></para>
15468 <entry colname="2">
15470 Failures of accepting incoming connection requests.
15471 This counter is not applicable to the
15472 <command>UDP</command> and
15473 <command>FDwatch</command> types.
15478 <entry colname="1">
15479 <para><command><TYPE>Accept</command></para>
15481 <entry colname="2">
15483 Incoming connections successfully accepted.
15484 This counter is not applicable to the
15485 <command>UDP</command> and
15486 <command>FDwatch</command> types.
15491 <entry colname="1">
15492 <para><command><TYPE>SendErr</command></para>
15494 <entry colname="2">
15496 Errors in socket send operations.
15497 This counter corresponds
15498 to <command>SErr</command> counter of
15499 <command>BIND</command> 8.
15504 <entry colname="1">
15505 <para><command><TYPE>RecvErr</command></para>
15507 <entry colname="2">
15509 Errors in socket receive operations.
15510 This includes errors of send operations on a
15511 connected UDP socket notified by an ICMP error
15521 <section xml:id="bind8_compatibility"><info><title>Compatibility with <emphasis>BIND</emphasis> 8 Counters</title></info>
15524 Most statistics counters that were available
15525 in <command>BIND</command> 8 are also supported in
15526 <command>BIND</command> 9 as shown in the above tables.
15527 Here are notes about other counters that do not appear
15533 <term><command>RFwdR,SFwdR</command></term>
15536 These counters are not supported
15537 because <command>BIND</command> 9 does not adopt
15538 the notion of <emphasis>forwarding</emphasis>
15539 as <command>BIND</command> 8 did.
15545 <term><command>RAXFR</command></term>
15548 This counter is accessible in the Incoming Queries section.
15554 <term><command>RIQ</command></term>
15557 This counter is accessible in the Incoming Requests section.
15563 <term><command>ROpts</command></term>
15566 This counter is not supported
15567 because <command>BIND</command> 9 does not care
15568 about IP options in the first place.
15578 <chapter xml:id="Bv9ARM.ch07"><info><title><acronym>BIND</acronym> 9 Security Considerations</title></info>
15580 <section xml:id="Access_Control_Lists"><info><title>Access Control Lists</title></info>
15583 Access Control Lists (ACLs) are address match lists that
15584 you can set up and nickname for future use in <command>allow-notify</command>,
15585 <command>allow-query</command>, <command>allow-query-on</command>,
15586 <command>allow-recursion</command>, <command>allow-recursion-on</command>,
15587 <command>blackhole</command>, <command>allow-transfer</command>,
15591 Using ACLs allows you to have finer control over who can access
15592 your name server, without cluttering up your config files with huge
15593 lists of IP addresses.
15596 It is a <emphasis>good idea</emphasis> to use ACLs, and to
15597 control access to your server. Limiting access to your server by
15598 outside parties can help prevent spoofing and denial of service (DoS) attacks against
15602 Here is an example of how to properly apply ACLs:
15606 // Set up an ACL named "bogusnets" that will block
15607 // RFC1918 space and some reserved space, which is
15608 // commonly used in spoofing attacks.
15610 0.0.0.0/8; 192.0.2.0/24; 224.0.0.0/3;
15611 10.0.0.0/8; 172.16.0.0/12; 192.168.0.0/16;
15614 // Set up an ACL called our-nets. Replace this with the
15615 // real IP numbers.
15616 acl our-nets { x.x.x.x/24; x.x.x.x/21; };
15620 allow-query { our-nets; };
15621 allow-recursion { our-nets; };
15623 blackhole { bogusnets; };
15627 zone "example.com" {
15629 file "m/example.com";
15630 allow-query { any; };
15635 This allows recursive queries of the server from the outside
15636 unless recursion has been previously disabled.
15639 <section xml:id="chroot_and_setuid"><info><title><command>Chroot</command> and <command>Setuid</command></title></info>
15642 On UNIX servers, it is possible to run <acronym>BIND</acronym>
15643 in a <emphasis>chrooted</emphasis> environment (using
15644 the <command>chroot()</command> function) by specifying
15645 the "<option>-t</option>" option for <command>named</command>.
15646 This can help improve system security by placing
15647 <acronym>BIND</acronym> in a "sandbox", which will limit
15648 the damage done if a server is compromised.
15651 Another useful feature in the UNIX version of <acronym>BIND</acronym> is the
15652 ability to run the daemon as an unprivileged user ( <option>-u</option> <replaceable>user</replaceable> ).
15653 We suggest running as an unprivileged user when using the <command>chroot</command> feature.
15656 Here is an example command line to load <acronym>BIND</acronym> in a <command>chroot</command> sandbox,
15657 <command>/var/named</command>, and to run <command>named</command> <command>setuid</command> to
15661 <userinput>/usr/local/sbin/named -u 202 -t /var/named</userinput>
15664 <section xml:id="chroot"><info><title>The <command>chroot</command> Environment</title></info>
15667 In order for a <command>chroot</command> environment
15669 work properly in a particular directory
15670 (for example, <filename>/var/named</filename>),
15671 you will need to set up an environment that includes everything
15672 <acronym>BIND</acronym> needs to run.
15673 From <acronym>BIND</acronym>'s point of view, <filename>/var/named</filename> is
15674 the root of the filesystem. You will need to adjust the values of
15676 like <command>directory</command> and <command>pid-file</command> to account
15680 Unlike with earlier versions of BIND, you typically will
15681 <emphasis>not</emphasis> need to compile <command>named</command>
15682 statically nor install shared libraries under the new root.
15683 However, depending on your operating system, you may need
15684 to set up things like
15685 <filename>/dev/zero</filename>,
15686 <filename>/dev/random</filename>,
15687 <filename>/dev/log</filename>, and
15688 <filename>/etc/localtime</filename>.
15692 <section xml:id="setuid"><info><title>Using the <command>setuid</command> Function</title></info>
15695 Prior to running the <command>named</command> daemon,
15697 the <command>touch</command> utility (to change file
15699 modification times) or the <command>chown</command>
15701 set the user id and/or group id) on files
15702 to which you want <acronym>BIND</acronym>
15706 If the <command>named</command> daemon is running as an
15707 unprivileged user, it will not be able to bind to new restricted
15708 ports if the server is reloaded.
15713 <section xml:id="dynamic_update_security"><info><title>Dynamic Update Security</title></info>
15716 Access to the dynamic
15717 update facility should be strictly limited. In earlier versions of
15718 <acronym>BIND</acronym>, the only way to do this was
15720 address of the host requesting the update, by listing an IP address
15722 network prefix in the <command>allow-update</command>
15724 This method is insecure since the source address of the update UDP
15726 is easily forged. Also note that if the IP addresses allowed by the
15727 <command>allow-update</command> option include the
15729 server which performs forwarding of dynamic updates, the master can
15731 trivially attacked by sending the update to the slave, which will
15732 forward it to the master with its own source IP address causing the
15733 master to approve it without question.
15737 For these reasons, we strongly recommend that updates be
15738 cryptographically authenticated by means of transaction signatures
15739 (TSIG). That is, the <command>allow-update</command>
15741 list only TSIG key names, not IP addresses or network
15742 prefixes. Alternatively, the new <command>update-policy</command>
15743 option can be used.
15747 Some sites choose to keep all dynamically-updated DNS data
15748 in a subdomain and delegate that subdomain to a separate zone. This
15749 way, the top-level zone containing critical data such as the IP
15751 of public web and mail servers need not allow dynamic update at
15758 <chapter xml:id="Bv9ARM.ch08"><info><title>Troubleshooting</title></info>
15760 <section xml:id="common_problems"><info><title>Common Problems</title></info>
15762 <section><info><title>It's not working; how can I figure out what's wrong?</title></info>
15765 The best solution to solving installation and
15766 configuration issues is to take preventative measures by setting
15767 up logging files beforehand. The log files provide a
15768 source of hints and information that can be used to figure out
15769 what went wrong and how to fix the problem.
15774 <section><info><title>Incrementing and Changing the Serial Number</title></info>
15777 Zone serial numbers are just numbers — they aren't
15778 date related. A lot of people set them to a number that
15779 represents a date, usually of the form YYYYMMDDRR.
15780 Occasionally they will make a mistake and set them to a
15781 "date in the future" then try to correct them by setting
15782 them to the "current date". This causes problems because
15783 serial numbers are used to indicate that a zone has been
15784 updated. If the serial number on the slave server is
15785 lower than the serial number on the master, the slave
15786 server will attempt to update its copy of the zone.
15790 Setting the serial number to a lower number on the master
15791 server than the slave server means that the slave will not perform
15792 updates to its copy of the zone.
15796 The solution to this is to add 2147483647 (2^31-1) to the
15797 number, reload the zone and make sure all slaves have updated to
15798 the new zone serial number, then reset the number to what you want
15799 it to be, and reload the zone again.
15803 <section xml:id="more_help"><info><title>Where Can I Get Help?</title></info>
15806 The Internet Systems Consortium
15807 (<acronym>ISC</acronym>) offers a wide range
15808 of support and service agreements for <acronym>BIND</acronym> and <acronym>DHCP</acronym> servers. Four
15809 levels of premium support are available and each level includes
15810 support for all <acronym>ISC</acronym> programs,
15811 significant discounts on products
15812 and training, and a recognized priority on bug fixes and
15813 non-funded feature requests. In addition, <acronym>ISC</acronym> offers a standard
15814 support agreement package which includes services ranging from bug
15815 fix announcements to remote support. It also includes training in
15816 <acronym>BIND</acronym> and <acronym>DHCP</acronym>.
15820 To discuss arrangements for support, contact
15821 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="mailto:info@isc.org">info@isc.org</link> or visit the
15822 <acronym>ISC</acronym> web page at
15823 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.isc.org/services/support/">http://www.isc.org/services/support/</link>
15829 <appendix xml:id="Bv9ARM.ch09"><info><title>Release Notes</title></info>
15830 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="notes.xml"/>
15833 <appendix xml:id="Bv9ARM.ch10"><info><title>A Brief History of the <acronym>DNS</acronym> and <acronym>BIND</acronym></title></info>
15834 <para xml:id="historical_dns_information">
15835 Although the "official" beginning of the Domain Name
15836 System occurred in 1984 with the publication of RFC 920, the
15837 core of the new system was described in 1983 in RFCs 882 and
15838 883. From 1984 to 1987, the ARPAnet (the precursor to today's
15839 Internet) became a testbed of experimentation for developing the
15840 new naming/addressing scheme in a rapidly expanding,
15841 operational network environment. New RFCs were written and
15842 published in 1987 that modified the original documents to
15843 incorporate improvements based on the working model. RFC 1034,
15844 "Domain Names-Concepts and Facilities", and RFC 1035, "Domain
15845 Names-Implementation and Specification" were published and
15846 became the standards upon which all <acronym>DNS</acronym> implementations are
15851 The first working domain name server, called "Jeeves", was
15852 written in 1983-84 by Paul Mockapetris for operation on DEC
15854 machines located at the University of Southern California's
15856 Sciences Institute (USC-ISI) and SRI International's Network
15858 Center (SRI-NIC). A <acronym>DNS</acronym> server for
15859 Unix machines, the Berkeley Internet
15860 Name Domain (<acronym>BIND</acronym>) package, was
15861 written soon after by a group of
15862 graduate students at the University of California at Berkeley
15864 a grant from the US Defense Advanced Research Projects
15869 Versions of <acronym>BIND</acronym> through
15870 4.8.3 were maintained by the Computer
15871 Systems Research Group (CSRG) at UC Berkeley. Douglas Terry, Mark
15872 Painter, David Riggle and Songnian Zhou made up the initial <acronym>BIND</acronym>
15873 project team. After that, additional work on the software package
15874 was done by Ralph Campbell. Kevin Dunlap, a Digital Equipment
15876 employee on loan to the CSRG, worked on <acronym>BIND</acronym> for 2 years, from 1985
15877 to 1987. Many other people also contributed to <acronym>BIND</acronym> development
15878 during that time: Doug Kingston, Craig Partridge, Smoot
15880 Mike Muuss, Jim Bloom and Mike Schwartz. <acronym>BIND</acronym> maintenance was subsequently
15881 handled by Mike Karels and Øivind Kure.
15884 <acronym>BIND</acronym> versions 4.9 and 4.9.1 were
15885 released by Digital Equipment
15886 Corporation (now Compaq Computer Corporation). Paul Vixie, then
15887 a DEC employee, became <acronym>BIND</acronym>'s
15888 primary caretaker. He was assisted
15889 by Phil Almquist, Robert Elz, Alan Barrett, Paul Albitz, Bryan
15891 Partan, Andy Cherenson, Tom Limoncelli, Berthold Paffrath, Fuat
15892 Baran, Anant Kumar, Art Harkin, Win Treese, Don Lewis, Christophe
15893 Wolfhugel, and others.
15896 In 1994, <acronym>BIND</acronym> version 4.9.2 was sponsored by
15897 Vixie Enterprises. Paul
15898 Vixie became <acronym>BIND</acronym>'s principal
15899 architect/programmer.
15902 <acronym>BIND</acronym> versions from 4.9.3 onward
15903 have been developed and maintained
15904 by the Internet Systems Consortium and its predecessor,
15905 the Internet Software Consortium, with support being provided
15909 As co-architects/programmers, Bob Halley and
15910 Paul Vixie released the first production-ready version of
15911 <acronym>BIND</acronym> version 8 in May 1997.
15914 BIND version 9 was released in September 2000 and is a
15915 major rewrite of nearly all aspects of the underlying
15919 BIND versions 4 and 8 are officially deprecated.
15920 No additional development is done
15921 on BIND version 4 or BIND version 8.
15924 <acronym>BIND</acronym> development work is made
15925 possible today by the sponsorship
15926 of several corporations, and by the tireless work efforts of
15927 numerous individuals.
15931 <appendix xml:id="Bv9ARM.ch11"><info><title>General <acronym>DNS</acronym> Reference Information</title></info>
15933 <section xml:id="ipv6addresses"><info><title>IPv6 addresses (AAAA)</title></info>
15936 IPv6 addresses are 128-bit identifiers for interfaces and
15937 sets of interfaces which were introduced in the <acronym>DNS</acronym> to facilitate
15938 scalable Internet routing. There are three types of addresses: <emphasis>Unicast</emphasis>,
15939 an identifier for a single interface;
15940 <emphasis>Anycast</emphasis>,
15941 an identifier for a set of interfaces; and <emphasis>Multicast</emphasis>,
15942 an identifier for a set of interfaces. Here we describe the global
15943 Unicast address scheme. For more information, see RFC 3587,
15944 "Global Unicast Address Format."
15947 IPv6 unicast addresses consist of a
15948 <emphasis>global routing prefix</emphasis>, a
15949 <emphasis>subnet identifier</emphasis>, and an
15950 <emphasis>interface identifier</emphasis>.
15953 The global routing prefix is provided by the
15954 upstream provider or ISP, and (roughly) corresponds to the
15955 IPv4 <emphasis>network</emphasis> section
15956 of the address range.
15958 The subnet identifier is for local subnetting, much the
15959 same as subnetting an
15960 IPv4 /16 network into /24 subnets.
15962 The interface identifier is the address of an individual
15963 interface on a given network; in IPv6, addresses belong to
15964 interfaces rather than to machines.
15967 The subnetting capability of IPv6 is much more flexible than
15968 that of IPv4: subnetting can be carried out on bit boundaries,
15969 in much the same way as Classless InterDomain Routing
15970 (CIDR), and the DNS PTR representation ("nibble" format)
15971 makes setting up reverse zones easier.
15974 The Interface Identifier must be unique on the local link,
15975 and is usually generated automatically by the IPv6
15976 implementation, although it is usually possible to
15977 override the default setting if necessary. A typical IPv6
15978 address might look like:
15979 <command>2001:db8:201:9:a00:20ff:fe81:2b32</command>
15982 IPv6 address specifications often contain long strings
15983 of zeros, so the architects have included a shorthand for
15985 them. The double colon (`::') indicates the longest possible
15987 of zeros that can fit, and can be used only once in an address.
15990 <section xml:id="bibliography"><info><title>Bibliography (and Suggested Reading)</title></info>
15992 <section xml:id="rfcs"><info><title>Request for Comments (RFCs)</title></info>
15995 Specification documents for the Internet protocol suite, including
15996 the <acronym>DNS</acronym>, are published as part of
15997 the Request for Comments (RFCs)
15998 series of technical notes. The standards themselves are defined
15999 by the Internet Engineering Task Force (IETF) and the Internet
16000 Engineering Steering Group (IESG). RFCs can be obtained online via FTP at:
16003 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ftp://www.isi.edu/in-notes/">
16004 ftp://www.isi.edu/in-notes/RFC<replaceable>xxxx</replaceable>.txt
16008 (where <replaceable>xxxx</replaceable> is
16009 the number of the RFC). RFCs are also available via the Web at:
16012 <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.ietf.org/rfc/">http://www.ietf.org/rfc/</link>.
16015 <bibliodiv><info><title>Standards</title></info>
16016 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
16019 <abbrev>RFC974</abbrev>
16020 <author><personname><surname>Partridge</surname><firstname>C.</firstname></personname></author>
16021 <citetitle>Mail Routing and the Domain System</citetitle>
16022 <pubdate>January 1986</pubdate>
16025 <abbrev>RFC1034</abbrev>
16026 <author><personname><surname>Mockapetris</surname><firstname>P.V.</firstname></personname></author>
16027 <citetitle>Domain Names — Concepts and Facilities</citetitle>
16028 <pubdate>November 1987</pubdate>
16031 <abbrev>RFC1035</abbrev>
16032 <author><personname><surname>Mockapetris</surname><firstname>P. V.</firstname></personname></author> <citetitle>Domain Names — Implementation and
16033 Specification</citetitle>
16034 <pubdate>November 1987</pubdate>
16037 <bibliodiv xml:id="proposed_standards" xreflabel="Proposed Standards"><info><title>Proposed Standards</title></info>
16039 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
16041 <abbrev>RFC2181</abbrev>
16042 <author><personname><surname>Elz</surname><firstname>R., R. Bush</firstname></personname></author>
16043 <citetitle>Clarifications to the <acronym>DNS</acronym>
16044 Specification</citetitle>
16045 <pubdate>July 1997</pubdate>
16048 <abbrev>RFC2308</abbrev>
16049 <author><personname><surname>Andrews</surname><firstname>M.</firstname></personname></author>
16050 <citetitle>Negative Caching of <acronym>DNS</acronym>
16051 Queries</citetitle>
16052 <pubdate>March 1998</pubdate>
16055 <abbrev>RFC1995</abbrev>
16056 <author><personname><surname>Ohta</surname><firstname>M.</firstname></personname></author>
16057 <citetitle>Incremental Zone Transfer in <acronym>DNS</acronym></citetitle>
16058 <pubdate>August 1996</pubdate>
16061 <abbrev>RFC1996</abbrev>
16062 <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author>
16063 <citetitle>A Mechanism for Prompt Notification of Zone Changes</citetitle>
16064 <pubdate>August 1996</pubdate>
16067 <abbrev>RFC2136</abbrev>
16069 <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author>
16070 <author><personname><firstname>S.</firstname><surname>Thomson</surname></personname></author>
16071 <author><personname><firstname>Y.</firstname><surname>Rekhter</surname></personname></author>
16072 <author><personname><firstname>J.</firstname><surname>Bound</surname></personname></author>
16074 <citetitle>Dynamic Updates in the Domain Name System</citetitle>
16075 <pubdate>April 1997</pubdate>
16078 <abbrev>RFC2671</abbrev>
16080 <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author>
16082 <citetitle>Extension Mechanisms for DNS (EDNS0)</citetitle>
16083 <pubdate>August 1997</pubdate>
16086 <abbrev>RFC2672</abbrev>
16088 <author><personname><firstname>M.</firstname><surname>Crawford</surname></personname></author>
16090 <citetitle>Non-Terminal DNS Name Redirection</citetitle>
16091 <pubdate>August 1999</pubdate>
16094 <abbrev>RFC2845</abbrev>
16096 <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author>
16097 <author><personname><firstname>O.</firstname><surname>Gudmundsson</surname></personname></author>
16098 <author><personname><firstname>D.</firstname><surname>Eastlake</surname><lineage>3rd</lineage></personname></author>
16099 <author><personname><firstname>B.</firstname><surname>Wellington</surname></personname></author>
16101 <citetitle>Secret Key Transaction Authentication for <acronym>DNS</acronym> (TSIG)</citetitle>
16102 <pubdate>May 2000</pubdate>
16105 <abbrev>RFC2930</abbrev>
16107 <author><personname><firstname>D.</firstname><surname>Eastlake</surname><lineage>3rd</lineage></personname></author>
16109 <citetitle>Secret Key Establishment for DNS (TKEY RR)</citetitle>
16110 <pubdate>September 2000</pubdate>
16113 <abbrev>RFC2931</abbrev>
16115 <author><personname><firstname>D.</firstname><surname>Eastlake</surname><lineage>3rd</lineage></personname></author>
16117 <citetitle>DNS Request and Transaction Signatures (SIG(0)s)</citetitle>
16118 <pubdate>September 2000</pubdate>
16121 <abbrev>RFC3007</abbrev>
16123 <author><personname><firstname>B.</firstname><surname>Wellington</surname></personname></author>
16125 <citetitle>Secure Domain Name System (DNS) Dynamic Update</citetitle>
16126 <pubdate>November 2000</pubdate>
16129 <abbrev>RFC3645</abbrev>
16131 <author><personname><firstname>S.</firstname><surname>Kwan</surname></personname></author>
16132 <author><personname><firstname>P.</firstname><surname>Garg</surname></personname></author>
16133 <author><personname><firstname>J.</firstname><surname>Gilroy</surname></personname></author>
16134 <author><personname><firstname>L.</firstname><surname>Esibov</surname></personname></author>
16135 <author><personname><firstname>J.</firstname><surname>Westhead</surname></personname></author>
16136 <author><personname><firstname>R.</firstname><surname>Hall</surname></personname></author>
16138 <citetitle>Generic Security Service Algorithm for Secret
16139 Key Transaction Authentication for DNS
16140 (GSS-TSIG)</citetitle>
16141 <pubdate>October 2003</pubdate>
16144 <bibliodiv><info><title><acronym>DNS</acronym> Security Proposed Standards</title></info>
16147 <abbrev>RFC3225</abbrev>
16149 <author><personname><firstname>D.</firstname><surname>Conrad</surname></personname></author>
16151 <citetitle>Indicating Resolver Support of DNSSEC</citetitle>
16152 <pubdate>December 2001</pubdate>
16155 <abbrev>RFC3833</abbrev>
16157 <author><personname><firstname>D.</firstname><surname>Atkins</surname></personname></author>
16158 <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author>
16160 <citetitle>Threat Analysis of the Domain Name System (DNS)</citetitle>
16161 <pubdate>August 2004</pubdate>
16164 <abbrev>RFC4033</abbrev>
16166 <author><personname><firstname>R.</firstname><surname>Arends</surname></personname></author>
16167 <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author>
16168 <author><personname><firstname>M.</firstname><surname>Larson</surname></personname></author>
16169 <author><personname><firstname>D.</firstname><surname>Massey</surname></personname></author>
16170 <author><personname><firstname>S.</firstname><surname>Rose</surname></personname></author>
16172 <citetitle>DNS Security Introduction and Requirements</citetitle>
16173 <pubdate>March 2005</pubdate>
16176 <abbrev>RFC4034</abbrev>
16178 <author><personname><firstname>R.</firstname><surname>Arends</surname></personname></author>
16179 <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author>
16180 <author><personname><firstname>M.</firstname><surname>Larson</surname></personname></author>
16181 <author><personname><firstname>D.</firstname><surname>Massey</surname></personname></author>
16182 <author><personname><firstname>S.</firstname><surname>Rose</surname></personname></author>
16184 <citetitle>Resource Records for the DNS Security Extensions</citetitle>
16185 <pubdate>March 2005</pubdate>
16188 <abbrev>RFC4035</abbrev>
16190 <author><personname><firstname>R.</firstname><surname>Arends</surname></personname></author>
16191 <author><personname><firstname>R.</firstname><surname>Austein</surname></personname></author>
16192 <author><personname><firstname>M.</firstname><surname>Larson</surname></personname></author>
16193 <author><personname><firstname>D.</firstname><surname>Massey</surname></personname></author>
16194 <author><personname><firstname>S.</firstname><surname>Rose</surname></personname></author>
16196 <citetitle>Protocol Modifications for the DNS
16197 Security Extensions</citetitle>
16198 <pubdate>March 2005</pubdate>
16201 <bibliodiv><info><title>Other Important RFCs About <acronym>DNS</acronym>
16202 Implementation</title></info>
16205 <abbrev>RFC1535</abbrev>
16206 <author><personname><surname>Gavron</surname><firstname>E.</firstname></personname></author>
16207 <citetitle>A Security Problem and Proposed Correction With Widely
16208 Deployed <acronym>DNS</acronym> Software.</citetitle>
16209 <pubdate>October 1993</pubdate>
16212 <abbrev>RFC1536</abbrev>
16214 <author><personname><surname>Kumar</surname><firstname>A.</firstname></personname></author>
16215 <author><personname><firstname>J.</firstname><surname>Postel</surname></personname></author>
16216 <author><personname><firstname>C.</firstname><surname>Neuman</surname></personname></author>
16217 <author><personname><firstname>P.</firstname><surname>Danzig</surname></personname></author>
16218 <author><personname><firstname>S.</firstname><surname>Miller</surname></personname></author>
16220 <citetitle>Common <acronym>DNS</acronym> Implementation
16221 Errors and Suggested Fixes</citetitle>
16222 <pubdate>October 1993</pubdate>
16225 <abbrev>RFC1982</abbrev>
16227 <author><personname><surname>Elz</surname><firstname>R.</firstname></personname></author>
16228 <author><personname><firstname>R.</firstname><surname>Bush</surname></personname></author>
16230 <citetitle>Serial Number Arithmetic</citetitle>
16231 <pubdate>August 1996</pubdate>
16234 <abbrev>RFC4074</abbrev>
16236 <author><personname><surname>Morishita</surname><firstname>Y.</firstname></personname></author>
16237 <author><personname><firstname>T.</firstname><surname>Jinmei</surname></personname></author>
16239 <citetitle>Common Misbehaviour Against <acronym>DNS</acronym>
16240 Queries for IPv6 Addresses</citetitle>
16241 <pubdate>May 2005</pubdate>
16244 <bibliodiv><info><title>Resource Record Types</title></info>
16247 <abbrev>RFC1183</abbrev>
16249 <author><personname><surname>Everhart</surname><firstname>C.F.</firstname></personname></author>
16250 <author><personname><firstname>L. A.</firstname><surname>Mamakos</surname></personname></author>
16251 <author><personname><firstname>R.</firstname><surname>Ullmann</surname></personname></author>
16252 <author><personname><firstname>P.</firstname><surname>Mockapetris</surname></personname></author>
16254 <citetitle>New <acronym>DNS</acronym> RR Definitions</citetitle>
16255 <pubdate>October 1990</pubdate>
16258 <abbrev>RFC1706</abbrev>
16260 <author><personname><surname>Manning</surname><firstname>B.</firstname></personname></author>
16261 <author><personname><firstname>R.</firstname><surname>Colella</surname></personname></author>
16263 <citetitle><acronym>DNS</acronym> NSAP Resource Records</citetitle>
16264 <pubdate>October 1994</pubdate>
16267 <abbrev>RFC2168</abbrev>
16269 <author><personname><surname>Daniel</surname><firstname>R.</firstname></personname></author>
16270 <author><personname><firstname>M.</firstname><surname>Mealling</surname></personname></author>
16272 <citetitle>Resolution of Uniform Resource Identifiers using
16273 the Domain Name System</citetitle>
16274 <pubdate>June 1997</pubdate>
16277 <abbrev>RFC1876</abbrev>
16279 <author><personname><surname>Davis</surname><firstname>C.</firstname></personname></author>
16280 <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author>
16281 <author><personname><firstname>T.</firstname><firstname>Goodwin</firstname></personname></author>
16282 <author><personname><firstname>I.</firstname><surname>Dickinson</surname></personname></author>
16284 <citetitle>A Means for Expressing Location Information in the
16286 Name System</citetitle>
16287 <pubdate>January 1996</pubdate>
16290 <abbrev>RFC2052</abbrev>
16292 <author><personname><surname>Gulbrandsen</surname><firstname>A.</firstname></personname></author>
16293 <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author>
16295 <citetitle>A <acronym>DNS</acronym> RR for Specifying the
16297 Services.</citetitle>
16298 <pubdate>October 1996</pubdate>
16301 <abbrev>RFC2163</abbrev>
16302 <author><personname><surname>Allocchio</surname><firstname>A.</firstname></personname></author>
16303 <citetitle>Using the Internet <acronym>DNS</acronym> to
16305 Conformant Global Address Mapping</citetitle>
16306 <pubdate>January 1998</pubdate>
16309 <abbrev>RFC2230</abbrev>
16310 <author><personname><surname>Atkinson</surname><firstname>R.</firstname></personname></author>
16311 <citetitle>Key Exchange Delegation Record for the <acronym>DNS</acronym></citetitle>
16312 <pubdate>October 1997</pubdate>
16315 <abbrev>RFC2536</abbrev>
16316 <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author>
16317 <citetitle>DSA KEYs and SIGs in the Domain Name System (DNS)</citetitle>
16318 <pubdate>March 1999</pubdate>
16321 <abbrev>RFC2537</abbrev>
16322 <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author>
16323 <citetitle>RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)</citetitle>
16324 <pubdate>March 1999</pubdate>
16327 <abbrev>RFC2538</abbrev>
16329 <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author>
16330 <author><personname><surname>Gudmundsson</surname><firstname>O.</firstname></personname></author>
16332 <citetitle>Storing Certificates in the Domain Name System (DNS)</citetitle>
16333 <pubdate>March 1999</pubdate>
16336 <abbrev>RFC2539</abbrev>
16338 <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author>
16340 <citetitle>Storage of Diffie-Hellman Keys in the Domain Name System (DNS)</citetitle>
16341 <pubdate>March 1999</pubdate>
16344 <abbrev>RFC2540</abbrev>
16346 <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author>
16348 <citetitle>Detached Domain Name System (DNS) Information</citetitle>
16349 <pubdate>March 1999</pubdate>
16352 <abbrev>RFC2782</abbrev>
16353 <author><personname><surname>Gulbrandsen</surname><firstname>A.</firstname></personname></author>
16354 <author><personname><surname>Vixie</surname><firstname>P.</firstname></personname></author>
16355 <author><personname><surname>Esibov</surname><firstname>L.</firstname></personname></author>
16356 <citetitle>A DNS RR for specifying the location of services (DNS SRV)</citetitle>
16357 <pubdate>February 2000</pubdate>
16360 <abbrev>RFC2915</abbrev>
16361 <author><personname><surname>Mealling</surname><firstname>M.</firstname></personname></author>
16362 <author><personname><surname>Daniel</surname><firstname>R.</firstname></personname></author>
16363 <citetitle>The Naming Authority Pointer (NAPTR) DNS Resource Record</citetitle>
16364 <pubdate>September 2000</pubdate>
16367 <abbrev>RFC3110</abbrev>
16368 <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author>
16369 <citetitle>RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)</citetitle>
16370 <pubdate>May 2001</pubdate>
16373 <abbrev>RFC3123</abbrev>
16374 <author><personname><surname>Koch</surname><firstname>P.</firstname></personname></author>
16375 <citetitle>A DNS RR Type for Lists of Address Prefixes (APL RR)</citetitle>
16376 <pubdate>June 2001</pubdate>
16379 <abbrev>RFC3596</abbrev>
16381 <author><personname><surname>Thomson</surname><firstname>S.</firstname></personname></author>
16382 <author><personname><firstname>C.</firstname><surname>Huitema</surname></personname></author>
16383 <author><personname><firstname>V.</firstname><surname>Ksinant</surname></personname></author>
16384 <author><personname><firstname>M.</firstname><surname>Souissi</surname></personname></author>
16386 <citetitle><acronym>DNS</acronym> Extensions to support IP
16387 version 6</citetitle>
16388 <pubdate>October 2003</pubdate>
16391 <abbrev>RFC3597</abbrev>
16392 <author><personname><surname>Gustafsson</surname><firstname>A.</firstname></personname></author>
16393 <citetitle>Handling of Unknown DNS Resource Record (RR) Types</citetitle>
16394 <pubdate>September 2003</pubdate>
16397 <bibliodiv><info><title><acronym>DNS</acronym> and the Internet</title></info>
16400 <abbrev>RFC1101</abbrev>
16401 <author><personname><surname>Mockapetris</surname><firstname>P. V.</firstname></personname></author>
16402 <citetitle><acronym>DNS</acronym> Encoding of Network Names
16403 and Other Types</citetitle>
16404 <pubdate>April 1989</pubdate>
16407 <abbrev>RFC1123</abbrev>
16408 <author><personname><surname>Braden</surname><surname>R.</surname></personname></author>
16409 <citetitle>Requirements for Internet Hosts - Application and
16410 Support</citetitle>
16411 <pubdate>October 1989</pubdate>
16414 <abbrev>RFC1591</abbrev>
16415 <author><personname><surname>Postel</surname><firstname>J.</firstname></personname></author>
16416 <citetitle>Domain Name System Structure and Delegation</citetitle>
16417 <pubdate>March 1994</pubdate>
16420 <abbrev>RFC2317</abbrev>
16422 <author><personname><surname>Eidnes</surname><firstname>H.</firstname></personname></author>
16423 <author><personname><firstname>G.</firstname><surname>de Groot</surname></personname></author>
16424 <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author>
16426 <citetitle>Classless IN-ADDR.ARPA Delegation</citetitle>
16427 <pubdate>March 1998</pubdate>
16430 <abbrev>RFC2826</abbrev>
16432 <author><personname><surname>Internet Architecture Board</surname></personname></author>
16434 <citetitle>IAB Technical Comment on the Unique DNS Root</citetitle>
16435 <pubdate>May 2000</pubdate>
16438 <abbrev>RFC2929</abbrev>
16440 <author><personname><surname>Eastlake</surname><firstname>D.</firstname><lineage>3rd</lineage></personname></author>
16441 <author><personname><surname>Brunner-Williams</surname><firstname>E.</firstname></personname></author>
16442 <author><personname><surname>Manning</surname><firstname>B.</firstname></personname></author>
16444 <citetitle>Domain Name System (DNS) IANA Considerations</citetitle>
16445 <pubdate>September 2000</pubdate>
16448 <bibliodiv><info><title><acronym>DNS</acronym> Operations</title></info>
16451 <abbrev>RFC1033</abbrev>
16452 <author><personname><surname>Lottor</surname><firstname>M.</firstname></personname></author>
16453 <citetitle>Domain administrators operations guide.</citetitle>
16454 <pubdate>November 1987</pubdate>
16457 <abbrev>RFC1537</abbrev>
16458 <author><personname><surname>Beertema</surname><firstname>P.</firstname></personname></author>
16459 <citetitle>Common <acronym>DNS</acronym> Data File
16460 Configuration Errors</citetitle>
16461 <pubdate>October 1993</pubdate>
16464 <abbrev>RFC1912</abbrev>
16465 <author><personname><surname>Barr</surname><firstname>D.</firstname></personname></author>
16466 <citetitle>Common <acronym>DNS</acronym> Operational and
16467 Configuration Errors</citetitle>
16468 <pubdate>February 1996</pubdate>
16471 <abbrev>RFC2010</abbrev>
16473 <author><personname><surname>Manning</surname><firstname>B.</firstname></personname></author>
16474 <author><personname><firstname>P.</firstname><surname>Vixie</surname></personname></author>
16476 <citetitle>Operational Criteria for Root Name Servers.</citetitle>
16477 <pubdate>October 1996</pubdate>
16480 <abbrev>RFC2219</abbrev>
16482 <author><personname><surname>Hamilton</surname><firstname>M.</firstname></personname></author>
16483 <author><personname><firstname>R.</firstname><surname>Wright</surname></personname></author>
16485 <citetitle>Use of <acronym>DNS</acronym> Aliases for
16486 Network Services.</citetitle>
16487 <pubdate>October 1997</pubdate>
16490 <bibliodiv><info><title>Internationalized Domain Names</title></info>
16493 <abbrev>RFC2825</abbrev>
16495 <author><personname><surname>IAB</surname></personname></author>
16496 <author><personname><surname>Daigle</surname><firstname>R.</firstname></personname></author>
16498 <citetitle>A Tangled Web: Issues of I18N, Domain Names,
16499 and the Other Internet protocols</citetitle>
16500 <pubdate>May 2000</pubdate>
16503 <abbrev>RFC3490</abbrev>
16505 <author><personname><surname>Faltstrom</surname><firstname>P.</firstname></personname></author>
16506 <author><personname><surname>Hoffman</surname><firstname>P.</firstname></personname></author>
16507 <author><personname><surname>Costello</surname><firstname>A.</firstname></personname></author>
16509 <citetitle>Internationalizing Domain Names in Applications (IDNA)</citetitle>
16510 <pubdate>March 2003</pubdate>
16513 <abbrev>RFC3491</abbrev>
16515 <author><personname><surname>Hoffman</surname><firstname>P.</firstname></personname></author>
16516 <author><personname><surname>Blanchet</surname><firstname>M.</firstname></personname></author>
16518 <citetitle>Nameprep: A Stringprep Profile for Internationalized Domain Names</citetitle>
16519 <pubdate>March 2003</pubdate>
16522 <abbrev>RFC3492</abbrev>
16524 <author><personname><surname>Costello</surname><firstname>A.</firstname></personname></author>
16526 <citetitle>Punycode: A Bootstring encoding of Unicode
16527 for Internationalized Domain Names in
16528 Applications (IDNA)</citetitle>
16529 <pubdate>March 2003</pubdate>
16532 <bibliodiv><info><title>Other <acronym>DNS</acronym>-related RFCs</title></info>
16536 Note: the following list of RFCs, although
16537 <acronym>DNS</acronym>-related, are not
16538 concerned with implementing software.
16542 <abbrev>RFC1464</abbrev>
16543 <author><personname><surname>Rosenbaum</surname><firstname>R.</firstname></personname></author>
16544 <citetitle>Using the Domain Name System To Store Arbitrary String
16545 Attributes</citetitle>
16546 <pubdate>May 1993</pubdate>
16549 <abbrev>RFC1713</abbrev>
16550 <author><personname><surname>Romao</surname><firstname>A.</firstname></personname></author>
16551 <citetitle>Tools for <acronym>DNS</acronym> Debugging</citetitle>
16552 <pubdate>November 1994</pubdate>
16555 <abbrev>RFC1794</abbrev>
16556 <author><personname><surname>Brisco</surname><firstname>T.</firstname></personname></author>
16557 <citetitle><acronym>DNS</acronym> Support for Load
16558 Balancing</citetitle>
16559 <pubdate>April 1995</pubdate>
16562 <abbrev>RFC2240</abbrev>
16563 <author><personname><surname>Vaughan</surname><firstname>O.</firstname></personname></author>
16564 <citetitle>A Legal Basis for Domain Name Allocation</citetitle>
16565 <pubdate>November 1997</pubdate>
16568 <abbrev>RFC2345</abbrev>
16570 <author><personname><surname>Klensin</surname><firstname>J.</firstname></personname></author>
16571 <author><personname><firstname>T.</firstname><surname>Wolf</surname></personname></author>
16572 <author><personname><firstname>G.</firstname><surname>Oglesby</surname></personname></author>
16574 <citetitle>Domain Names and Company Name Retrieval</citetitle>
16575 <pubdate>May 1998</pubdate>
16578 <abbrev>RFC2352</abbrev>
16579 <author><personname><surname>Vaughan</surname><firstname>O.</firstname></personname></author>
16580 <citetitle>A Convention For Using Legal Names as Domain Names</citetitle>
16581 <pubdate>May 1998</pubdate>
16584 <abbrev>RFC3071</abbrev>
16586 <author><personname><surname>Klensin</surname><firstname>J.</firstname></personname></author>
16588 <citetitle>Reflections on the DNS, RFC 1591, and Categories of Domains</citetitle>
16589 <pubdate>February 2001</pubdate>
16592 <abbrev>RFC3258</abbrev>
16594 <author><personname><surname>Hardie</surname><firstname>T.</firstname></personname></author>
16596 <citetitle>Distributing Authoritative Name Servers via
16597 Shared Unicast Addresses</citetitle>
16598 <pubdate>April 2002</pubdate>
16601 <abbrev>RFC3901</abbrev>
16603 <author><personname><surname>Durand</surname><firstname>A.</firstname></personname></author>
16604 <author><personname><firstname>J.</firstname><surname>Ihren</surname></personname></author>
16606 <citetitle>DNS IPv6 Transport Operational Guidelines</citetitle>
16607 <pubdate>September 2004</pubdate>
16610 <bibliodiv><info><title>Obsolete and Unimplemented Experimental RFC</title></info>
16613 <abbrev>RFC1712</abbrev>
16615 <author><personname><surname>Farrell</surname><firstname>C.</firstname></personname></author>
16616 <author><personname><firstname>M.</firstname><surname>Schulze</surname></personname></author>
16617 <author><personname><firstname>S.</firstname><surname>Pleitner</surname></personname></author>
16618 <author><personname><firstname>D.</firstname><surname>Baldoni</surname></personname></author>
16620 <citetitle><acronym>DNS</acronym> Encoding of Geographical
16621 Location</citetitle>
16622 <pubdate>November 1994</pubdate>
16625 <abbrev>RFC2673</abbrev>
16627 <author><personname><surname>Crawford</surname><firstname>M.</firstname></personname></author>
16629 <citetitle>Binary Labels in the Domain Name System</citetitle>
16630 <pubdate>August 1999</pubdate>
16633 <abbrev>RFC2874</abbrev>
16635 <author><personname><surname>Crawford</surname><firstname>M.</firstname></personname></author>
16636 <author><personname><surname>Huitema</surname><firstname>C.</firstname></personname></author>
16638 <citetitle>DNS Extensions to Support IPv6 Address Aggregation
16639 and Renumbering</citetitle>
16640 <pubdate>July 2000</pubdate>
16643 <bibliodiv><info><title>Obsoleted DNS Security RFCs</title></info>
16647 Most of these have been consolidated into RFC4033,
16648 RFC4034 and RFC4035 which collectively describe DNSSECbis.
16652 <abbrev>RFC2065</abbrev>
16654 <author><personname><surname>Eastlake</surname><lineage>3rd</lineage><firstname>D.</firstname></personname></author>
16655 <author><personname><firstname>C.</firstname><surname>Kaufman</surname></personname></author>
16657 <citetitle>Domain Name System Security Extensions</citetitle>
16658 <pubdate>January 1997</pubdate>
16661 <abbrev>RFC2137</abbrev>
16662 <author><personname><surname>Eastlake</surname><lineage>3rd</lineage><firstname>D.</firstname></personname></author>
16663 <citetitle>Secure Domain Name System Dynamic Update</citetitle>
16664 <pubdate>April 1997</pubdate>
16667 <abbrev>RFC2535</abbrev>
16669 <author><personname><surname>Eastlake</surname><lineage>3rd</lineage><firstname>D.</firstname></personname></author>
16671 <citetitle>Domain Name System Security Extensions</citetitle>
16672 <pubdate>March 1999</pubdate>
16675 <abbrev>RFC3008</abbrev>
16677 <author><personname><surname>Wellington</surname><firstname>B.</firstname></personname></author>
16679 <citetitle>Domain Name System Security (DNSSEC)
16680 Signing Authority</citetitle>
16681 <pubdate>November 2000</pubdate>
16684 <abbrev>RFC3090</abbrev>
16686 <author><personname><surname>Lewis</surname><firstname>E.</firstname></personname></author>
16688 <citetitle>DNS Security Extension Clarification on Zone Status</citetitle>
16689 <pubdate>March 2001</pubdate>
16692 <abbrev>RFC3445</abbrev>
16694 <author><personname><surname>Massey</surname><firstname>D.</firstname></personname></author>
16695 <author><personname><surname>Rose</surname><firstname>S.</firstname></personname></author>
16697 <citetitle>Limiting the Scope of the KEY Resource Record (RR)</citetitle>
16698 <pubdate>December 2002</pubdate>
16701 <abbrev>RFC3655</abbrev>
16703 <author><personname><surname>Wellington</surname><firstname>B.</firstname></personname></author>
16704 <author><personname><surname>Gudmundsson</surname><firstname>O.</firstname></personname></author>
16706 <citetitle>Redefinition of DNS Authenticated Data (AD) bit</citetitle>
16707 <pubdate>November 2003</pubdate>
16710 <abbrev>RFC3658</abbrev>
16712 <author><personname><surname>Gudmundsson</surname><firstname>O.</firstname></personname></author>
16714 <citetitle>Delegation Signer (DS) Resource Record (RR)</citetitle>
16715 <pubdate>December 2003</pubdate>
16718 <abbrev>RFC3755</abbrev>
16720 <author><personname><surname>Weiler</surname><firstname>S.</firstname></personname></author>
16722 <citetitle>Legacy Resolver Compatibility for Delegation Signer (DS)</citetitle>
16723 <pubdate>May 2004</pubdate>
16726 <abbrev>RFC3757</abbrev>
16728 <author><personname><surname>Kolkman</surname><firstname>O.</firstname></personname></author>
16729 <author><personname><surname>Schlyter</surname><firstname>J.</firstname></personname></author>
16730 <author><personname><surname>Lewis</surname><firstname>E.</firstname></personname></author>
16732 <citetitle>Domain Name System KEY (DNSKEY) Resource Record
16733 (RR) Secure Entry Point (SEP) Flag</citetitle>
16734 <pubdate>April 2004</pubdate>
16737 <abbrev>RFC3845</abbrev>
16739 <author><personname><surname>Schlyter</surname><firstname>J.</firstname></personname></author>
16741 <citetitle>DNS Security (DNSSEC) NextSECure (NSEC) RDATA Format</citetitle>
16742 <pubdate>August 2004</pubdate>
16747 <section xml:id="internet_drafts"><info><title>Internet Drafts</title></info>
16750 Internet Drafts (IDs) are rough-draft working documents of
16751 the Internet Engineering Task Force. They are, in essence, RFCs
16752 in the preliminary stages of development. Implementors are
16754 to regard IDs as archival, and they should not be quoted or cited
16755 in any formal documents unless accompanied by the disclaimer that
16756 they are "works in progress." IDs have a lifespan of six months
16757 after which they are deleted unless updated by their authors.
16760 <section xml:id="more_about_bind"><info><title>Other Documents About <acronym>BIND</acronym></title></info>
16766 <author><personname><surname>Albitz</surname><firstname>Paul</firstname></personname></author>
16767 <author><personname><firstname>Cricket</firstname><surname>Liu</surname></personname></author>
16769 <citetitle><acronym>DNS</acronym> and <acronym>BIND</acronym></citetitle>
16772 <holder>Sebastopol, CA: O'Reilly and Associates</holder>
16780 <appendix xml:id="Bv9ARM.ch12"><info><title>BIND 9 DNS Library Support</title></info>
16781 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="libdns.xml"/>
16784 <reference xml:id="Bv9ARM.ch13"><info><title>Manual pages</title></info>
16785 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dig/dig.docbook"/>
16786 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dig/host.docbook"/>
16787 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/python/dnssec-checkds.docbook"/>
16788 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/python/dnssec-coverage.docbook"/>
16789 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-dsfromkey.docbook"/>
16790 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-importkey.docbook"/>
16791 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-keyfromlabel.docbook"/>
16792 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-keygen.docbook"/>
16793 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-revoke.docbook"/>
16794 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-settime.docbook"/>
16795 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-signzone.docbook"/>
16796 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/dnssec/dnssec-verify.docbook"/>
16797 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/check/named-checkconf.docbook"/>
16798 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/check/named-checkzone.docbook"/>
16799 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/named/named.docbook"/>
16800 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/named/named.conf.docbook"/>
16801 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/named/lwresd.docbook"/>
16802 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/named-journalprint.docbook"/>
16803 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/nsupdate/nsupdate.docbook"/>
16804 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/rndc/rndc.docbook"/>
16805 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/rndc/rndc.conf.docbook"/>
16806 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/confgen/rndc-confgen.docbook"/>
16807 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/confgen/ddns-confgen.docbook"/>
16808 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/arpaname.docbook"/>
16809 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/genrandom.docbook"/>
16810 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/isc-hmac-fixup.docbook"/>
16811 <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="../../bin/tools/nsec3hash.docbook"/>