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21 <!-- File: $Id: Bv9ARM-book.xml,v 1.478.8.2.2.1 2011-06-09 03:17:11 marka Exp $ -->
22 <book xmlns:xi="http://www.w3.org/2001/XInclude">
23 <title>BIND 9 Administrator Reference Manual</title>
35 <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
42 <holder>Internet Software Consortium.</holder>
46 <chapter id="Bv9ARM.ch01">
47 <title>Introduction</title>
49 The Internet Domain Name System (<acronym>DNS</acronym>)
50 consists of the syntax
51 to specify the names of entities in the Internet in a hierarchical
52 manner, the rules used for delegating authority over names, and the
53 system implementation that actually maps names to Internet
54 addresses. <acronym>DNS</acronym> data is maintained in a
56 hierarchical databases.
60 <title>Scope of Document</title>
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.
73 This version of the manual corresponds to BIND version 9.7.
78 <title>Organization of This Document</title>
80 In this document, <emphasis>Chapter 1</emphasis> introduces
81 the basic <acronym>DNS</acronym> and <acronym>BIND</acronym> concepts. <emphasis>Chapter 2</emphasis>
82 describes resource requirements for running <acronym>BIND</acronym> in various
83 environments. Information in <emphasis>Chapter 3</emphasis> is
84 <emphasis>task-oriented</emphasis> in its presentation and is
85 organized functionally, to aid in the process of installing the
86 <acronym>BIND</acronym> 9 software. The task-oriented
87 section is followed by
88 <emphasis>Chapter 4</emphasis>, which contains more advanced
89 concepts that the system administrator may need for implementing
90 certain options. <emphasis>Chapter 5</emphasis>
91 describes the <acronym>BIND</acronym> 9 lightweight
92 resolver. The contents of <emphasis>Chapter 6</emphasis> are
93 organized as in a reference manual to aid in the ongoing
94 maintenance of the software. <emphasis>Chapter 7</emphasis> addresses
95 security considerations, and
96 <emphasis>Chapter 8</emphasis> contains troubleshooting help. The
97 main body of the document is followed by several
98 <emphasis>appendices</emphasis> which contain useful reference
99 information, such as a <emphasis>bibliography</emphasis> and
100 historic information related to <acronym>BIND</acronym>
106 <title>Conventions Used in This Document</title>
109 In this document, we use the following general typographic
115 <colspec colname="1" colnum="1" colwidth="3.000in"/>
116 <colspec colname="2" colnum="2" colwidth="2.625in"/>
121 <emphasis>To describe:</emphasis>
126 <emphasis>We use the style:</emphasis>
133 a pathname, filename, URL, hostname,
134 mailing list name, or new term or concept
139 <filename>Fixed width</filename>
152 <userinput>Fixed Width Bold</userinput>
164 <computeroutput>Fixed Width</computeroutput>
173 The following conventions are used in descriptions of the
174 <acronym>BIND</acronym> configuration file:<informaltable colsep="0" frame="all" rowsep="0">
175 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
176 <colspec colname="1" colnum="1" colsep="0" colwidth="3.000in"/>
177 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
180 <entry colname="1" colsep="1" rowsep="1">
182 <emphasis>To describe:</emphasis>
185 <entry colname="2" rowsep="1">
187 <emphasis>We use the style:</emphasis>
192 <entry colname="1" colsep="1" rowsep="1">
197 <entry colname="2" rowsep="1">
199 <literal>Fixed Width</literal>
204 <entry colname="1" colsep="1" rowsep="1">
209 <entry colname="2" rowsep="1">
211 <varname>Fixed Width</varname>
216 <entry colname="1" colsep="1">
223 <optional>Text is enclosed in square brackets</optional>
233 <title>The Domain Name System (<acronym>DNS</acronym>)</title>
235 The purpose of this document is to explain the installation
236 and upkeep of the <acronym>BIND</acronym> (Berkeley Internet
237 Name Domain) software package, and we
238 begin by reviewing the fundamentals of the Domain Name System
239 (<acronym>DNS</acronym>) as they relate to <acronym>BIND</acronym>.
243 <title>DNS Fundamentals</title>
246 The Domain Name System (DNS) is a hierarchical, distributed
247 database. It stores information for mapping Internet host names to
249 addresses and vice versa, mail routing information, and other data
250 used by Internet applications.
254 Clients look up information in the DNS by calling a
255 <emphasis>resolver</emphasis> library, which sends queries to one or
256 more <emphasis>name servers</emphasis> and interprets the responses.
257 The <acronym>BIND</acronym> 9 software distribution
259 name server, <command>named</command>, and a resolver
260 library, <command>liblwres</command>. The older
261 <command>libbind</command> resolver library is also available
262 from ISC as a separate download.
266 <title>Domains and Domain Names</title>
269 The data stored in the DNS is identified by <emphasis>domain names</emphasis> that are organized as a tree according to
270 organizational or administrative boundaries. Each node of the tree,
271 called a <emphasis>domain</emphasis>, is given a label. The domain
273 node is the concatenation of all the labels on the path from the
274 node to the <emphasis>root</emphasis> node. This is represented
275 in written form as a string of labels listed from right to left and
276 separated by dots. A label need only be unique within its parent
281 For example, a domain name for a host at the
282 company <emphasis>Example, Inc.</emphasis> could be
283 <literal>ourhost.example.com</literal>,
284 where <literal>com</literal> is the
285 top level domain to which
286 <literal>ourhost.example.com</literal> belongs,
287 <literal>example</literal> is
288 a subdomain of <literal>com</literal>, and
289 <literal>ourhost</literal> is the
294 For administrative purposes, the name space is partitioned into
295 areas called <emphasis>zones</emphasis>, each starting at a node and
296 extending down to the leaf nodes or to nodes where other zones
298 The data for each zone is stored in a <emphasis>name server</emphasis>, which answers queries about the zone using the
299 <emphasis>DNS protocol</emphasis>.
303 The data associated with each domain name is stored in the
304 form of <emphasis>resource records</emphasis> (<acronym>RR</acronym>s).
305 Some of the supported resource record types are described in
306 <xref linkend="types_of_resource_records_and_when_to_use_them"/>.
310 For more detailed information about the design of the DNS and
311 the DNS protocol, please refer to the standards documents listed in
312 <xref linkend="rfcs"/>.
319 To properly operate a name server, it is important to understand
320 the difference between a <emphasis>zone</emphasis>
321 and a <emphasis>domain</emphasis>.
325 As stated previously, a zone is a point of delegation in
326 the <acronym>DNS</acronym> tree. A zone consists of
327 those contiguous parts of the domain
328 tree for which a name server has complete information and over which
329 it has authority. It contains all domain names from a certain point
330 downward in the domain tree except those which are delegated to
331 other zones. A delegation point is marked by one or more
332 <emphasis>NS records</emphasis> in the
333 parent zone, which should be matched by equivalent NS records at
334 the root of the delegated zone.
338 For instance, consider the <literal>example.com</literal>
339 domain which includes names
340 such as <literal>host.aaa.example.com</literal> and
341 <literal>host.bbb.example.com</literal> even though
342 the <literal>example.com</literal> zone includes
343 only delegations for the <literal>aaa.example.com</literal> and
344 <literal>bbb.example.com</literal> zones. A zone can
346 exactly to a single domain, but could also include only part of a
347 domain, the rest of which could be delegated to other
348 name servers. Every name in the <acronym>DNS</acronym>
350 <emphasis>domain</emphasis>, even if it is
351 <emphasis>terminal</emphasis>, that is, has no
352 <emphasis>subdomains</emphasis>. Every subdomain is a domain and
353 every domain except the root is also a subdomain. The terminology is
354 not intuitive and we suggest that you read RFCs 1033, 1034 and 1035
356 gain a complete understanding of this difficult and subtle
361 Though <acronym>BIND</acronym> is called a "domain name
363 it deals primarily in terms of zones. The master and slave
364 declarations in the <filename>named.conf</filename> file
366 zones, not domains. When you ask some other site if it is willing to
367 be a slave server for your <emphasis>domain</emphasis>, you are
368 actually asking for slave service for some collection of zones.
373 <title>Authoritative Name Servers</title>
376 Each zone is served by at least
377 one <emphasis>authoritative name server</emphasis>,
378 which contains the complete data for the zone.
379 To make the DNS tolerant of server and network failures,
380 most zones have two or more authoritative servers, on
385 Responses from authoritative servers have the "authoritative
386 answer" (AA) bit set in the response packets. This makes them
387 easy to identify when debugging DNS configurations using tools like
388 <command>dig</command> (<xref linkend="diagnostic_tools"/>).
392 <title>The Primary Master</title>
395 The authoritative server where the master copy of the zone
396 data is maintained is called the
397 <emphasis>primary master</emphasis> server, or simply the
398 <emphasis>primary</emphasis>. Typically it loads the zone
399 contents from some local file edited by humans or perhaps
400 generated mechanically from some other local file which is
401 edited by humans. This file is called the
402 <emphasis>zone file</emphasis> or
403 <emphasis>master file</emphasis>.
407 In some cases, however, the master file may not be edited
408 by humans at all, but may instead be the result of
409 <emphasis>dynamic update</emphasis> operations.
414 <title>Slave Servers</title>
416 The other authoritative servers, the <emphasis>slave</emphasis>
417 servers (also known as <emphasis>secondary</emphasis> servers)
419 the zone contents from another server using a replication process
420 known as a <emphasis>zone transfer</emphasis>. Typically the data
422 transferred directly from the primary master, but it is also
424 to transfer it from another slave. In other words, a slave server
425 may itself act as a master to a subordinate slave server.
430 <title>Stealth Servers</title>
433 Usually all of the zone's authoritative servers are listed in
434 NS records in the parent zone. These NS records constitute
435 a <emphasis>delegation</emphasis> of the zone from the parent.
436 The authoritative servers are also listed in the zone file itself,
437 at the <emphasis>top level</emphasis> or <emphasis>apex</emphasis>
438 of the zone. You can list servers in the zone's top-level NS
439 records that are not in the parent's NS delegation, but you cannot
440 list servers in the parent's delegation that are not present at
441 the zone's top level.
445 A <emphasis>stealth server</emphasis> is a server that is
446 authoritative for a zone but is not listed in that zone's NS
447 records. Stealth servers can be used for keeping a local copy of
449 zone to speed up access to the zone's records or to make sure that
451 zone is available even if all the "official" servers for the zone
457 A configuration where the primary master server itself is a
458 stealth server is often referred to as a "hidden primary"
459 configuration. One use for this configuration is when the primary
461 is behind a firewall and therefore unable to communicate directly
462 with the outside world.
470 <title>Caching Name Servers</title>
473 - Terminology here is inconsistent. Probably ought to
474 - convert to using "recursive name server" everywhere
475 - with just a note about "caching" terminology.
479 The resolver libraries provided by most operating systems are
480 <emphasis>stub resolvers</emphasis>, meaning that they are not
482 performing the full DNS resolution process by themselves by talking
483 directly to the authoritative servers. Instead, they rely on a
485 name server to perform the resolution on their behalf. Such a
487 is called a <emphasis>recursive</emphasis> name server; it performs
488 <emphasis>recursive lookups</emphasis> for local clients.
492 To improve performance, recursive servers cache the results of
493 the lookups they perform. Since the processes of recursion and
494 caching are intimately connected, the terms
495 <emphasis>recursive server</emphasis> and
496 <emphasis>caching server</emphasis> are often used synonymously.
500 The length of time for which a record may be retained in
501 the cache of a caching name server is controlled by the
502 Time To Live (TTL) field associated with each resource record.
506 <title>Forwarding</title>
509 Even a caching name server does not necessarily perform
510 the complete recursive lookup itself. Instead, it can
511 <emphasis>forward</emphasis> some or all of the queries
512 that it cannot satisfy from its cache to another caching name
514 commonly referred to as a <emphasis>forwarder</emphasis>.
518 There may be one or more forwarders,
519 and they are queried in turn until the list is exhausted or an
521 is found. Forwarders are typically used when you do not
522 wish all the servers at a given site to interact directly with the
524 the Internet servers. A typical scenario would involve a number
525 of internal <acronym>DNS</acronym> servers and an
526 Internet firewall. Servers unable
527 to pass packets through the firewall would forward to the server
528 that can do it, and that server would query the Internet <acronym>DNS</acronym> servers
529 on the internal server's behalf.
536 <title>Name Servers in Multiple Roles</title>
539 The <acronym>BIND</acronym> name server can
540 simultaneously act as
541 a master for some zones, a slave for other zones, and as a caching
542 (recursive) server for a set of local clients.
546 However, since the functions of authoritative name service
547 and caching/recursive name service are logically separate, it is
548 often advantageous to run them on separate server machines.
550 A server that only provides authoritative name service
551 (an <emphasis>authoritative-only</emphasis> server) can run with
552 recursion disabled, improving reliability and security.
554 A server that is not authoritative for any zones and only provides
555 recursive service to local
556 clients (a <emphasis>caching-only</emphasis> server)
557 does not need to be reachable from the Internet at large and can
558 be placed inside a firewall.
566 <chapter id="Bv9ARM.ch02">
567 <title><acronym>BIND</acronym> Resource Requirements</title>
570 <title>Hardware requirements</title>
573 <acronym>DNS</acronym> hardware requirements have
574 traditionally been quite modest.
575 For many installations, servers that have been pensioned off from
576 active duty have performed admirably as <acronym>DNS</acronym> servers.
579 The DNSSEC features of <acronym>BIND</acronym> 9
580 may prove to be quite
581 CPU intensive however, so organizations that make heavy use of these
582 features may wish to consider larger systems for these applications.
583 <acronym>BIND</acronym> 9 is fully multithreaded, allowing
585 multiprocessor systems for installations that need it.
589 <title>CPU Requirements</title>
591 CPU requirements for <acronym>BIND</acronym> 9 range from
593 for serving of static zones without caching, to enterprise-class
594 machines if you intend to process many dynamic updates and DNSSEC
595 signed zones, serving many thousands of queries per second.
600 <title>Memory Requirements</title>
602 The memory of the server has to be large enough to fit the
603 cache and zones loaded off disk. The <command>max-cache-size</command>
604 option can be used to limit the amount of memory used by the cache,
605 at the expense of reducing cache hit rates and causing more <acronym>DNS</acronym>
607 Additionally, if additional section caching
608 (<xref linkend="acache"/>) is enabled,
609 the <command>max-acache-size</command> option can be used to
611 of memory used by the mechanism.
612 It is still good practice to have enough memory to load
613 all zone and cache data into memory — unfortunately, the best
615 to determine this for a given installation is to watch the name server
616 in operation. After a few weeks the server process should reach
617 a relatively stable size where entries are expiring from the cache as
618 fast as they are being inserted.
621 - Add something here about leaving overhead for attacks?
622 - How much overhead? Percentage?
627 <title>Name Server Intensive Environment Issues</title>
629 For name server intensive environments, there are two alternative
630 configurations that may be used. The first is where clients and
631 any second-level internal name servers query a main name server, which
632 has enough memory to build a large cache. This approach minimizes
633 the bandwidth used by external name lookups. The second alternative
634 is to set up second-level internal name servers to make queries
636 In this configuration, none of the individual machines needs to
637 have as much memory or CPU power as in the first alternative, but
638 this has the disadvantage of making many more external queries,
639 as none of the name servers share their cached data.
644 <title>Supported Operating Systems</title>
646 ISC <acronym>BIND</acronym> 9 compiles and runs on a large
648 of Unix-like operating systems and on
649 Microsoft Windows Server 2003 and 2008, and Windows XP and Vista.
651 list of supported systems, see the README file in the top level
653 of the BIND 9 source distribution.
658 <chapter id="Bv9ARM.ch03">
659 <title>Name Server Configuration</title>
661 In this chapter we provide some suggested configurations along
662 with guidelines for their use. We suggest reasonable values for
663 certain option settings.
666 <sect1 id="sample_configuration">
667 <title>Sample Configurations</title>
669 <title>A Caching-only Name Server</title>
671 The following sample configuration is appropriate for a caching-only
672 name server for use by clients internal to a corporation. All
674 from outside clients are refused using the <command>allow-query</command>
675 option. Alternatively, the same effect could be achieved using
681 // Two corporate subnets we wish to allow queries from.
682 acl corpnets { 192.168.4.0/24; 192.168.7.0/24; };
685 directory "/etc/namedb";
687 allow-query { corpnets; };
689 // Provide a reverse mapping for the loopback
691 zone "0.0.127.in-addr.arpa" {
693 file "localhost.rev";
701 <title>An Authoritative-only Name Server</title>
703 This sample configuration is for an authoritative-only server
704 that is the master server for "<filename>example.com</filename>"
705 and a slave for the subdomain "<filename>eng.example.com</filename>".
711 directory "/etc/namedb";
712 // Do not allow access to cache
713 allow-query-cache { none; };
714 // This is the default
715 allow-query { any; };
716 // Do not provide recursive service
720 // Provide a reverse mapping for the loopback
722 zone "0.0.127.in-addr.arpa" {
724 file "localhost.rev";
727 // We are the master server for example.com
730 file "example.com.db";
731 // IP addresses of slave servers allowed to
732 // transfer example.com
738 // We are a slave server for eng.example.com
739 zone "eng.example.com" {
741 file "eng.example.com.bk";
742 // IP address of eng.example.com master server
743 masters { 192.168.4.12; };
751 <title>Load Balancing</title>
753 - Add explanation of why load balancing is fragile at best
754 - and completely pointless in the general case.
758 A primitive form of load balancing can be achieved in
759 the <acronym>DNS</acronym> by using multiple records
760 (such as multiple A records) for one name.
764 For example, if you have three WWW servers with network addresses
765 of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the
766 following means that clients will connect to each machine one third
770 <informaltable colsep="0" rowsep="0">
771 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="2Level-table">
772 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
773 <colspec colname="2" colnum="2" colsep="0" colwidth="0.500in"/>
774 <colspec colname="3" colnum="3" colsep="0" colwidth="0.750in"/>
775 <colspec colname="4" colnum="4" colsep="0" colwidth="0.750in"/>
776 <colspec colname="5" colnum="5" colsep="0" colwidth="2.028in"/>
801 Resource Record (RR) Data
808 <literal>www</literal>
813 <literal>600</literal>
818 <literal>IN</literal>
828 <literal>10.0.0.1</literal>
838 <literal>600</literal>
843 <literal>IN</literal>
853 <literal>10.0.0.2</literal>
863 <literal>600</literal>
868 <literal>IN</literal>
878 <literal>10.0.0.3</literal>
886 When a resolver queries for these records, <acronym>BIND</acronym> will rotate
887 them and respond to the query with the records in a different
888 order. In the example above, clients will randomly receive
889 records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients
890 will use the first record returned and discard the rest.
893 For more detail on ordering responses, check the
894 <command>rrset-order</command> sub-statement in the
895 <command>options</command> statement, see
896 <xref endterm="rrset_ordering_title" linkend="rrset_ordering"/>.
902 <title>Name Server Operations</title>
905 <title>Tools for Use With the Name Server Daemon</title>
907 This section describes several indispensable diagnostic,
908 administrative and monitoring tools available to the system
909 administrator for controlling and debugging the name server
912 <sect3 id="diagnostic_tools">
913 <title>Diagnostic Tools</title>
915 The <command>dig</command>, <command>host</command>, and
916 <command>nslookup</command> programs are all command
918 for manually querying name servers. They differ in style and
924 <term id="dig"><command>dig</command></term>
927 The domain information groper (<command>dig</command>)
928 is the most versatile and complete of these lookup tools.
929 It has two modes: simple interactive
930 mode for a single query, and batch mode which executes a
932 each in a list of several query lines. All query options are
934 from the command line.
936 <cmdsynopsis label="Usage">
937 <command>dig</command>
938 <arg>@<replaceable>server</replaceable></arg>
939 <arg choice="plain"><replaceable>domain</replaceable></arg>
940 <arg><replaceable>query-type</replaceable></arg>
941 <arg><replaceable>query-class</replaceable></arg>
942 <arg>+<replaceable>query-option</replaceable></arg>
943 <arg>-<replaceable>dig-option</replaceable></arg>
944 <arg>%<replaceable>comment</replaceable></arg>
947 The usual simple use of <command>dig</command> will take the form
950 <command>dig @server domain query-type query-class</command>
953 For more information and a list of available commands and
954 options, see the <command>dig</command> man
961 <term><command>host</command></term>
964 The <command>host</command> utility emphasizes
966 and ease of use. By default, it converts
967 between host names and Internet addresses, but its
969 can be extended with the use of options.
971 <cmdsynopsis label="Usage">
972 <command>host</command>
973 <arg>-aCdlnrsTwv</arg>
974 <arg>-c <replaceable>class</replaceable></arg>
975 <arg>-N <replaceable>ndots</replaceable></arg>
976 <arg>-t <replaceable>type</replaceable></arg>
977 <arg>-W <replaceable>timeout</replaceable></arg>
978 <arg>-R <replaceable>retries</replaceable></arg>
979 <arg>-m <replaceable>flag</replaceable></arg>
982 <arg choice="plain"><replaceable>hostname</replaceable></arg>
983 <arg><replaceable>server</replaceable></arg>
986 For more information and a list of available commands and
987 options, see the <command>host</command> man
994 <term><command>nslookup</command></term>
996 <para><command>nslookup</command>
997 has two modes: interactive and
998 non-interactive. Interactive mode allows the user to
999 query name servers for information about various
1000 hosts and domains or to print a list of hosts in a
1001 domain. Non-interactive mode is used to print just
1002 the name and requested information for a host or
1005 <cmdsynopsis label="Usage">
1006 <command>nslookup</command>
1007 <arg rep="repeat">-option</arg>
1009 <arg><replaceable>host-to-find</replaceable></arg>
1010 <arg>- <arg>server</arg></arg>
1014 Interactive mode is entered when no arguments are given (the
1015 default name server will be used) or when the first argument
1017 hyphen (`-') and the second argument is the host name or
1022 Non-interactive mode is used when the name or Internet
1024 of the host to be looked up is given as the first argument.
1026 optional second argument specifies the host name or address
1030 Due to its arcane user interface and frequently inconsistent
1031 behavior, we do not recommend the use of <command>nslookup</command>.
1032 Use <command>dig</command> instead.
1040 <sect3 id="admin_tools">
1041 <title>Administrative Tools</title>
1043 Administrative tools play an integral part in the management
1047 <varlistentry id="named-checkconf" xreflabel="Named Configuration Checking application">
1049 <term><command>named-checkconf</command></term>
1052 The <command>named-checkconf</command> program
1053 checks the syntax of a <filename>named.conf</filename> file.
1055 <cmdsynopsis label="Usage">
1056 <command>named-checkconf</command>
1058 <arg>-t <replaceable>directory</replaceable></arg>
1059 <arg><replaceable>filename</replaceable></arg>
1063 <varlistentry id="named-checkzone" xreflabel="Zone Checking application">
1065 <term><command>named-checkzone</command></term>
1068 The <command>named-checkzone</command> program
1069 checks a master file for
1070 syntax and consistency.
1072 <cmdsynopsis label="Usage">
1073 <command>named-checkzone</command>
1075 <arg>-c <replaceable>class</replaceable></arg>
1076 <arg>-o <replaceable>output</replaceable></arg>
1077 <arg>-t <replaceable>directory</replaceable></arg>
1078 <arg>-w <replaceable>directory</replaceable></arg>
1079 <arg>-k <replaceable>(ignore|warn|fail)</replaceable></arg>
1080 <arg>-n <replaceable>(ignore|warn|fail)</replaceable></arg>
1081 <arg>-W <replaceable>(ignore|warn)</replaceable></arg>
1082 <arg choice="plain"><replaceable>zone</replaceable></arg>
1083 <arg><replaceable>filename</replaceable></arg>
1087 <varlistentry id="named-compilezone" xreflabel="Zone Compilation application">
1088 <term><command>named-compilezone</command></term>
1091 Similar to <command>named-checkzone,</command> but
1092 it always dumps the zone content to a specified file
1093 (typically in a different format).
1097 <varlistentry id="rndc" xreflabel="Remote Name Daemon Control application">
1099 <term><command>rndc</command></term>
1102 The remote name daemon control
1103 (<command>rndc</command>) program allows the
1105 administrator to control the operation of a name server.
1106 Since <acronym>BIND</acronym> 9.2, <command>rndc</command>
1107 supports all the commands of the BIND 8 <command>ndc</command>
1108 utility except <command>ndc start</command> and
1109 <command>ndc restart</command>, which were also
1110 not supported in <command>ndc</command>'s
1112 If you run <command>rndc</command> without any
1114 it will display a usage message as follows:
1116 <cmdsynopsis label="Usage">
1117 <command>rndc</command>
1118 <arg>-c <replaceable>config</replaceable></arg>
1119 <arg>-s <replaceable>server</replaceable></arg>
1120 <arg>-p <replaceable>port</replaceable></arg>
1121 <arg>-y <replaceable>key</replaceable></arg>
1122 <arg choice="plain"><replaceable>command</replaceable></arg>
1123 <arg rep="repeat"><replaceable>command</replaceable></arg>
1125 <para>The <command>command</command>
1126 is one of the following:
1132 <term><userinput>reload</userinput></term>
1135 Reload configuration file and zones.
1141 <term><userinput>reload <replaceable>zone</replaceable>
1142 <optional><replaceable>class</replaceable>
1143 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1146 Reload the given zone.
1152 <term><userinput>refresh <replaceable>zone</replaceable>
1153 <optional><replaceable>class</replaceable>
1154 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1157 Schedule zone maintenance for the given zone.
1163 <term><userinput>retransfer <replaceable>zone</replaceable>
1165 <optional><replaceable>class</replaceable>
1166 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1169 Retransfer the given zone from the master.
1175 <term><userinput>sign <replaceable>zone</replaceable>
1176 <optional><replaceable>class</replaceable>
1177 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1180 Fetch all DNSSEC keys for the given zone
1181 from the key directory (see
1182 <command>key-directory</command> in
1183 <xref linkend="options"/>). If they are within
1184 their publication period, merge them into the
1185 zone's DNSKEY RRset. If the DNSKEY RRset
1186 is changed, then the zone is automatically
1187 re-signed with the new key set.
1190 This command requires that the
1191 <command>auto-dnssec</command> zone option to be set
1192 to <literal>allow</literal>,
1193 <literal>maintain</literal>, or
1194 <literal>create</literal>, and also requires
1195 the zone to be configured to allow dynamic DNS.
1196 See <xref linkend="dynamic_update_policies"/> for
1203 <term><userinput>loadkeys <replaceable>zone</replaceable>
1204 <optional><replaceable>class</replaceable>
1205 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1208 Fetch all DNSSEC keys for the given zone
1209 from the key directory (see
1210 <command>key-directory</command> in
1211 <xref linkend="options"/>). If they are within
1212 their publication period, merge them into the
1213 zone's DNSKEY RRset. Unlike <command>rndc
1214 sign</command>, however, the zone is not
1215 immediately re-signed by the new keys, but is
1216 allowed to incrementally re-sign over time.
1219 This command requires that the
1220 <command>auto-dnssec</command> zone option to
1221 be set to <literal>maintain</literal> or
1222 <literal>create</literal>, and also requires
1223 the zone to be configured to allow dynamic DNS.
1224 See <xref linkend="dynamic_update_policies"/> for
1231 <term><userinput>freeze
1232 <optional><replaceable>zone</replaceable>
1233 <optional><replaceable>class</replaceable>
1234 <optional><replaceable>view</replaceable></optional></optional></optional></userinput></term>
1237 Suspend updates to a dynamic zone. If no zone is
1239 then all zones are suspended. This allows manual
1240 edits to be made to a zone normally updated by dynamic
1242 also causes changes in the journal file to be synced
1244 and the journal file to be removed. All dynamic
1245 update attempts will
1246 be refused while the zone is frozen.
1252 <term><userinput>thaw
1253 <optional><replaceable>zone</replaceable>
1254 <optional><replaceable>class</replaceable>
1255 <optional><replaceable>view</replaceable></optional></optional></optional></userinput></term>
1258 Enable updates to a frozen dynamic zone. If no zone
1260 specified, then all frozen zones are enabled. This
1262 the server to reload the zone from disk, and
1263 re-enables dynamic updates
1264 after the load has completed. After a zone is thawed,
1266 will no longer be refused.
1272 <term><userinput>notify <replaceable>zone</replaceable>
1273 <optional><replaceable>class</replaceable>
1274 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1277 Resend NOTIFY messages for the zone.
1283 <term><userinput>reconfig</userinput></term>
1286 Reload the configuration file and load new zones,
1287 but do not reload existing zone files even if they
1289 This is faster than a full <command>reload</command> when there
1290 is a large number of zones because it avoids the need
1292 modification times of the zones files.
1298 <term><userinput>stats</userinput></term>
1301 Write server statistics to the statistics file.
1307 <term><userinput>querylog</userinput></term>
1310 Toggle query logging. Query logging can also be enabled
1311 by explicitly directing the <command>queries</command>
1312 <command>category</command> to a
1313 <command>channel</command> in the
1314 <command>logging</command> section of
1315 <filename>named.conf</filename> or by specifying
1316 <command>querylog yes;</command> in the
1317 <command>options</command> section of
1318 <filename>named.conf</filename>.
1324 <term><userinput>dumpdb
1325 <optional>-all|-cache|-zone</optional>
1326 <optional><replaceable>view ...</replaceable></optional></userinput></term>
1329 Dump the server's caches (default) and/or zones to
1331 dump file for the specified views. If no view is
1339 <term><userinput>secroots
1340 <optional><replaceable>view ...</replaceable></optional></userinput></term>
1343 Dump the server's security roots to the secroots
1344 file for the specified views. If no view is
1345 specified, security roots for all
1352 <term><userinput>stop <optional>-p</optional></userinput></term>
1355 Stop the server, making sure any recent changes
1356 made through dynamic update or IXFR are first saved to
1357 the master files of the updated zones.
1358 If <option>-p</option> is specified <command>named</command>'s process id is returned.
1359 This allows an external process to determine when <command>named</command>
1360 had completed stopping.
1366 <term><userinput>halt <optional>-p</optional></userinput></term>
1369 Stop the server immediately. Recent changes
1370 made through dynamic update or IXFR are not saved to
1371 the master files, but will be rolled forward from the
1372 journal files when the server is restarted.
1373 If <option>-p</option> is specified <command>named</command>'s process id is returned.
1374 This allows an external process to determine when <command>named</command>
1375 had completed halting.
1381 <term><userinput>trace</userinput></term>
1384 Increment the servers debugging level by one.
1390 <term><userinput>trace <replaceable>level</replaceable></userinput></term>
1393 Sets the server's debugging level to an explicit
1400 <term><userinput>notrace</userinput></term>
1403 Sets the server's debugging level to 0.
1409 <term><userinput>flush</userinput></term>
1412 Flushes the server's cache.
1418 <term><userinput>flushname</userinput> <replaceable>name</replaceable></term>
1421 Flushes the given name from the server's cache.
1427 <term><userinput>status</userinput></term>
1430 Display status of the server.
1431 Note that the number of zones includes the internal <command>bind/CH</command> zone
1432 and the default <command>./IN</command>
1433 hint zone if there is not an
1434 explicit root zone configured.
1440 <term><userinput>recursing</userinput></term>
1443 Dump the list of queries <command>named</command> is currently recursing
1450 <term><userinput>validation
1451 <optional>on|off</optional>
1452 <optional><replaceable>view ...</replaceable></optional>
1456 Enable or disable DNSSEC validation.
1457 Note <command>dnssec-enable</command> also needs to be
1458 set to <userinput>yes</userinput> to be effective.
1459 It defaults to enabled.
1465 <term><userinput>addzone
1466 <replaceable>zone</replaceable>
1467 <optional><replaceable>class</replaceable>
1468 <optional><replaceable>view</replaceable></optional></optional>
1469 <replaceable>configuration</replaceable>
1473 Add a zone while the server is running. This
1474 command requires the
1475 <command>allow-new-zones</command> option to be set
1476 to <userinput>yes</userinput>. The
1477 <replaceable>configuration</replaceable> string
1478 specified on the command line is the zone
1479 configuration text that would ordinarily be
1480 placed in <filename>named.conf</filename>.
1483 The configuration is saved in a file called
1484 <filename><replaceable>hash</replaceable>.nzf</filename>,
1485 where <replaceable>hash</replaceable> is a
1486 cryptographic hash generated from the name of
1487 the view. When <command>named</command> is
1488 restarted, the file will be loaded into the view
1489 configuration, so that zones that were added
1490 can persist after a restart.
1493 This sample <command>addzone</command> command
1494 would add the zone <literal>example.com</literal>
1495 to the default view:
1498 <prompt>$ </prompt><userinput>rndc addzone example.com '{ type master; file "example.com.db"; };'</userinput>
1501 (Note the brackets and semi-colon around the zone
1502 configuration text.)
1508 <term><userinput>delzone
1509 <replaceable>zone</replaceable>
1510 <optional><replaceable>class</replaceable>
1511 <optional><replaceable>view</replaceable></optional></optional>
1515 Delete a zone while the server is running.
1516 Only zones that were originally added via
1517 <command>rndc addzone</command> can be deleted
1526 A configuration file is required, since all
1527 communication with the server is authenticated with
1528 digital signatures that rely on a shared secret, and
1529 there is no way to provide that secret other than with a
1530 configuration file. The default location for the
1531 <command>rndc</command> configuration file is
1532 <filename>/etc/rndc.conf</filename>, but an
1534 location can be specified with the <option>-c</option>
1535 option. If the configuration file is not found,
1536 <command>rndc</command> will also look in
1537 <filename>/etc/rndc.key</filename> (or whatever
1538 <varname>sysconfdir</varname> was defined when
1539 the <acronym>BIND</acronym> build was
1541 The <filename>rndc.key</filename> file is
1543 running <command>rndc-confgen -a</command> as
1545 <xref linkend="controls_statement_definition_and_usage"/>.
1549 The format of the configuration file is similar to
1550 that of <filename>named.conf</filename>, but
1552 only four statements, the <command>options</command>,
1553 <command>key</command>, <command>server</command> and
1554 <command>include</command>
1555 statements. These statements are what associate the
1556 secret keys to the servers with which they are meant to
1557 be shared. The order of statements is not
1562 The <command>options</command> statement has
1564 <command>default-server</command>, <command>default-key</command>,
1565 and <command>default-port</command>.
1566 <command>default-server</command> takes a
1567 host name or address argument and represents the server
1569 be contacted if no <option>-s</option>
1570 option is provided on the command line.
1571 <command>default-key</command> takes
1572 the name of a key as its argument, as defined by a <command>key</command> statement.
1573 <command>default-port</command> specifies the
1575 <command>rndc</command> should connect if no
1576 port is given on the command line or in a
1577 <command>server</command> statement.
1581 The <command>key</command> statement defines a
1583 by <command>rndc</command> when authenticating
1585 <command>named</command>. Its syntax is
1587 <command>key</command> statement in <filename>named.conf</filename>.
1588 The keyword <userinput>key</userinput> is
1589 followed by a key name, which must be a valid
1590 domain name, though it need not actually be hierarchical;
1592 a string like "<userinput>rndc_key</userinput>" is a valid
1594 The <command>key</command> statement has two
1596 <command>algorithm</command> and <command>secret</command>.
1597 While the configuration parser will accept any string as the
1599 to algorithm, currently only the string "<userinput>hmac-md5</userinput>"
1600 has any meaning. The secret is a base-64 encoded string
1601 as specified in RFC 3548.
1605 The <command>server</command> statement
1607 defined using the <command>key</command>
1608 statement with a server.
1609 The keyword <userinput>server</userinput> is followed by a
1610 host name or address. The <command>server</command> statement
1611 has two clauses: <command>key</command> and <command>port</command>.
1612 The <command>key</command> clause specifies the
1614 to be used when communicating with this server, and the
1615 <command>port</command> clause can be used to
1616 specify the port <command>rndc</command> should
1622 A sample minimal configuration file is as follows:
1627 algorithm "hmac-md5";
1629 "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
1632 default-server 127.0.0.1;
1633 default-key rndc_key;
1638 This file, if installed as <filename>/etc/rndc.conf</filename>,
1639 would allow the command:
1643 <prompt>$ </prompt><userinput>rndc reload</userinput>
1647 to connect to 127.0.0.1 port 953 and cause the name server
1648 to reload, if a name server on the local machine were
1650 following controls statements:
1656 allow { localhost; } keys { rndc_key; };
1661 and it had an identical key statement for
1662 <literal>rndc_key</literal>.
1666 Running the <command>rndc-confgen</command>
1668 conveniently create a <filename>rndc.conf</filename>
1669 file for you, and also display the
1670 corresponding <command>controls</command>
1671 statement that you need to
1672 add to <filename>named.conf</filename>.
1674 you can run <command>rndc-confgen -a</command>
1676 a <filename>rndc.key</filename> file and not
1678 <filename>named.conf</filename> at all.
1689 <title>Signals</title>
1691 Certain UNIX signals cause the name server to take specific
1692 actions, as described in the following table. These signals can
1693 be sent using the <command>kill</command> command.
1695 <informaltable frame="all">
1697 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
1698 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
1702 <para><command>SIGHUP</command></para>
1706 Causes the server to read <filename>named.conf</filename> and
1707 reload the database.
1713 <para><command>SIGTERM</command></para>
1717 Causes the server to clean up and exit.
1723 <para><command>SIGINT</command></para>
1727 Causes the server to clean up and exit.
1738 <chapter id="Bv9ARM.ch04">
1739 <title>Advanced DNS Features</title>
1743 <title>Notify</title>
1745 <acronym>DNS</acronym> NOTIFY is a mechanism that allows master
1746 servers to notify their slave servers of changes to a zone's data. In
1747 response to a <command>NOTIFY</command> from a master server, the
1748 slave will check to see that its version of the zone is the
1749 current version and, if not, initiate a zone transfer.
1753 For more information about <acronym>DNS</acronym>
1754 <command>NOTIFY</command>, see the description of the
1755 <command>notify</command> option in <xref linkend="boolean_options"/> and
1756 the description of the zone option <command>also-notify</command> in
1757 <xref linkend="zone_transfers"/>. The <command>NOTIFY</command>
1758 protocol is specified in RFC 1996.
1762 As a slave zone can also be a master to other slaves, <command>named</command>,
1763 by default, sends <command>NOTIFY</command> messages for every zone
1764 it loads. Specifying <command>notify master-only;</command> will
1765 cause <command>named</command> to only send <command>NOTIFY</command> for master
1766 zones that it loads.
1771 <sect1 id="dynamic_update">
1772 <title>Dynamic Update</title>
1775 Dynamic Update is a method for adding, replacing or deleting
1776 records in a master server by sending it a special form of DNS
1777 messages. The format and meaning of these messages is specified
1782 Dynamic update is enabled by including an
1783 <command>allow-update</command> or an <command>update-policy</command>
1784 clause in the <command>zone</command> statement.
1788 If the zone's <command>update-policy</command> is set to
1789 <userinput>local</userinput>, updates to the zone
1790 will be permitted for the key <varname>local-ddns</varname>,
1791 which will be generated by <command>named</command> at startup.
1792 See <xref linkend="dynamic_update_policies"/> for more details.
1796 Dynamic updates using Kerberos signed requests can be made
1797 using the TKEY/GSS protocol by setting either the
1798 <command>tkey-gssapi-keytab</command> option, or alternatively
1799 by setting both the <command>tkey-gssapi-credential</command>
1800 and <command>tkey-domain</command> options. Once enabled,
1801 Kerberos signed requests will be matched against the update
1802 policies for the zone, using the Kerberos principal as the
1803 signer for the request.
1807 Updating of secure zones (zones using DNSSEC) follows RFC
1808 3007: RRSIG, NSEC and NSEC3 records affected by updates are
1809 automatically regenerated by the server using an online
1810 zone key. Update authorization is based on transaction
1811 signatures and an explicit server policy.
1814 <sect2 id="journal">
1815 <title>The journal file</title>
1818 All changes made to a zone using dynamic update are stored
1819 in the zone's journal file. This file is automatically created
1820 by the server when the first dynamic update takes place.
1821 The name of the journal file is formed by appending the extension
1822 <filename>.jnl</filename> to the name of the
1824 file unless specifically overridden. The journal file is in a
1825 binary format and should not be edited manually.
1829 The server will also occasionally write ("dump")
1830 the complete contents of the updated zone to its zone file.
1831 This is not done immediately after
1832 each dynamic update, because that would be too slow when a large
1833 zone is updated frequently. Instead, the dump is delayed by
1834 up to 15 minutes, allowing additional updates to take place.
1835 During the dump process, transient files will be created
1836 with the extensions <filename>.jnw</filename> and
1837 <filename>.jbk</filename>; under ordinary circumstances, these
1838 will be removed when the dump is complete, and can be safely
1843 When a server is restarted after a shutdown or crash, it will replay
1844 the journal file to incorporate into the zone any updates that
1846 place after the last zone dump.
1850 Changes that result from incoming incremental zone transfers are
1852 journalled in a similar way.
1856 The zone files of dynamic zones cannot normally be edited by
1857 hand because they are not guaranteed to contain the most recent
1858 dynamic changes — those are only in the journal file.
1859 The only way to ensure that the zone file of a dynamic zone
1860 is up to date is to run <command>rndc stop</command>.
1864 If you have to make changes to a dynamic zone
1865 manually, the following procedure will work: Disable dynamic updates
1867 <command>rndc freeze <replaceable>zone</replaceable></command>.
1868 This will also remove the zone's <filename>.jnl</filename> file
1869 and update the master file. Edit the zone file. Run
1870 <command>rndc thaw <replaceable>zone</replaceable></command>
1871 to reload the changed zone and re-enable dynamic updates.
1878 <sect1 id="incremental_zone_transfers">
1879 <title>Incremental Zone Transfers (IXFR)</title>
1882 The incremental zone transfer (IXFR) protocol is a way for
1883 slave servers to transfer only changed data, instead of having to
1884 transfer the entire zone. The IXFR protocol is specified in RFC
1885 1995. See <xref linkend="proposed_standards"/>.
1889 When acting as a master, <acronym>BIND</acronym> 9
1890 supports IXFR for those zones
1891 where the necessary change history information is available. These
1892 include master zones maintained by dynamic update and slave zones
1893 whose data was obtained by IXFR. For manually maintained master
1894 zones, and for slave zones obtained by performing a full zone
1895 transfer (AXFR), IXFR is supported only if the option
1896 <command>ixfr-from-differences</command> is set
1897 to <userinput>yes</userinput>.
1901 When acting as a slave, <acronym>BIND</acronym> 9 will
1902 attempt to use IXFR unless
1903 it is explicitly disabled. For more information about disabling
1904 IXFR, see the description of the <command>request-ixfr</command> clause
1905 of the <command>server</command> statement.
1910 <title>Split DNS</title>
1912 Setting up different views, or visibility, of the DNS space to
1913 internal and external resolvers is usually referred to as a
1914 <emphasis>Split DNS</emphasis> setup. There are several
1915 reasons an organization would want to set up its DNS this way.
1918 One common reason for setting up a DNS system this way is
1919 to hide "internal" DNS information from "external" clients on the
1920 Internet. There is some debate as to whether or not this is actually
1922 Internal DNS information leaks out in many ways (via email headers,
1923 for example) and most savvy "attackers" can find the information
1924 they need using other means.
1925 However, since listing addresses of internal servers that
1926 external clients cannot possibly reach can result in
1927 connection delays and other annoyances, an organization may
1928 choose to use a Split DNS to present a consistent view of itself
1929 to the outside world.
1932 Another common reason for setting up a Split DNS system is
1933 to allow internal networks that are behind filters or in RFC 1918
1934 space (reserved IP space, as documented in RFC 1918) to resolve DNS
1935 on the Internet. Split DNS can also be used to allow mail from outside
1936 back in to the internal network.
1939 <title>Example split DNS setup</title>
1941 Let's say a company named <emphasis>Example, Inc.</emphasis>
1942 (<literal>example.com</literal>)
1943 has several corporate sites that have an internal network with
1945 Internet Protocol (IP) space and an external demilitarized zone (DMZ),
1946 or "outside" section of a network, that is available to the public.
1949 <emphasis>Example, Inc.</emphasis> wants its internal clients
1950 to be able to resolve external hostnames and to exchange mail with
1951 people on the outside. The company also wants its internal resolvers
1952 to have access to certain internal-only zones that are not available
1953 at all outside of the internal network.
1956 In order to accomplish this, the company will set up two sets
1957 of name servers. One set will be on the inside network (in the
1959 IP space) and the other set will be on bastion hosts, which are
1961 hosts that can talk to both sides of its network, in the DMZ.
1964 The internal servers will be configured to forward all queries,
1965 except queries for <filename>site1.internal</filename>, <filename>site2.internal</filename>, <filename>site1.example.com</filename>,
1966 and <filename>site2.example.com</filename>, to the servers
1968 DMZ. These internal servers will have complete sets of information
1969 for <filename>site1.example.com</filename>, <filename>site2.example.com</filename>, <filename>site1.internal</filename>,
1970 and <filename>site2.internal</filename>.
1973 To protect the <filename>site1.internal</filename> and <filename>site2.internal</filename> domains,
1974 the internal name servers must be configured to disallow all queries
1975 to these domains from any external hosts, including the bastion
1979 The external servers, which are on the bastion hosts, will
1980 be configured to serve the "public" version of the <filename>site1</filename> and <filename>site2.example.com</filename> zones.
1981 This could include things such as the host records for public servers
1982 (<filename>www.example.com</filename> and <filename>ftp.example.com</filename>),
1983 and mail exchange (MX) records (<filename>a.mx.example.com</filename> and <filename>b.mx.example.com</filename>).
1986 In addition, the public <filename>site1</filename> and <filename>site2.example.com</filename> zones
1987 should have special MX records that contain wildcard (`*') records
1988 pointing to the bastion hosts. This is needed because external mail
1989 servers do not have any other way of looking up how to deliver mail
1990 to those internal hosts. With the wildcard records, the mail will
1991 be delivered to the bastion host, which can then forward it on to
1995 Here's an example of a wildcard MX record:
1997 <programlisting>* IN MX 10 external1.example.com.</programlisting>
1999 Now that they accept mail on behalf of anything in the internal
2000 network, the bastion hosts will need to know how to deliver mail
2001 to internal hosts. In order for this to work properly, the resolvers
2003 the bastion hosts will need to be configured to point to the internal
2004 name servers for DNS resolution.
2007 Queries for internal hostnames will be answered by the internal
2008 servers, and queries for external hostnames will be forwarded back
2009 out to the DNS servers on the bastion hosts.
2012 In order for all this to work properly, internal clients will
2013 need to be configured to query <emphasis>only</emphasis> the internal
2014 name servers for DNS queries. This could also be enforced via
2016 filtering on the network.
2019 If everything has been set properly, <emphasis>Example, Inc.</emphasis>'s
2020 internal clients will now be able to:
2025 Look up any hostnames in the <literal>site1</literal>
2027 <literal>site2.example.com</literal> zones.
2032 Look up any hostnames in the <literal>site1.internal</literal> and
2033 <literal>site2.internal</literal> domains.
2037 <simpara>Look up any hostnames on the Internet.</simpara>
2040 <simpara>Exchange mail with both internal and external people.</simpara>
2044 Hosts on the Internet will be able to:
2049 Look up any hostnames in the <literal>site1</literal>
2051 <literal>site2.example.com</literal> zones.
2056 Exchange mail with anyone in the <literal>site1</literal> and
2057 <literal>site2.example.com</literal> zones.
2063 Here is an example configuration for the setup we just
2064 described above. Note that this is only configuration information;
2065 for information on how to configure your zone files, see <xref linkend="sample_configuration"/>.
2069 Internal DNS server config:
2074 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
2076 acl externals { <varname>bastion-ips-go-here</varname>; };
2082 // forward to external servers
2084 <varname>bastion-ips-go-here</varname>;
2086 // sample allow-transfer (no one)
2087 allow-transfer { none; };
2088 // restrict query access
2089 allow-query { internals; externals; };
2090 // restrict recursion
2091 allow-recursion { internals; };
2096 // sample master zone
2097 zone "site1.example.com" {
2099 file "m/site1.example.com";
2100 // do normal iterative resolution (do not forward)
2102 allow-query { internals; externals; };
2103 allow-transfer { internals; };
2106 // sample slave zone
2107 zone "site2.example.com" {
2109 file "s/site2.example.com";
2110 masters { 172.16.72.3; };
2112 allow-query { internals; externals; };
2113 allow-transfer { internals; };
2116 zone "site1.internal" {
2118 file "m/site1.internal";
2120 allow-query { internals; };
2121 allow-transfer { internals; }
2124 zone "site2.internal" {
2126 file "s/site2.internal";
2127 masters { 172.16.72.3; };
2129 allow-query { internals };
2130 allow-transfer { internals; }
2135 External (bastion host) DNS server config:
2139 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
2141 acl externals { bastion-ips-go-here; };
2146 // sample allow-transfer (no one)
2147 allow-transfer { none; };
2148 // default query access
2149 allow-query { any; };
2150 // restrict cache access
2151 allow-query-cache { internals; externals; };
2152 // restrict recursion
2153 allow-recursion { internals; externals; };
2158 // sample slave zone
2159 zone "site1.example.com" {
2161 file "m/site1.foo.com";
2162 allow-transfer { internals; externals; };
2165 zone "site2.example.com" {
2167 file "s/site2.foo.com";
2168 masters { another_bastion_host_maybe; };
2169 allow-transfer { internals; externals; }
2174 In the <filename>resolv.conf</filename> (or equivalent) on
2175 the bastion host(s):
2180 nameserver 172.16.72.2
2181 nameserver 172.16.72.3
2182 nameserver 172.16.72.4
2190 This is a short guide to setting up Transaction SIGnatures
2191 (TSIG) based transaction security in <acronym>BIND</acronym>. It describes changes
2192 to the configuration file as well as what changes are required for
2193 different features, including the process of creating transaction
2194 keys and using transaction signatures with <acronym>BIND</acronym>.
2197 <acronym>BIND</acronym> primarily supports TSIG for server
2198 to server communication.
2199 This includes zone transfer, notify, and recursive query messages.
2200 Resolvers based on newer versions of <acronym>BIND</acronym> 8 have limited support
2205 TSIG can also be useful for dynamic update. A primary
2206 server for a dynamic zone should control access to the dynamic
2207 update service, but IP-based access control is insufficient.
2208 The cryptographic access control provided by TSIG
2209 is far superior. The <command>nsupdate</command>
2210 program supports TSIG via the <option>-k</option> and
2211 <option>-y</option> command line options or inline by use
2212 of the <command>key</command>.
2216 <title>Generate Shared Keys for Each Pair of Hosts</title>
2218 A shared secret is generated to be shared between <emphasis>host1</emphasis> and <emphasis>host2</emphasis>.
2219 An arbitrary key name is chosen: "host1-host2.". The key name must
2220 be the same on both hosts.
2223 <title>Automatic Generation</title>
2225 The following command will generate a 128-bit (16 byte) HMAC-SHA256
2226 key as described above. Longer keys are better, but shorter keys
2227 are easier to read. Note that the maximum key length is the digest
2228 length, here 256 bits.
2231 <userinput>dnssec-keygen -a hmac-sha256 -b 128 -n HOST host1-host2.</userinput>
2234 The key is in the file <filename>Khost1-host2.+163+00000.private</filename>.
2235 Nothing directly uses this file, but the base-64 encoded string
2236 following "<literal>Key:</literal>"
2237 can be extracted from the file and used as a shared secret:
2239 <programlisting>Key: La/E5CjG9O+os1jq0a2jdA==</programlisting>
2241 The string "<literal>La/E5CjG9O+os1jq0a2jdA==</literal>" can
2242 be used as the shared secret.
2246 <title>Manual Generation</title>
2248 The shared secret is simply a random sequence of bits, encoded
2249 in base-64. Most ASCII strings are valid base-64 strings (assuming
2250 the length is a multiple of 4 and only valid characters are used),
2251 so the shared secret can be manually generated.
2254 Also, a known string can be run through <command>mmencode</command> or
2255 a similar program to generate base-64 encoded data.
2260 <title>Copying the Shared Secret to Both Machines</title>
2262 This is beyond the scope of DNS. A secure transport mechanism
2263 should be used. This could be secure FTP, ssh, telephone, etc.
2267 <title>Informing the Servers of the Key's Existence</title>
2269 Imagine <emphasis>host1</emphasis> and <emphasis>host 2</emphasis>
2271 both servers. The following is added to each server's <filename>named.conf</filename> file:
2276 algorithm hmac-sha256;
2277 secret "La/E5CjG9O+os1jq0a2jdA==";
2282 The secret is the one generated above. Since this is a secret, it
2283 is recommended that either <filename>named.conf</filename> be
2284 non-world readable, or the key directive be added to a non-world
2285 readable file that is included by <filename>named.conf</filename>.
2288 At this point, the key is recognized. This means that if the
2289 server receives a message signed by this key, it can verify the
2290 signature. If the signature is successfully verified, the
2291 response is signed by the same key.
2296 <title>Instructing the Server to Use the Key</title>
2298 Since keys are shared between two hosts only, the server must
2299 be told when keys are to be used. The following is added to the <filename>named.conf</filename> file
2300 for <emphasis>host1</emphasis>, if the IP address of <emphasis>host2</emphasis> is
2306 keys { host1-host2. ;};
2311 Multiple keys may be present, but only the first is used.
2312 This directive does not contain any secrets, so it may be in a
2317 If <emphasis>host1</emphasis> sends a message that is a request
2318 to that address, the message will be signed with the specified key. <emphasis>host1</emphasis> will
2319 expect any responses to signed messages to be signed with the same
2323 A similar statement must be present in <emphasis>host2</emphasis>'s
2324 configuration file (with <emphasis>host1</emphasis>'s address) for <emphasis>host2</emphasis> to
2325 sign request messages to <emphasis>host1</emphasis>.
2329 <title>TSIG Key Based Access Control</title>
2331 <acronym>BIND</acronym> allows IP addresses and ranges
2332 to be specified in ACL
2334 <command>allow-{ query | transfer | update }</command>
2336 This has been extended to allow TSIG keys also. The above key would
2337 be denoted <command>key host1-host2.</command>
2340 An example of an <command>allow-update</command> directive would be:
2344 allow-update { key host1-host2. ;};
2348 This allows dynamic updates to succeed only if the request
2349 was signed by a key named "<command>host1-host2.</command>".
2353 See <xref linkend="dynamic_update_policies"/> for a discussion of
2354 the more flexible <command>update-policy</command> statement.
2359 <title>Errors</title>
2362 The processing of TSIG signed messages can result in
2363 several errors. If a signed message is sent to a non-TSIG aware
2364 server, a FORMERR (format error) will be returned, since the server will not
2365 understand the record. This is a result of misconfiguration,
2366 since the server must be explicitly configured to send a TSIG
2367 signed message to a specific server.
2371 If a TSIG aware server receives a message signed by an
2372 unknown key, the response will be unsigned with the TSIG
2373 extended error code set to BADKEY. If a TSIG aware server
2374 receives a message with a signature that does not validate, the
2375 response will be unsigned with the TSIG extended error code set
2376 to BADSIG. If a TSIG aware server receives a message with a time
2377 outside of the allowed range, the response will be signed with
2378 the TSIG extended error code set to BADTIME, and the time values
2379 will be adjusted so that the response can be successfully
2380 verified. In any of these cases, the message's rcode (response code) is set to
2381 NOTAUTH (not authenticated).
2389 <para><command>TKEY</command>
2390 is a mechanism for automatically generating a shared secret
2391 between two hosts. There are several "modes" of
2392 <command>TKEY</command> that specify how the key is generated
2393 or assigned. <acronym>BIND</acronym> 9 implements only one of
2394 these modes, the Diffie-Hellman key exchange. Both hosts are
2395 required to have a Diffie-Hellman KEY record (although this
2396 record is not required to be present in a zone). The
2397 <command>TKEY</command> process must use signed messages,
2398 signed either by TSIG or SIG(0). The result of
2399 <command>TKEY</command> is a shared secret that can be used to
2400 sign messages with TSIG. <command>TKEY</command> can also be
2401 used to delete shared secrets that it had previously
2406 The <command>TKEY</command> process is initiated by a
2408 or server by sending a signed <command>TKEY</command>
2410 (including any appropriate KEYs) to a TKEY-aware server. The
2411 server response, if it indicates success, will contain a
2412 <command>TKEY</command> record and any appropriate keys.
2414 this exchange, both participants have enough information to
2415 determine the shared secret; the exact process depends on the
2416 <command>TKEY</command> mode. When using the
2418 <command>TKEY</command> mode, Diffie-Hellman keys are
2420 and the shared secret is derived by both participants.
2425 <title>SIG(0)</title>
2428 <acronym>BIND</acronym> 9 partially supports DNSSEC SIG(0)
2429 transaction signatures as specified in RFC 2535 and RFC 2931.
2431 uses public/private keys to authenticate messages. Access control
2432 is performed in the same manner as TSIG keys; privileges can be
2433 granted or denied based on the key name.
2437 When a SIG(0) signed message is received, it will only be
2438 verified if the key is known and trusted by the server; the server
2439 will not attempt to locate and/or validate the key.
2443 SIG(0) signing of multiple-message TCP streams is not
2448 The only tool shipped with <acronym>BIND</acronym> 9 that
2449 generates SIG(0) signed messages is <command>nsupdate</command>.
2454 <title>DNSSEC</title>
2457 Cryptographic authentication of DNS information is possible
2458 through the DNS Security (<emphasis>DNSSEC-bis</emphasis>) extensions,
2459 defined in RFC 4033, RFC 4034, and RFC 4035.
2460 This section describes the creation and use of DNSSEC signed zones.
2464 In order to set up a DNSSEC secure zone, there are a series
2465 of steps which must be followed. <acronym>BIND</acronym>
2468 that are used in this process, which are explained in more detail
2469 below. In all cases, the <option>-h</option> option prints a
2470 full list of parameters. Note that the DNSSEC tools require the
2471 keyset files to be in the working directory or the
2472 directory specified by the <option>-d</option> option, and
2473 that the tools shipped with BIND 9.2.x and earlier are not compatible
2474 with the current ones.
2478 There must also be communication with the administrators of
2479 the parent and/or child zone to transmit keys. A zone's security
2480 status must be indicated by the parent zone for a DNSSEC capable
2481 resolver to trust its data. This is done through the presence
2482 or absence of a <literal>DS</literal> record at the
2488 For other servers to trust data in this zone, they must
2489 either be statically configured with this zone's zone key or the
2490 zone key of another zone above this one in the DNS tree.
2494 <title>Generating Keys</title>
2497 The <command>dnssec-keygen</command> program is used to
2502 A secure zone must contain one or more zone keys. The
2503 zone keys will sign all other records in the zone, as well as
2504 the zone keys of any secure delegated zones. Zone keys must
2505 have the same name as the zone, a name type of
2506 <command>ZONE</command>, and must be usable for
2508 It is recommended that zone keys use a cryptographic algorithm
2509 designated as "mandatory to implement" by the IETF; currently
2510 the only one is RSASHA1.
2514 The following command will generate a 768-bit RSASHA1 key for
2515 the <filename>child.example</filename> zone:
2519 <userinput>dnssec-keygen -a RSASHA1 -b 768 -n ZONE child.example.</userinput>
2523 Two output files will be produced:
2524 <filename>Kchild.example.+005+12345.key</filename> and
2525 <filename>Kchild.example.+005+12345.private</filename>
2527 12345 is an example of a key tag). The key filenames contain
2528 the key name (<filename>child.example.</filename>),
2530 is DSA, 1 is RSAMD5, 5 is RSASHA1, etc.), and the key tag (12345 in
2532 The private key (in the <filename>.private</filename>
2534 used to generate signatures, and the public key (in the
2535 <filename>.key</filename> file) is used for signature
2540 To generate another key with the same properties (but with
2541 a different key tag), repeat the above command.
2545 The <command>dnssec-keyfromlabel</command> program is used
2546 to get a key pair from a crypto hardware and build the key
2547 files. Its usage is similar to <command>dnssec-keygen</command>.
2551 The public keys should be inserted into the zone file by
2552 including the <filename>.key</filename> files using
2553 <command>$INCLUDE</command> statements.
2558 <title>Signing the Zone</title>
2561 The <command>dnssec-signzone</command> program is used
2566 Any <filename>keyset</filename> files corresponding to
2567 secure subzones should be present. The zone signer will
2568 generate <literal>NSEC</literal>, <literal>NSEC3</literal>
2569 and <literal>RRSIG</literal> records for the zone, as
2570 well as <literal>DS</literal> for the child zones if
2571 <literal>'-g'</literal> is specified. If <literal>'-g'</literal>
2572 is not specified, then DS RRsets for the secure child
2573 zones need to be added manually.
2577 The following command signs the zone, assuming it is in a
2578 file called <filename>zone.child.example</filename>. By
2579 default, all zone keys which have an available private key are
2580 used to generate signatures.
2584 <userinput>dnssec-signzone -o child.example zone.child.example</userinput>
2588 One output file is produced:
2589 <filename>zone.child.example.signed</filename>. This
2591 should be referenced by <filename>named.conf</filename>
2593 input file for the zone.
2596 <para><command>dnssec-signzone</command>
2597 will also produce a keyset and dsset files and optionally a
2598 dlvset file. These are used to provide the parent zone
2599 administrators with the <literal>DNSKEYs</literal> (or their
2600 corresponding <literal>DS</literal> records) that are the
2601 secure entry point to the zone.
2607 <title>Configuring Servers</title>
2610 To enable <command>named</command> to respond appropriately
2611 to DNS requests from DNSSEC aware clients,
2612 <command>dnssec-enable</command> must be set to yes.
2613 (This is the default setting.)
2617 To enable <command>named</command> to validate answers from
2618 other servers, the <command>dnssec-enable</command> option
2619 must be set to <userinput>yes</userinput>, and the
2620 <command>dnssec-validation</command> options must be set to
2621 <userinput>yes</userinput> or <userinput>auto</userinput>.
2625 If <command>dnssec-validation</command> is set to
2626 <userinput>auto</userinput>, then a default
2627 trust anchor for the DNS root zone will be used.
2628 If it is set to <userinput>yes</userinput>, however,
2629 then at least one trust anchor must be configured
2630 with a <command>trusted-keys</command> or
2631 <command>managed-keys</command> statement in
2632 <filename>named.conf</filename>, or DNSSEC validation
2633 will not occur. The default setting is
2634 <userinput>yes</userinput>.
2638 <command>trusted-keys</command> are copies of DNSKEY RRs
2639 for zones that are used to form the first link in the
2640 cryptographic chain of trust. All keys listed in
2641 <command>trusted-keys</command> (and corresponding zones)
2642 are deemed to exist and only the listed keys will be used
2643 to validated the DNSKEY RRset that they are from.
2647 <command>managed-keys</command> are trusted keys which are
2648 automatically kept up to date via RFC 5011 trust anchor
2653 <command>trusted-keys</command> and
2654 <command>managed-keys</command> are described in more detail
2655 later in this document.
2659 Unlike <acronym>BIND</acronym> 8, <acronym>BIND</acronym>
2660 9 does not verify signatures on load, so zone keys for
2661 authoritative zones do not need to be specified in the
2666 After DNSSEC gets established, a typical DNSSEC configuration
2667 will look something like the following. It has one or
2668 more public keys for the root. This allows answers from
2669 outside the organization to be validated. It will also
2670 have several keys for parts of the namespace the organization
2671 controls. These are here to ensure that <command>named</command>
2672 is immune to compromises in the DNSSEC components of the security
2679 "." initial-key 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS
2680 JxrGkxJWoZu6I7PzJu/E9gx4UC1zGAHlXKdE4zYIpRh
2681 aBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3zy2Xy
2682 4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYg
2683 hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp
2684 5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M/lUUVRbke
2685 g1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq
2686 66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ
2687 97S+LKUTpQcq27R7AT3/V5hRQxScINqwcz4jYqZD2fQ
2688 dgxbcDTClU0CRBdiieyLMNzXG3";
2692 /* Key for our organization's forward zone */
2693 example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6
2694 5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z
2695 GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb
2696 4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL
2697 kBOUKUf/mC7HvfwYH/Be22GnClrinKJp1O
2698 g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S
2699 TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq
2700 FxmAVZP20igTixin/1LcrgX/KMEGd/biuv
2701 F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm
2702 /oyWR8BW/hWdzOvnSCThlHf3xiYleDbt/o
2705 /* Key for our reverse zone. */
2706 2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwc
2707 xOdNax071L18QqZnQQQAVVr+i
2708 LhGTnNGp3HoWQLUIzKrJVZ3zg
2709 gy3WwNT6kZo6c0tszYqbtvchm
2710 gQC8CzKojM/W16i6MG/eafGU3
2711 siaOdS0yOI6BgPsw+YZdzlYMa
2712 IJGf4M4dyoKIhzdZyQ2bYQrjy
2713 Q4LB0lC7aOnsMyYKHHYeRvPxj
2714 IQXmdqgOJGq+vsevG06zW+1xg
2715 YJh9rCIfnm1GX/KMgxLPG2vXT
2716 D/RnLX+D3T3UL7HJYHJhAZD5L
2717 59VvjSPsZJHeDCUyWYrvPZesZ
2718 DIRvhDD52SKvbheeTJUm6Ehkz
2719 ytNN2SN96QRk8j/iI8ib";
2725 dnssec-validation yes;
2730 None of the keys listed in this example are valid. In particular,
2731 the root key is not valid.
2735 When DNSSEC validation is enabled and properly configured,
2736 the resolver will reject any answers from signed, secure zones
2737 which fail to validate, and will return SERVFAIL to the client.
2741 Responses may fail to validate for any of several reasons,
2742 including missing, expired, or invalid signatures, a key which
2743 does not match the DS RRset in the parent zone, or an insecure
2744 response from a zone which, according to its parent, should have
2750 When the validator receives a response from an unsigned zone
2751 that has a signed parent, it must confirm with the parent
2752 that the zone was intentionally left unsigned. It does
2753 this by verifying, via signed and validated NSEC/NSEC3 records,
2754 that the parent zone contains no DS records for the child.
2757 If the validator <emphasis>can</emphasis> prove that the zone
2758 is insecure, then the response is accepted. However, if it
2759 cannot, then it must assume an insecure response to be a
2760 forgery; it rejects the response and logs an error.
2763 The logged error reads "insecurity proof failed" and
2764 "got insecure response; parent indicates it should be secure".
2765 (Prior to BIND 9.7, the logged error was "not insecure".
2766 This referred to the zone, not the response.)
2773 <xi:include href="dnssec.xml"/>
2775 <xi:include href="managed-keys.xml"/>
2777 <xi:include href="pkcs11.xml"/>
2780 <title>IPv6 Support in <acronym>BIND</acronym> 9</title>
2783 <acronym>BIND</acronym> 9 fully supports all currently
2784 defined forms of IPv6 name to address and address to name
2785 lookups. It will also use IPv6 addresses to make queries when
2786 running on an IPv6 capable system.
2790 For forward lookups, <acronym>BIND</acronym> 9 supports
2791 only AAAA records. RFC 3363 deprecated the use of A6 records,
2792 and client-side support for A6 records was accordingly removed
2793 from <acronym>BIND</acronym> 9.
2794 However, authoritative <acronym>BIND</acronym> 9 name servers still
2795 load zone files containing A6 records correctly, answer queries
2796 for A6 records, and accept zone transfer for a zone containing A6
2801 For IPv6 reverse lookups, <acronym>BIND</acronym> 9 supports
2802 the traditional "nibble" format used in the
2803 <emphasis>ip6.arpa</emphasis> domain, as well as the older, deprecated
2804 <emphasis>ip6.int</emphasis> domain.
2805 Older versions of <acronym>BIND</acronym> 9
2806 supported the "binary label" (also known as "bitstring") format,
2807 but support of binary labels has been completely removed per
2809 Many applications in <acronym>BIND</acronym> 9 do not understand
2810 the binary label format at all any more, and will return an
2812 In particular, an authoritative <acronym>BIND</acronym> 9
2813 name server will not load a zone file containing binary labels.
2817 For an overview of the format and structure of IPv6 addresses,
2818 see <xref linkend="ipv6addresses"/>.
2822 <title>Address Lookups Using AAAA Records</title>
2825 The IPv6 AAAA record is a parallel to the IPv4 A record,
2826 and, unlike the deprecated A6 record, specifies the entire
2827 IPv6 address in a single record. For example,
2831 $ORIGIN example.com.
2832 host 3600 IN AAAA 2001:db8::1
2836 Use of IPv4-in-IPv6 mapped addresses is not recommended.
2837 If a host has an IPv4 address, use an A record, not
2838 a AAAA, with <literal>::ffff:192.168.42.1</literal> as
2843 <title>Address to Name Lookups Using Nibble Format</title>
2846 When looking up an address in nibble format, the address
2847 components are simply reversed, just as in IPv4, and
2848 <literal>ip6.arpa.</literal> is appended to the
2850 For example, the following would provide reverse name lookup for
2852 <literal>2001:db8::1</literal>.
2856 $ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
2857 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR (
2865 <chapter id="Bv9ARM.ch05">
2866 <title>The <acronym>BIND</acronym> 9 Lightweight Resolver</title>
2868 <title>The Lightweight Resolver Library</title>
2870 Traditionally applications have been linked with a stub resolver
2871 library that sends recursive DNS queries to a local caching name
2875 IPv6 once introduced new complexity into the resolution process,
2876 such as following A6 chains and DNAME records, and simultaneous
2877 lookup of IPv4 and IPv6 addresses. Though most of the complexity was
2878 then removed, these are hard or impossible
2879 to implement in a traditional stub resolver.
2882 <acronym>BIND</acronym> 9 therefore can also provide resolution
2883 services to local clients
2884 using a combination of a lightweight resolver library and a resolver
2885 daemon process running on the local host. These communicate using
2886 a simple UDP-based protocol, the "lightweight resolver protocol"
2887 that is distinct from and simpler than the full DNS protocol.
2891 <title>Running a Resolver Daemon</title>
2894 To use the lightweight resolver interface, the system must
2895 run the resolver daemon <command>lwresd</command> or a
2897 name server configured with a <command>lwres</command>
2902 By default, applications using the lightweight resolver library will
2904 UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
2906 address can be overridden by <command>lwserver</command>
2908 <filename>/etc/resolv.conf</filename>.
2912 The daemon currently only looks in the DNS, but in the future
2913 it may use other sources such as <filename>/etc/hosts</filename>,
2918 The <command>lwresd</command> daemon is essentially a
2919 caching-only name server that responds to requests using the
2921 resolver protocol rather than the DNS protocol. Because it needs
2922 to run on each host, it is designed to require no or minimal
2924 Unless configured otherwise, it uses the name servers listed on
2925 <command>nameserver</command> lines in <filename>/etc/resolv.conf</filename>
2926 as forwarders, but is also capable of doing the resolution
2931 The <command>lwresd</command> daemon may also be
2933 <filename>named.conf</filename> style configuration file,
2935 <filename>/etc/lwresd.conf</filename> by default. A name
2937 be configured to act as a lightweight resolver daemon using the
2938 <command>lwres</command> statement in <filename>named.conf</filename>.
2944 <chapter id="Bv9ARM.ch06">
2945 <title><acronym>BIND</acronym> 9 Configuration Reference</title>
2948 <acronym>BIND</acronym> 9 configuration is broadly similar
2949 to <acronym>BIND</acronym> 8; however, there are a few new
2951 of configuration, such as views. <acronym>BIND</acronym>
2952 8 configuration files should work with few alterations in <acronym>BIND</acronym>
2953 9, although more complex configurations should be reviewed to check
2954 if they can be more efficiently implemented using the new features
2955 found in <acronym>BIND</acronym> 9.
2959 <acronym>BIND</acronym> 4 configuration files can be
2960 converted to the new format
2961 using the shell script
2962 <filename>contrib/named-bootconf/named-bootconf.sh</filename>.
2964 <sect1 id="configuration_file_elements">
2965 <title>Configuration File Elements</title>
2967 Following is a list of elements used throughout the <acronym>BIND</acronym> configuration
2970 <informaltable colsep="0" rowsep="0">
2971 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
2972 <colspec colname="1" colnum="1" colsep="0" colwidth="1.855in"/>
2973 <colspec colname="2" colnum="2" colsep="0" colwidth="3.770in"/>
2978 <varname>acl_name</varname>
2983 The name of an <varname>address_match_list</varname> as
2984 defined by the <command>acl</command> statement.
2991 <varname>address_match_list</varname>
2996 A list of one or more
2997 <varname>ip_addr</varname>,
2998 <varname>ip_prefix</varname>, <varname>key_id</varname>,
2999 or <varname>acl_name</varname> elements, see
3000 <xref linkend="address_match_lists"/>.
3007 <varname>masters_list</varname>
3012 A named list of one or more <varname>ip_addr</varname>
3013 with optional <varname>key_id</varname> and/or
3014 <varname>ip_port</varname>.
3015 A <varname>masters_list</varname> may include other
3016 <varname>masters_lists</varname>.
3023 <varname>domain_name</varname>
3028 A quoted string which will be used as
3029 a DNS name, for example "<literal>my.test.domain</literal>".
3036 <varname>namelist</varname>
3041 A list of one or more <varname>domain_name</varname>
3049 <varname>dotted_decimal</varname>
3054 One to four integers valued 0 through
3055 255 separated by dots (`.'), such as <command>123</command>,
3056 <command>45.67</command> or <command>89.123.45.67</command>.
3063 <varname>ip4_addr</varname>
3068 An IPv4 address with exactly four elements
3069 in <varname>dotted_decimal</varname> notation.
3076 <varname>ip6_addr</varname>
3081 An IPv6 address, such as <command>2001:db8::1234</command>.
3082 IPv6 scoped addresses that have ambiguity on their
3083 scope zones must be disambiguated by an appropriate
3084 zone ID with the percent character (`%') as
3085 delimiter. It is strongly recommended to use
3086 string zone names rather than numeric identifiers,
3087 in order to be robust against system configuration
3088 changes. However, since there is no standard
3089 mapping for such names and identifier values,
3090 currently only interface names as link identifiers
3091 are supported, assuming one-to-one mapping between
3092 interfaces and links. For example, a link-local
3093 address <command>fe80::1</command> on the link
3094 attached to the interface <command>ne0</command>
3095 can be specified as <command>fe80::1%ne0</command>.
3096 Note that on most systems link-local addresses
3097 always have the ambiguity, and need to be
3105 <varname>ip_addr</varname>
3110 An <varname>ip4_addr</varname> or <varname>ip6_addr</varname>.
3117 <varname>ip_port</varname>
3122 An IP port <varname>number</varname>.
3123 The <varname>number</varname> is limited to 0
3124 through 65535, with values
3125 below 1024 typically restricted to use by processes running
3127 In some cases, an asterisk (`*') character can be used as a
3129 select a random high-numbered port.
3136 <varname>ip_prefix</varname>
3141 An IP network specified as an <varname>ip_addr</varname>,
3142 followed by a slash (`/') and then the number of bits in the
3144 Trailing zeros in a <varname>ip_addr</varname>
3146 For example, <command>127/8</command> is the
3147 network <command>127.0.0.0</command> with
3148 netmask <command>255.0.0.0</command> and <command>1.2.3.0/28</command> is
3149 network <command>1.2.3.0</command> with netmask <command>255.255.255.240</command>.
3152 When specifying a prefix involving a IPv6 scoped address
3153 the scope may be omitted. In that case the prefix will
3154 match packets from any scope.
3161 <varname>key_id</varname>
3166 A <varname>domain_name</varname> representing
3167 the name of a shared key, to be used for transaction
3175 <varname>key_list</varname>
3180 A list of one or more
3181 <varname>key_id</varname>s,
3182 separated by semicolons and ending with a semicolon.
3189 <varname>number</varname>
3194 A non-negative 32-bit integer
3195 (i.e., a number between 0 and 4294967295, inclusive).
3196 Its acceptable value might further
3197 be limited by the context in which it is used.
3204 <varname>path_name</varname>
3209 A quoted string which will be used as
3210 a pathname, such as <filename>zones/master/my.test.domain</filename>.
3217 <varname>port_list</varname>
3222 A list of an <varname>ip_port</varname> or a port
3224 A port range is specified in the form of
3225 <userinput>range</userinput> followed by
3226 two <varname>ip_port</varname>s,
3227 <varname>port_low</varname> and
3228 <varname>port_high</varname>, which represents
3229 port numbers from <varname>port_low</varname> through
3230 <varname>port_high</varname>, inclusive.
3231 <varname>port_low</varname> must not be larger than
3232 <varname>port_high</varname>.
3234 <userinput>range 1024 65535</userinput> represents
3235 ports from 1024 through 65535.
3236 In either case an asterisk (`*') character is not
3237 allowed as a valid <varname>ip_port</varname>.
3244 <varname>size_spec</varname>
3249 A number, the word <userinput>unlimited</userinput>,
3250 or the word <userinput>default</userinput>.
3253 An <varname>unlimited</varname> <varname>size_spec</varname> requests unlimited
3254 use, or the maximum available amount. A <varname>default size_spec</varname> uses
3255 the limit that was in force when the server was started.
3258 A <varname>number</varname> can optionally be
3259 followed by a scaling factor:
3260 <userinput>K</userinput> or <userinput>k</userinput>
3262 <userinput>M</userinput> or <userinput>m</userinput>
3264 <userinput>G</userinput> or <userinput>g</userinput> for gigabytes,
3265 which scale by 1024, 1024*1024, and 1024*1024*1024
3269 The value must be representable as a 64-bit unsigned integer
3270 (0 to 18446744073709551615, inclusive).
3271 Using <varname>unlimited</varname> is the best
3273 to safely set a really large number.
3280 <varname>yes_or_no</varname>
3285 Either <userinput>yes</userinput> or <userinput>no</userinput>.
3286 The words <userinput>true</userinput> and <userinput>false</userinput> are
3287 also accepted, as are the numbers <userinput>1</userinput>
3288 and <userinput>0</userinput>.
3295 <varname>dialup_option</varname>
3300 One of <userinput>yes</userinput>,
3301 <userinput>no</userinput>, <userinput>notify</userinput>,
3302 <userinput>notify-passive</userinput>, <userinput>refresh</userinput> or
3303 <userinput>passive</userinput>.
3304 When used in a zone, <userinput>notify-passive</userinput>,
3305 <userinput>refresh</userinput>, and <userinput>passive</userinput>
3306 are restricted to slave and stub zones.
3313 <sect2 id="address_match_lists">
3314 <title>Address Match Lists</title>
3316 <title>Syntax</title>
3318 <programlisting><varname>address_match_list</varname> = address_match_list_element ;
3319 <optional> address_match_list_element; ... </optional>
3320 <varname>address_match_list_element</varname> = <optional> ! </optional> (ip_address <optional>/length</optional> |
3321 key key_id | acl_name | { address_match_list } )
3326 <title>Definition and Usage</title>
3328 Address match lists are primarily used to determine access
3329 control for various server operations. They are also used in
3330 the <command>listen-on</command> and <command>sortlist</command>
3331 statements. The elements which constitute an address match
3332 list can be any of the following:
3336 <simpara>an IP address (IPv4 or IPv6)</simpara>
3339 <simpara>an IP prefix (in `/' notation)</simpara>
3343 a key ID, as defined by the <command>key</command>
3348 <simpara>the name of an address match list defined with
3349 the <command>acl</command> statement
3353 <simpara>a nested address match list enclosed in braces</simpara>
3358 Elements can be negated with a leading exclamation mark (`!'),
3359 and the match list names "any", "none", "localhost", and
3360 "localnets" are predefined. More information on those names
3361 can be found in the description of the acl statement.
3365 The addition of the key clause made the name of this syntactic
3366 element something of a misnomer, since security keys can be used
3367 to validate access without regard to a host or network address.
3368 Nonetheless, the term "address match list" is still used
3369 throughout the documentation.
3373 When a given IP address or prefix is compared to an address
3374 match list, the comparison takes place in approximately O(1)
3375 time. However, key comparisons require that the list of keys
3376 be traversed until a matching key is found, and therefore may
3381 The interpretation of a match depends on whether the list is being
3382 used for access control, defining <command>listen-on</command> ports, or in a
3383 <command>sortlist</command>, and whether the element was negated.
3387 When used as an access control list, a non-negated match
3388 allows access and a negated match denies access. If
3389 there is no match, access is denied. The clauses
3390 <command>allow-notify</command>,
3391 <command>allow-recursion</command>,
3392 <command>allow-recursion-on</command>,
3393 <command>allow-query</command>,
3394 <command>allow-query-on</command>,
3395 <command>allow-query-cache</command>,
3396 <command>allow-query-cache-on</command>,
3397 <command>allow-transfer</command>,
3398 <command>allow-update</command>,
3399 <command>allow-update-forwarding</command>, and
3400 <command>blackhole</command> all use address match
3401 lists. Similarly, the <command>listen-on</command> option will cause the
3402 server to refuse queries on any of the machine's
3403 addresses which do not match the list.
3407 Order of insertion is significant. If more than one element
3408 in an ACL is found to match a given IP address or prefix,
3409 preference will be given to the one that came
3410 <emphasis>first</emphasis> in the ACL definition.
3411 Because of this first-match behavior, an element that
3412 defines a subset of another element in the list should
3413 come before the broader element, regardless of whether
3414 either is negated. For example, in
3415 <command>1.2.3/24; ! 1.2.3.13;</command>
3416 the 1.2.3.13 element is completely useless because the
3417 algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
3418 element. Using <command>! 1.2.3.13; 1.2.3/24</command> fixes
3419 that problem by having 1.2.3.13 blocked by the negation, but
3420 all other 1.2.3.* hosts fall through.
3426 <title>Comment Syntax</title>
3429 The <acronym>BIND</acronym> 9 comment syntax allows for
3431 anywhere that whitespace may appear in a <acronym>BIND</acronym> configuration
3432 file. To appeal to programmers of all kinds, they can be written
3433 in the C, C++, or shell/perl style.
3437 <title>Syntax</title>
3440 <programlisting>/* This is a <acronym>BIND</acronym> comment as in C */</programlisting>
3441 <programlisting>// This is a <acronym>BIND</acronym> comment as in C++</programlisting>
3442 <programlisting># This is a <acronym>BIND</acronym> comment as in common UNIX shells
3443 # and perl</programlisting>
3447 <title>Definition and Usage</title>
3449 Comments may appear anywhere that whitespace may appear in
3450 a <acronym>BIND</acronym> configuration file.
3453 C-style comments start with the two characters /* (slash,
3454 star) and end with */ (star, slash). Because they are completely
3455 delimited with these characters, they can be used to comment only
3456 a portion of a line or to span multiple lines.
3459 C-style comments cannot be nested. For example, the following
3460 is not valid because the entire comment ends with the first */:
3464 <programlisting>/* This is the start of a comment.
3465 This is still part of the comment.
3466 /* This is an incorrect attempt at nesting a comment. */
3467 This is no longer in any comment. */
3473 C++-style comments start with the two characters // (slash,
3474 slash) and continue to the end of the physical line. They cannot
3475 be continued across multiple physical lines; to have one logical
3476 comment span multiple lines, each line must use the // pair.
3481 <programlisting>// This is the start of a comment. The next line
3482 // is a new comment, even though it is logically
3483 // part of the previous comment.
3488 Shell-style (or perl-style, if you prefer) comments start
3489 with the character <literal>#</literal> (number sign)
3490 and continue to the end of the
3491 physical line, as in C++ comments.
3497 <programlisting># This is the start of a comment. The next line
3498 # is a new comment, even though it is logically
3499 # part of the previous comment.
3506 You cannot use the semicolon (`;') character
3507 to start a comment such as you would in a zone file. The
3508 semicolon indicates the end of a configuration
3516 <sect1 id="Configuration_File_Grammar">
3517 <title>Configuration File Grammar</title>
3520 A <acronym>BIND</acronym> 9 configuration consists of
3521 statements and comments.
3522 Statements end with a semicolon. Statements and comments are the
3523 only elements that can appear without enclosing braces. Many
3524 statements contain a block of sub-statements, which are also
3525 terminated with a semicolon.
3529 The following statements are supported:
3532 <informaltable colsep="0" rowsep="0">
3533 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
3534 <colspec colname="1" colnum="1" colsep="0" colwidth="1.336in"/>
3535 <colspec colname="2" colnum="2" colsep="0" colwidth="3.778in"/>
3539 <para><command>acl</command></para>
3543 defines a named IP address
3544 matching list, for access control and other uses.
3550 <para><command>controls</command></para>
3554 declares control channels to be used
3555 by the <command>rndc</command> utility.
3561 <para><command>include</command></para>
3571 <para><command>key</command></para>
3575 specifies key information for use in
3576 authentication and authorization using TSIG.
3582 <para><command>logging</command></para>
3586 specifies what the server logs, and where
3587 the log messages are sent.
3593 <para><command>lwres</command></para>
3597 configures <command>named</command> to
3598 also act as a light-weight resolver daemon (<command>lwresd</command>).
3604 <para><command>masters</command></para>
3608 defines a named masters list for
3609 inclusion in stub and slave zone masters clauses.
3615 <para><command>options</command></para>
3619 controls global server configuration
3620 options and sets defaults for other statements.
3626 <para><command>server</command></para>
3630 sets certain configuration options on
3637 <para><command>statistics-channels</command></para>
3641 declares communication channels to get access to
3642 <command>named</command> statistics.
3648 <para><command>trusted-keys</command></para>
3652 defines trusted DNSSEC keys.
3658 <para><command>managed-keys</command></para>
3662 lists DNSSEC keys to be kept up to date
3663 using RFC 5011 trust anchor maintenance.
3669 <para><command>view</command></para>
3679 <para><command>zone</command></para>
3692 The <command>logging</command> and
3693 <command>options</command> statements may only occur once
3699 <title><command>acl</command> Statement Grammar</title>
3701 <programlisting><command>acl</command> acl-name {
3708 <title><command>acl</command> Statement Definition and
3712 The <command>acl</command> statement assigns a symbolic
3713 name to an address match list. It gets its name from a primary
3714 use of address match lists: Access Control Lists (ACLs).
3718 Note that an address match list's name must be defined
3719 with <command>acl</command> before it can be used
3720 elsewhere; no forward references are allowed.
3724 The following ACLs are built-in:
3727 <informaltable colsep="0" rowsep="0">
3728 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
3729 <colspec colname="1" colnum="1" colsep="0" colwidth="1.130in"/>
3730 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
3734 <para><command>any</command></para>
3744 <para><command>none</command></para>
3754 <para><command>localhost</command></para>
3758 Matches the IPv4 and IPv6 addresses of all network
3759 interfaces on the system.
3765 <para><command>localnets</command></para>
3769 Matches any host on an IPv4 or IPv6 network
3770 for which the system has an interface.
3771 Some systems do not provide a way to determine the prefix
3773 local IPv6 addresses.
3774 In such a case, <command>localnets</command>
3775 only matches the local
3776 IPv6 addresses, just like <command>localhost</command>.
3786 <title><command>controls</command> Statement Grammar</title>
3788 <programlisting><command>controls</command> {
3789 [ inet ( ip_addr | * ) [ port ip_port ]
3790 allow { <replaceable> address_match_list </replaceable> }
3791 keys { <replaceable>key_list</replaceable> }; ]
3793 [ unix <replaceable>path</replaceable> perm <replaceable>number</replaceable> owner <replaceable>number</replaceable> group <replaceable>number</replaceable>
3794 keys { <replaceable>key_list</replaceable> }; ]
3801 <sect2 id="controls_statement_definition_and_usage">
3802 <title><command>controls</command> Statement Definition and
3806 The <command>controls</command> statement declares control
3807 channels to be used by system administrators to control the
3808 operation of the name server. These control channels are
3809 used by the <command>rndc</command> utility to send
3810 commands to and retrieve non-DNS results from a name server.
3814 An <command>inet</command> control channel is a TCP socket
3815 listening at the specified <command>ip_port</command> on the
3816 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
3817 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
3818 interpreted as the IPv4 wildcard address; connections will be
3819 accepted on any of the system's IPv4 addresses.
3820 To listen on the IPv6 wildcard address,
3821 use an <command>ip_addr</command> of <literal>::</literal>.
3822 If you will only use <command>rndc</command> on the local host,
3823 using the loopback address (<literal>127.0.0.1</literal>
3824 or <literal>::1</literal>) is recommended for maximum security.
3828 If no port is specified, port 953 is used. The asterisk
3829 "<literal>*</literal>" cannot be used for <command>ip_port</command>.
3833 The ability to issue commands over the control channel is
3834 restricted by the <command>allow</command> and
3835 <command>keys</command> clauses.
3836 Connections to the control channel are permitted based on the
3837 <command>address_match_list</command>. This is for simple
3838 IP address based filtering only; any <command>key_id</command>
3839 elements of the <command>address_match_list</command>
3844 A <command>unix</command> control channel is a UNIX domain
3845 socket listening at the specified path in the file system.
3846 Access to the socket is specified by the <command>perm</command>,
3847 <command>owner</command> and <command>group</command> clauses.
3848 Note on some platforms (SunOS and Solaris) the permissions
3849 (<command>perm</command>) are applied to the parent directory
3850 as the permissions on the socket itself are ignored.
3854 The primary authorization mechanism of the command
3855 channel is the <command>key_list</command>, which
3856 contains a list of <command>key_id</command>s.
3857 Each <command>key_id</command> in the <command>key_list</command>
3858 is authorized to execute commands over the control channel.
3859 See <xref linkend="rndc"/> in <xref linkend="admin_tools"/>)
3860 for information about configuring keys in <command>rndc</command>.
3864 If no <command>controls</command> statement is present,
3865 <command>named</command> will set up a default
3866 control channel listening on the loopback address 127.0.0.1
3867 and its IPv6 counterpart ::1.
3868 In this case, and also when the <command>controls</command> statement
3869 is present but does not have a <command>keys</command> clause,
3870 <command>named</command> will attempt to load the command channel key
3871 from the file <filename>rndc.key</filename> in
3872 <filename>/etc</filename> (or whatever <varname>sysconfdir</varname>
3873 was specified as when <acronym>BIND</acronym> was built).
3874 To create a <filename>rndc.key</filename> file, run
3875 <userinput>rndc-confgen -a</userinput>.
3879 The <filename>rndc.key</filename> feature was created to
3880 ease the transition of systems from <acronym>BIND</acronym> 8,
3881 which did not have digital signatures on its command channel
3882 messages and thus did not have a <command>keys</command> clause.
3884 It makes it possible to use an existing <acronym>BIND</acronym> 8
3885 configuration file in <acronym>BIND</acronym> 9 unchanged,
3886 and still have <command>rndc</command> work the same way
3887 <command>ndc</command> worked in BIND 8, simply by executing the
3888 command <userinput>rndc-confgen -a</userinput> after BIND 9 is
3893 Since the <filename>rndc.key</filename> feature
3894 is only intended to allow the backward-compatible usage of
3895 <acronym>BIND</acronym> 8 configuration files, this
3897 have a high degree of configurability. You cannot easily change
3898 the key name or the size of the secret, so you should make a
3899 <filename>rndc.conf</filename> with your own key if you
3901 those things. The <filename>rndc.key</filename> file
3903 permissions set such that only the owner of the file (the user that
3904 <command>named</command> is running as) can access it.
3906 desire greater flexibility in allowing other users to access
3907 <command>rndc</command> commands, then you need to create
3909 <filename>rndc.conf</filename> file and make it group
3911 that contains the users who should have access.
3915 To disable the command channel, use an empty
3916 <command>controls</command> statement:
3917 <command>controls { };</command>.
3922 <title><command>include</command> Statement Grammar</title>
3923 <programlisting><command>include</command> <replaceable>filename</replaceable>;</programlisting>
3926 <title><command>include</command> Statement Definition and
3930 The <command>include</command> statement inserts the
3931 specified file at the point where the <command>include</command>
3932 statement is encountered. The <command>include</command>
3933 statement facilitates the administration of configuration
3935 by permitting the reading or writing of some things but not
3936 others. For example, the statement could include private keys
3937 that are readable only by the name server.
3942 <title><command>key</command> Statement Grammar</title>
3944 <programlisting><command>key</command> <replaceable>key_id</replaceable> {
3945 algorithm <replaceable>string</replaceable>;
3946 secret <replaceable>string</replaceable>;
3953 <title><command>key</command> Statement Definition and Usage</title>
3956 The <command>key</command> statement defines a shared
3957 secret key for use with TSIG (see <xref linkend="tsig"/>)
3958 or the command channel
3959 (see <xref linkend="controls_statement_definition_and_usage"/>).
3963 The <command>key</command> statement can occur at the
3965 of the configuration file or inside a <command>view</command>
3966 statement. Keys defined in top-level <command>key</command>
3967 statements can be used in all views. Keys intended for use in
3968 a <command>controls</command> statement
3969 (see <xref linkend="controls_statement_definition_and_usage"/>)
3970 must be defined at the top level.
3974 The <replaceable>key_id</replaceable>, also known as the
3975 key name, is a domain name uniquely identifying the key. It can
3976 be used in a <command>server</command>
3977 statement to cause requests sent to that
3978 server to be signed with this key, or in address match lists to
3979 verify that incoming requests have been signed with a key
3980 matching this name, algorithm, and secret.
3984 The <replaceable>algorithm_id</replaceable> is a string
3985 that specifies a security/authentication algorithm. Named
3986 supports <literal>hmac-md5</literal>,
3987 <literal>hmac-sha1</literal>, <literal>hmac-sha224</literal>,
3988 <literal>hmac-sha256</literal>, <literal>hmac-sha384</literal>
3989 and <literal>hmac-sha512</literal> TSIG authentication.
3990 Truncated hashes are supported by appending the minimum
3991 number of required bits preceded by a dash, e.g.
3992 <literal>hmac-sha1-80</literal>. The
3993 <replaceable>secret_string</replaceable> is the secret
3994 to be used by the algorithm, and is treated as a base-64
4000 <title><command>logging</command> Statement Grammar</title>
4002 <programlisting><command>logging</command> {
4003 [ <command>channel</command> <replaceable>channel_name</replaceable> {
4004 ( <command>file</command> <replaceable>path_name</replaceable>
4005 [ <command>versions</command> ( <replaceable>number</replaceable> | <command>unlimited</command> ) ]
4006 [ <command>size</command> <replaceable>size spec</replaceable> ]
4007 | <command>syslog</command> <replaceable>syslog_facility</replaceable>
4008 | <command>stderr</command>
4009 | <command>null</command> );
4010 [ <command>severity</command> (<option>critical</option> | <option>error</option> | <option>warning</option> | <option>notice</option> |
4011 <option>info</option> | <option>debug</option> [ <replaceable>level</replaceable> ] | <option>dynamic</option> ); ]
4012 [ <command>print-category</command> <option>yes</option> or <option>no</option>; ]
4013 [ <command>print-severity</command> <option>yes</option> or <option>no</option>; ]
4014 [ <command>print-time</command> <option>yes</option> or <option>no</option>; ]
4016 [ <command>category</command> <replaceable>category_name</replaceable> {
4017 <replaceable>channel_name</replaceable> ; [ <replaceable>channel_name</replaceable> ; ... ]
4026 <title><command>logging</command> Statement Definition and
4030 The <command>logging</command> statement configures a
4032 variety of logging options for the name server. Its <command>channel</command> phrase
4033 associates output methods, format options and severity levels with
4034 a name that can then be used with the <command>category</command> phrase
4035 to select how various classes of messages are logged.
4038 Only one <command>logging</command> statement is used to
4040 as many channels and categories as are wanted. If there is no <command>logging</command> statement,
4041 the logging configuration will be:
4044 <programlisting>logging {
4045 category default { default_syslog; default_debug; };
4046 category unmatched { null; };
4051 In <acronym>BIND</acronym> 9, the logging configuration
4052 is only established when
4053 the entire configuration file has been parsed. In <acronym>BIND</acronym> 8, it was
4054 established as soon as the <command>logging</command>
4056 was parsed. When the server is starting up, all logging messages
4057 regarding syntax errors in the configuration file go to the default
4058 channels, or to standard error if the "<option>-g</option>" option
4063 <title>The <command>channel</command> Phrase</title>
4066 All log output goes to one or more <emphasis>channels</emphasis>;
4067 you can make as many of them as you want.
4071 Every channel definition must include a destination clause that
4072 says whether messages selected for the channel go to a file, to a
4073 particular syslog facility, to the standard error stream, or are
4074 discarded. It can optionally also limit the message severity level
4075 that will be accepted by the channel (the default is
4076 <command>info</command>), and whether to include a
4077 <command>named</command>-generated time stamp, the
4079 and/or severity level (the default is not to include any).
4083 The <command>null</command> destination clause
4084 causes all messages sent to the channel to be discarded;
4085 in that case, other options for the channel are meaningless.
4089 The <command>file</command> destination clause directs
4091 to a disk file. It can include limitations
4092 both on how large the file is allowed to become, and how many
4094 of the file will be saved each time the file is opened.
4098 If you use the <command>versions</command> log file
4100 <command>named</command> will retain that many backup
4101 versions of the file by
4102 renaming them when opening. For example, if you choose to keep
4104 of the file <filename>lamers.log</filename>, then just
4106 <filename>lamers.log.1</filename> is renamed to
4107 <filename>lamers.log.2</filename>, <filename>lamers.log.0</filename> is renamed
4108 to <filename>lamers.log.1</filename>, and <filename>lamers.log</filename> is
4109 renamed to <filename>lamers.log.0</filename>.
4110 You can say <command>versions unlimited</command> to
4112 the number of versions.
4113 If a <command>size</command> option is associated with
4115 then renaming is only done when the file being opened exceeds the
4116 indicated size. No backup versions are kept by default; any
4118 log file is simply appended.
4122 The <command>size</command> option for files is used
4124 growth. If the file ever exceeds the size, then <command>named</command> will
4125 stop writing to the file unless it has a <command>versions</command> option
4126 associated with it. If backup versions are kept, the files are
4128 described above and a new one begun. If there is no
4129 <command>versions</command> option, no more data will
4130 be written to the log
4131 until some out-of-band mechanism removes or truncates the log to
4133 maximum size. The default behavior is not to limit the size of
4139 Example usage of the <command>size</command> and
4140 <command>versions</command> options:
4143 <programlisting>channel an_example_channel {
4144 file "example.log" versions 3 size 20m;
4151 The <command>syslog</command> destination clause
4153 channel to the system log. Its argument is a
4154 syslog facility as described in the <command>syslog</command> man
4155 page. Known facilities are <command>kern</command>, <command>user</command>,
4156 <command>mail</command>, <command>daemon</command>, <command>auth</command>,
4157 <command>syslog</command>, <command>lpr</command>, <command>news</command>,
4158 <command>uucp</command>, <command>cron</command>, <command>authpriv</command>,
4159 <command>ftp</command>, <command>local0</command>, <command>local1</command>,
4160 <command>local2</command>, <command>local3</command>, <command>local4</command>,
4161 <command>local5</command>, <command>local6</command> and
4162 <command>local7</command>, however not all facilities
4164 all operating systems.
4165 How <command>syslog</command> will handle messages
4167 this facility is described in the <command>syslog.conf</command> man
4168 page. If you have a system which uses a very old version of <command>syslog</command> that
4169 only uses two arguments to the <command>openlog()</command> function,
4170 then this clause is silently ignored.
4173 The <command>severity</command> clause works like <command>syslog</command>'s
4174 "priorities", except that they can also be used if you are writing
4175 straight to a file rather than using <command>syslog</command>.
4176 Messages which are not at least of the severity level given will
4177 not be selected for the channel; messages of higher severity
4182 If you are using <command>syslog</command>, then the <command>syslog.conf</command> priorities
4183 will also determine what eventually passes through. For example,
4184 defining a channel facility and severity as <command>daemon</command> and <command>debug</command> but
4185 only logging <command>daemon.warning</command> via <command>syslog.conf</command> will
4186 cause messages of severity <command>info</command> and
4187 <command>notice</command> to
4188 be dropped. If the situation were reversed, with <command>named</command> writing
4189 messages of only <command>warning</command> or higher,
4190 then <command>syslogd</command> would
4191 print all messages it received from the channel.
4195 The <command>stderr</command> destination clause
4197 channel to the server's standard error stream. This is intended
4199 use when the server is running as a foreground process, for
4201 when debugging a configuration.
4205 The server can supply extensive debugging information when
4206 it is in debugging mode. If the server's global debug level is
4208 than zero, then debugging mode will be active. The global debug
4209 level is set either by starting the <command>named</command> server
4210 with the <option>-d</option> flag followed by a positive integer,
4211 or by running <command>rndc trace</command>.
4212 The global debug level
4213 can be set to zero, and debugging mode turned off, by running <command>rndc
4214 notrace</command>. All debugging messages in the server have a debug
4215 level, and higher debug levels give more detailed output. Channels
4216 that specify a specific debug severity, for example:
4219 <programlisting>channel specific_debug_level {
4226 will get debugging output of level 3 or less any time the
4227 server is in debugging mode, regardless of the global debugging
4228 level. Channels with <command>dynamic</command>
4230 server's global debug level to determine what messages to print.
4233 If <command>print-time</command> has been turned on,
4235 the date and time will be logged. <command>print-time</command> may
4236 be specified for a <command>syslog</command> channel,
4238 pointless since <command>syslog</command> also logs
4240 time. If <command>print-category</command> is
4242 category of the message will be logged as well. Finally, if <command>print-severity</command> is
4243 on, then the severity level of the message will be logged. The <command>print-</command> options may
4244 be used in any combination, and will always be printed in the
4246 order: time, category, severity. Here is an example where all
4247 three <command>print-</command> options
4252 <computeroutput>28-Feb-2000 15:05:32.863 general: notice: running</computeroutput>
4256 There are four predefined channels that are used for
4257 <command>named</command>'s default logging as follows.
4259 used is described in <xref linkend="the_category_phrase"/>.
4262 <programlisting>channel default_syslog {
4263 // send to syslog's daemon facility
4265 // only send priority info and higher
4268 channel default_debug {
4269 // write to named.run in the working directory
4270 // Note: stderr is used instead of "named.run" if
4271 // the server is started with the '-f' option.
4273 // log at the server's current debug level
4277 channel default_stderr {
4280 // only send priority info and higher
4285 // toss anything sent to this channel
4291 The <command>default_debug</command> channel has the
4293 property that it only produces output when the server's debug
4295 nonzero. It normally writes to a file called <filename>named.run</filename>
4296 in the server's working directory.
4300 For security reasons, when the "<option>-u</option>"
4301 command line option is used, the <filename>named.run</filename> file
4302 is created only after <command>named</command> has
4304 new UID, and any debug output generated while <command>named</command> is
4305 starting up and still running as root is discarded. If you need
4306 to capture this output, you must run the server with the "<option>-g</option>"
4307 option and redirect standard error to a file.
4311 Once a channel is defined, it cannot be redefined. Thus you
4312 cannot alter the built-in channels directly, but you can modify
4313 the default logging by pointing categories at channels you have
4318 <sect3 id="the_category_phrase">
4319 <title>The <command>category</command> Phrase</title>
4322 There are many categories, so you can send the logs you want
4323 to see wherever you want, without seeing logs you don't want. If
4324 you don't specify a list of channels for a category, then log
4326 in that category will be sent to the <command>default</command> category
4327 instead. If you don't specify a default category, the following
4328 "default default" is used:
4331 <programlisting>category default { default_syslog; default_debug; };
4335 As an example, let's say you want to log security events to
4336 a file, but you also want keep the default logging behavior. You'd
4337 specify the following:
4340 <programlisting>channel my_security_channel {
4341 file "my_security_file";
4345 my_security_channel;
4351 To discard all messages in a category, specify the <command>null</command> channel:
4354 <programlisting>category xfer-out { null; };
4355 category notify { null; };
4359 Following are the available categories and brief descriptions
4360 of the types of log information they contain. More
4361 categories may be added in future <acronym>BIND</acronym> releases.
4363 <informaltable colsep="0" rowsep="0">
4364 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4365 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4366 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4370 <para><command>default</command></para>
4374 The default category defines the logging
4375 options for those categories where no specific
4376 configuration has been
4383 <para><command>general</command></para>
4387 The catch-all. Many things still aren't
4388 classified into categories, and they all end up here.
4394 <para><command>database</command></para>
4398 Messages relating to the databases used
4399 internally by the name server to store zone and cache
4406 <para><command>security</command></para>
4410 Approval and denial of requests.
4416 <para><command>config</command></para>
4420 Configuration file parsing and processing.
4426 <para><command>resolver</command></para>
4430 DNS resolution, such as the recursive
4431 lookups performed on behalf of clients by a caching name
4438 <para><command>xfer-in</command></para>
4442 Zone transfers the server is receiving.
4448 <para><command>xfer-out</command></para>
4452 Zone transfers the server is sending.
4458 <para><command>notify</command></para>
4462 The NOTIFY protocol.
4468 <para><command>client</command></para>
4472 Processing of client requests.
4478 <para><command>unmatched</command></para>
4482 Messages that <command>named</command> was unable to determine the
4483 class of or for which there was no matching <command>view</command>.
4484 A one line summary is also logged to the <command>client</command> category.
4485 This category is best sent to a file or stderr, by
4486 default it is sent to
4487 the <command>null</command> channel.
4493 <para><command>network</command></para>
4503 <para><command>update</command></para>
4513 <para><command>update-security</command></para>
4517 Approval and denial of update requests.
4523 <para><command>queries</command></para>
4527 Specify where queries should be logged to.
4530 At startup, specifying the category <command>queries</command> will also
4531 enable query logging unless <command>querylog</command> option has been
4536 The query log entry reports the client's IP
4537 address and port number, and the query name,
4538 class and type. Next it reports whether the
4539 Recursion Desired flag was set (+ if set, -
4540 if not set), if the query was signed (S),
4541 EDNS was in use (E), if TCP was used (T), if
4542 DO (DNSSEC Ok) was set (D), or if CD (Checking
4543 Disabled) was set (C). After this the
4544 destination address the query was sent to is
4549 <computeroutput>client 127.0.0.1#62536: query: www.example.com IN AAAA +SE</computeroutput>
4552 <computeroutput>client ::1#62537: query: www.example.net IN AAAA -SE</computeroutput>
4558 <para><command>query-errors</command></para>
4562 Information about queries that resulted in some
4569 <para><command>dispatch</command></para>
4573 Dispatching of incoming packets to the
4574 server modules where they are to be processed.
4580 <para><command>dnssec</command></para>
4584 DNSSEC and TSIG protocol processing.
4590 <para><command>lame-servers</command></para>
4594 Lame servers. These are misconfigurations
4595 in remote servers, discovered by BIND 9 when trying to
4596 query those servers during resolution.
4602 <para><command>delegation-only</command></para>
4606 Delegation only. Logs queries that have been
4607 forced to NXDOMAIN as the result of a
4608 delegation-only zone or a
4609 <command>delegation-only</command> in a hint
4610 or stub zone declaration.
4616 <para><command>edns-disabled</command></para>
4620 Log queries that have been forced to use plain
4621 DNS due to timeouts. This is often due to
4622 the remote servers not being RFC 1034 compliant
4623 (not always returning FORMERR or similar to
4624 EDNS queries and other extensions to the DNS
4625 when they are not understood). In other words, this is
4626 targeted at servers that fail to respond to
4627 DNS queries that they don't understand.
4630 Note: the log message can also be due to
4631 packet loss. Before reporting servers for
4632 non-RFC 1034 compliance they should be re-tested
4633 to determine the nature of the non-compliance.
4634 This testing should prevent or reduce the
4635 number of false-positive reports.
4638 Note: eventually <command>named</command> will have to stop
4639 treating such timeouts as due to RFC 1034 non
4640 compliance and start treating it as plain
4641 packet loss. Falsely classifying packet
4642 loss as due to RFC 1034 non compliance impacts
4643 on DNSSEC validation which requires EDNS for
4644 the DNSSEC records to be returned.
4653 <title>The <command>query-errors</command> Category</title>
4655 The <command>query-errors</command> category is
4656 specifically intended for debugging purposes: To identify
4657 why and how specific queries result in responses which
4659 Messages of this category are therefore only logged
4660 with <command>debug</command> levels.
4664 At the debug levels of 1 or higher, each response with the
4665 rcode of SERVFAIL is logged as follows:
4668 <computeroutput>client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</computeroutput>
4671 This means an error resulting in SERVFAIL was
4672 detected at line 3880 of source file
4673 <filename>query.c</filename>.
4674 Log messages of this level will particularly
4675 help identify the cause of SERVFAIL for an
4676 authoritative server.
4679 At the debug levels of 2 or higher, detailed context
4680 information of recursive resolutions that resulted in
4682 The log message will look like as follows:
4685 <!-- NOTE: newlines and some spaces added so this would fit on page -->
4687 fetch completed at resolver.c:2970 for www.example.com/A
4688 in 30.000183: timed out/success [domain:example.com,
4689 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
4690 badresp:1,adberr:0,findfail:0,valfail:0]
4694 The first part before the colon shows that a recursive
4695 resolution for AAAA records of www.example.com completed
4696 in 30.000183 seconds and the final result that led to the
4697 SERVFAIL was determined at line 2970 of source file
4698 <filename>resolver.c</filename>.
4701 The following part shows the detected final result and the
4702 latest result of DNSSEC validation.
4703 The latter is always success when no validation attempt
4705 In this example, this query resulted in SERVFAIL probably
4706 because all name servers are down or unreachable, leading
4707 to a timeout in 30 seconds.
4708 DNSSEC validation was probably not attempted.
4711 The last part enclosed in square brackets shows statistics
4712 information collected for this particular resolution
4714 The <varname>domain</varname> field shows the deepest zone
4715 that the resolver reached;
4716 it is the zone where the error was finally detected.
4717 The meaning of the other fields is summarized in the
4721 <informaltable colsep="0" rowsep="0">
4722 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4723 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4724 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4728 <para><varname>referral</varname></para>
4732 The number of referrals the resolver received
4733 throughout the resolution process.
4734 In the above example this is 2, which are most
4735 likely com and example.com.
4741 <para><varname>restart</varname></para>
4745 The number of cycles that the resolver tried
4746 remote servers at the <varname>domain</varname>
4748 In each cycle the resolver sends one query
4749 (possibly resending it, depending on the response)
4750 to each known name server of
4751 the <varname>domain</varname> zone.
4757 <para><varname>qrysent</varname></para>
4761 The number of queries the resolver sent at the
4762 <varname>domain</varname> zone.
4768 <para><varname>timeout</varname></para>
4772 The number of timeouts since the resolver
4773 received the last response.
4779 <para><varname>lame</varname></para>
4783 The number of lame servers the resolver detected
4784 at the <varname>domain</varname> zone.
4785 A server is detected to be lame either by an
4786 invalid response or as a result of lookup in
4787 BIND9's address database (ADB), where lame
4794 <para><varname>neterr</varname></para>
4798 The number of erroneous results that the
4799 resolver encountered in sending queries
4800 at the <varname>domain</varname> zone.
4801 One common case is the remote server is
4802 unreachable and the resolver receives an ICMP
4803 unreachable error message.
4809 <para><varname>badresp</varname></para>
4813 The number of unexpected responses (other than
4814 <varname>lame</varname>) to queries sent by the
4815 resolver at the <varname>domain</varname> zone.
4821 <para><varname>adberr</varname></para>
4825 Failures in finding remote server addresses
4826 of the <varname>domain</varname> zone in the ADB.
4827 One common case of this is that the remote
4828 server's name does not have any address records.
4834 <para><varname>findfail</varname></para>
4838 Failures of resolving remote server addresses.
4839 This is a total number of failures throughout
4840 the resolution process.
4846 <para><varname>valfail</varname></para>
4850 Failures of DNSSEC validation.
4851 Validation failures are counted throughout
4852 the resolution process (not limited to
4853 the <varname>domain</varname> zone), but should
4854 only happen in <varname>domain</varname>.
4862 At the debug levels of 3 or higher, the same messages
4863 as those at the debug 1 level are logged for other errors
4865 Note that negative responses such as NXDOMAIN are not
4866 regarded as errors here.
4869 At the debug levels of 4 or higher, the same messages
4870 as those at the debug 2 level are logged for other errors
4872 Unlike the above case of level 3, messages are logged for
4874 This is because any unexpected results can be difficult to
4875 debug in the recursion case.
4881 <title><command>lwres</command> Statement Grammar</title>
4884 This is the grammar of the <command>lwres</command>
4885 statement in the <filename>named.conf</filename> file:
4888 <programlisting><command>lwres</command> {
4889 <optional> listen-on { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
4890 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
4891 <optional> view <replaceable>view_name</replaceable>; </optional>
4892 <optional> search { <replaceable>domain_name</replaceable> ; <optional> <replaceable>domain_name</replaceable> ; ... </optional> }; </optional>
4893 <optional> ndots <replaceable>number</replaceable>; </optional>
4899 <title><command>lwres</command> Statement Definition and Usage</title>
4902 The <command>lwres</command> statement configures the
4904 server to also act as a lightweight resolver server. (See
4905 <xref linkend="lwresd"/>.) There may be multiple
4906 <command>lwres</command> statements configuring
4907 lightweight resolver servers with different properties.
4911 The <command>listen-on</command> statement specifies a
4913 addresses (and ports) that this instance of a lightweight resolver
4915 should accept requests on. If no port is specified, port 921 is
4917 If this statement is omitted, requests will be accepted on
4923 The <command>view</command> statement binds this
4925 lightweight resolver daemon to a view in the DNS namespace, so that
4927 response will be constructed in the same manner as a normal DNS
4929 matching this view. If this statement is omitted, the default view
4931 used, and if there is no default view, an error is triggered.
4935 The <command>search</command> statement is equivalent to
4937 <command>search</command> statement in
4938 <filename>/etc/resolv.conf</filename>. It provides a
4940 which are appended to relative names in queries.
4944 The <command>ndots</command> statement is equivalent to
4946 <command>ndots</command> statement in
4947 <filename>/etc/resolv.conf</filename>. It indicates the
4949 number of dots in a relative domain name that should result in an
4950 exact match lookup before search path elements are appended.
4954 <title><command>masters</command> Statement Grammar</title>
4957 <command>masters</command> <replaceable>name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> |
4958 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> };
4964 <title><command>masters</command> Statement Definition and
4966 <para><command>masters</command>
4967 lists allow for a common set of masters to be easily used by
4968 multiple stub and slave zones.
4973 <title><command>options</command> Statement Grammar</title>
4976 This is the grammar of the <command>options</command>
4977 statement in the <filename>named.conf</filename> file:
4980 <programlisting><command>options</command> {
4981 <optional> attach-cache <replaceable>cache_name</replaceable>; </optional>
4982 <optional> version <replaceable>version_string</replaceable>; </optional>
4983 <optional> hostname <replaceable>hostname_string</replaceable>; </optional>
4984 <optional> server-id <replaceable>server_id_string</replaceable>; </optional>
4985 <optional> directory <replaceable>path_name</replaceable>; </optional>
4986 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
4987 <optional> managed-keys-directory <replaceable>path_name</replaceable>; </optional>
4988 <optional> named-xfer <replaceable>path_name</replaceable>; </optional>
4989 <optional> tkey-gssapi-keytab <replaceable>path_name</replaceable>; </optional>
4990 <optional> tkey-gssapi-credential <replaceable>principal</replaceable>; </optional>
4991 <optional> tkey-domain <replaceable>domainname</replaceable>; </optional>
4992 <optional> tkey-dhkey <replaceable>key_name</replaceable> <replaceable>key_tag</replaceable>; </optional>
4993 <optional> cache-file <replaceable>path_name</replaceable>; </optional>
4994 <optional> dump-file <replaceable>path_name</replaceable>; </optional>
4995 <optional> bindkeys-file <replaceable>path_name</replaceable>; </optional>
4996 <optional> memstatistics <replaceable>yes_or_no</replaceable>; </optional>
4997 <optional> memstatistics-file <replaceable>path_name</replaceable>; </optional>
4998 <optional> pid-file <replaceable>path_name</replaceable>; </optional>
4999 <optional> recursing-file <replaceable>path_name</replaceable>; </optional>
5000 <optional> statistics-file <replaceable>path_name</replaceable>; </optional>
5001 <optional> zone-statistics <replaceable>yes_or_no</replaceable>; </optional>
5002 <optional> auth-nxdomain <replaceable>yes_or_no</replaceable>; </optional>
5003 <optional> deallocate-on-exit <replaceable>yes_or_no</replaceable>; </optional>
5004 <optional> dialup <replaceable>dialup_option</replaceable>; </optional>
5005 <optional> fake-iquery <replaceable>yes_or_no</replaceable>; </optional>
5006 <optional> fetch-glue <replaceable>yes_or_no</replaceable>; </optional>
5007 <optional> flush-zones-on-shutdown <replaceable>yes_or_no</replaceable>; </optional>
5008 <optional> has-old-clients <replaceable>yes_or_no</replaceable>; </optional>
5009 <optional> host-statistics <replaceable>yes_or_no</replaceable>; </optional>
5010 <optional> host-statistics-max <replaceable>number</replaceable>; </optional>
5011 <optional> minimal-responses <replaceable>yes_or_no</replaceable>; </optional>
5012 <optional> multiple-cnames <replaceable>yes_or_no</replaceable>; </optional>
5013 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable>; </optional>
5014 <optional> recursion <replaceable>yes_or_no</replaceable>; </optional>
5015 <optional> rfc2308-type1 <replaceable>yes_or_no</replaceable>; </optional>
5016 <optional> use-id-pool <replaceable>yes_or_no</replaceable>; </optional>
5017 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable>; </optional>
5018 <optional> ixfr-from-differences (<replaceable>yes_or_no</replaceable> | <constant>master</constant> | <constant>slave</constant>); </optional>
5019 <optional> dnssec-enable <replaceable>yes_or_no</replaceable>; </optional>
5020 <optional> dnssec-validation (<replaceable>yes_or_no</replaceable> | <constant>auto</constant>); </optional>
5021 <optional> dnssec-lookaside ( <replaceable>auto</replaceable> |
5022 <replaceable>domain</replaceable> trust-anchor <replaceable>domain</replaceable> ); </optional>
5023 <optional> dnssec-must-be-secure <replaceable>domain yes_or_no</replaceable>; </optional>
5024 <optional> dnssec-accept-expired <replaceable>yes_or_no</replaceable>; </optional>
5025 <optional> forward ( <replaceable>only</replaceable> | <replaceable>first</replaceable> ); </optional>
5026 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
5027 <optional> dual-stack-servers <optional>port <replaceable>ip_port</replaceable></optional> {
5028 ( <replaceable>domain_name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> |
5029 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ) ;
5031 <optional> check-names ( <replaceable>master</replaceable> | <replaceable>slave</replaceable> | <replaceable>response</replaceable> )
5032 ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5033 <optional> check-dup-records ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5034 <optional> check-mx ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5035 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
5036 <optional> check-integrity <replaceable>yes_or_no</replaceable>; </optional>
5037 <optional> check-mx-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5038 <optional> check-srv-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5039 <optional> check-sibling <replaceable>yes_or_no</replaceable>; </optional>
5040 <optional> allow-new-zones { <replaceable>yes_or_no</replaceable> }; </optional>
5041 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
5042 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
5043 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
5044 <optional> allow-query-cache { <replaceable>address_match_list</replaceable> }; </optional>
5045 <optional> allow-query-cache-on { <replaceable>address_match_list</replaceable> }; </optional>
5046 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
5047 <optional> allow-recursion { <replaceable>address_match_list</replaceable> }; </optional>
5048 <optional> allow-recursion-on { <replaceable>address_match_list</replaceable> }; </optional>
5049 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
5050 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
5051 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
5052 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
5053 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ;</optional>
5054 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
5055 <optional> allow-v6-synthesis { <replaceable>address_match_list</replaceable> }; </optional>
5056 <optional> blackhole { <replaceable>address_match_list</replaceable> }; </optional>
5057 <optional> use-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5058 <optional> avoid-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5059 <optional> use-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5060 <optional> avoid-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5061 <optional> listen-on <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
5062 <optional> listen-on-v6 <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
5063 <optional> query-source ( ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> )
5064 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
5065 <optional> address ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
5066 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
5067 <optional> query-source-v6 ( ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> )
5068 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
5069 <optional> address ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
5070 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
5071 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
5072 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
5073 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
5074 <optional> max-transfer-time-in <replaceable>number</replaceable>; </optional>
5075 <optional> max-transfer-time-out <replaceable>number</replaceable>; </optional>
5076 <optional> max-transfer-idle-in <replaceable>number</replaceable>; </optional>
5077 <optional> max-transfer-idle-out <replaceable>number</replaceable>; </optional>
5078 <optional> tcp-clients <replaceable>number</replaceable>; </optional>
5079 <optional> reserved-sockets <replaceable>number</replaceable>; </optional>
5080 <optional> recursive-clients <replaceable>number</replaceable>; </optional>
5081 <optional> serial-query-rate <replaceable>number</replaceable>; </optional>
5082 <optional> serial-queries <replaceable>number</replaceable>; </optional>
5083 <optional> tcp-listen-queue <replaceable>number</replaceable>; </optional>
5084 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable>; </optional>
5085 <optional> transfers-in <replaceable>number</replaceable>; </optional>
5086 <optional> transfers-out <replaceable>number</replaceable>; </optional>
5087 <optional> transfers-per-ns <replaceable>number</replaceable>; </optional>
5088 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5089 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5090 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5091 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
5092 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5093 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
5094 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
5095 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5096 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5097 <optional> notify-to-soa <replaceable>yes_or_no</replaceable> ; </optional>
5098 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
5099 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
5100 <optional> max-ixfr-log-size <replaceable>number</replaceable>; </optional>
5101 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
5102 <optional> coresize <replaceable>size_spec</replaceable> ; </optional>
5103 <optional> datasize <replaceable>size_spec</replaceable> ; </optional>
5104 <optional> files <replaceable>size_spec</replaceable> ; </optional>
5105 <optional> stacksize <replaceable>size_spec</replaceable> ; </optional>
5106 <optional> cleaning-interval <replaceable>number</replaceable>; </optional>
5107 <optional> heartbeat-interval <replaceable>number</replaceable>; </optional>
5108 <optional> interface-interval <replaceable>number</replaceable>; </optional>
5109 <optional> statistics-interval <replaceable>number</replaceable>; </optional>
5110 <optional> topology { <replaceable>address_match_list</replaceable> }</optional>;
5111 <optional> sortlist { <replaceable>address_match_list</replaceable> }</optional>;
5112 <optional> rrset-order { <replaceable>order_spec</replaceable> ; <optional> <replaceable>order_spec</replaceable> ; ... </optional> </optional> };
5113 <optional> lame-ttl <replaceable>number</replaceable>; </optional>
5114 <optional> max-ncache-ttl <replaceable>number</replaceable>; </optional>
5115 <optional> max-cache-ttl <replaceable>number</replaceable>; </optional>
5116 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
5117 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
5118 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
5119 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
5120 <optional> min-roots <replaceable>number</replaceable>; </optional>
5121 <optional> use-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
5122 <optional> provide-ixfr <replaceable>yes_or_no</replaceable>; </optional>
5123 <optional> request-ixfr <replaceable>yes_or_no</replaceable>; </optional>
5124 <optional> treat-cr-as-space <replaceable>yes_or_no</replaceable> ; </optional>
5125 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
5126 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
5127 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
5128 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
5129 <optional> port <replaceable>ip_port</replaceable>; </optional>
5130 <optional> additional-from-auth <replaceable>yes_or_no</replaceable> ; </optional>
5131 <optional> additional-from-cache <replaceable>yes_or_no</replaceable> ; </optional>
5132 <optional> random-device <replaceable>path_name</replaceable> ; </optional>
5133 <optional> max-cache-size <replaceable>size_spec</replaceable> ; </optional>
5134 <optional> match-mapped-addresses <replaceable>yes_or_no</replaceable>; </optional>
5135 <optional> filter-aaaa-on-v4 ( <replaceable>yes_or_no</replaceable> | <replaceable>break-dnssec</replaceable> ); </optional>
5136 <optional> filter-aaaa { <replaceable>address_match_list</replaceable> }; </optional>
5137 <optional> dns64 <replaceable>IPv6-prefix</replaceable> {
5138 <optional> clients { <replaceable>address_match_list</replaceable> }; </optional>
5139 <optional> mapped { <replaceable>address_match_list</replaceable> }; </optional>
5140 <optional> exclude { <replaceable>address_match_list</replaceable> }; </optional>
5141 <optional> suffix IPv6-address; </optional>
5142 <optional> recursive-only <replaceable>yes_or_no</replaceable>; </optional>
5143 <optional> break-dnssec <replaceable>yes_or_no</replaceable>; </optional>
5145 <optional> dns64-server <replaceable>name</replaceable> </optional>
5146 <optional> dns64-contact <replaceable>name</replaceable> </optional>
5147 <optional> preferred-glue ( <replaceable>A</replaceable> | <replaceable>AAAA</replaceable> | <replaceable>NONE</replaceable> ); </optional>
5148 <optional> edns-udp-size <replaceable>number</replaceable>; </optional>
5149 <optional> max-udp-size <replaceable>number</replaceable>; </optional>
5150 <optional> root-delegation-only <optional> exclude { <replaceable>namelist</replaceable> } </optional> ; </optional>
5151 <optional> querylog <replaceable>yes_or_no</replaceable> ; </optional>
5152 <optional> disable-algorithms <replaceable>domain</replaceable> { <replaceable>algorithm</replaceable>;
5153 <optional> <replaceable>algorithm</replaceable>; </optional> }; </optional>
5154 <optional> acache-enable <replaceable>yes_or_no</replaceable> ; </optional>
5155 <optional> acache-cleaning-interval <replaceable>number</replaceable>; </optional>
5156 <optional> max-acache-size <replaceable>size_spec</replaceable> ; </optional>
5157 <optional> clients-per-query <replaceable>number</replaceable> ; </optional>
5158 <optional> max-clients-per-query <replaceable>number</replaceable> ; </optional>
5159 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
5160 <optional> empty-server <replaceable>name</replaceable> ; </optional>
5161 <optional> empty-contact <replaceable>name</replaceable> ; </optional>
5162 <optional> empty-zones-enable <replaceable>yes_or_no</replaceable> ; </optional>
5163 <optional> disable-empty-zone <replaceable>zone_name</replaceable> ; </optional>
5164 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
5165 <optional> zero-no-soa-ttl-cache <replaceable>yes_or_no</replaceable> ; </optional>
5166 <optional> resolver-query-timeout <replaceable>number</replaceable> ; </optional>
5167 <optional> deny-answer-addresses { <replaceable>address_match_list</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
5168 <optional> deny-answer-aliases { <replaceable>namelist</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
5169 <optional> response-policy { <replaceable>zone_name</replaceable> <optional> policy <replaceable>given</replaceable> | <replaceable>no-op</replaceable> | <replaceable>nxdomain</replaceable> | <replaceable>nodata</replaceable> | <replaceable>cname domain</replaceable> </optional> ; } ; </optional>
5175 <sect2 id="options">
5176 <title><command>options</command> Statement Definition and
5180 The <command>options</command> statement sets up global
5182 to be used by <acronym>BIND</acronym>. This statement
5184 once in a configuration file. If there is no <command>options</command>
5185 statement, an options block with each option set to its default will
5192 <term><command>attach-cache</command></term>
5195 Allows multiple views to share a single cache
5197 Each view has its own cache database by default, but
5198 if multiple views have the same operational policy
5199 for name resolution and caching, those views can
5200 share a single cache to save memory and possibly
5201 improve resolution efficiency by using this option.
5205 The <command>attach-cache</command> option
5206 may also be specified in <command>view</command>
5207 statements, in which case it overrides the
5208 global <command>attach-cache</command> option.
5212 The <replaceable>cache_name</replaceable> specifies
5213 the cache to be shared.
5214 When the <command>named</command> server configures
5215 views which are supposed to share a cache, it
5216 creates a cache with the specified name for the
5217 first view of these sharing views.
5218 The rest of the views will simply refer to the
5219 already created cache.
5223 One common configuration to share a cache would be to
5224 allow all views to share a single cache.
5225 This can be done by specifying
5226 the <command>attach-cache</command> as a global
5227 option with an arbitrary name.
5231 Another possible operation is to allow a subset of
5232 all views to share a cache while the others to
5233 retain their own caches.
5234 For example, if there are three views A, B, and C,
5235 and only A and B should share a cache, specify the
5236 <command>attach-cache</command> option as a view A (or
5237 B)'s option, referring to the other view name:
5242 // this view has its own cache
5246 // this view refers to A's cache
5250 // this view has its own cache
5256 Views that share a cache must have the same policy
5257 on configurable parameters that may affect caching.
5258 The current implementation requires the following
5259 configurable options be consistent among these
5261 <command>check-names</command>,
5262 <command>cleaning-interval</command>,
5263 <command>dnssec-accept-expired</command>,
5264 <command>dnssec-validation</command>,
5265 <command>max-cache-ttl</command>,
5266 <command>max-ncache-ttl</command>,
5267 <command>max-cache-size</command>, and
5268 <command>zero-no-soa-ttl</command>.
5272 Note that there may be other parameters that may
5273 cause confusion if they are inconsistent for
5274 different views that share a single cache.
5275 For example, if these views define different sets of
5276 forwarders that can return different answers for the
5277 same question, sharing the answer does not make
5278 sense or could even be harmful.
5279 It is administrator's responsibility to ensure
5280 configuration differences in different views do
5281 not cause disruption with a shared cache.
5288 <term><command>directory</command></term>
5291 The working directory of the server.
5292 Any non-absolute pathnames in the configuration file will be
5294 as relative to this directory. The default location for most
5296 output files (e.g. <filename>named.run</filename>)
5298 If a directory is not specified, the working directory
5299 defaults to `<filename>.</filename>', the directory from
5301 was started. The directory specified should be an absolute
5308 <term><command>key-directory</command></term>
5311 When performing dynamic update of secure zones, the
5312 directory where the public and private DNSSEC key files
5313 should be found, if different than the current working
5314 directory. (Note that this option has no effect on the
5315 paths for files containing non-DNSSEC keys such as
5316 <filename>bind.keys</filename>,
5317 <filename>rndc.key</filename> or
5318 <filename>session.key</filename>.)
5324 <term><command>managed-keys-directory</command></term>
5327 The directory used to hold the files used to track managed keys.
5328 By default it is the working directory. It there are no
5329 views then the file <filename>managed-keys.bind</filename>
5330 otherwise a SHA256 hash of the view name is used with
5331 <filename>.mkeys</filename> extension added.
5337 <term><command>named-xfer</command></term>
5340 <emphasis>This option is obsolete.</emphasis> It
5341 was used in <acronym>BIND</acronym> 8 to specify
5342 the pathname to the <command>named-xfer</command>
5343 program. In <acronym>BIND</acronym> 9, no separate
5344 <command>named-xfer</command> program is needed;
5345 its functionality is built into the name server.
5351 <term><command>tkey-gssapi-keytab</command></term>
5354 The KRB5 keytab file to use for GSS-TSIG updates. If
5355 this option is set and tkey-gssapi-credential is not
5356 set, then updates will be allowed with any key
5357 matching a principal in the specified keytab.
5363 <term><command>tkey-gssapi-credential</command></term>
5366 The security credential with which the server should
5367 authenticate keys requested by the GSS-TSIG protocol.
5368 Currently only Kerberos 5 authentication is available
5369 and the credential is a Kerberos principal which the
5370 server can acquire through the default system key
5371 file, normally <filename>/etc/krb5.keytab</filename>.
5372 The location keytab file can be overridden using the
5373 tkey-gssapi-keytab option. Normally this principal is
5374 of the form "<userinput>DNS/</userinput><varname>server.domain</varname>".
5375 To use GSS-TSIG, <command>tkey-domain</command> must
5376 also be set if a specific keytab is not set with
5383 <term><command>tkey-domain</command></term>
5386 The domain appended to the names of all shared keys
5387 generated with <command>TKEY</command>. When a
5388 client requests a <command>TKEY</command> exchange,
5389 it may or may not specify the desired name for the
5390 key. If present, the name of the shared key will
5391 be <varname>client specified part</varname> +
5392 <varname>tkey-domain</varname>. Otherwise, the
5393 name of the shared key will be <varname>random hex
5394 digits</varname> + <varname>tkey-domain</varname>.
5395 In most cases, the <command>domainname</command>
5396 should be the server's domain name, or an otherwise
5397 non-existent subdomain like
5398 "_tkey.<varname>domainname</varname>". If you are
5399 using GSS-TSIG, this variable must be defined, unless
5400 you specify a specific keytab using tkey-gssapi-keytab.
5406 <term><command>tkey-dhkey</command></term>
5409 The Diffie-Hellman key used by the server
5410 to generate shared keys with clients using the Diffie-Hellman
5412 of <command>TKEY</command>. The server must be
5414 public and private keys from files in the working directory.
5416 most cases, the keyname should be the server's host name.
5422 <term><command>cache-file</command></term>
5425 This is for testing only. Do not use.
5431 <term><command>dump-file</command></term>
5434 The pathname of the file the server dumps
5435 the database to when instructed to do so with
5436 <command>rndc dumpdb</command>.
5437 If not specified, the default is <filename>named_dump.db</filename>.
5443 <term><command>memstatistics-file</command></term>
5446 The pathname of the file the server writes memory
5447 usage statistics to on exit. If not specified,
5448 the default is <filename>named.memstats</filename>.
5454 <term><command>pid-file</command></term>
5457 The pathname of the file the server writes its process ID
5458 in. If not specified, the default is
5459 <filename>/var/run/named/named.pid</filename>.
5460 The PID file is used by programs that want to send signals to
5462 name server. Specifying <command>pid-file none</command> disables the
5463 use of a PID file — no file will be written and any
5464 existing one will be removed. Note that <command>none</command>
5465 is a keyword, not a filename, and therefore is not enclosed
5473 <term><command>recursing-file</command></term>
5476 The pathname of the file the server dumps
5477 the queries that are currently recursing when instructed
5478 to do so with <command>rndc recursing</command>.
5479 If not specified, the default is <filename>named.recursing</filename>.
5485 <term><command>statistics-file</command></term>
5488 The pathname of the file the server appends statistics
5489 to when instructed to do so using <command>rndc stats</command>.
5490 If not specified, the default is <filename>named.stats</filename> in the
5491 server's current directory. The format of the file is
5493 in <xref linkend="statsfile"/>.
5499 <term><command>bindkeys-file</command></term>
5502 The pathname of a file to override the built-in trusted
5503 keys provided by <command>named</command>.
5504 See the discussion of <command>dnssec-lookaside</command>
5505 and <command>dnssec-validation</command> for details.
5506 If not specified, the default is
5507 <filename>/etc/bind.keys</filename>.
5513 <term><command>secroots-file</command></term>
5516 The pathname of the file the server dumps
5517 security roots to when instructed to do so with
5518 <command>rndc secroots</command>.
5519 If not specified, the default is <filename>named.secroots</filename>.
5525 <term><command>session-keyfile</command></term>
5528 The pathname of the file into which to write a TSIG
5529 session key generated by <command>named</command> for use by
5530 <command>nsupdate -l</command>. If not specified, the
5531 default is <filename>/var/run/named/session.key</filename>.
5532 (See <xref linkend="dynamic_update_policies"/>, and in
5533 particular the discussion of the
5534 <command>update-policy</command> statement's
5535 <userinput>local</userinput> option for more
5536 information about this feature.)
5542 <term><command>session-keyname</command></term>
5545 The key name to use for the TSIG session key.
5546 If not specified, the default is "local-ddns".
5552 <term><command>session-keyalg</command></term>
5555 The algorithm to use for the TSIG session key.
5556 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
5557 hmac-sha384, hmac-sha512 and hmac-md5. If not
5558 specified, the default is hmac-sha256.
5564 <term><command>session-keyfile</command></term>
5567 The pathname of the file into which to write a session TSIG
5568 key for use by <command>nsupdate -l</command>. (See the
5569 discussion of the <command>update-policy</command>
5570 statement's <userinput>local</userinput> option for more
5571 details on this feature.)
5577 <term><command>port</command></term>
5580 The UDP/TCP port number the server uses for
5581 receiving and sending DNS protocol traffic.
5582 The default is 53. This option is mainly intended for server
5584 a server using a port other than 53 will not be able to
5592 <term><command>random-device</command></term>
5595 The source of entropy to be used by the server. Entropy is
5597 for DNSSEC operations, such as TKEY transactions and dynamic
5599 zones. This options specifies the device (or file) from which
5601 entropy. If this is a file, operations requiring entropy will
5603 file has been exhausted. If not specified, the default value
5605 <filename>/dev/random</filename>
5606 (or equivalent) when present, and none otherwise. The
5607 <command>random-device</command> option takes
5609 the initial configuration load at server startup time and
5610 is ignored on subsequent reloads.
5616 <term><command>preferred-glue</command></term>
5619 If specified, the listed type (A or AAAA) will be emitted
5621 in the additional section of a query response.
5622 The default is not to prefer any type (NONE).
5627 <varlistentry id="root_delegation_only">
5628 <term><command>root-delegation-only</command></term>
5631 Turn on enforcement of delegation-only in TLDs
5632 (top level domains) and root zones with an optional
5636 DS queries are expected to be made to and be answered by
5637 delegation only zones. Such queries and responses are
5638 treated as an exception to delegation-only processing
5639 and are not converted to NXDOMAIN responses provided
5640 a CNAME is not discovered at the query name.
5643 If a delegation only zone server also serves a child
5644 zone it is not always possible to determine whether
5645 an answer comes from the delegation only zone or the
5646 child zone. SOA NS and DNSKEY records are apex
5647 only records and a matching response that contains
5648 these records or DS is treated as coming from a
5649 child zone. RRSIG records are also examined to see
5650 if they are signed by a child zone or not. The
5651 authority section is also examined to see if there
5652 is evidence that the answer is from the child zone.
5653 Answers that are determined to be from a child zone
5654 are not converted to NXDOMAIN responses. Despite
5655 all these checks there is still a possibility of
5656 false negatives when a child zone is being served.
5659 Similarly false positives can arise from empty nodes
5660 (no records at the name) in the delegation only zone
5661 when the query type is not ANY.
5664 Note some TLDs are not delegation only (e.g. "DE", "LV",
5665 "US" and "MUSEUM"). This list is not exhaustive.
5670 root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
5678 <term><command>disable-algorithms</command></term>
5681 Disable the specified DNSSEC algorithms at and below the
5683 Multiple <command>disable-algorithms</command>
5684 statements are allowed.
5685 Only the most specific will be applied.
5691 <term><command>dnssec-lookaside</command></term>
5694 When set, <command>dnssec-lookaside</command> provides the
5695 validator with an alternate method to validate DNSKEY
5696 records at the top of a zone. When a DNSKEY is at or
5697 below a domain specified by the deepest
5698 <command>dnssec-lookaside</command>, and the normal DNSSEC
5699 validation has left the key untrusted, the trust-anchor
5700 will be appended to the key name and a DLV record will be
5701 looked up to see if it can validate the key. If the DLV
5702 record validates a DNSKEY (similarly to the way a DS
5703 record does) the DNSKEY RRset is deemed to be trusted.
5706 If <command>dnssec-lookaside</command> is set to
5707 <userinput>auto</userinput>, then built-in default
5708 values for the DLV domain and trust anchor will be
5709 used, along with a built-in key for validation.
5712 The default DLV key is stored in the file
5713 <filename>bind.keys</filename>;
5714 <command>named</command> will load that key at
5715 startup if <command>dnssec-lookaside</command> is set to
5716 <constant>auto</constant>. A copy of the file is
5717 installed along with <acronym>BIND</acronym> 9, and is
5718 current as of the release date. If the DLV key expires, a
5719 new copy of <filename>bind.keys</filename> can be downloaded
5720 from <ulink>https://www.isc.org/solutions/dlv</ulink>.
5723 (To prevent problems if <filename>bind.keys</filename> is
5724 not found, the current key is also compiled in to
5725 <command>named</command>. Relying on this is not
5726 recommended, however, as it requires <command>named</command>
5727 to be recompiled with a new key when the DLV key expires.)
5730 NOTE: <command>named</command> only loads certain specific
5731 keys from <filename>bind.keys</filename>: those for the
5732 DLV zone and for the DNS root zone. The file cannot be
5733 used to store keys for other zones.
5739 <term><command>dnssec-must-be-secure</command></term>
5742 Specify hierarchies which must be or may not be secure
5743 (signed and validated). If <userinput>yes</userinput>,
5744 then <command>named</command> will only accept answers if
5745 they are secure. If <userinput>no</userinput>, then normal
5746 DNSSEC validation applies allowing for insecure answers to
5747 be accepted. The specified domain must be under a
5748 <command>trusted-keys</command> or
5749 <command>managed-keys</command> statement, or
5750 <command>dnssec-lookaside</command> must be active.
5756 <term><command>dns64</command></term>
5759 This directive instructs <command>named</command> to
5760 return mapped IPv4 addresses to AAAA queries when
5761 there are no AAAA records. It is intended to be
5762 used in conjunction with a NAT64. Each
5763 <command>dns64</command> defines one DNS64 prefix.
5764 Multiple DNS64 prefixes can be defined.
5767 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
5768 64 and 96 as per RFC 6052.
5771 Additionally a reverse IP6.ARPA zone will be created for
5772 the prefix to provide a mapping from the IP6.ARPA names
5773 to the corresponding IN-ADDR.ARPA names using synthesized
5774 CNAMEs. <command>dns64-server</command> and
5775 <command>dns64-contact</command> can be used to specify
5776 the name of the server and contact for the zones. These
5777 are settable at the view / options level. These are
5778 not settable on a per-prefix basis.
5781 Each <command>dns64</command> supports an optional
5782 <command>clients</command> ACL that determines which
5783 clients are affected by this directive. If not defined,
5784 it defaults to <userinput>any;</userinput>.
5787 Each <command>dns64</command> supports an optional
5788 <command>mapped</command> ACL that selects which
5789 IPv4 addresses are to be mapped in the corresponding
5790 A RRset. If not defined it defaults to
5791 <userinput>any;</userinput>.
5794 Each <command>dns64</command> supports an optional
5795 <command>exclude</command> ACL that selects which
5796 IPv6 addresses will be ignored for the purposes
5797 of determining whether dns64 is to be applied.
5798 Any non-matching address will prevent further
5799 DNS64 processing from occurring for this client.
5802 A optional <command>suffix</command> can also
5803 be defined to set the bits trailing the mapped
5804 IPv4 address bits. By default these bits are
5805 set to <userinput>::</userinput>. The bits
5806 matching the prefix and mapped IPv4 address
5810 acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
5812 dns64 64:FF9B::/96 {
5814 mapped { !rfc1918; any; };
5815 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
5824 <sect3 id="boolean_options">
5825 <title>Boolean Options</title>
5830 <term><command>allow-new-zones</command></term>
5833 If <userinput>yes</userinput>, then zones can be
5834 added at runtime via <command>rndc addzone</command>
5835 or deleted via <command>rndc delzone</command>.
5836 The default is <userinput>no</userinput>.
5842 <term><command>auth-nxdomain</command></term>
5845 If <userinput>yes</userinput>, then the <command>AA</command> bit
5846 is always set on NXDOMAIN responses, even if the server is
5848 authoritative. The default is <userinput>no</userinput>;
5850 a change from <acronym>BIND</acronym> 8. If you
5851 are using very old DNS software, you
5852 may need to set it to <userinput>yes</userinput>.
5858 <term><command>deallocate-on-exit</command></term>
5861 This option was used in <acronym>BIND</acronym>
5862 8 to enable checking
5863 for memory leaks on exit. <acronym>BIND</acronym> 9 ignores the option and always performs
5870 <term><command>memstatistics</command></term>
5873 Write memory statistics to the file specified by
5874 <command>memstatistics-file</command> at exit.
5875 The default is <userinput>no</userinput> unless
5876 '-m record' is specified on the command line in
5877 which case it is <userinput>yes</userinput>.
5883 <term><command>dialup</command></term>
5886 If <userinput>yes</userinput>, then the
5887 server treats all zones as if they are doing zone transfers
5889 a dial-on-demand dialup link, which can be brought up by
5891 originating from this server. This has different effects
5893 to zone type and concentrates the zone maintenance so that
5895 happens in a short interval, once every <command>heartbeat-interval</command> and
5896 hopefully during the one call. It also suppresses some of
5898 zone maintenance traffic. The default is <userinput>no</userinput>.
5901 The <command>dialup</command> option
5902 may also be specified in the <command>view</command> and
5903 <command>zone</command> statements,
5904 in which case it overrides the global <command>dialup</command>
5908 If the zone is a master zone, then the server will send out a
5910 request to all the slaves (default). This should trigger the
5912 number check in the slave (providing it supports NOTIFY)
5914 to verify the zone while the connection is active.
5915 The set of servers to which NOTIFY is sent can be controlled
5917 <command>notify</command> and <command>also-notify</command>.
5921 zone is a slave or stub zone, then the server will suppress
5923 "zone up to date" (refresh) queries and only perform them
5925 <command>heartbeat-interval</command> expires in
5930 Finer control can be achieved by using
5931 <userinput>notify</userinput> which only sends NOTIFY
5933 <userinput>notify-passive</userinput> which sends NOTIFY
5935 suppresses the normal refresh queries, <userinput>refresh</userinput>
5936 which suppresses normal refresh processing and sends refresh
5938 when the <command>heartbeat-interval</command>
5940 <userinput>passive</userinput> which just disables normal
5945 <informaltable colsep="0" rowsep="0">
5946 <tgroup cols="4" colsep="0" rowsep="0" tgroupstyle="4Level-table">
5947 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
5948 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
5949 <colspec colname="3" colnum="3" colsep="0" colwidth="1.150in"/>
5950 <colspec colname="4" colnum="4" colsep="0" colwidth="1.150in"/>
5976 <para><command>no</command> (default)</para>
5996 <para><command>yes</command></para>
6016 <para><command>notify</command></para>
6036 <para><command>refresh</command></para>
6056 <para><command>passive</command></para>
6076 <para><command>notify-passive</command></para>
6099 Note that normal NOTIFY processing is not affected by
6100 <command>dialup</command>.
6107 <term><command>fake-iquery</command></term>
6110 In <acronym>BIND</acronym> 8, this option
6111 enabled simulating the obsolete DNS query type
6112 IQUERY. <acronym>BIND</acronym> 9 never does
6119 <term><command>fetch-glue</command></term>
6122 This option is obsolete.
6123 In BIND 8, <userinput>fetch-glue yes</userinput>
6124 caused the server to attempt to fetch glue resource records
6126 didn't have when constructing the additional
6127 data section of a response. This is now considered a bad
6129 and BIND 9 never does it.
6135 <term><command>flush-zones-on-shutdown</command></term>
6138 When the nameserver exits due receiving SIGTERM,
6139 flush or do not flush any pending zone writes. The default
6141 <command>flush-zones-on-shutdown</command> <userinput>no</userinput>.
6147 <term><command>has-old-clients</command></term>
6150 This option was incorrectly implemented
6151 in <acronym>BIND</acronym> 8, and is ignored by <acronym>BIND</acronym> 9.
6152 To achieve the intended effect
6154 <command>has-old-clients</command> <userinput>yes</userinput>, specify
6155 the two separate options <command>auth-nxdomain</command> <userinput>yes</userinput>
6156 and <command>rfc2308-type1</command> <userinput>no</userinput> instead.
6162 <term><command>host-statistics</command></term>
6165 In BIND 8, this enables keeping of
6166 statistics for every host that the name server interacts
6168 Not implemented in BIND 9.
6174 <term><command>maintain-ixfr-base</command></term>
6177 <emphasis>This option is obsolete</emphasis>.
6178 It was used in <acronym>BIND</acronym> 8 to
6179 determine whether a transaction log was
6180 kept for Incremental Zone Transfer. <acronym>BIND</acronym> 9 maintains a transaction
6181 log whenever possible. If you need to disable outgoing
6183 transfers, use <command>provide-ixfr</command> <userinput>no</userinput>.
6189 <term><command>minimal-responses</command></term>
6192 If <userinput>yes</userinput>, then when generating
6193 responses the server will only add records to the authority
6194 and additional data sections when they are required (e.g.
6195 delegations, negative responses). This may improve the
6196 performance of the server.
6197 The default is <userinput>no</userinput>.
6203 <term><command>multiple-cnames</command></term>
6206 This option was used in <acronym>BIND</acronym> 8 to allow
6207 a domain name to have multiple CNAME records in violation of
6208 the DNS standards. <acronym>BIND</acronym> 9.2 onwards
6209 always strictly enforces the CNAME rules both in master
6210 files and dynamic updates.
6216 <term><command>notify</command></term>
6219 If <userinput>yes</userinput> (the default),
6220 DNS NOTIFY messages are sent when a zone the server is
6222 changes, see <xref linkend="notify"/>. The messages are
6224 servers listed in the zone's NS records (except the master
6226 in the SOA MNAME field), and to any servers listed in the
6227 <command>also-notify</command> option.
6230 If <userinput>master-only</userinput>, notifies are only
6233 If <userinput>explicit</userinput>, notifies are sent only
6235 servers explicitly listed using <command>also-notify</command>.
6236 If <userinput>no</userinput>, no notifies are sent.
6239 The <command>notify</command> option may also be
6240 specified in the <command>zone</command>
6242 in which case it overrides the <command>options notify</command> statement.
6243 It would only be necessary to turn off this option if it
6251 <term><command>notify-to-soa</command></term>
6254 If <userinput>yes</userinput> do not check the nameservers
6255 in the NS RRset against the SOA MNAME. Normally a NOTIFY
6256 message is not sent to the SOA MNAME (SOA ORIGIN) as it is
6257 supposed to contain the name of the ultimate master.
6258 Sometimes, however, a slave is listed as the SOA MNAME in
6259 hidden master configurations and in that case you would
6260 want the ultimate master to still send NOTIFY messages to
6261 all the nameservers listed in the NS RRset.
6267 <term><command>recursion</command></term>
6270 If <userinput>yes</userinput>, and a
6271 DNS query requests recursion, then the server will attempt
6273 all the work required to answer the query. If recursion is
6275 and the server does not already know the answer, it will
6277 referral response. The default is
6278 <userinput>yes</userinput>.
6279 Note that setting <command>recursion no</command> does not prevent
6280 clients from getting data from the server's cache; it only
6281 prevents new data from being cached as an effect of client
6283 Caching may still occur as an effect the server's internal
6284 operation, such as NOTIFY address lookups.
6285 See also <command>fetch-glue</command> above.
6291 <term><command>rfc2308-type1</command></term>
6294 Setting this to <userinput>yes</userinput> will
6295 cause the server to send NS records along with the SOA
6297 answers. The default is <userinput>no</userinput>.
6301 Not yet implemented in <acronym>BIND</acronym>
6309 <term><command>use-id-pool</command></term>
6312 <emphasis>This option is obsolete</emphasis>.
6313 <acronym>BIND</acronym> 9 always allocates query
6320 <term><command>zone-statistics</command></term>
6323 If <userinput>yes</userinput>, the server will collect
6324 statistical data on all zones (unless specifically turned
6326 on a per-zone basis by specifying <command>zone-statistics no</command>
6327 in the <command>zone</command> statement).
6328 The default is <userinput>no</userinput>.
6329 These statistics may be accessed
6330 using <command>rndc stats</command>, which will
6331 dump them to the file listed
6332 in the <command>statistics-file</command>. See
6333 also <xref linkend="statsfile"/>.
6339 <term><command>use-ixfr</command></term>
6342 <emphasis>This option is obsolete</emphasis>.
6343 If you need to disable IXFR to a particular server or
6345 the information on the <command>provide-ixfr</command> option
6346 in <xref linkend="server_statement_definition_and_usage"/>.
6348 <xref linkend="incremental_zone_transfers"/>.
6354 <term><command>provide-ixfr</command></term>
6357 See the description of
6358 <command>provide-ixfr</command> in
6359 <xref linkend="server_statement_definition_and_usage"/>.
6365 <term><command>request-ixfr</command></term>
6368 See the description of
6369 <command>request-ixfr</command> in
6370 <xref linkend="server_statement_definition_and_usage"/>.
6376 <term><command>treat-cr-as-space</command></term>
6379 This option was used in <acronym>BIND</acronym>
6381 the server treat carriage return ("<command>\r</command>") characters the same way
6382 as a space or tab character,
6383 to facilitate loading of zone files on a UNIX system that
6385 on an NT or DOS machine. In <acronym>BIND</acronym> 9, both UNIX "<command>\n</command>"
6386 and NT/DOS "<command>\r\n</command>" newlines
6387 are always accepted,
6388 and the option is ignored.
6394 <term><command>additional-from-auth</command></term>
6395 <term><command>additional-from-cache</command></term>
6399 These options control the behavior of an authoritative
6401 answering queries which have additional data, or when
6407 When both of these options are set to <userinput>yes</userinput>
6409 query is being answered from authoritative data (a zone
6410 configured into the server), the additional data section of
6412 reply will be filled in using data from other authoritative
6414 and from the cache. In some situations this is undesirable,
6416 as when there is concern over the correctness of the cache,
6418 in servers where slave zones may be added and modified by
6419 untrusted third parties. Also, avoiding
6420 the search for this additional data will speed up server
6422 at the possible expense of additional queries to resolve
6424 otherwise be provided in the additional section.
6428 For example, if a query asks for an MX record for host <literal>foo.example.com</literal>,
6429 and the record found is "<literal>MX 10 mail.example.net</literal>", normally the address
6430 records (A and AAAA) for <literal>mail.example.net</literal> will be provided as well,
6431 if known, even though they are not in the example.com zone.
6432 Setting these options to <command>no</command>
6433 disables this behavior and makes
6434 the server only search for additional data in the zone it
6439 These options are intended for use in authoritative-only
6440 servers, or in authoritative-only views. Attempts to set
6441 them to <command>no</command> without also
6443 <command>recursion no</command> will cause the
6445 ignore the options and log a warning message.
6449 Specifying <command>additional-from-cache no</command> actually
6450 disables the use of the cache not only for additional data
6452 but also when looking up the answer. This is usually the
6454 behavior in an authoritative-only server where the
6456 the cached data is an issue.
6460 When a name server is non-recursively queried for a name
6462 below the apex of any served zone, it normally answers with
6464 "upwards referral" to the root servers or the servers of
6466 known parent of the query name. Since the data in an
6468 comes from the cache, the server will not be able to provide
6470 referrals when <command>additional-from-cache no</command>
6471 has been specified. Instead, it will respond to such
6473 with REFUSED. This should not cause any problems since
6474 upwards referrals are not required for the resolution
6482 <term><command>match-mapped-addresses</command></term>
6485 If <userinput>yes</userinput>, then an
6486 IPv4-mapped IPv6 address will match any address match
6487 list entries that match the corresponding IPv4 address.
6490 This option was introduced to work around a kernel quirk
6491 in some operating systems that causes IPv4 TCP
6492 connections, such as zone transfers, to be accepted on an
6493 IPv6 socket using mapped addresses. This caused address
6494 match lists designed for IPv4 to fail to match. However,
6495 <command>named</command> now solves this problem
6496 internally. The use of this option is discouraged.
6502 <term><command>filter-aaaa-on-v4</command></term>
6505 This option is only available when
6506 <acronym>BIND</acronym> 9 is compiled with the
6507 <userinput>--enable-filter-aaaa</userinput> option on the
6508 "configure" command line. It is intended to help the
6509 transition from IPv4 to IPv6 by not giving IPv6 addresses
6510 to DNS clients unless they have connections to the IPv6
6511 Internet. This is not recommended unless absolutely
6512 necessary. The default is <userinput>no</userinput>.
6513 The <command>filter-aaaa-on-v4</command> option
6514 may also be specified in <command>view</command> statements
6515 to override the global <command>filter-aaaa-on-v4</command>
6519 If <userinput>yes</userinput>,
6520 the DNS client is at an IPv4 address, in <command>filter-aaaa</command>,
6521 and if the response does not include DNSSEC signatures,
6522 then all AAAA records are deleted from the response.
6523 This filtering applies to all responses and not only
6524 authoritative responses.
6527 If <userinput>break-dnssec</userinput>,
6528 then AAAA records are deleted even when dnssec is enabled.
6529 As suggested by the name, this makes the response not verify,
6530 because the DNSSEC protocol is designed detect deletions.
6533 This mechanism can erroneously cause other servers to
6534 not give AAAA records to their clients.
6535 A recursing server with both IPv6 and IPv4 network connections
6536 that queries an authoritative server using this mechanism
6537 via IPv4 will be denied AAAA records even if its client is
6541 This mechanism is applied to authoritative as well as
6542 non-authoritative records.
6543 A client using IPv4 that is not allowed recursion can
6544 erroneously be given AAAA records because the server is not
6545 allowed to check for A records.
6548 Some AAAA records are given to IPv4 clients in glue records.
6549 IPv4 clients that are servers can then erroneously
6550 answer requests for AAAA records received via IPv4.
6556 <term><command>ixfr-from-differences</command></term>
6559 When <userinput>yes</userinput> and the server loads a new version of a master
6560 zone from its zone file or receives a new version of a slave
6561 file by a non-incremental zone transfer, it will compare
6562 the new version to the previous one and calculate a set
6563 of differences. The differences are then logged in the
6564 zone's journal file such that the changes can be transmitted
6565 to downstream slaves as an incremental zone transfer.
6568 By allowing incremental zone transfers to be used for
6569 non-dynamic zones, this option saves bandwidth at the
6570 expense of increased CPU and memory consumption at the
6572 In particular, if the new version of a zone is completely
6573 different from the previous one, the set of differences
6574 will be of a size comparable to the combined size of the
6575 old and new zone version, and the server will need to
6576 temporarily allocate memory to hold this complete
6579 <para><command>ixfr-from-differences</command>
6580 also accepts <command>master</command> and
6581 <command>slave</command> at the view and options
6583 <command>ixfr-from-differences</command> to be enabled for
6584 all <command>master</command> or
6585 <command>slave</command> zones respectively.
6586 It is off by default.
6592 <term><command>multi-master</command></term>
6595 This should be set when you have multiple masters for a zone
6597 addresses refer to different machines. If <userinput>yes</userinput>, <command>named</command> will
6599 when the serial number on the master is less than what <command>named</command>
6601 has. The default is <userinput>no</userinput>.
6607 <term><command>dnssec-enable</command></term>
6610 Enable DNSSEC support in <command>named</command>. Unless set to <userinput>yes</userinput>,
6611 <command>named</command> behaves as if it does not support DNSSEC.
6612 The default is <userinput>yes</userinput>.
6618 <term><command>dnssec-validation</command></term>
6621 Enable DNSSEC validation in <command>named</command>.
6622 Note <command>dnssec-enable</command> also needs to be
6623 set to <userinput>yes</userinput> to be effective.
6624 If set to <userinput>no</userinput>, DNSSEC validation
6625 is disabled. If set to <userinput>auto</userinput>,
6626 DNSSEC validation is enabled, and a default
6627 trust-anchor for the DNS root zone is used. If set to
6628 <userinput>yes</userinput>, DNSSEC validation is enabled,
6629 but a trust anchor must be manually configured using
6630 a <command>trusted-keys</command> or
6631 <command>managed-keys</command> statement. The default
6632 is <userinput>yes</userinput>.
6638 <term><command>dnssec-accept-expired</command></term>
6641 Accept expired signatures when verifying DNSSEC signatures.
6642 The default is <userinput>no</userinput>.
6643 Setting this option to <userinput>yes</userinput>
6644 leaves <command>named</command> vulnerable to
6651 <term><command>querylog</command></term>
6654 Specify whether query logging should be started when <command>named</command>
6656 If <command>querylog</command> is not specified,
6657 then the query logging
6658 is determined by the presence of the logging category <command>queries</command>.
6664 <term><command>check-names</command></term>
6667 This option is used to restrict the character set and syntax
6669 certain domain names in master files and/or DNS responses
6671 from the network. The default varies according to usage
6673 <command>master</command> zones the default is <command>fail</command>.
6674 For <command>slave</command> zones the default
6675 is <command>warn</command>.
6676 For answers received from the network (<command>response</command>)
6677 the default is <command>ignore</command>.
6680 The rules for legal hostnames and mail domains are derived
6681 from RFC 952 and RFC 821 as modified by RFC 1123.
6683 <para><command>check-names</command>
6684 applies to the owner names of A, AAAA and MX records.
6685 It also applies to the domain names in the RDATA of NS, SOA,
6686 MX, and SRV records.
6687 It also applies to the RDATA of PTR records where the owner
6688 name indicated that it is a reverse lookup of a hostname
6689 (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
6695 <term><command>check-dup-records</command></term>
6698 Check master zones for records that are treated as different
6699 by DNSSEC but are semantically equal in plain DNS. The
6700 default is to <command>warn</command>. Other possible
6701 values are <command>fail</command> and
6702 <command>ignore</command>.
6708 <term><command>check-mx</command></term>
6711 Check whether the MX record appears to refer to a IP address.
6712 The default is to <command>warn</command>. Other possible
6713 values are <command>fail</command> and
6714 <command>ignore</command>.
6720 <term><command>check-wildcard</command></term>
6723 This option is used to check for non-terminal wildcards.
6724 The use of non-terminal wildcards is almost always as a
6726 to understand the wildcard matching algorithm (RFC 1034).
6728 affects master zones. The default (<command>yes</command>) is to check
6729 for non-terminal wildcards and issue a warning.
6735 <term><command>check-integrity</command></term>
6738 Perform post load zone integrity checks on master
6739 zones. This checks that MX and SRV records refer
6740 to address (A or AAAA) records and that glue
6741 address records exist for delegated zones. For
6742 MX and SRV records only in-zone hostnames are
6743 checked (for out-of-zone hostnames use
6744 <command>named-checkzone</command>).
6745 For NS records only names below top of zone are
6746 checked (for out-of-zone names and glue consistency
6747 checks use <command>named-checkzone</command>).
6748 The default is <command>yes</command>.
6754 <term><command>check-mx-cname</command></term>
6757 If <command>check-integrity</command> is set then
6758 fail, warn or ignore MX records that refer
6759 to CNAMES. The default is to <command>warn</command>.
6765 <term><command>check-srv-cname</command></term>
6768 If <command>check-integrity</command> is set then
6769 fail, warn or ignore SRV records that refer
6770 to CNAMES. The default is to <command>warn</command>.
6776 <term><command>check-sibling</command></term>
6779 When performing integrity checks, also check that
6780 sibling glue exists. The default is <command>yes</command>.
6786 <term><command>zero-no-soa-ttl</command></term>
6789 When returning authoritative negative responses to
6790 SOA queries set the TTL of the SOA record returned in
6791 the authority section to zero.
6792 The default is <command>yes</command>.
6798 <term><command>zero-no-soa-ttl-cache</command></term>
6801 When caching a negative response to a SOA query
6802 set the TTL to zero.
6803 The default is <command>no</command>.
6809 <term><command>update-check-ksk</command></term>
6812 When set to the default value of <literal>yes</literal>,
6813 check the KSK bit in each key to determine how the key
6814 should be used when generating RRSIGs for a secure zone.
6817 Ordinarily, zone-signing keys (that is, keys without the
6818 KSK bit set) are used to sign the entire zone, while
6819 key-signing keys (keys with the KSK bit set) are only
6820 used to sign the DNSKEY RRset at the zone apex.
6821 However, if this option is set to <literal>no</literal>,
6822 then the KSK bit is ignored; KSKs are treated as if they
6823 were ZSKs and are used to sign the entire zone. This is
6824 similar to the <command>dnssec-signzone -z</command>
6825 command line option.
6828 When this option is set to <literal>yes</literal>, there
6829 must be at least two active keys for every algorithm
6830 represented in the DNSKEY RRset: at least one KSK and one
6831 ZSK per algorithm. If there is any algorithm for which
6832 this requirement is not met, this option will be ignored
6839 <term><command>dnssec-dnskey-kskonly</command></term>
6842 When this option and <command>update-check-ksk</command>
6843 are both set to <literal>yes</literal>, only key-signing
6844 keys (that is, keys with the KSK bit set) will be used
6845 to sign the DNSKEY RRset at the zone apex. Zone-signing
6846 keys (keys without the KSK bit set) will be used to sign
6847 the remainder of the zone, but not the DNSKEY RRset.
6848 This is similar to the
6849 <command>dnssec-signzone -x</command> command line option.
6852 The default is <command>no</command>. If
6853 <command>update-check-ksk</command> is set to
6854 <literal>no</literal>, this option is ignored.
6860 <term><command>try-tcp-refresh</command></term>
6863 Try to refresh the zone using TCP if UDP queries fail.
6864 For BIND 8 compatibility, the default is
6865 <command>yes</command>.
6871 <term><command>dnssec-secure-to-insecure</command></term>
6874 Allow a dynamic zone to transition from secure to
6875 insecure (i.e., signed to unsigned) by deleting all
6876 of the DNSKEY records. The default is <command>no</command>.
6877 If set to <command>yes</command>, and if the DNSKEY RRset
6878 at the zone apex is deleted, all RRSIG and NSEC records
6879 will be removed from the zone as well.
6882 If the zone uses NSEC3, then it is also necessary to
6883 delete the NSEC3PARAM RRset from the zone apex; this will
6884 cause the removal of all corresponding NSEC3 records.
6885 (It is expected that this requirement will be eliminated
6886 in a future release.)
6889 Note that if a zone has been configured with
6890 <command>auto-dnssec maintain</command> and the
6891 private keys remain accessible in the key repository,
6892 then the zone will be automatically signed again the
6893 next time <command>named</command> is started.
6903 <title>Forwarding</title>
6905 The forwarding facility can be used to create a large site-wide
6906 cache on a few servers, reducing traffic over links to external
6907 name servers. It can also be used to allow queries by servers that
6908 do not have direct access to the Internet, but wish to look up
6910 names anyway. Forwarding occurs only on those queries for which
6911 the server is not authoritative and does not have the answer in
6917 <term><command>forward</command></term>
6920 This option is only meaningful if the
6921 forwarders list is not empty. A value of <varname>first</varname>,
6922 the default, causes the server to query the forwarders
6924 if that doesn't answer the question, the server will then
6926 the answer itself. If <varname>only</varname> is
6928 server will only query the forwarders.
6934 <term><command>forwarders</command></term>
6937 Specifies the IP addresses to be used
6938 for forwarding. The default is the empty list (no
6947 Forwarding can also be configured on a per-domain basis, allowing
6948 for the global forwarding options to be overridden in a variety
6949 of ways. You can set particular domains to use different
6951 or have a different <command>forward only/first</command> behavior,
6952 or not forward at all, see <xref linkend="zone_statement_grammar"/>.
6957 <title>Dual-stack Servers</title>
6959 Dual-stack servers are used as servers of last resort to work
6961 problems in reachability due the lack of support for either IPv4
6963 on the host machine.
6968 <term><command>dual-stack-servers</command></term>
6971 Specifies host names or addresses of machines with access to
6972 both IPv4 and IPv6 transports. If a hostname is used, the
6974 to resolve the name using only the transport it has. If the
6976 stacked, then the <command>dual-stack-servers</command> have no effect unless
6977 access to a transport has been disabled on the command line
6978 (e.g. <command>named -4</command>).
6985 <sect3 id="access_control">
6986 <title>Access Control</title>
6989 Access to the server can be restricted based on the IP address
6990 of the requesting system. See <xref linkend="address_match_lists"/> for
6991 details on how to specify IP address lists.
6997 <term><command>allow-notify</command></term>
7000 Specifies which hosts are allowed to
7001 notify this server, a slave, of zone changes in addition
7002 to the zone masters.
7003 <command>allow-notify</command> may also be
7005 <command>zone</command> statement, in which case
7007 <command>options allow-notify</command>
7008 statement. It is only meaningful
7009 for a slave zone. If not specified, the default is to
7010 process notify messages
7011 only from a zone's master.
7017 <term><command>allow-query</command></term>
7020 Specifies which hosts are allowed to ask ordinary
7021 DNS questions. <command>allow-query</command> may
7022 also be specified in the <command>zone</command>
7023 statement, in which case it overrides the
7024 <command>options allow-query</command> statement.
7025 If not specified, the default is to allow queries
7030 <command>allow-query-cache</command> is now
7031 used to specify access to the cache.
7038 <term><command>allow-query-on</command></term>
7041 Specifies which local addresses can accept ordinary
7042 DNS questions. This makes it possible, for instance,
7043 to allow queries on internal-facing interfaces but
7044 disallow them on external-facing ones, without
7045 necessarily knowing the internal network's addresses.
7048 <command>allow-query-on</command> may
7049 also be specified in the <command>zone</command>
7050 statement, in which case it overrides the
7051 <command>options allow-query-on</command> statement.
7054 If not specified, the default is to allow queries
7059 <command>allow-query-cache</command> is
7060 used to specify access to the cache.
7067 <term><command>allow-query-cache</command></term>
7070 Specifies which hosts are allowed to get answers
7071 from the cache. If <command>allow-query-cache</command>
7072 is not set then <command>allow-recursion</command>
7073 is used if set, otherwise <command>allow-query</command>
7074 is used if set unless <command>recursion no;</command> is
7075 set in which case <command>none;</command> is used,
7076 otherwise the default (<command>localnets;</command>
7077 <command>localhost;</command>) is used.
7083 <term><command>allow-query-cache-on</command></term>
7086 Specifies which local addresses can give answers
7087 from the cache. If not specified, the default is
7088 to allow cache queries on any address,
7089 <command>localnets</command> and
7090 <command>localhost</command>.
7096 <term><command>allow-recursion</command></term>
7099 Specifies which hosts are allowed to make recursive
7100 queries through this server. If
7101 <command>allow-recursion</command> is not set
7102 then <command>allow-query-cache</command> is
7103 used if set, otherwise <command>allow-query</command>
7104 is used if set, otherwise the default
7105 (<command>localnets;</command>
7106 <command>localhost;</command>) is used.
7112 <term><command>allow-recursion-on</command></term>
7115 Specifies which local addresses can accept recursive
7116 queries. If not specified, the default is to allow
7117 recursive queries on all addresses.
7123 <term><command>allow-update</command></term>
7126 Specifies which hosts are allowed to
7127 submit Dynamic DNS updates for master zones. The default is
7129 updates from all hosts. Note that allowing updates based
7130 on the requestor's IP address is insecure; see
7131 <xref linkend="dynamic_update_security"/> for details.
7137 <term><command>allow-update-forwarding</command></term>
7140 Specifies which hosts are allowed to
7141 submit Dynamic DNS updates to slave zones to be forwarded to
7143 master. The default is <userinput>{ none; }</userinput>,
7145 means that no update forwarding will be performed. To
7147 update forwarding, specify
7148 <userinput>allow-update-forwarding { any; };</userinput>.
7149 Specifying values other than <userinput>{ none; }</userinput> or
7150 <userinput>{ any; }</userinput> is usually
7151 counterproductive, since
7152 the responsibility for update access control should rest
7154 master server, not the slaves.
7157 Note that enabling the update forwarding feature on a slave
7159 may expose master servers relying on insecure IP address
7161 access control to attacks; see <xref linkend="dynamic_update_security"/>
7168 <term><command>allow-v6-synthesis</command></term>
7171 This option was introduced for the smooth transition from
7173 to A6 and from "nibble labels" to binary labels.
7174 However, since both A6 and binary labels were then
7176 this option was also deprecated.
7177 It is now ignored with some warning messages.
7183 <term><command>allow-transfer</command></term>
7186 Specifies which hosts are allowed to
7187 receive zone transfers from the server. <command>allow-transfer</command> may
7188 also be specified in the <command>zone</command>
7190 case it overrides the <command>options allow-transfer</command> statement.
7191 If not specified, the default is to allow transfers to all
7198 <term><command>blackhole</command></term>
7201 Specifies a list of addresses that the
7202 server will not accept queries from or use to resolve a
7204 from these addresses will not be responded to. The default
7205 is <userinput>none</userinput>.
7211 <term><command>filter-aaaa</command></term>
7214 Specifies a list of addresses to which
7215 <command>filter-aaaa-on-v4</command>
7216 is applies. The default is <userinput>any</userinput>.
7222 <term><command>resolver-query-timeout</command></term>
7225 The amount of time the resolver will spend attempting
7226 to resolve a recursive query before failing. The
7227 default is <literal>10</literal> and the maximum is
7228 <literal>30</literal>. Setting it to <literal>0</literal>
7229 will result in the default being used.
7238 <title>Interfaces</title>
7240 The interfaces and ports that the server will answer queries
7241 from may be specified using the <command>listen-on</command> option. <command>listen-on</command> takes
7242 an optional port and an <varname>address_match_list</varname>.
7243 The server will listen on all interfaces allowed by the address
7244 match list. If a port is not specified, port 53 will be used.
7247 Multiple <command>listen-on</command> statements are
7252 <programlisting>listen-on { 5.6.7.8; };
7253 listen-on port 1234 { !1.2.3.4; 1.2/16; };
7257 will enable the name server on port 53 for the IP address
7258 5.6.7.8, and on port 1234 of an address on the machine in net
7259 1.2 that is not 1.2.3.4.
7263 If no <command>listen-on</command> is specified, the
7264 server will listen on port 53 on all IPv4 interfaces.
7268 The <command>listen-on-v6</command> option is used to
7269 specify the interfaces and the ports on which the server will
7271 for incoming queries sent using IPv6.
7275 When <programlisting>{ any; }</programlisting> is
7277 as the <varname>address_match_list</varname> for the
7278 <command>listen-on-v6</command> option,
7279 the server does not bind a separate socket to each IPv6 interface
7280 address as it does for IPv4 if the operating system has enough API
7281 support for IPv6 (specifically if it conforms to RFC 3493 and RFC
7283 Instead, it listens on the IPv6 wildcard address.
7284 If the system only has incomplete API support for IPv6, however,
7285 the behavior is the same as that for IPv4.
7289 A list of particular IPv6 addresses can also be specified, in
7291 the server listens on a separate socket for each specified
7293 regardless of whether the desired API is supported by the system.
7297 Multiple <command>listen-on-v6</command> options can
7302 <programlisting>listen-on-v6 { any; };
7303 listen-on-v6 port 1234 { !2001:db8::/32; any; };
7307 will enable the name server on port 53 for any IPv6 addresses
7308 (with a single wildcard socket),
7309 and on port 1234 of IPv6 addresses that is not in the prefix
7310 2001:db8::/32 (with separate sockets for each matched address.)
7314 To make the server not listen on any IPv6 address, use
7317 <programlisting>listen-on-v6 { none; };
7321 If no <command>listen-on-v6</command> option is
7322 specified, the server will not listen on any IPv6 address
7323 unless <command>-6</command> is specified when <command>named</command> is
7324 invoked. If <command>-6</command> is specified then
7325 <command>named</command> will listen on port 53 on all IPv6 interfaces by default.
7329 <sect3 id="query_address">
7330 <title>Query Address</title>
7332 If the server doesn't know the answer to a question, it will
7333 query other name servers. <command>query-source</command> specifies
7334 the address and port used for such queries. For queries sent over
7335 IPv6, there is a separate <command>query-source-v6</command> option.
7336 If <command>address</command> is <command>*</command> (asterisk) or is omitted,
7337 a wildcard IP address (<command>INADDR_ANY</command>)
7342 If <command>port</command> is <command>*</command> or is omitted,
7343 a random port number from a pre-configured
7344 range is picked up and will be used for each query.
7345 The port range(s) is that specified in
7346 the <command>use-v4-udp-ports</command> (for IPv4)
7347 and <command>use-v6-udp-ports</command> (for IPv6)
7348 options, excluding the ranges specified in
7349 the <command>avoid-v4-udp-ports</command>
7350 and <command>avoid-v6-udp-ports</command> options, respectively.
7354 The defaults of the <command>query-source</command> and
7355 <command>query-source-v6</command> options
7359 <programlisting>query-source address * port *;
7360 query-source-v6 address * port *;
7364 If <command>use-v4-udp-ports</command> or
7365 <command>use-v6-udp-ports</command> is unspecified,
7366 <command>named</command> will check if the operating
7367 system provides a programming interface to retrieve the
7368 system's default range for ephemeral ports.
7369 If such an interface is available,
7370 <command>named</command> will use the corresponding system
7371 default range; otherwise, it will use its own defaults:
7374 <programlisting>use-v4-udp-ports { range 1024 65535; };
7375 use-v6-udp-ports { range 1024 65535; };
7379 Note: make sure the ranges be sufficiently large for
7380 security. A desirable size depends on various parameters,
7381 but we generally recommend it contain at least 16384 ports
7382 (14 bits of entropy).
7383 Note also that the system's default range when used may be
7384 too small for this purpose, and that the range may even be
7385 changed while <command>named</command> is running; the new
7386 range will automatically be applied when <command>named</command>
7389 configure <command>use-v4-udp-ports</command> and
7390 <command>use-v6-udp-ports</command> explicitly so that the
7391 ranges are sufficiently large and are reasonably
7392 independent from the ranges used by other applications.
7396 Note: the operational configuration
7397 where <command>named</command> runs may prohibit the use
7398 of some ports. For example, UNIX systems will not allow
7399 <command>named</command> running without a root privilege
7400 to use ports less than 1024.
7401 If such ports are included in the specified (or detected)
7402 set of query ports, the corresponding query attempts will
7403 fail, resulting in resolution failures or delay.
7404 It is therefore important to configure the set of ports
7405 that can be safely used in the expected operational environment.
7409 The defaults of the <command>avoid-v4-udp-ports</command> and
7410 <command>avoid-v6-udp-ports</command> options
7414 <programlisting>avoid-v4-udp-ports {};
7415 avoid-v6-udp-ports {};
7419 Note: BIND 9.5.0 introduced
7420 the <command>use-queryport-pool</command>
7421 option to support a pool of such random ports, but this
7422 option is now obsolete because reusing the same ports in
7423 the pool may not be sufficiently secure.
7424 For the same reason, it is generally strongly discouraged to
7425 specify a particular port for the
7426 <command>query-source</command> or
7427 <command>query-source-v6</command> options;
7428 it implicitly disables the use of randomized port numbers.
7433 <term><command>use-queryport-pool</command></term>
7436 This option is obsolete.
7442 <term><command>queryport-pool-ports</command></term>
7445 This option is obsolete.
7451 <term><command>queryport-pool-updateinterval</command></term>
7454 This option is obsolete.
7462 The address specified in the <command>query-source</command> option
7463 is used for both UDP and TCP queries, but the port applies only
7464 to UDP queries. TCP queries always use a random
7470 Solaris 2.5.1 and earlier does not support setting the source
7471 address for TCP sockets.
7476 See also <command>transfer-source</command> and
7477 <command>notify-source</command>.
7482 <sect3 id="zone_transfers">
7483 <title>Zone Transfers</title>
7485 <acronym>BIND</acronym> has mechanisms in place to
7486 facilitate zone transfers
7487 and set limits on the amount of load that transfers place on the
7488 system. The following options apply to zone transfers.
7494 <term><command>also-notify</command></term>
7497 Defines a global list of IP addresses of name servers
7498 that are also sent NOTIFY messages whenever a fresh copy of
7500 zone is loaded, in addition to the servers listed in the
7502 This helps to ensure that copies of the zones will
7503 quickly converge on stealth servers.
7504 Optionally, a port may be specified with each
7505 <command>also-notify</command> address to send
7506 the notify messages to a port other than the
7508 If an <command>also-notify</command> list
7509 is given in a <command>zone</command> statement,
7511 the <command>options also-notify</command>
7512 statement. When a <command>zone notify</command>
7514 is set to <command>no</command>, the IP
7515 addresses in the global <command>also-notify</command> list will
7516 not be sent NOTIFY messages for that zone. The default is
7518 list (no global notification list).
7524 <term><command>max-transfer-time-in</command></term>
7527 Inbound zone transfers running longer than
7528 this many minutes will be terminated. The default is 120
7530 (2 hours). The maximum value is 28 days (40320 minutes).
7536 <term><command>max-transfer-idle-in</command></term>
7539 Inbound zone transfers making no progress
7540 in this many minutes will be terminated. The default is 60
7542 (1 hour). The maximum value is 28 days (40320 minutes).
7548 <term><command>max-transfer-time-out</command></term>
7551 Outbound zone transfers running longer than
7552 this many minutes will be terminated. The default is 120
7554 (2 hours). The maximum value is 28 days (40320 minutes).
7560 <term><command>max-transfer-idle-out</command></term>
7563 Outbound zone transfers making no progress
7564 in this many minutes will be terminated. The default is 60
7566 hour). The maximum value is 28 days (40320 minutes).
7572 <term><command>serial-query-rate</command></term>
7575 Slave servers will periodically query master servers
7576 to find out if zone serial numbers have changed. Each such
7578 a minute amount of the slave server's network bandwidth. To
7580 amount of bandwidth used, BIND 9 limits the rate at which
7582 sent. The value of the <command>serial-query-rate</command> option,
7583 an integer, is the maximum number of queries sent per
7591 <term><command>serial-queries</command></term>
7594 In BIND 8, the <command>serial-queries</command>
7596 set the maximum number of concurrent serial number queries
7597 allowed to be outstanding at any given time.
7598 BIND 9 does not limit the number of outstanding
7599 serial queries and ignores the <command>serial-queries</command> option.
7600 Instead, it limits the rate at which the queries are sent
7601 as defined using the <command>serial-query-rate</command> option.
7607 <term><command>transfer-format</command></term>
7611 Zone transfers can be sent using two different formats,
7612 <command>one-answer</command> and
7613 <command>many-answers</command>.
7614 The <command>transfer-format</command> option is used
7615 on the master server to determine which format it sends.
7616 <command>one-answer</command> uses one DNS message per
7617 resource record transferred.
7618 <command>many-answers</command> packs as many resource
7619 records as possible into a message.
7620 <command>many-answers</command> is more efficient, but is
7621 only supported by relatively new slave servers,
7622 such as <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
7623 8.x and <acronym>BIND</acronym> 4.9.5 onwards.
7624 The <command>many-answers</command> format is also supported by
7625 recent Microsoft Windows nameservers.
7626 The default is <command>many-answers</command>.
7627 <command>transfer-format</command> may be overridden on a
7628 per-server basis by using the <command>server</command>
7636 <term><command>transfers-in</command></term>
7639 The maximum number of inbound zone transfers
7640 that can be running concurrently. The default value is <literal>10</literal>.
7641 Increasing <command>transfers-in</command> may
7642 speed up the convergence
7643 of slave zones, but it also may increase the load on the
7650 <term><command>transfers-out</command></term>
7653 The maximum number of outbound zone transfers
7654 that can be running concurrently. Zone transfer requests in
7656 of the limit will be refused. The default value is <literal>10</literal>.
7662 <term><command>transfers-per-ns</command></term>
7665 The maximum number of inbound zone transfers
7666 that can be concurrently transferring from a given remote
7668 The default value is <literal>2</literal>.
7669 Increasing <command>transfers-per-ns</command>
7671 speed up the convergence of slave zones, but it also may
7673 the load on the remote name server. <command>transfers-per-ns</command> may
7674 be overridden on a per-server basis by using the <command>transfers</command> phrase
7675 of the <command>server</command> statement.
7681 <term><command>transfer-source</command></term>
7683 <para><command>transfer-source</command>
7684 determines which local address will be bound to IPv4
7685 TCP connections used to fetch zones transferred
7686 inbound by the server. It also determines the
7687 source IPv4 address, and optionally the UDP port,
7688 used for the refresh queries and forwarded dynamic
7689 updates. If not set, it defaults to a system
7690 controlled value which will usually be the address
7691 of the interface "closest to" the remote end. This
7692 address must appear in the remote end's
7693 <command>allow-transfer</command> option for the
7694 zone being transferred, if one is specified. This
7696 <command>transfer-source</command> for all zones,
7697 but can be overridden on a per-view or per-zone
7698 basis by including a
7699 <command>transfer-source</command> statement within
7700 the <command>view</command> or
7701 <command>zone</command> block in the configuration
7706 Solaris 2.5.1 and earlier does not support setting the
7707 source address for TCP sockets.
7714 <term><command>transfer-source-v6</command></term>
7717 The same as <command>transfer-source</command>,
7718 except zone transfers are performed using IPv6.
7724 <term><command>alt-transfer-source</command></term>
7727 An alternate transfer source if the one listed in
7728 <command>transfer-source</command> fails and
7729 <command>use-alt-transfer-source</command> is
7733 If you do not wish the alternate transfer source
7734 to be used, you should set
7735 <command>use-alt-transfer-source</command>
7736 appropriately and you should not depend upon
7737 getting an answer back to the first refresh
7744 <term><command>alt-transfer-source-v6</command></term>
7747 An alternate transfer source if the one listed in
7748 <command>transfer-source-v6</command> fails and
7749 <command>use-alt-transfer-source</command> is
7756 <term><command>use-alt-transfer-source</command></term>
7759 Use the alternate transfer sources or not. If views are
7760 specified this defaults to <command>no</command>
7761 otherwise it defaults to
7762 <command>yes</command> (for BIND 8
7769 <term><command>notify-source</command></term>
7771 <para><command>notify-source</command>
7772 determines which local source address, and
7773 optionally UDP port, will be used to send NOTIFY
7774 messages. This address must appear in the slave
7775 server's <command>masters</command> zone clause or
7776 in an <command>allow-notify</command> clause. This
7777 statement sets the <command>notify-source</command>
7778 for all zones, but can be overridden on a per-zone or
7779 per-view basis by including a
7780 <command>notify-source</command> statement within
7781 the <command>zone</command> or
7782 <command>view</command> block in the configuration
7787 Solaris 2.5.1 and earlier does not support setting the
7788 source address for TCP sockets.
7795 <term><command>notify-source-v6</command></term>
7798 Like <command>notify-source</command>,
7799 but applies to notify messages sent to IPv6 addresses.
7809 <title>UDP Port Lists</title>
7811 <command>use-v4-udp-ports</command>,
7812 <command>avoid-v4-udp-ports</command>,
7813 <command>use-v6-udp-ports</command>, and
7814 <command>avoid-v6-udp-ports</command>
7815 specify a list of IPv4 and IPv6 UDP ports that will be
7816 used or not used as source ports for UDP messages.
7817 See <xref linkend="query_address"/> about how the
7818 available ports are determined.
7819 For example, with the following configuration
7823 use-v6-udp-ports { range 32768 65535; };
7824 avoid-v6-udp-ports { 40000; range 50000 60000; };
7828 UDP ports of IPv6 messages sent
7829 from <command>named</command> will be in one
7830 of the following ranges: 32768 to 39999, 40001 to 49999,
7835 <command>avoid-v4-udp-ports</command> and
7836 <command>avoid-v6-udp-ports</command> can be used
7837 to prevent <command>named</command> from choosing as its random source port a
7838 port that is blocked by your firewall or a port that is
7839 used by other applications;
7840 if a query went out with a source port blocked by a
7842 answer would not get by the firewall and the name server would
7843 have to query again.
7844 Note: the desired range can also be represented only with
7845 <command>use-v4-udp-ports</command> and
7846 <command>use-v6-udp-ports</command>, and the
7847 <command>avoid-</command> options are redundant in that
7848 sense; they are provided for backward compatibility and
7849 to possibly simplify the port specification.
7854 <title>Operating System Resource Limits</title>
7857 The server's usage of many system resources can be limited.
7858 Scaled values are allowed when specifying resource limits. For
7859 example, <command>1G</command> can be used instead of
7860 <command>1073741824</command> to specify a limit of
7862 gigabyte. <command>unlimited</command> requests
7863 unlimited use, or the
7864 maximum available amount. <command>default</command>
7866 that was in force when the server was started. See the description
7867 of <command>size_spec</command> in <xref linkend="configuration_file_elements"/>.
7871 The following options set operating system resource limits for
7872 the name server process. Some operating systems don't support
7874 any of the limits. On such systems, a warning will be issued if
7876 unsupported limit is used.
7882 <term><command>coresize</command></term>
7885 The maximum size of a core dump. The default
7886 is <literal>default</literal>.
7892 <term><command>datasize</command></term>
7895 The maximum amount of data memory the server
7896 may use. The default is <literal>default</literal>.
7897 This is a hard limit on server memory usage.
7898 If the server attempts to allocate memory in excess of this
7899 limit, the allocation will fail, which may in turn leave
7900 the server unable to perform DNS service. Therefore,
7901 this option is rarely useful as a way of limiting the
7902 amount of memory used by the server, but it can be used
7903 to raise an operating system data size limit that is
7904 too small by default. If you wish to limit the amount
7905 of memory used by the server, use the
7906 <command>max-cache-size</command> and
7907 <command>recursive-clients</command>
7914 <term><command>files</command></term>
7917 The maximum number of files the server
7918 may have open concurrently. The default is <literal>unlimited</literal>.
7924 <term><command>stacksize</command></term>
7927 The maximum amount of stack memory the server
7928 may use. The default is <literal>default</literal>.
7937 <sect3 id="server_resource_limits">
7938 <title>Server Resource Limits</title>
7941 The following options set limits on the server's
7942 resource consumption that are enforced internally by the
7943 server rather than the operating system.
7949 <term><command>max-ixfr-log-size</command></term>
7952 This option is obsolete; it is accepted
7953 and ignored for BIND 8 compatibility. The option
7954 <command>max-journal-size</command> performs a
7955 similar function in BIND 9.
7961 <term><command>max-journal-size</command></term>
7964 Sets a maximum size for each journal file
7965 (see <xref linkend="journal"/>). When the journal file
7967 the specified size, some of the oldest transactions in the
7969 will be automatically removed. The default is
7970 <literal>unlimited</literal>.
7971 This may also be set on a per-zone basis.
7977 <term><command>host-statistics-max</command></term>
7980 In BIND 8, specifies the maximum number of host statistics
7982 Not implemented in BIND 9.
7988 <term><command>recursive-clients</command></term>
7991 The maximum number of simultaneous recursive lookups
7992 the server will perform on behalf of clients. The default
7994 <literal>1000</literal>. Because each recursing
7996 bit of memory, on the order of 20 kilobytes, the value of
7998 <command>recursive-clients</command> option may
7999 have to be decreased
8000 on hosts with limited memory.
8006 <term><command>tcp-clients</command></term>
8009 The maximum number of simultaneous client TCP
8010 connections that the server will accept.
8011 The default is <literal>100</literal>.
8017 <term><command>reserved-sockets</command></term>
8020 The number of file descriptors reserved for TCP, stdio,
8021 etc. This needs to be big enough to cover the number of
8022 interfaces <command>named</command> listens on, <command>tcp-clients</command> as well as
8023 to provide room for outgoing TCP queries and incoming zone
8024 transfers. The default is <literal>512</literal>.
8025 The minimum value is <literal>128</literal> and the
8026 maximum value is <literal>128</literal> less than
8027 maxsockets (-S). This option may be removed in the future.
8030 This option has little effect on Windows.
8036 <term><command>max-cache-size</command></term>
8039 The maximum amount of memory to use for the
8040 server's cache, in bytes.
8041 When the amount of data in the cache
8042 reaches this limit, the server will cause records to expire
8043 prematurely based on an LRU based strategy so that
8044 the limit is not exceeded.
8045 A value of 0 is special, meaning that
8046 records are purged from the cache only when their
8048 Another special keyword <userinput>unlimited</userinput>
8049 means the maximum value of 32-bit unsigned integers
8050 (0xffffffff), which may not have the same effect as
8051 0 on machines that support more than 32 bits of
8053 Any positive values less than 2MB will be ignored reset
8055 In a server with multiple views, the limit applies
8056 separately to the cache of each view.
8063 <term><command>tcp-listen-queue</command></term>
8066 The listen queue depth. The default and minimum is 3.
8067 If the kernel supports the accept filter "dataready" this
8069 many TCP connections that will be queued in kernel space
8071 some data before being passed to accept. Values less than 3
8083 <title>Periodic Task Intervals</title>
8088 <term><command>cleaning-interval</command></term>
8091 This interval is effectively obsolete. Previously,
8092 the server would remove expired resource records
8093 from the cache every <command>cleaning-interval</command> minutes.
8094 <acronym>BIND</acronym> 9 now manages cache
8095 memory in a more sophisticated manner and does not
8096 rely on the periodic cleaning any more.
8097 Specifying this option therefore has no effect on
8098 the server's behavior.
8104 <term><command>heartbeat-interval</command></term>
8107 The server will perform zone maintenance tasks
8108 for all zones marked as <command>dialup</command> whenever this
8109 interval expires. The default is 60 minutes. Reasonable
8111 to 1 day (1440 minutes). The maximum value is 28 days
8113 If set to 0, no zone maintenance for these zones will occur.
8119 <term><command>interface-interval</command></term>
8122 The server will scan the network interface list
8123 every <command>interface-interval</command>
8124 minutes. The default
8125 is 60 minutes. The maximum value is 28 days (40320 minutes).
8126 If set to 0, interface scanning will only occur when
8127 the configuration file is loaded. After the scan, the
8129 begin listening for queries on any newly discovered
8130 interfaces (provided they are allowed by the
8131 <command>listen-on</command> configuration), and
8133 stop listening on interfaces that have gone away.
8139 <term><command>statistics-interval</command></term>
8142 Name server statistics will be logged
8143 every <command>statistics-interval</command>
8144 minutes. The default is
8145 60. The maximum value is 28 days (40320 minutes).
8146 If set to 0, no statistics will be logged.
8149 Not yet implemented in
8150 <acronym>BIND</acronym> 9.
8160 <sect3 id="topology">
8161 <title>Topology</title>
8164 All other things being equal, when the server chooses a name
8166 to query from a list of name servers, it prefers the one that is
8167 topologically closest to itself. The <command>topology</command> statement
8168 takes an <command>address_match_list</command> and
8170 in a special way. Each top-level list element is assigned a
8172 Non-negated elements get a distance based on their position in the
8173 list, where the closer the match is to the start of the list, the
8174 shorter the distance is between it and the server. A negated match
8175 will be assigned the maximum distance from the server. If there
8176 is no match, the address will get a distance which is further than
8177 any non-negated list element, and closer than any negated element.
8181 <programlisting>topology {
8188 will prefer servers on network 10 the most, followed by hosts
8189 on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
8190 exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
8191 is preferred least of all.
8194 The default topology is
8197 <programlisting> topology { localhost; localnets; };
8202 The <command>topology</command> option
8203 is not implemented in <acronym>BIND</acronym> 9.
8208 <sect3 id="the_sortlist_statement">
8210 <title>The <command>sortlist</command> Statement</title>
8213 The response to a DNS query may consist of multiple resource
8214 records (RRs) forming a resource records set (RRset).
8215 The name server will normally return the
8216 RRs within the RRset in an indeterminate order
8217 (but see the <command>rrset-order</command>
8218 statement in <xref linkend="rrset_ordering"/>).
8219 The client resolver code should rearrange the RRs as appropriate,
8220 that is, using any addresses on the local net in preference to
8222 However, not all resolvers can do this or are correctly
8224 When a client is using a local server, the sorting can be performed
8225 in the server, based on the client's address. This only requires
8226 configuring the name servers, not all the clients.
8230 The <command>sortlist</command> statement (see below)
8232 an <command>address_match_list</command> and
8234 more specifically than the <command>topology</command>
8236 does (<xref linkend="topology"/>).
8237 Each top level statement in the <command>sortlist</command> must
8238 itself be an explicit <command>address_match_list</command> with
8239 one or two elements. The first element (which may be an IP
8241 an IP prefix, an ACL name or a nested <command>address_match_list</command>)
8242 of each top level list is checked against the source address of
8243 the query until a match is found.
8246 Once the source address of the query has been matched, if
8247 the top level statement contains only one element, the actual
8249 element that matched the source address is used to select the
8251 in the response to move to the beginning of the response. If the
8252 statement is a list of two elements, then the second element is
8253 treated the same as the <command>address_match_list</command> in
8254 a <command>topology</command> statement. Each top
8256 is assigned a distance and the address in the response with the
8258 distance is moved to the beginning of the response.
8261 In the following example, any queries received from any of
8262 the addresses of the host itself will get responses preferring
8264 on any of the locally connected networks. Next most preferred are
8266 on the 192.168.1/24 network, and after that either the
8269 192.168.3/24 network with no preference shown between these two
8270 networks. Queries received from a host on the 192.168.1/24 network
8271 will prefer other addresses on that network to the 192.168.2/24
8273 192.168.3/24 networks. Queries received from a host on the
8275 or the 192.168.5/24 network will only prefer other addresses on
8276 their directly connected networks.
8279 <programlisting>sortlist {
8280 // IF the local host
8281 // THEN first fit on the following nets
8285 { 192.168.2/24; 192.168.3/24; }; }; };
8286 // IF on class C 192.168.1 THEN use .1, or .2 or .3
8289 { 192.168.2/24; 192.168.3/24; }; }; };
8290 // IF on class C 192.168.2 THEN use .2, or .1 or .3
8293 { 192.168.1/24; 192.168.3/24; }; }; };
8294 // IF on class C 192.168.3 THEN use .3, or .1 or .2
8297 { 192.168.1/24; 192.168.2/24; }; }; };
8298 // IF .4 or .5 THEN prefer that net
8299 { { 192.168.4/24; 192.168.5/24; };
8304 The following example will give reasonable behavior for the
8305 local host and hosts on directly connected networks. It is similar
8306 to the behavior of the address sort in <acronym>BIND</acronym> 4.9.x. Responses sent
8307 to queries from the local host will favor any of the directly
8309 networks. Responses sent to queries from any other hosts on a
8311 connected network will prefer addresses on that same network.
8313 to other queries will not be sorted.
8316 <programlisting>sortlist {
8317 { localhost; localnets; };
8323 <sect3 id="rrset_ordering">
8324 <title id="rrset_ordering_title">RRset Ordering</title>
8326 When multiple records are returned in an answer it may be
8327 useful to configure the order of the records placed into the
8329 The <command>rrset-order</command> statement permits
8331 of the ordering of the records in a multiple record response.
8332 See also the <command>sortlist</command> statement,
8333 <xref linkend="the_sortlist_statement"/>.
8337 An <command>order_spec</command> is defined as
8341 <optional>class <replaceable>class_name</replaceable></optional>
8342 <optional>type <replaceable>type_name</replaceable></optional>
8343 <optional>name <replaceable>"domain_name"</replaceable></optional>
8344 order <replaceable>ordering</replaceable>
8347 If no class is specified, the default is <command>ANY</command>.
8348 If no type is specified, the default is <command>ANY</command>.
8349 If no name is specified, the default is "<command>*</command>" (asterisk).
8352 The legal values for <command>ordering</command> are:
8354 <informaltable colsep="0" rowsep="0">
8355 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
8356 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
8357 <colspec colname="2" colnum="2" colsep="0" colwidth="3.750in"/>
8361 <para><command>fixed</command></para>
8365 Records are returned in the order they
8366 are defined in the zone file.
8372 <para><command>random</command></para>
8376 Records are returned in some random order.
8382 <para><command>cyclic</command></para>
8386 Records are returned in a cyclic round-robin order.
8389 If <acronym>BIND</acronym> is configured with the
8390 "--enable-fixed-rrset" option at compile time, then
8391 the initial ordering of the RRset will match the
8392 one specified in the zone file.
8403 <programlisting>rrset-order {
8404 class IN type A name "host.example.com" order random;
8410 will cause any responses for type A records in class IN that
8411 have "<literal>host.example.com</literal>" as a
8412 suffix, to always be returned
8413 in random order. All other records are returned in cyclic order.
8416 If multiple <command>rrset-order</command> statements
8418 they are not combined — the last one applies.
8423 In this release of <acronym>BIND</acronym> 9, the
8424 <command>rrset-order</command> statement does not support
8425 "fixed" ordering by default. Fixed ordering can be enabled
8426 at compile time by specifying "--enable-fixed-rrset" on
8427 the "configure" command line.
8433 <title>Tuning</title>
8438 <term><command>lame-ttl</command></term>
8441 Sets the number of seconds to cache a
8442 lame server indication. 0 disables caching. (This is
8443 <emphasis role="bold">NOT</emphasis> recommended.)
8444 The default is <literal>600</literal> (10 minutes) and the
8446 <literal>1800</literal> (30 minutes).
8450 Lame-ttl also controls the amount of time DNSSEC
8451 validation failures are cached. There is a minimum
8452 of 30 seconds applied to bad cache entries if the
8453 lame-ttl is set to less than 30 seconds.
8460 <term><command>max-ncache-ttl</command></term>
8463 To reduce network traffic and increase performance,
8464 the server stores negative answers. <command>max-ncache-ttl</command> is
8465 used to set a maximum retention time for these answers in
8467 in seconds. The default
8468 <command>max-ncache-ttl</command> is <literal>10800</literal> seconds (3 hours).
8469 <command>max-ncache-ttl</command> cannot exceed
8471 be silently truncated to 7 days if set to a greater value.
8477 <term><command>max-cache-ttl</command></term>
8480 Sets the maximum time for which the server will
8481 cache ordinary (positive) answers. The default is
8483 A value of zero may cause all queries to return
8484 SERVFAIL, because of lost caches of intermediate
8485 RRsets (such as NS and glue AAAA/A records) in the
8492 <term><command>min-roots</command></term>
8495 The minimum number of root servers that
8496 is required for a request for the root servers to be
8497 accepted. The default
8498 is <userinput>2</userinput>.
8502 Not implemented in <acronym>BIND</acronym> 9.
8509 <term><command>sig-validity-interval</command></term>
8512 Specifies the number of days into the future when
8513 DNSSEC signatures automatically generated as a
8514 result of dynamic updates (<xref
8515 linkend="dynamic_update"/>) will expire. There
8516 is an optional second field which specifies how
8517 long before expiry that the signatures will be
8518 regenerated. If not specified, the signatures will
8519 be regenerated at 1/4 of base interval. The second
8520 field is specified in days if the base interval is
8521 greater than 7 days otherwise it is specified in hours.
8522 The default base interval is <literal>30</literal> days
8523 giving a re-signing interval of 7 1/2 days. The maximum
8524 values are 10 years (3660 days).
8527 The signature inception time is unconditionally
8528 set to one hour before the current time to allow
8529 for a limited amount of clock skew.
8532 The <command>sig-validity-interval</command>
8533 should be, at least, several multiples of the SOA
8534 expire interval to allow for reasonable interaction
8535 between the various timer and expiry dates.
8541 <term><command>sig-signing-nodes</command></term>
8544 Specify the maximum number of nodes to be
8545 examined in each quantum when signing a zone with
8546 a new DNSKEY. The default is
8547 <literal>100</literal>.
8553 <term><command>sig-signing-signatures</command></term>
8556 Specify a threshold number of signatures that
8557 will terminate processing a quantum when signing
8558 a zone with a new DNSKEY. The default is
8559 <literal>10</literal>.
8565 <term><command>sig-signing-type</command></term>
8568 Specify a private RDATA type to be used when generating
8569 key signing records. The default is
8570 <literal>65535</literal>.
8573 It is expected that this parameter may be removed
8574 in a future version once there is a standard type.
8580 <term><command>min-refresh-time</command></term>
8581 <term><command>max-refresh-time</command></term>
8582 <term><command>min-retry-time</command></term>
8583 <term><command>max-retry-time</command></term>
8586 These options control the server's behavior on refreshing a
8588 (querying for SOA changes) or retrying failed transfers.
8589 Usually the SOA values for the zone are used, but these
8591 are set by the master, giving slave server administrators
8593 control over their contents.
8596 These options allow the administrator to set a minimum and
8598 refresh and retry time either per-zone, per-view, or
8600 These options are valid for slave and stub zones,
8601 and clamp the SOA refresh and retry times to the specified
8605 The following defaults apply.
8606 <command>min-refresh-time</command> 300 seconds,
8607 <command>max-refresh-time</command> 2419200 seconds
8608 (4 weeks), <command>min-retry-time</command> 500 seconds,
8609 and <command>max-retry-time</command> 1209600 seconds
8616 <term><command>edns-udp-size</command></term>
8619 Sets the advertised EDNS UDP buffer size in bytes
8620 to control the size of packets received.
8621 Valid values are 1024 to 4096 (values outside this range
8622 will be silently adjusted). The default value
8623 is 4096. The usual reason for setting
8624 <command>edns-udp-size</command> to a non-default
8625 value is to get UDP answers to pass through broken
8626 firewalls that block fragmented packets and/or
8627 block UDP packets that are greater than 512 bytes.
8630 <command>named</command> will fallback to using 512 bytes
8631 if it get a series of timeout at the initial value. 512
8632 bytes is not being offered to encourage sites to fix their
8633 firewalls. Small EDNS UDP sizes will result in the
8634 excessive use of TCP.
8640 <term><command>max-udp-size</command></term>
8643 Sets the maximum EDNS UDP message size
8644 <command>named</command> will send in bytes.
8645 Valid values are 512 to 4096 (values outside this
8646 range will be silently adjusted). The default
8647 value is 4096. The usual reason for setting
8648 <command>max-udp-size</command> to a non-default
8649 value is to get UDP answers to pass through broken
8650 firewalls that block fragmented packets and/or
8651 block UDP packets that are greater than 512 bytes.
8652 This is independent of the advertised receive
8653 buffer (<command>edns-udp-size</command>).
8656 Setting this to a low value will encourage additional
8657 TCP traffic to the nameserver.
8663 <term><command>masterfile-format</command></term>
8666 the file format of zone files (see
8667 <xref linkend="zonefile_format"/>).
8668 The default value is <constant>text</constant>, which is the
8669 standard textual representation. Files in other formats
8670 than <constant>text</constant> are typically expected
8671 to be generated by the <command>named-compilezone</command> tool.
8672 Note that when a zone file in a different format than
8673 <constant>text</constant> is loaded, <command>named</command>
8674 may omit some of the checks which would be performed for a
8675 file in the <constant>text</constant> format. In particular,
8676 <command>check-names</command> checks do not apply
8677 for the <constant>raw</constant> format. This means
8678 a zone file in the <constant>raw</constant> format
8679 must be generated with the same check level as that
8680 specified in the <command>named</command> configuration
8681 file. This statement sets the
8682 <command>masterfile-format</command> for all zones,
8683 but can be overridden on a per-zone or per-view basis
8684 by including a <command>masterfile-format</command>
8685 statement within the <command>zone</command> or
8686 <command>view</command> block in the configuration
8692 <varlistentry id="clients-per-query">
8693 <term><command>clients-per-query</command></term>
8694 <term><command>max-clients-per-query</command></term>
8697 initial value (minimum) and maximum number of recursive
8698 simultaneous clients for any given query
8699 (<qname,qtype,qclass>) that the server will accept
8700 before dropping additional clients. <command>named</command> will attempt to
8701 self tune this value and changes will be logged. The
8702 default values are 10 and 100.
8705 This value should reflect how many queries come in for
8706 a given name in the time it takes to resolve that name.
8707 If the number of queries exceed this value, <command>named</command> will
8708 assume that it is dealing with a non-responsive zone
8709 and will drop additional queries. If it gets a response
8710 after dropping queries, it will raise the estimate. The
8711 estimate will then be lowered in 20 minutes if it has
8715 If <command>clients-per-query</command> is set to zero,
8716 then there is no limit on the number of clients per query
8717 and no queries will be dropped.
8720 If <command>max-clients-per-query</command> is set to zero,
8721 then there is no upper bound other than imposed by
8722 <command>recursive-clients</command>.
8728 <term><command>notify-delay</command></term>
8731 The delay, in seconds, between sending sets of notify
8732 messages for a zone. The default is five (5) seconds.
8740 <sect3 id="builtin">
8741 <title>Built-in server information zones</title>
8744 The server provides some helpful diagnostic information
8745 through a number of built-in zones under the
8746 pseudo-top-level-domain <literal>bind</literal> in the
8747 <command>CHAOS</command> class. These zones are part
8749 built-in view (see <xref linkend="view_statement_grammar"/>) of
8751 <command>CHAOS</command> which is separate from the
8753 class <command>IN</command>; therefore, any global
8755 such as <command>allow-query</command> do not apply
8757 If you feel the need to disable these zones, use the options
8758 below, or hide the built-in <command>CHAOS</command>
8760 defining an explicit view of class <command>CHAOS</command>
8761 that matches all clients.
8767 <term><command>version</command></term>
8770 The version the server should report
8771 via a query of the name <literal>version.bind</literal>
8772 with type <command>TXT</command>, class <command>CHAOS</command>.
8773 The default is the real version number of this server.
8774 Specifying <command>version none</command>
8775 disables processing of the queries.
8781 <term><command>hostname</command></term>
8784 The hostname the server should report via a query of
8785 the name <filename>hostname.bind</filename>
8786 with type <command>TXT</command>, class <command>CHAOS</command>.
8787 This defaults to the hostname of the machine hosting the
8789 found by the gethostname() function. The primary purpose of such queries
8791 identify which of a group of anycast servers is actually
8792 answering your queries. Specifying <command>hostname none;</command>
8793 disables processing of the queries.
8799 <term><command>server-id</command></term>
8802 The ID the server should report when receiving a Name
8803 Server Identifier (NSID) query, or a query of the name
8804 <filename>ID.SERVER</filename> with type
8805 <command>TXT</command>, class <command>CHAOS</command>.
8806 The primary purpose of such queries is to
8807 identify which of a group of anycast servers is actually
8808 answering your queries. Specifying <command>server-id none;</command>
8809 disables processing of the queries.
8810 Specifying <command>server-id hostname;</command> will cause <command>named</command> to
8811 use the hostname as found by the gethostname() function.
8812 The default <command>server-id</command> is <command>none</command>.
8822 <title>Built-in Empty Zones</title>
8824 Named has some built-in empty zones (SOA and NS records only).
8825 These are for zones that should normally be answered locally
8826 and which queries should not be sent to the Internet's root
8827 servers. The official servers which cover these namespaces
8828 return NXDOMAIN responses to these queries. In particular,
8829 these cover the reverse namespace for addresses from RFC 1918 and
8830 RFC 3330. They also include the reverse namespace for IPv6 local
8831 address (locally assigned), IPv6 link local addresses, the IPv6
8832 loopback address and the IPv6 unknown address.
8835 Named will attempt to determine if a built-in zone already exists
8836 or is active (covered by a forward-only forwarding declaration)
8837 and will not create an empty zone in that case.
8840 The current list of empty zones is:
8842 <!-- XXX: The RFC1918 addresses are #defined out in sources currently.
8843 <listitem>10.IN-ADDR.ARPA</listitem>
8844 <listitem>16.172.IN-ADDR.ARPA</listitem>
8845 <listitem>17.172.IN-ADDR.ARPA</listitem>
8846 <listitem>18.172.IN-ADDR.ARPA</listitem>
8847 <listitem>19.172.IN-ADDR.ARPA</listitem>
8848 <listitem>20.172.IN-ADDR.ARPA</listitem>
8849 <listitem>21.172.IN-ADDR.ARPA</listitem>
8850 <listitem>22.172.IN-ADDR.ARPA</listitem>
8851 <listitem>23.172.IN-ADDR.ARPA</listitem>
8852 <listitem>24.172.IN-ADDR.ARPA</listitem>
8853 <listitem>25.172.IN-ADDR.ARPA</listitem>
8854 <listitem>26.172.IN-ADDR.ARPA</listitem>
8855 <listitem>27.172.IN-ADDR.ARPA</listitem>
8856 <listitem>28.172.IN-ADDR.ARPA</listitem>
8857 <listitem>29.172.IN-ADDR.ARPA</listitem>
8858 <listitem>30.172.IN-ADDR.ARPA</listitem>
8859 <listitem>31.172.IN-ADDR.ARPA</listitem>
8860 <listitem>168.192.IN-ADDR.ARPA</listitem>
8861 XXX: end of RFC1918 addresses #defined out -->
8862 <listitem>0.IN-ADDR.ARPA</listitem>
8863 <listitem>127.IN-ADDR.ARPA</listitem>
8864 <listitem>254.169.IN-ADDR.ARPA</listitem>
8865 <listitem>2.0.192.IN-ADDR.ARPA</listitem>
8866 <listitem>100.51.198.IN-ADDR.ARPA</listitem>
8867 <listitem>113.0.203.IN-ADDR.ARPA</listitem>
8868 <listitem>255.255.255.255.IN-ADDR.ARPA</listitem>
8869 <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>
8870 <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>
8871 <listitem>8.B.D.0.1.0.0.2.IP6.ARPA</listitem>
8872 <listitem>D.F.IP6.ARPA</listitem>
8873 <listitem>8.E.F.IP6.ARPA</listitem>
8874 <listitem>9.E.F.IP6.ARPA</listitem>
8875 <listitem>A.E.F.IP6.ARPA</listitem>
8876 <listitem>B.E.F.IP6.ARPA</listitem>
8880 Empty zones are settable at the view level and only apply to
8881 views of class IN. Disabled empty zones are only inherited
8882 from options if there are no disabled empty zones specified
8883 at the view level. To override the options list of disabled
8884 zones, you can disable the root zone at the view level, for example:
8886 disable-empty-zone ".";
8890 If you are using the address ranges covered here, you should
8891 already have reverse zones covering the addresses you use.
8892 In practice this appears to not be the case with many queries
8893 being made to the infrastructure servers for names in these
8894 spaces. So many in fact that sacrificial servers were needed
8895 to be deployed to channel the query load away from the
8896 infrastructure servers.
8899 The real parent servers for these zones should disable all
8900 empty zone under the parent zone they serve. For the real
8901 root servers, this is all built-in empty zones. This will
8902 enable them to return referrals to deeper in the tree.
8906 <term><command>empty-server</command></term>
8909 Specify what server name will appear in the returned
8910 SOA record for empty zones. If none is specified, then
8911 the zone's name will be used.
8917 <term><command>empty-contact</command></term>
8920 Specify what contact name will appear in the returned
8921 SOA record for empty zones. If none is specified, then
8928 <term><command>empty-zones-enable</command></term>
8931 Enable or disable all empty zones. By default, they
8938 <term><command>disable-empty-zone</command></term>
8941 Disable individual empty zones. By default, none are
8942 disabled. This option can be specified multiple times.
8950 <title>Additional Section Caching</title>
8953 The additional section cache, also called <command>acache</command>,
8954 is an internal cache to improve the response performance of BIND 9.
8955 When additional section caching is enabled, BIND 9 will
8956 cache an internal short-cut to the additional section content for
8958 Note that <command>acache</command> is an internal caching
8959 mechanism of BIND 9, and is not related to the DNS caching
8964 Additional section caching does not change the
8965 response content (except the RRsets ordering of the additional
8966 section, see below), but can improve the response performance
8968 It is particularly effective when BIND 9 acts as an authoritative
8969 server for a zone that has many delegations with many glue RRs.
8973 In order to obtain the maximum performance improvement
8974 from additional section caching, setting
8975 <command>additional-from-cache</command>
8976 to <command>no</command> is recommended, since the current
8977 implementation of <command>acache</command>
8978 does not short-cut of additional section information from the
8983 One obvious disadvantage of <command>acache</command> is
8984 that it requires much more
8985 memory for the internal cached data.
8986 Thus, if the response performance does not matter and memory
8987 consumption is much more critical, the
8988 <command>acache</command> mechanism can be
8989 disabled by setting <command>acache-enable</command> to
8990 <command>no</command>.
8991 It is also possible to specify the upper limit of memory
8993 for acache by using <command>max-acache-size</command>.
8997 Additional section caching also has a minor effect on the
8998 RRset ordering in the additional section.
8999 Without <command>acache</command>,
9000 <command>cyclic</command> order is effective for the additional
9001 section as well as the answer and authority sections.
9002 However, additional section caching fixes the ordering when it
9003 first caches an RRset for the additional section, and the same
9004 ordering will be kept in succeeding responses, regardless of the
9005 setting of <command>rrset-order</command>.
9006 The effect of this should be minor, however, since an
9007 RRset in the additional section
9008 typically only contains a small number of RRs (and in many cases
9009 it only contains a single RR), in which case the
9010 ordering does not matter much.
9014 The following is a summary of options related to
9015 <command>acache</command>.
9021 <term><command>acache-enable</command></term>
9024 If <command>yes</command>, additional section caching is
9025 enabled. The default value is <command>no</command>.
9031 <term><command>acache-cleaning-interval</command></term>
9034 The server will remove stale cache entries, based on an LRU
9036 algorithm, every <command>acache-cleaning-interval</command> minutes.
9037 The default is 60 minutes.
9038 If set to 0, no periodic cleaning will occur.
9044 <term><command>max-acache-size</command></term>
9047 The maximum amount of memory in bytes to use for the server's acache.
9048 When the amount of data in the acache reaches this limit,
9050 will clean more aggressively so that the limit is not
9052 In a server with multiple views, the limit applies
9054 acache of each view.
9055 The default is <literal>16M</literal>.
9065 <title>Content Filtering</title>
9067 <acronym>BIND</acronym> 9 provides the ability to filter
9068 out DNS responses from external DNS servers containing
9069 certain types of data in the answer section.
9070 Specifically, it can reject address (A or AAAA) records if
9071 the corresponding IPv4 or IPv6 addresses match the given
9072 <varname>address_match_list</varname> of the
9073 <command>deny-answer-addresses</command> option.
9074 It can also reject CNAME or DNAME records if the "alias"
9075 name (i.e., the CNAME alias or the substituted query name
9076 due to DNAME) matches the
9077 given <varname>namelist</varname> of the
9078 <command>deny-answer-aliases</command> option, where
9079 "match" means the alias name is a subdomain of one of
9080 the <varname>name_list</varname> elements.
9081 If the optional <varname>namelist</varname> is specified
9082 with <command>except-from</command>, records whose query name
9083 matches the list will be accepted regardless of the filter
9085 Likewise, if the alias name is a subdomain of the
9086 corresponding zone, the <command>deny-answer-aliases</command>
9087 filter will not apply;
9088 for example, even if "example.com" is specified for
9089 <command>deny-answer-aliases</command>,
9091 <programlisting>www.example.com. CNAME xxx.example.com.</programlisting>
9094 returned by an "example.com" server will be accepted.
9098 In the <varname>address_match_list</varname> of the
9099 <command>deny-answer-addresses</command> option, only
9100 <varname>ip_addr</varname>
9101 and <varname>ip_prefix</varname>
9103 any <varname>key_id</varname> will be silently ignored.
9107 If a response message is rejected due to the filtering,
9108 the entire message is discarded without being cached, and
9109 a SERVFAIL error will be returned to the client.
9113 This filtering is intended to prevent "DNS rebinding attacks," in
9114 which an attacker, in response to a query for a domain name the
9115 attacker controls, returns an IP address within your own network or
9116 an alias name within your own domain.
9117 A naive web browser or script could then serve as an
9118 unintended proxy, allowing the attacker
9119 to get access to an internal node of your local network
9120 that couldn't be externally accessed otherwise.
9121 See the paper available at
9123 http://portal.acm.org/citation.cfm?id=1315245.1315298
9125 for more details about the attacks.
9129 For example, if you own a domain named "example.net" and
9130 your internal network uses an IPv4 prefix 192.0.2.0/24,
9131 you might specify the following rules:
9134 <programlisting>deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
9135 deny-answer-aliases { "example.net"; };
9139 If an external attacker lets a web browser in your local
9140 network look up an IPv4 address of "attacker.example.com",
9141 the attacker's DNS server would return a response like this:
9144 <programlisting>attacker.example.com. A 192.0.2.1</programlisting>
9147 in the answer section.
9148 Since the rdata of this record (the IPv4 address) matches
9149 the specified prefix 192.0.2.0/24, this response will be
9154 On the other hand, if the browser looks up a legitimate
9155 internal web server "www.example.net" and the
9156 following response is returned to
9157 the <acronym>BIND</acronym> 9 server
9160 <programlisting>www.example.net. A 192.0.2.2</programlisting>
9163 it will be accepted since the owner name "www.example.net"
9164 matches the <command>except-from</command> element,
9169 Note that this is not really an attack on the DNS per se.
9170 In fact, there is nothing wrong for an "external" name to
9171 be mapped to your "internal" IP address or domain name
9172 from the DNS point of view.
9173 It might actually be provided for a legitimate purpose,
9174 such as for debugging.
9175 As long as the mapping is provided by the correct owner,
9176 it is not possible or does not make sense to detect
9177 whether the intent of the mapping is legitimate or not
9179 The "rebinding" attack must primarily be protected at the
9180 application that uses the DNS.
9181 For a large site, however, it may be difficult to protect
9182 all possible applications at once.
9183 This filtering feature is provided only to help such an
9184 operational environment;
9185 it is generally discouraged to turn it on unless you are
9186 very sure you have no other choice and the attack is a
9187 real threat for your applications.
9191 Care should be particularly taken if you want to use this
9192 option for addresses within 127.0.0.0/8.
9193 These addresses are obviously "internal", but many
9194 applications conventionally rely on a DNS mapping from
9195 some name to such an address.
9196 Filtering out DNS records containing this address
9197 spuriously can break such applications.
9202 <title>Response Policy Zone (RPZ) Rewriting</title>
9204 <acronym>BIND</acronym> 9 includes an intentionally limited
9205 mechanism to modify DNS responses for recursive requests
9206 similar to email anti-spam DNS blacklists.
9207 All response policy zones are named in the
9208 <command>response-policy</command> option for the view or among the
9209 global options if there is no response-policy option for the view.
9213 The rules encoded in a response policy zone (RPZ) are applied
9214 only to responses to queries that ask for recursion (RD=1).
9215 RPZs are normal DNS zones containing RRsets
9216 that can be queried normally if allowed.
9217 It is usually best to restrict those queries with something like
9218 <command>allow-query {none; };</command> or
9219 <command>allow-query { 127.0.0.1; };</command>.
9223 There are four kinds of RPZ rewrite rules. QNAME rules are
9224 applied to query names in requests and to targets of CNAME
9225 records resolved in the process of generating the response.
9226 The owner name of a QNAME rule is the query name relativized
9228 The records in a rewrite rule are usually A, AAAA, or special
9229 CNAMEs, but can be any type except DNAME.
9233 IP rules are triggered by addresses in A and AAAA records.
9234 All IP addresses in A or AAAA RRsets are tested and the rule
9235 longest prefix is applied. Ties between rules with equal prefixes
9236 are broken in favor of the first RPZ mentioned in the
9237 response-policy option.
9238 The rule matching the smallest IP address is chosen among equal
9239 prefix rules from a single RPZ.
9240 IP rules are expressed in RRsets with owner names that are
9241 subdomains of rpz-ip and encoding an IP address block, reversed
9243 prefix.B.B.B.B with prefix between 1 and 32 and B between 1 and 255
9244 encodes an IPv4 address.
9245 IPv6 addresses are encoded by with prefix.W.W.W.W.W.W.W.W or
9246 prefix.WORDS.zz.WORDS. The words in the standard IPv6 text
9247 representation are reversed, "::" is replaced with ".zz.",
9248 and ":" becomes ".".
9252 NSDNAME rules match names in NS RRsets for the response or a
9253 parent. They are encoded as subdomains of rpz-nsdomain relativized
9254 to the RPZ origin name.
9258 NSIP rules match IP addresses in A and AAAA RRsets for names of
9259 responsible servers or the names that can be matched by NSDNAME
9260 rules. The are encoded like IP rules except as subdomains of
9265 Authority verification issues and variations in authority data in
9266 the current version of <acronym>BIND</acronym> 9 can cause
9267 inconsistent results from NSIP and NSDNAME. So they are available
9268 only when <acronym>BIND</acronym> is built with the
9269 <userinput>--enable-rpz-nsip</userinput> or
9270 <userinput>--enable-rpz-nsdname</userinput> options
9271 on the "configure" command line.
9275 Four policies can be expressed.
9276 The <command>NXDOMAIN</command> policy causes a NXDOMAIN response
9277 and is expressed with an RRset consisting of a single CNAME
9278 whose target is the root domain (.).
9279 <command>NODATA</command> generates NODATA or ANCOUNT=1 regardless
9281 It is expressed with a CNAME whose target is the wildcard
9282 top-level domain (*.).
9283 The <command>NO-OP</command> policy does not change the response
9284 and is used to "poke holes" in policies for larger CIDR blocks or in
9285 zones named later in the <command>response-policy</command> option.
9286 The NO-OP policy is expressed by a CNAME with a target consisting
9287 of the variable part of the owner name, such as "example.com." for
9288 a QNAME rule or "128.1.0.0.127." for an IP rule.
9289 The <command>CNAME</command> policy is used to replace the RRsets
9291 A and AAAA RRsets are most common and useful to capture
9292 an evil domain in a walled garden, but any valid set of RRsets
9297 All of the policies in an RPZ can be overridden with a
9298 <command>policy</command> clause.
9299 <command>given</command> says "do not override."
9300 <command>no-op</command> says "do nothing" regardless of the policy
9302 <command>nxdomain</command> causes all RPZ rules to generate
9304 <command>nodata</command> gives nodata.
9305 <command>cname domain</command> causes all RPZ rules to act as if
9306 the consisted of a "cname domain" record.
9310 For example, you might use this option statement
9312 <programlisting>response-policy { zone "bl"; };</programlisting>
9314 and this zone statement
9316 <programlisting>zone "bl" {type master; file "example/bl"; allow-query {none;}; };</programlisting>
9320 <programlisting>$TTL 1H
9321 @ SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
9324 nxdomain.domain.com CNAME .
9325 nodata.domain.com CNAME *.
9326 bad.domain.com A 10.0.0.1
9328 ok.domain.com CNAME ok.domain.com.
9329 *.badzone.domain.com CNAME garden.example.com.
9331 ; IP rules rewriting all answers for 127/8 except 127.0.0.1
9332 8.0.0.0.127.ip CNAME .
9333 32.1.0.0.127.ip CNAME 32.1.0.0.127.
9335 ; NSDNAME and NSIP rules
9336 ns.domain.com.rpz-nsdname CNAME .
9337 48.zz.2.2001.rpz-nsip CNAME .
9342 <sect2 id="server_statement_grammar">
9343 <title><command>server</command> Statement Grammar</title>
9345 <programlisting><command>server</command> <replaceable>ip_addr[/prefixlen]</replaceable> {
9346 <optional> bogus <replaceable>yes_or_no</replaceable> ; </optional>
9347 <optional> provide-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9348 <optional> request-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9349 <optional> edns <replaceable>yes_or_no</replaceable> ; </optional>
9350 <optional> edns-udp-size <replaceable>number</replaceable> ; </optional>
9351 <optional> max-udp-size <replaceable>number</replaceable> ; </optional>
9352 <optional> transfers <replaceable>number</replaceable> ; </optional>
9353 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable> ; ]</optional>
9354 <optional> keys <replaceable>{ string ; <optional> string ; <optional>...</optional></optional> }</replaceable> ; </optional>
9355 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9356 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9357 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9358 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9359 <optional> query-source <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9360 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9361 <optional> query-source-v6 <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9362 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9363 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
9364 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
9365 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
9371 <sect2 id="server_statement_definition_and_usage">
9372 <title><command>server</command> Statement Definition and
9376 The <command>server</command> statement defines
9378 to be associated with a remote name server. If a prefix length is
9379 specified, then a range of servers is covered. Only the most
9381 server clause applies regardless of the order in
9382 <filename>named.conf</filename>.
9386 The <command>server</command> statement can occur at
9387 the top level of the
9388 configuration file or inside a <command>view</command>
9390 If a <command>view</command> statement contains
9391 one or more <command>server</command> statements, only
9393 apply to the view and any top-level ones are ignored.
9394 If a view contains no <command>server</command>
9396 any top-level <command>server</command> statements are
9402 If you discover that a remote server is giving out bad data,
9403 marking it as bogus will prevent further queries to it. The
9405 value of <command>bogus</command> is <command>no</command>.
9408 The <command>provide-ixfr</command> clause determines
9410 the local server, acting as master, will respond with an
9412 zone transfer when the given remote server, a slave, requests it.
9413 If set to <command>yes</command>, incremental transfer
9415 whenever possible. If set to <command>no</command>,
9417 to the remote server will be non-incremental. If not set, the
9419 of the <command>provide-ixfr</command> option in the
9421 global options block is used as a default.
9425 The <command>request-ixfr</command> clause determines
9427 the local server, acting as a slave, will request incremental zone
9428 transfers from the given remote server, a master. If not set, the
9429 value of the <command>request-ixfr</command> option in
9431 global options block is used as a default.
9435 IXFR requests to servers that do not support IXFR will
9437 fall back to AXFR. Therefore, there is no need to manually list
9438 which servers support IXFR and which ones do not; the global
9440 of <command>yes</command> should always work.
9441 The purpose of the <command>provide-ixfr</command> and
9442 <command>request-ixfr</command> clauses is
9443 to make it possible to disable the use of IXFR even when both
9445 and slave claim to support it, for example if one of the servers
9446 is buggy and crashes or corrupts data when IXFR is used.
9450 The <command>edns</command> clause determines whether
9451 the local server will attempt to use EDNS when communicating
9452 with the remote server. The default is <command>yes</command>.
9456 The <command>edns-udp-size</command> option sets the EDNS UDP size
9457 that is advertised by <command>named</command> when querying the remote server.
9458 Valid values are 512 to 4096 bytes (values outside this range will be
9459 silently adjusted). This option is useful when you wish to
9460 advertises a different value to this server than the value you
9461 advertise globally, for example, when there is a firewall at the
9462 remote site that is blocking large replies.
9466 The <command>max-udp-size</command> option sets the
9467 maximum EDNS UDP message size <command>named</command> will send. Valid
9468 values are 512 to 4096 bytes (values outside this range will
9469 be silently adjusted). This option is useful when you
9470 know that there is a firewall that is blocking large
9471 replies from <command>named</command>.
9475 The server supports two zone transfer methods. The first, <command>one-answer</command>,
9476 uses one DNS message per resource record transferred. <command>many-answers</command> packs
9477 as many resource records as possible into a message. <command>many-answers</command> is
9478 more efficient, but is only known to be understood by <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
9479 8.x, and patched versions of <acronym>BIND</acronym>
9480 4.9.5. You can specify which method
9481 to use for a server with the <command>transfer-format</command> option.
9482 If <command>transfer-format</command> is not
9483 specified, the <command>transfer-format</command>
9485 by the <command>options</command> statement will be
9489 <para><command>transfers</command>
9490 is used to limit the number of concurrent inbound zone
9491 transfers from the specified server. If no
9492 <command>transfers</command> clause is specified, the
9493 limit is set according to the
9494 <command>transfers-per-ns</command> option.
9498 The <command>keys</command> clause identifies a
9499 <command>key_id</command> defined by the <command>key</command> statement,
9500 to be used for transaction security (TSIG, <xref linkend="tsig"/>)
9501 when talking to the remote server.
9502 When a request is sent to the remote server, a request signature
9503 will be generated using the key specified here and appended to the
9504 message. A request originating from the remote server is not
9506 to be signed by this key.
9510 Although the grammar of the <command>keys</command>
9512 allows for multiple keys, only a single key per server is
9518 The <command>transfer-source</command> and
9519 <command>transfer-source-v6</command> clauses specify
9520 the IPv4 and IPv6 source
9521 address to be used for zone transfer with the remote server,
9523 For an IPv4 remote server, only <command>transfer-source</command> can
9525 Similarly, for an IPv6 remote server, only
9526 <command>transfer-source-v6</command> can be
9528 For more details, see the description of
9529 <command>transfer-source</command> and
9530 <command>transfer-source-v6</command> in
9531 <xref linkend="zone_transfers"/>.
9535 The <command>notify-source</command> and
9536 <command>notify-source-v6</command> clauses specify the
9537 IPv4 and IPv6 source address to be used for notify
9538 messages sent to remote servers, respectively. For an
9539 IPv4 remote server, only <command>notify-source</command>
9540 can be specified. Similarly, for an IPv6 remote server,
9541 only <command>notify-source-v6</command> can be specified.
9545 The <command>query-source</command> and
9546 <command>query-source-v6</command> clauses specify the
9547 IPv4 and IPv6 source address to be used for queries
9548 sent to remote servers, respectively. For an IPv4
9549 remote server, only <command>query-source</command> can
9550 be specified. Similarly, for an IPv6 remote server,
9551 only <command>query-source-v6</command> can be specified.
9556 <sect2 id="statschannels">
9557 <title><command>statistics-channels</command> Statement Grammar</title>
9559 <programlisting><command>statistics-channels</command> {
9560 [ inet ( ip_addr | * ) [ port ip_port ]
9561 [ allow { <replaceable> address_match_list </replaceable> } ]; ]
9568 <title><command>statistics-channels</command> Statement Definition and
9572 The <command>statistics-channels</command> statement
9573 declares communication channels to be used by system
9574 administrators to get access to statistics information of
9579 This statement intends to be flexible to support multiple
9580 communication protocols in the future, but currently only
9581 HTTP access is supported.
9582 It requires that BIND 9 be compiled with libxml2;
9583 the <command>statistics-channels</command> statement is
9584 still accepted even if it is built without the library,
9585 but any HTTP access will fail with an error.
9589 An <command>inet</command> control channel is a TCP socket
9590 listening at the specified <command>ip_port</command> on the
9591 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
9592 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
9593 interpreted as the IPv4 wildcard address; connections will be
9594 accepted on any of the system's IPv4 addresses.
9595 To listen on the IPv6 wildcard address,
9596 use an <command>ip_addr</command> of <literal>::</literal>.
9600 If no port is specified, port 80 is used for HTTP channels.
9601 The asterisk "<literal>*</literal>" cannot be used for
9602 <command>ip_port</command>.
9606 The attempt of opening a statistics channel is
9607 restricted by the optional <command>allow</command> clause.
9608 Connections to the statistics channel are permitted based on the
9609 <command>address_match_list</command>.
9610 If no <command>allow</command> clause is present,
9611 <command>named</command> accepts connection
9612 attempts from any address; since the statistics may
9613 contain sensitive internal information, it is highly
9614 recommended to restrict the source of connection requests
9619 If no <command>statistics-channels</command> statement is present,
9620 <command>named</command> will not open any communication channels.
9625 <sect2 id="trusted-keys">
9626 <title><command>trusted-keys</command> Statement Grammar</title>
9628 <programlisting><command>trusted-keys</command> {
9629 <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9630 <optional> <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9636 <title><command>trusted-keys</command> Statement Definition
9639 The <command>trusted-keys</command> statement defines
9640 DNSSEC security roots. DNSSEC is described in <xref
9641 linkend="DNSSEC"/>. A security root is defined when the
9642 public key for a non-authoritative zone is known, but
9643 cannot be securely obtained through DNS, either because
9644 it is the DNS root zone or because its parent zone is
9645 unsigned. Once a key has been configured as a trusted
9646 key, it is treated as if it had been validated and
9647 proven secure. The resolver attempts DNSSEC validation
9648 on all DNS data in subdomains of a security root.
9651 All keys (and corresponding zones) listed in
9652 <command>trusted-keys</command> are deemed to exist regardless
9653 of what parent zones say. Similarly for all keys listed in
9654 <command>trusted-keys</command> only those keys are
9655 used to validate the DNSKEY RRset. The parent's DS RRset
9659 The <command>trusted-keys</command> statement can contain
9660 multiple key entries, each consisting of the key's
9661 domain name, flags, protocol, algorithm, and the Base-64
9662 representation of the key data.
9663 Spaces, tabs, newlines and carriage returns are ignored
9664 in the key data, so the configuration may be split up into
9668 <command>trusted-keys</command> may be set at the top level
9669 of <filename>named.conf</filename> or within a view. If it is
9670 set in both places, they are additive: keys defined at the top
9671 level are inherited by all views, but keys defined in a view
9672 are only used within that view.
9677 <title><command>managed-keys</command> Statement Grammar</title>
9679 <programlisting><command>managed-keys</command> {
9680 <replaceable>string</replaceable> initial-key <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9681 <optional> <replaceable>string</replaceable> initial-key <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9686 <sect2 id="managed-keys">
9687 <title><command>managed-keys</command> Statement Definition
9690 The <command>managed-keys</command> statement, like
9691 <command>trusted-keys</command>, defines DNSSEC
9692 security roots. The difference is that
9693 <command>managed-keys</command> can be kept up to date
9694 automatically, without intervention from the resolver
9698 Suppose, for example, that a zone's key-signing
9699 key was compromised, and the zone owner had to revoke and
9700 replace the key. A resolver which had the old key in a
9701 <command>trusted-keys</command> statement would be
9702 unable to validate this zone any longer; it would
9703 reply with a SERVFAIL response code. This would
9704 continue until the resolver operator had updated the
9705 <command>trusted-keys</command> statement with the new key.
9708 If, however, the zone were listed in a
9709 <command>managed-keys</command> statement instead, then the
9710 zone owner could add a "stand-by" key to the zone in advance.
9711 <command>named</command> would store the stand-by key, and
9712 when the original key was revoked, <command>named</command>
9713 would be able to transition smoothly to the new key. It would
9714 also recognize that the old key had been revoked, and cease
9715 using that key to validate answers, minimizing the damage that
9716 the compromised key could do.
9719 A <command>managed-keys</command> statement contains a list of
9720 the keys to be managed, along with information about how the
9721 keys are to be initialized for the first time. The only
9722 initialization method currently supported (as of
9723 <acronym>BIND</acronym> 9.7.0) is <literal>initial-key</literal>.
9724 This means the <command>managed-keys</command> statement must
9725 contain a copy of the initializing key. (Future releases may
9726 allow keys to be initialized by other methods, eliminating this
9730 Consequently, a <command>managed-keys</command> statement
9731 appears similar to a <command>trusted-keys</command>, differing
9732 in the presence of the second field, containing the keyword
9733 <literal>initial-key</literal>. The difference is, whereas the
9734 keys listed in a <command>trusted-keys</command> continue to be
9735 trusted until they are removed from
9736 <filename>named.conf</filename>, an initializing key listed
9737 in a <command>managed-keys</command> statement is only trusted
9738 <emphasis>once</emphasis>: for as long as it takes to load the
9739 managed key database and start the RFC 5011 key maintenance
9743 The first time <command>named</command> runs with a managed key
9744 configured in <filename>named.conf</filename>, it fetches the
9745 DNSKEY RRset directly from the zone apex, and validates it
9746 using the key specified in the <command>managed-keys</command>
9747 statement. If the DNSKEY RRset is validly signed, then it is
9748 used as the basis for a new managed keys database.
9751 From that point on, whenever <command>named</command> runs, it
9752 sees the <command>managed-keys</command> statement, checks to
9753 make sure RFC 5011 key maintenance has already been initialized
9754 for the specified domain, and if so, it simply moves on. The
9755 key specified in the <command>managed-keys</command> is not
9756 used to validate answers; it has been superseded by the key or
9757 keys stored in the managed keys database.
9760 The next time <command>named</command> runs after a name
9761 has been <emphasis>removed</emphasis> from the
9762 <command>managed-keys</command> statement, the corresponding
9763 zone will be removed from the managed keys database,
9764 and RFC 5011 key maintenance will no longer be used for that
9768 <command>named</command> only maintains a single managed keys
9769 database; consequently, unlike <command>trusted-keys</command>,
9770 <command>managed-keys</command> may only be set at the top
9771 level of <filename>named.conf</filename>, not within a view.
9774 In the current implementation, the managed keys database is
9775 stored as a master-format zone file called
9776 <filename>managed-keys.bind</filename>. When the key database
9777 is changed, the zone is updated. As with any other dynamic
9778 zone, changes will be written into a journal file,
9779 <filename>managed-keys.bind.jnl</filename>. They are committed
9780 to the master file as soon as possible afterward; in the case
9781 of the managed key database, this will usually occur within 30
9782 seconds. So, whenever <command>named</command> is using
9783 automatic key maintenance, those two files can be expected to
9784 exist in the working directory. (For this reason among others,
9785 the working directory should be always be writable by
9786 <command>named</command>.)
9789 If the <command>dnssec-lookaside</command> option is
9790 set to <userinput>auto</userinput>, <command>named</command>
9791 will automatically initialize a managed key for the
9792 zone <literal>dlv.isc.org</literal>. The key that is
9793 used to initialize the key maintenance process is built
9794 into <command>named</command>, and can be overridden
9795 from <command>bindkeys-file</command>.
9799 <sect2 id="view_statement_grammar">
9800 <title><command>view</command> Statement Grammar</title>
9802 <programlisting><command>view</command> <replaceable>view_name</replaceable>
9803 <optional><replaceable>class</replaceable></optional> {
9804 match-clients { <replaceable>address_match_list</replaceable> };
9805 match-destinations { <replaceable>address_match_list</replaceable> };
9806 match-recursive-only <replaceable>yes_or_no</replaceable> ;
9807 <optional> <replaceable>view_option</replaceable>; ...</optional>
9808 <optional> <replaceable>zone_statement</replaceable>; ...</optional>
9814 <title><command>view</command> Statement Definition and Usage</title>
9817 The <command>view</command> statement is a powerful
9819 of <acronym>BIND</acronym> 9 that lets a name server
9820 answer a DNS query differently
9821 depending on who is asking. It is particularly useful for
9823 split DNS setups without having to run multiple servers.
9827 Each <command>view</command> statement defines a view
9829 DNS namespace that will be seen by a subset of clients. A client
9831 a view if its source IP address matches the
9832 <varname>address_match_list</varname> of the view's
9833 <command>match-clients</command> clause and its
9834 destination IP address matches
9835 the <varname>address_match_list</varname> of the
9837 <command>match-destinations</command> clause. If not
9839 <command>match-clients</command> and <command>match-destinations</command>
9840 default to matching all addresses. In addition to checking IP
9842 <command>match-clients</command> and <command>match-destinations</command>
9843 can also take <command>keys</command> which provide an
9845 client to select the view. A view can also be specified
9846 as <command>match-recursive-only</command>, which
9847 means that only recursive
9848 requests from matching clients will match that view.
9849 The order of the <command>view</command> statements is
9851 a client request will be resolved in the context of the first
9852 <command>view</command> that it matches.
9856 Zones defined within a <command>view</command>
9858 only be accessible to clients that match the <command>view</command>.
9859 By defining a zone of the same name in multiple views, different
9860 zone data can be given to different clients, for example,
9862 and "external" clients in a split DNS setup.
9866 Many of the options given in the <command>options</command> statement
9867 can also be used within a <command>view</command>
9869 apply only when resolving queries with that view. When no
9871 value is given, the value in the <command>options</command> statement
9872 is used as a default. Also, zone options can have default values
9874 in the <command>view</command> statement; these
9875 view-specific defaults
9876 take precedence over those in the <command>options</command> statement.
9880 Views are class specific. If no class is given, class IN
9881 is assumed. Note that all non-IN views must contain a hint zone,
9882 since only the IN class has compiled-in default hints.
9886 If there are no <command>view</command> statements in
9888 file, a default view that matches any client is automatically
9890 in class IN. Any <command>zone</command> statements
9892 the top level of the configuration file are considered to be part
9894 this default view, and the <command>options</command>
9896 apply to the default view. If any explicit <command>view</command>
9897 statements are present, all <command>zone</command>
9899 occur inside <command>view</command> statements.
9903 Here is an example of a typical split DNS setup implemented
9904 using <command>view</command> statements:
9907 <programlisting>view "internal" {
9908 // This should match our internal networks.
9909 match-clients { 10.0.0.0/8; };
9911 // Provide recursive service to internal
9915 // Provide a complete view of the example.com
9916 // zone including addresses of internal hosts.
9917 zone "example.com" {
9919 file "example-internal.db";
9924 // Match all clients not matched by the
9926 match-clients { any; };
9928 // Refuse recursive service to external clients.
9931 // Provide a restricted view of the example.com
9932 // zone containing only publicly accessible hosts.
9933 zone "example.com" {
9935 file "example-external.db";
9941 <sect2 id="zone_statement_grammar">
9942 <title><command>zone</command>
9943 Statement Grammar</title>
9945 <programlisting><command>zone</command> <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9947 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
9948 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
9949 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
9950 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
9951 <optional> update-policy <replaceable>local</replaceable> | { <replaceable>update_policy_rule</replaceable> <optional>...</optional> }; </optional>
9952 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
9953 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9954 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
9955 <optional> check-mx (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
9956 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
9957 <optional> check-integrity <replaceable>yes_or_no</replaceable> ; </optional>
9958 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
9959 <optional> file <replaceable>string</replaceable> ; </optional>
9960 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
9961 <optional> journal <replaceable>string</replaceable> ; </optional>
9962 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
9963 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
9964 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
9965 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
9966 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
9967 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
9968 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
9969 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
9970 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
9971 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
9972 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
9973 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
9974 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
9975 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
9976 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9977 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9978 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
9979 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
9980 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
9981 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
9982 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
9983 <optional> database <replaceable>string</replaceable> ; </optional>
9984 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
9985 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
9986 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
9987 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
9988 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
9989 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>create</constant>|<constant>off</constant>; </optional>
9990 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
9993 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
9995 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
9996 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
9997 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
9998 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
9999 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
10000 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
10001 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
10002 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ; </optional>
10003 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
10004 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
10005 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10006 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10007 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10008 <optional> file <replaceable>string</replaceable> ; </optional>
10009 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10010 <optional> journal <replaceable>string</replaceable> ; </optional>
10011 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
10012 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10013 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10014 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
10015 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
10016 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
10017 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
10018 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10019 <optional>port <replaceable>ip_port</replaceable></optional>
10020 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10021 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
10022 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10023 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
10024 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10025 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
10026 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
10027 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
10028 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
10029 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10030 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10031 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10032 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10033 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10034 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10035 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10036 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10037 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10038 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10039 <optional> database <replaceable>string</replaceable> ; </optional>
10040 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10041 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10042 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10043 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10044 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10045 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
10048 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10050 file <replaceable>string</replaceable> ;
10051 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10052 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional> // Not Implemented.
10055 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10057 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10058 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10059 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10060 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10061 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10062 <optional> file <replaceable>string</replaceable> ; </optional>
10063 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10064 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10065 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10066 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10067 <optional>port <replaceable>ip_port</replaceable></optional>
10068 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10069 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10070 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10071 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10072 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10073 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10074 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10075 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10076 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10077 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10078 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10079 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10080 <optional> database <replaceable>string</replaceable> ; </optional>
10081 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10082 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10083 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10084 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10085 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10088 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10090 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10091 <optional> server-addresses { <optional> <replaceable>ip_addr</replaceable> ; ... </optional> }; </optional>
10092 <optional> server-names { <optional> <replaceable>namelist</replaceable> </optional> }; </optional>
10093 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10096 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10098 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10099 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10100 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10103 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10104 type delegation-only;
10111 <title><command>zone</command> Statement Definition and Usage</title>
10113 <title>Zone Types</title>
10114 <informaltable colsep="0" rowsep="0">
10115 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
10116 <!--colspec colname="1" colnum="1" colsep="0" colwidth="1.108in"/-->
10117 <!--colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/-->
10118 <colspec colname="1" colnum="1" colsep="0"/>
10119 <colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/>
10122 <entry colname="1">
10124 <varname>master</varname>
10127 <entry colname="2">
10129 The server has a master copy of the data
10130 for the zone and will be able to provide authoritative
10137 <entry colname="1">
10139 <varname>slave</varname>
10142 <entry colname="2">
10144 A slave zone is a replica of a master
10145 zone. The <command>masters</command> list
10146 specifies one or more IP addresses
10147 of master servers that the slave contacts to update
10148 its copy of the zone.
10149 Masters list elements can also be names of other
10151 By default, transfers are made from port 53 on the
10153 be changed for all servers by specifying a port number
10155 list of IP addresses, or on a per-server basis after
10157 Authentication to the master can also be done with
10158 per-server TSIG keys.
10159 If a file is specified, then the
10160 replica will be written to this file whenever the zone
10162 and reloaded from this file on a server restart. Use
10164 recommended, since it often speeds server startup and
10166 a needless waste of bandwidth. Note that for large
10168 tens or hundreds of thousands) of zones per server, it
10170 use a two-level naming scheme for zone filenames. For
10172 a slave server for the zone <literal>example.com</literal> might place
10173 the zone contents into a file called
10174 <filename>ex/example.com</filename> where <filename>ex/</filename> is
10175 just the first two letters of the zone name. (Most
10177 behave very slowly if you put 100000 files into
10178 a single directory.)
10183 <entry colname="1">
10185 <varname>stub</varname>
10188 <entry colname="2">
10190 A stub zone is similar to a slave zone,
10191 except that it replicates only the NS records of a
10192 master zone instead
10193 of the entire zone. Stub zones are not a standard part
10195 they are a feature specific to the <acronym>BIND</acronym> implementation.
10199 Stub zones can be used to eliminate the need for glue
10201 in a parent zone at the expense of maintaining a stub
10203 a set of name server addresses in <filename>named.conf</filename>.
10204 This usage is not recommended for new configurations,
10206 supports it only in a limited way.
10207 In <acronym>BIND</acronym> 4/8, zone
10208 transfers of a parent zone
10209 included the NS records from stub children of that
10211 that, in some cases, users could get away with
10212 configuring child stubs
10213 only in the master server for the parent zone. <acronym>BIND</acronym>
10214 9 never mixes together zone data from different zones
10216 way. Therefore, if a <acronym>BIND</acronym> 9 master serving a parent
10217 zone has child stub zones configured, all the slave
10219 parent zone also need to have the same child stub
10225 Stub zones can also be used as a way of forcing the
10227 of a given domain to use a particular set of
10228 authoritative servers.
10229 For example, the caching name servers on a private
10231 RFC1918 addressing may be configured with stub zones
10233 <literal>10.in-addr.arpa</literal>
10234 to use a set of internal name servers as the
10236 servers for that domain.
10241 <entry colname="1">
10243 <varname>static-stub</varname>
10246 <entry colname="2">
10248 A static-stub zone is similar to a stub zone
10249 with the following exceptions:
10250 the zone data is statically configured, rather
10251 than transferred from a master server;
10252 when recursion is necessary for a query that
10253 matches a static-stub zone, the locally
10254 configured data (nameserver names and glue addresses)
10255 is always used even if different authoritative
10256 information is cached.
10259 Zone data is configured via the
10260 <command>server-addresses</command> and
10261 <command>server-names</command> zone options.
10264 The zone data is maintained in the form of NS
10265 and (if necessary) glue A or AAAA RRs
10266 internally, which can be seen by dumping zone
10267 databases by <command>rndc dumpdb -all</command>.
10268 The configured RRs are considered local configuration
10269 parameters rather than public data.
10270 Non recursive queries (i.e., those with the RD
10271 bit off) to a static-stub zone are therefore
10272 prohibited and will be responded with REFUSED.
10275 Since the data is statically configured, no
10276 zone maintenance action takes place for a static-stub
10278 For example, there is no periodic refresh
10279 attempt, and an incoming notify message
10280 will be rejected with an rcode of NOTAUTH.
10283 Each static-stub zone is configured with
10284 internally generated NS and (if necessary)
10290 <entry colname="1">
10292 <varname>forward</varname>
10295 <entry colname="2">
10297 A "forward zone" is a way to configure
10298 forwarding on a per-domain basis. A <command>zone</command> statement
10299 of type <command>forward</command> can
10300 contain a <command>forward</command>
10301 and/or <command>forwarders</command>
10303 which will apply to queries within the domain given by
10305 name. If no <command>forwarders</command>
10306 statement is present or
10307 an empty list for <command>forwarders</command> is given, then no
10308 forwarding will be done for the domain, canceling the
10310 any forwarders in the <command>options</command> statement. Thus
10311 if you want to use this type of zone to change the
10313 global <command>forward</command> option
10314 (that is, "forward first"
10315 to, then "forward only", or vice versa, but want to
10317 servers as set globally) you need to re-specify the
10323 <entry colname="1">
10325 <varname>hint</varname>
10328 <entry colname="2">
10330 The initial set of root name servers is
10331 specified using a "hint zone". When the server starts
10333 the root hints to find a root name server and get the
10335 list of root name servers. If no hint zone is
10336 specified for class
10337 IN, the server uses a compiled-in default set of root
10339 Classes other than IN have no built-in defaults hints.
10344 <entry colname="1">
10346 <varname>delegation-only</varname>
10349 <entry colname="2">
10351 This is used to enforce the delegation-only
10352 status of infrastructure zones (e.g. COM,
10353 NET, ORG). Any answer that is received
10354 without an explicit or implicit delegation
10355 in the authority section will be treated
10356 as NXDOMAIN. This does not apply to the
10357 zone apex. This should not be applied to
10361 <varname>delegation-only</varname> has no
10362 effect on answers received from forwarders.
10365 See caveats in <xref linkend="root_delegation_only"/>.
10375 <title>Class</title>
10377 The zone's name may optionally be followed by a class. If
10378 a class is not specified, class <literal>IN</literal> (for <varname>Internet</varname>),
10379 is assumed. This is correct for the vast majority of cases.
10382 The <literal>hesiod</literal> class is
10383 named for an information service from MIT's Project Athena. It
10385 used to share information about various systems databases, such
10386 as users, groups, printers and so on. The keyword
10387 <literal>HS</literal> is
10388 a synonym for hesiod.
10391 Another MIT development is Chaosnet, a LAN protocol created
10392 in the mid-1970s. Zone data for it can be specified with the <literal>CHAOS</literal> class.
10397 <title>Zone Options</title>
10402 <term><command>allow-notify</command></term>
10405 See the description of
10406 <command>allow-notify</command> in <xref linkend="access_control"/>.
10412 <term><command>allow-query</command></term>
10415 See the description of
10416 <command>allow-query</command> in <xref linkend="access_control"/>.
10422 <term><command>allow-query-on</command></term>
10425 See the description of
10426 <command>allow-query-on</command> in <xref linkend="access_control"/>.
10432 <term><command>allow-transfer</command></term>
10435 See the description of <command>allow-transfer</command>
10436 in <xref linkend="access_control"/>.
10442 <term><command>allow-update</command></term>
10445 See the description of <command>allow-update</command>
10446 in <xref linkend="access_control"/>.
10452 <term><command>update-policy</command></term>
10455 Specifies a "Simple Secure Update" policy. See
10456 <xref linkend="dynamic_update_policies"/>.
10462 <term><command>allow-update-forwarding</command></term>
10465 See the description of <command>allow-update-forwarding</command>
10466 in <xref linkend="access_control"/>.
10472 <term><command>also-notify</command></term>
10475 Only meaningful if <command>notify</command>
10477 active for this zone. The set of machines that will
10479 <literal>DNS NOTIFY</literal> message
10480 for this zone is made up of all the listed name servers
10482 the primary master) for the zone plus any IP addresses
10484 with <command>also-notify</command>. A port
10486 with each <command>also-notify</command>
10487 address to send the notify
10488 messages to a port other than the default of 53.
10489 <command>also-notify</command> is not
10490 meaningful for stub zones.
10491 The default is the empty list.
10497 <term><command>check-names</command></term>
10500 This option is used to restrict the character set and
10502 certain domain names in master files and/or DNS responses
10504 network. The default varies according to zone type. For <command>master</command> zones the default is <command>fail</command>. For <command>slave</command>
10505 zones the default is <command>warn</command>.
10506 It is not implemented for <command>hint</command> zones.
10512 <term><command>check-mx</command></term>
10515 See the description of
10516 <command>check-mx</command> in <xref linkend="boolean_options"/>.
10522 <term><command>check-wildcard</command></term>
10525 See the description of
10526 <command>check-wildcard</command> in <xref linkend="boolean_options"/>.
10532 <term><command>check-integrity</command></term>
10535 See the description of
10536 <command>check-integrity</command> in <xref linkend="boolean_options"/>.
10542 <term><command>check-sibling</command></term>
10545 See the description of
10546 <command>check-sibling</command> in <xref linkend="boolean_options"/>.
10552 <term><command>zero-no-soa-ttl</command></term>
10555 See the description of
10556 <command>zero-no-soa-ttl</command> in <xref linkend="boolean_options"/>.
10562 <term><command>update-check-ksk</command></term>
10565 See the description of
10566 <command>update-check-ksk</command> in <xref linkend="boolean_options"/>.
10572 <term><command>dnssec-dnskey-kskonly</command></term>
10575 See the description of
10576 <command>dnssec-dnskey-kskonly</command> in <xref linkend="boolean_options"/>.
10582 <term><command>try-tcp-refresh</command></term>
10585 See the description of
10586 <command>try-tcp-refresh</command> in <xref linkend="boolean_options"/>.
10592 <term><command>database</command></term>
10595 Specify the type of database to be used for storing the
10596 zone data. The string following the <command>database</command> keyword
10597 is interpreted as a list of whitespace-delimited words.
10599 identifies the database type, and any subsequent words are
10601 as arguments to the database to be interpreted in a way
10603 to the database type.
10606 The default is <userinput>"rbt"</userinput>, BIND 9's
10608 red-black-tree database. This database does not take
10612 Other values are possible if additional database drivers
10613 have been linked into the server. Some sample drivers are
10615 with the distribution but none are linked in by default.
10621 <term><command>dialup</command></term>
10624 See the description of
10625 <command>dialup</command> in <xref linkend="boolean_options"/>.
10631 <term><command>delegation-only</command></term>
10634 The flag only applies to hint and stub zones. If set
10635 to <userinput>yes</userinput>, then the zone will also be
10636 treated as if it is also a delegation-only type zone.
10639 See caveats in <xref linkend="root_delegation_only"/>.
10645 <term><command>forward</command></term>
10648 Only meaningful if the zone has a forwarders
10649 list. The <command>only</command> value causes
10651 after trying the forwarders and getting no answer, while <command>first</command> would
10652 allow a normal lookup to be tried.
10658 <term><command>forwarders</command></term>
10661 Used to override the list of global forwarders.
10662 If it is not specified in a zone of type <command>forward</command>,
10663 no forwarding is done for the zone and the global options are
10670 <term><command>ixfr-base</command></term>
10673 Was used in <acronym>BIND</acronym> 8 to
10675 of the transaction log (journal) file for dynamic update
10677 <acronym>BIND</acronym> 9 ignores the option
10678 and constructs the name of the journal
10679 file by appending "<filename>.jnl</filename>"
10687 <term><command>ixfr-tmp-file</command></term>
10690 Was an undocumented option in <acronym>BIND</acronym> 8.
10691 Ignored in <acronym>BIND</acronym> 9.
10697 <term><command>journal</command></term>
10700 Allow the default journal's filename to be overridden.
10701 The default is the zone's filename with "<filename>.jnl</filename>" appended.
10702 This is applicable to <command>master</command> and <command>slave</command> zones.
10708 <term><command>max-journal-size</command></term>
10711 See the description of
10712 <command>max-journal-size</command> in <xref linkend="server_resource_limits"/>.
10718 <term><command>max-transfer-time-in</command></term>
10721 See the description of
10722 <command>max-transfer-time-in</command> in <xref linkend="zone_transfers"/>.
10728 <term><command>max-transfer-idle-in</command></term>
10731 See the description of
10732 <command>max-transfer-idle-in</command> in <xref linkend="zone_transfers"/>.
10738 <term><command>max-transfer-time-out</command></term>
10741 See the description of
10742 <command>max-transfer-time-out</command> in <xref linkend="zone_transfers"/>.
10748 <term><command>max-transfer-idle-out</command></term>
10751 See the description of
10752 <command>max-transfer-idle-out</command> in <xref linkend="zone_transfers"/>.
10758 <term><command>notify</command></term>
10761 See the description of
10762 <command>notify</command> in <xref linkend="boolean_options"/>.
10768 <term><command>notify-delay</command></term>
10771 See the description of
10772 <command>notify-delay</command> in <xref linkend="tuning"/>.
10778 <term><command>notify-to-soa</command></term>
10781 See the description of
10782 <command>notify-to-soa</command> in
10783 <xref linkend="boolean_options"/>.
10789 <term><command>pubkey</command></term>
10792 In <acronym>BIND</acronym> 8, this option was
10793 intended for specifying
10794 a public zone key for verification of signatures in DNSSEC
10796 zones when they are loaded from disk. <acronym>BIND</acronym> 9 does not verify signatures
10797 on load and ignores the option.
10803 <term><command>zone-statistics</command></term>
10806 If <userinput>yes</userinput>, the server will keep
10808 information for this zone, which can be dumped to the
10809 <command>statistics-file</command> defined in
10810 the server options.
10816 <term><command>server-addresses</command></term>
10819 Only meaningful for static-stub zones.
10820 This is a list of IP addresses to which queries
10821 should be sent in recursive resolution for the
10823 A non empty list for this option will internally
10824 configure the apex NS RR with associated glue A or
10828 For example, if "example.com" is configured as a
10829 static-stub zone with 192.0.2.1 and 2001:db8::1234
10830 in a <command>server-addresses</command> option,
10831 the following RRs will be internally configured.
10833 <programlisting>example.com. NS example.com.
10834 example.com. A 192.0.2.1
10835 example.com. AAAA 2001:db8::1234</programlisting>
10837 These records are internally used to resolve
10838 names under the static-stub zone.
10839 For instance, if the server receives a query for
10840 "www.example.com" with the RD bit on, the server
10841 will initiate recursive resolution and send
10842 queries to 192.0.2.1 and/or 2001:db8::1234.
10848 <term><command>server-names</command></term>
10851 Only meaningful for static-stub zones.
10852 This is a list of domain names of nameservers that
10853 act as authoritative servers of the static-stub
10855 These names will be resolved to IP addresses when
10856 <command>named</command> needs to send queries to
10858 To make this supplemental resolution successful,
10859 these names must not be a subdomain of the origin
10860 name of static-stub zone.
10861 That is, when "example.net" is the origin of a
10862 static-stub zone, "ns.example" and
10863 "master.example.com" can be specified in the
10864 <command>server-names</command> option, but
10865 "ns.example.net" cannot, and will be rejected by
10866 the configuration parser.
10869 A non empty list for this option will internally
10870 configure the apex NS RR with the specified names.
10871 For example, if "example.com" is configured as a
10872 static-stub zone with "ns1.example.net" and
10874 in a <command>server-names</command> option,
10875 the following RRs will be internally configured.
10877 <programlisting>example.com. NS ns1.example.net.
10878 example.com. NS ns2.example.net.
10881 These records are internally used to resolve
10882 names under the static-stub zone.
10883 For instance, if the server receives a query for
10884 "www.example.com" with the RD bit on, the server
10885 initiate recursive resolution,
10886 resolve "ns1.example.net" and/or
10887 "ns2.example.net" to IP addresses, and then send
10888 queries to (one or more of) these addresses.
10894 <term><command>sig-validity-interval</command></term>
10897 See the description of
10898 <command>sig-validity-interval</command> in <xref linkend="tuning"/>.
10904 <term><command>sig-signing-nodes</command></term>
10907 See the description of
10908 <command>sig-signing-nodes</command> in <xref linkend="tuning"/>.
10914 <term><command>sig-signing-signatures</command></term>
10917 See the description of
10918 <command>sig-signing-signatures</command> in <xref linkend="tuning"/>.
10924 <term><command>sig-signing-type</command></term>
10927 See the description of
10928 <command>sig-signing-type</command> in <xref linkend="tuning"/>.
10934 <term><command>transfer-source</command></term>
10937 See the description of
10938 <command>transfer-source</command> in <xref linkend="zone_transfers"/>.
10944 <term><command>transfer-source-v6</command></term>
10947 See the description of
10948 <command>transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
10954 <term><command>alt-transfer-source</command></term>
10957 See the description of
10958 <command>alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
10964 <term><command>alt-transfer-source-v6</command></term>
10967 See the description of
10968 <command>alt-transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
10974 <term><command>use-alt-transfer-source</command></term>
10977 See the description of
10978 <command>use-alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
10985 <term><command>notify-source</command></term>
10988 See the description of
10989 <command>notify-source</command> in <xref linkend="zone_transfers"/>.
10995 <term><command>notify-source-v6</command></term>
10998 See the description of
10999 <command>notify-source-v6</command> in <xref linkend="zone_transfers"/>.
11005 <term><command>min-refresh-time</command></term>
11006 <term><command>max-refresh-time</command></term>
11007 <term><command>min-retry-time</command></term>
11008 <term><command>max-retry-time</command></term>
11011 See the description in <xref linkend="tuning"/>.
11017 <term><command>ixfr-from-differences</command></term>
11020 See the description of
11021 <command>ixfr-from-differences</command> in <xref linkend="boolean_options"/>.
11022 (Note that the <command>ixfr-from-differences</command>
11023 <userinput>master</userinput> and
11024 <userinput>slave</userinput> choices are not
11025 available at the zone level.)
11031 <term><command>key-directory</command></term>
11034 See the description of
11035 <command>key-directory</command> in <xref linkend="options"/>.
11041 <term><command>auto-dnssec</command></term>
11044 Zones configured for dynamic DNS may also use this
11045 option to allow varying levels of automatic DNSSEC key
11046 management. There are four possible settings:
11049 <command>auto-dnssec allow;</command> permits
11050 keys to be updated and the zone fully re-signed
11051 whenever the user issues the command <command>rndc sign
11052 <replaceable>zonename</replaceable></command>.
11055 <command>auto-dnssec maintain;</command> includes the
11056 above, but also automatically adjusts the zone's DNSSEC
11057 keys on schedule, according to the keys' timing metadata
11058 (see <xref linkend="man.dnssec-keygen"/> and
11059 <xref linkend="man.dnssec-settime"/>). The command
11061 <replaceable>zonename</replaceable></command> causes
11062 <command>named</command> to load keys from the key
11063 repository and sign the zone with all keys that are
11065 <command>rndc loadkeys
11066 <replaceable>zonename</replaceable></command> causes
11067 <command>named</command> to load keys from the key
11068 repository and schedule key maintenance events to occur
11069 in the future, but it does not sign the full zone
11073 <command>auto-dnssec create;</command> includes the
11074 above, but also allows <command>named</command>
11075 to create new keys in the key repository when needed.
11076 (NOTE: This option is not yet implemented; the syntax is
11077 being reserved for future use.)
11080 The default setting is <command>auto-dnssec off</command>.
11086 <term><command>multi-master</command></term>
11089 See the description of <command>multi-master</command> in
11090 <xref linkend="boolean_options"/>.
11096 <term><command>masterfile-format</command></term>
11099 See the description of <command>masterfile-format</command>
11100 in <xref linkend="tuning"/>.
11106 <term><command>dnssec-secure-to-insecure</command></term>
11109 See the description of
11110 <command>dnssec-secure-to-insecure</command> in <xref linkend="boolean_options"/>.
11118 <sect3 id="dynamic_update_policies">
11119 <title>Dynamic Update Policies</title>
11120 <para><acronym>BIND</acronym> 9 supports two alternative
11121 methods of granting clients the right to perform
11122 dynamic updates to a zone, configured by the
11123 <command>allow-update</command> and
11124 <command>update-policy</command> option, respectively.
11127 The <command>allow-update</command> clause works the
11128 same way as in previous versions of <acronym>BIND</acronym>.
11129 It grants given clients the permission to update any
11130 record of any name in the zone.
11133 The <command>update-policy</command> clause
11134 allows more fine-grained control over what updates are
11135 allowed. A set of rules is specified, where each rule
11136 either grants or denies permissions for one or more
11137 names to be updated by one or more identities. If
11138 the dynamic update request message is signed (that is,
11139 it includes either a TSIG or SIG(0) record), the
11140 identity of the signer can be determined.
11143 Rules are specified in the <command>update-policy</command>
11144 zone option, and are only meaningful for master zones.
11145 When the <command>update-policy</command> statement
11146 is present, it is a configuration error for the
11147 <command>allow-update</command> statement to be
11148 present. The <command>update-policy</command> statement
11149 only examines the signer of a message; the source
11150 address is not relevant.
11153 There is a pre-defined <command>update-policy</command>
11154 rule which can be switched on with the command
11155 <command>update-policy local;</command>.
11156 Switching on this rule in a zone causes
11157 <command>named</command> to generate a TSIG session
11158 key and place it in a file, and to allow that key
11159 to update the zone. (By default, the file is
11160 <filename>/var/run/named/session.key</filename>, the key
11161 name is "local-ddns" and the key algorithm is HMAC-SHA256,
11162 but these values are configurable with the
11163 <command>session-keyfile</command>,
11164 <command>session-keyname</command> and
11165 <command>session-keyalg</command> options, respectively).
11168 A client running on the local system, and with appropriate
11169 permissions, may read that file and use the key to sign update
11170 requests. The zone's update policy will be set to allow that
11171 key to change any record within the zone. Assuming the
11172 key name is "local-ddns", this policy is equivalent to:
11175 <programlisting>update-policy { grant local-ddns zonesub any; };
11179 The command <command>nsupdate -l</command> sends update
11180 requests to localhost, and signs them using the session key.
11184 Other rule definitions look like this:
11188 ( <command>grant</command> | <command>deny</command> ) <replaceable>identity</replaceable> <replaceable>nametype</replaceable> <optional> <replaceable>name</replaceable> </optional> <optional> <replaceable>types</replaceable> </optional>
11192 Each rule grants or denies privileges. Once a message has
11193 successfully matched a rule, the operation is immediately
11194 granted or denied and no further rules are examined. A rule
11195 is matched when the signer matches the identity field, the
11196 name matches the name field in accordance with the nametype
11197 field, and the type matches the types specified in the type
11201 No signer is required for <replaceable>tcp-self</replaceable>
11202 or <replaceable>6to4-self</replaceable> however the standard
11203 reverse mapping / prefix conversion must match the identity
11207 The identity field specifies a name or a wildcard
11208 name. Normally, this is the name of the TSIG or
11209 SIG(0) key used to sign the update request. When a
11210 TKEY exchange has been used to create a shared secret,
11211 the identity of the shared secret is the same as the
11212 identity of the key used to authenticate the TKEY
11213 exchange. TKEY is also the negotiation method used
11214 by GSS-TSIG, which establishes an identity that is
11215 the Kerberos principal of the client, such as
11216 <userinput>"user@host.domain"</userinput>. When the
11217 <replaceable>identity</replaceable> field specifies
11218 a wildcard name, it is subject to DNS wildcard
11219 expansion, so the rule will apply to multiple identities.
11220 The <replaceable>identity</replaceable> field must
11221 contain a fully-qualified domain name.
11225 The <replaceable>nametype</replaceable> field has 13
11227 <varname>name</varname>, <varname>subdomain</varname>,
11228 <varname>wildcard</varname>, <varname>self</varname>,
11229 <varname>selfsub</varname>, <varname>selfwild</varname>,
11230 <varname>krb5-self</varname>, <varname>ms-self</varname>,
11231 <varname>krb5-subdomain</varname>,
11232 <varname>ms-subdomain</varname>,
11233 <varname>tcp-self</varname>, <varname>6to4-self</varname>,
11234 <varname>zonesub</varname>, and <varname>external</varname>.
11237 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11238 <colspec colname="1" colnum="1" colsep="0" colwidth="0.819in"/>
11239 <colspec colname="2" colnum="2" colsep="0" colwidth="3.681in"/>
11242 <entry colname="1">
11244 <varname>name</varname>
11246 </entry> <entry colname="2">
11248 Exact-match semantics. This rule matches
11249 when the name being updated is identical
11250 to the contents of the
11251 <replaceable>name</replaceable> field.
11256 <entry colname="1">
11258 <varname>subdomain</varname>
11260 </entry> <entry colname="2">
11262 This rule matches when the name being updated
11263 is a subdomain of, or identical to, the
11264 contents of the <replaceable>name</replaceable>
11270 <entry colname="1">
11272 <varname>zonesub</varname>
11274 </entry> <entry colname="2">
11276 This rule is similar to subdomain, except that
11277 it matches when the name being updated is a
11278 subdomain of the zone in which the
11279 <command>update-policy</command> statement
11280 appears. This obviates the need to type the zone
11281 name twice, and enables the use of a standard
11282 <command>update-policy</command> statement in
11283 multiple zones without modification.
11286 When this rule is used, the
11287 <replaceable>name</replaceable> field is omitted.
11292 <entry colname="1">
11294 <varname>wildcard</varname>
11296 </entry> <entry colname="2">
11298 The <replaceable>name</replaceable> field
11299 is subject to DNS wildcard expansion, and
11300 this rule matches when the name being updated
11301 name is a valid expansion of the wildcard.
11306 <entry colname="1">
11308 <varname>self</varname>
11311 <entry colname="2">
11313 This rule matches when the name being updated
11314 matches the contents of the
11315 <replaceable>identity</replaceable> field.
11316 The <replaceable>name</replaceable> field
11317 is ignored, but should be the same as the
11318 <replaceable>identity</replaceable> field.
11319 The <varname>self</varname> nametype is
11320 most useful when allowing using one key per
11321 name to update, where the key has the same
11322 name as the name to be updated. The
11323 <replaceable>identity</replaceable> would
11324 be specified as <constant>*</constant> (an asterisk) in
11330 <entry colname="1">
11332 <varname>selfsub</varname>
11334 </entry> <entry colname="2">
11336 This rule is similar to <varname>self</varname>
11337 except that subdomains of <varname>self</varname>
11338 can also be updated.
11343 <entry colname="1">
11345 <varname>selfwild</varname>
11347 </entry> <entry colname="2">
11349 This rule is similar to <varname>self</varname>
11350 except that only subdomains of
11351 <varname>self</varname> can be updated.
11356 <entry colname="1">
11358 <varname>tcp-self</varname>
11360 </entry> <entry colname="2">
11362 Allow updates that have been sent via TCP and
11363 for which the standard mapping from the initiating
11364 IP address into the IN-ADDR.ARPA and IP6.ARPA
11365 namespaces match the name to be updated.
11368 It is theoretically possible to spoof these TCP
11374 <entry colname="1">
11376 <varname>6to4-self</varname>
11378 </entry> <entry colname="2">
11380 Allow the 6to4 prefix to be update by any TCP
11381 connection from the 6to4 network or from the
11382 corresponding IPv4 address. This is intended
11383 to allow NS or DNAME RRsets to be added to the
11387 It is theoretically possible to spoof these TCP
11393 <entry colname="1">
11395 <varname>external</varname>
11397 </entry> <entry colname="2">
11399 This rule allows <command>named</command>
11400 to defer the decision of whether to allow a
11401 given update to an external daemon.
11404 The method of communicating with the daemon is
11405 specified in the <replaceable>identity</replaceable>
11406 field, the format of which is
11407 "<constant>local:</constant><replaceable>path</replaceable>",
11408 where <replaceable>path</replaceable> is the location
11409 of a UNIX-domain socket. (Currently, "local" is the
11410 only supported mechanism.)
11413 Requests to the external daemon are sent over the
11414 UNIX-domain socket as datagrams with the following
11418 Protocol version number (4 bytes, network byte order, currently 1)
11419 Request length (4 bytes, network byte order)
11420 Signer (null-terminated string)
11421 Name (null-terminated string)
11422 TCP source address (null-terminated string)
11423 Rdata type (null-terminated string)
11424 Key (null-terminated string)
11425 TKEY token length (4 bytes, network byte order)
11426 TKEY token (remainder of packet)</programlisting>
11428 The daemon replies with a four-byte value in
11429 network byte order, containing either 0 or 1; 0
11430 indicates that the specified update is not
11431 permitted, and 1 indicates that it is.
11440 In all cases, the <replaceable>name</replaceable>
11441 field must specify a fully-qualified domain name.
11445 If no types are explicitly specified, this rule matches
11446 all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
11447 may be specified by name, including "ANY" (ANY matches
11448 all types except NSEC and NSEC3, which can never be
11449 updated). Note that when an attempt is made to delete
11450 all records associated with a name, the rules are
11451 checked for each existing record type.
11457 <title>Zone File</title>
11458 <sect2 id="types_of_resource_records_and_when_to_use_them">
11459 <title>Types of Resource Records and When to Use Them</title>
11461 This section, largely borrowed from RFC 1034, describes the
11462 concept of a Resource Record (RR) and explains when each is used.
11463 Since the publication of RFC 1034, several new RRs have been
11465 and implemented in the DNS. These are also included.
11468 <title>Resource Records</title>
11471 A domain name identifies a node. Each node has a set of
11472 resource information, which may be empty. The set of resource
11473 information associated with a particular name is composed of
11474 separate RRs. The order of RRs in a set is not significant and
11475 need not be preserved by name servers, resolvers, or other
11476 parts of the DNS. However, sorting of multiple RRs is
11477 permitted for optimization purposes, for example, to specify
11478 that a particular nearby server be tried first. See <xref linkend="the_sortlist_statement"/> and <xref linkend="rrset_ordering"/>.
11482 The components of a Resource Record are:
11484 <informaltable colsep="0" rowsep="0">
11485 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11486 <colspec colname="1" colnum="1" colsep="0" colwidth="1.000in"/>
11487 <colspec colname="2" colnum="2" colsep="0" colwidth="3.500in"/>
11490 <entry colname="1">
11495 <entry colname="2">
11497 The domain name where the RR is found.
11502 <entry colname="1">
11507 <entry colname="2">
11509 An encoded 16-bit value that specifies
11510 the type of the resource record.
11515 <entry colname="1">
11520 <entry colname="2">
11522 The time-to-live of the RR. This field
11523 is a 32-bit integer in units of seconds, and is
11525 resolvers when they cache RRs. The TTL describes how
11527 be cached before it should be discarded.
11532 <entry colname="1">
11537 <entry colname="2">
11539 An encoded 16-bit value that identifies
11540 a protocol family or instance of a protocol.
11545 <entry colname="1">
11550 <entry colname="2">
11552 The resource data. The format of the
11553 data is type (and sometimes class) specific.
11561 The following are <emphasis>types</emphasis> of valid RRs:
11563 <informaltable colsep="0" rowsep="0">
11564 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11565 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
11566 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
11569 <entry colname="1">
11574 <entry colname="2">
11576 A host address. In the IN class, this is a
11577 32-bit IP address. Described in RFC 1035.
11582 <entry colname="1">
11587 <entry colname="2">
11589 IPv6 address. Described in RFC 1886.
11594 <entry colname="1">
11599 <entry colname="2">
11601 IPv6 address. This can be a partial
11602 address (a suffix) and an indirection to the name
11603 where the rest of the
11604 address (the prefix) can be found. Experimental.
11605 Described in RFC 2874.
11610 <entry colname="1">
11615 <entry colname="2">
11617 Location of AFS database servers.
11618 Experimental. Described in RFC 1183.
11623 <entry colname="1">
11628 <entry colname="2">
11630 Address prefix list. Experimental.
11631 Described in RFC 3123.
11636 <entry colname="1">
11641 <entry colname="2">
11643 Holds a digital certificate.
11644 Described in RFC 2538.
11649 <entry colname="1">
11654 <entry colname="2">
11656 Identifies the canonical name of an alias.
11657 Described in RFC 1035.
11662 <entry colname="1">
11667 <entry colname="2">
11669 Is used for identifying which DHCP client is
11670 associated with this name. Described in RFC 4701.
11675 <entry colname="1">
11680 <entry colname="2">
11682 Replaces the domain name specified with
11683 another name to be looked up, effectively aliasing an
11685 subtree of the domain name space rather than a single
11687 as in the case of the CNAME RR.
11688 Described in RFC 2672.
11693 <entry colname="1">
11698 <entry colname="2">
11700 Stores a public key associated with a signed
11701 DNS zone. Described in RFC 4034.
11706 <entry colname="1">
11711 <entry colname="2">
11713 Stores the hash of a public key associated with a
11714 signed DNS zone. Described in RFC 4034.
11719 <entry colname="1">
11724 <entry colname="2">
11726 Specifies the global position. Superseded by LOC.
11731 <entry colname="1">
11736 <entry colname="2">
11738 Identifies the CPU and OS used by a host.
11739 Described in RFC 1035.
11744 <entry colname="1">
11749 <entry colname="2">
11751 Provides a method for storing IPsec keying material in
11752 DNS. Described in RFC 4025.
11757 <entry colname="1">
11762 <entry colname="2">
11764 Representation of ISDN addresses.
11765 Experimental. Described in RFC 1183.
11770 <entry colname="1">
11775 <entry colname="2">
11777 Stores a public key associated with a
11778 DNS name. Used in original DNSSEC; replaced
11779 by DNSKEY in DNSSECbis, but still used with
11780 SIG(0). Described in RFCs 2535 and 2931.
11785 <entry colname="1">
11790 <entry colname="2">
11792 Identifies a key exchanger for this
11793 DNS name. Described in RFC 2230.
11798 <entry colname="1">
11803 <entry colname="2">
11805 For storing GPS info. Described in RFC 1876.
11811 <entry colname="1">
11816 <entry colname="2">
11818 Identifies a mail exchange for the domain with
11819 a 16-bit preference value (lower is better)
11820 followed by the host name of the mail exchange.
11821 Described in RFC 974, RFC 1035.
11826 <entry colname="1">
11831 <entry colname="2">
11833 Name authority pointer. Described in RFC 2915.
11838 <entry colname="1">
11843 <entry colname="2">
11845 A network service access point.
11846 Described in RFC 1706.
11851 <entry colname="1">
11856 <entry colname="2">
11858 The authoritative name server for the
11859 domain. Described in RFC 1035.
11864 <entry colname="1">
11869 <entry colname="2">
11871 Used in DNSSECbis to securely indicate that
11872 RRs with an owner name in a certain name interval do
11874 a zone and indicate what RR types are present for an
11876 Described in RFC 4034.
11881 <entry colname="1">
11886 <entry colname="2">
11888 Used in DNSSECbis to securely indicate that
11889 RRs with an owner name in a certain name
11890 interval do not exist in a zone and indicate
11891 what RR types are present for an existing
11892 name. NSEC3 differs from NSEC in that it
11893 prevents zone enumeration but is more
11894 computationally expensive on both the server
11895 and the client than NSEC. Described in RFC
11901 <entry colname="1">
11906 <entry colname="2">
11908 Used in DNSSECbis to tell the authoritative
11909 server which NSEC3 chains are available to use.
11910 Described in RFC 5155.
11915 <entry colname="1">
11920 <entry colname="2">
11922 Used in DNSSEC to securely indicate that
11923 RRs with an owner name in a certain name interval do
11925 a zone and indicate what RR types are present for an
11927 Used in original DNSSEC; replaced by NSEC in
11929 Described in RFC 2535.
11934 <entry colname="1">
11939 <entry colname="2">
11941 A pointer to another part of the domain
11942 name space. Described in RFC 1035.
11947 <entry colname="1">
11952 <entry colname="2">
11954 Provides mappings between RFC 822 and X.400
11955 addresses. Described in RFC 2163.
11960 <entry colname="1">
11965 <entry colname="2">
11967 Information on persons responsible
11968 for the domain. Experimental. Described in RFC 1183.
11973 <entry colname="1">
11978 <entry colname="2">
11980 Contains DNSSECbis signature data. Described
11986 <entry colname="1">
11991 <entry colname="2">
11993 Route-through binding for hosts that
11994 do not have their own direct wide area network
11996 Experimental. Described in RFC 1183.
12001 <entry colname="1">
12006 <entry colname="2">
12008 Contains DNSSEC signature data. Used in
12009 original DNSSEC; replaced by RRSIG in
12010 DNSSECbis, but still used for SIG(0).
12011 Described in RFCs 2535 and 2931.
12016 <entry colname="1">
12021 <entry colname="2">
12023 Identifies the start of a zone of authority.
12024 Described in RFC 1035.
12029 <entry colname="1">
12034 <entry colname="2">
12036 Contains the Sender Policy Framework information
12037 for a given email domain. Described in RFC 4408.
12042 <entry colname="1">
12047 <entry colname="2">
12049 Information about well known network
12050 services (replaces WKS). Described in RFC 2782.
12055 <entry colname="1">
12060 <entry colname="2">
12062 Provides a way to securely publish a secure shell key's
12063 fingerprint. Described in RFC 4255.
12068 <entry colname="1">
12073 <entry colname="2">
12075 Text records. Described in RFC 1035.
12080 <entry colname="1">
12085 <entry colname="2">
12087 Information about which well known
12088 network services, such as SMTP, that a domain
12089 supports. Historical.
12094 <entry colname="1">
12099 <entry colname="2">
12101 Representation of X.25 network addresses.
12102 Experimental. Described in RFC 1183.
12110 The following <emphasis>classes</emphasis> of resource records
12111 are currently valid in the DNS:
12113 <informaltable colsep="0" rowsep="0"><tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12114 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
12115 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
12119 <entry colname="1">
12124 <entry colname="2">
12132 <entry colname="1">
12137 <entry colname="2">
12139 Chaosnet, a LAN protocol created at MIT in the
12141 Rarely used for its historical purpose, but reused for
12143 built-in server information zones, e.g.,
12144 <literal>version.bind</literal>.
12150 <entry colname="1">
12155 <entry colname="2">
12157 Hesiod, an information service
12158 developed by MIT's Project Athena. It is used to share
12160 about various systems databases, such as users,
12172 The owner name is often implicit, rather than forming an
12174 part of the RR. For example, many name servers internally form
12176 or hash structures for the name space, and chain RRs off nodes.
12177 The remaining RR parts are the fixed header (type, class, TTL)
12178 which is consistent for all RRs, and a variable part (RDATA)
12180 fits the needs of the resource being described.
12183 The meaning of the TTL field is a time limit on how long an
12184 RR can be kept in a cache. This limit does not apply to
12186 data in zones; it is also timed out, but by the refreshing
12188 for the zone. The TTL is assigned by the administrator for the
12189 zone where the data originates. While short TTLs can be used to
12190 minimize caching, and a zero TTL prohibits caching, the
12192 of Internet performance suggest that these times should be on
12194 order of days for the typical host. If a change can be
12196 the TTL can be reduced prior to the change to minimize
12198 during the change, and then increased back to its former value
12203 The data in the RDATA section of RRs is carried as a combination
12204 of binary strings and domain names. The domain names are
12206 used as "pointers" to other data in the DNS.
12210 <title>Textual expression of RRs</title>
12212 RRs are represented in binary form in the packets of the DNS
12213 protocol, and are usually represented in highly encoded form
12215 stored in a name server or resolver. In the examples provided
12217 RFC 1034, a style similar to that used in master files was
12219 in order to show the contents of RRs. In this format, most RRs
12220 are shown on a single line, although continuation lines are
12225 The start of the line gives the owner of the RR. If a line
12226 begins with a blank, then the owner is assumed to be the same as
12227 that of the previous RR. Blank lines are often included for
12231 Following the owner, we list the TTL, type, and class of the
12232 RR. Class and type use the mnemonics defined above, and TTL is
12233 an integer before the type field. In order to avoid ambiguity
12235 parsing, type and class mnemonics are disjoint, TTLs are
12237 and the type mnemonic is always last. The IN class and TTL
12239 are often omitted from examples in the interests of clarity.
12242 The resource data or RDATA section of the RR are given using
12243 knowledge of the typical representation for the data.
12246 For example, we might show the RRs carried in a message as:
12248 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12249 <colspec colname="1" colnum="1" colsep="0" colwidth="1.381in"/>
12250 <colspec colname="2" colnum="2" colsep="0" colwidth="1.020in"/>
12251 <colspec colname="3" colnum="3" colsep="0" colwidth="2.099in"/>
12254 <entry colname="1">
12256 <literal>ISI.EDU.</literal>
12259 <entry colname="2">
12261 <literal>MX</literal>
12264 <entry colname="3">
12266 <literal>10 VENERA.ISI.EDU.</literal>
12271 <entry colname="1">
12274 <entry colname="2">
12276 <literal>MX</literal>
12279 <entry colname="3">
12281 <literal>10 VAXA.ISI.EDU</literal>
12286 <entry colname="1">
12288 <literal>VENERA.ISI.EDU</literal>
12291 <entry colname="2">
12293 <literal>A</literal>
12296 <entry colname="3">
12298 <literal>128.9.0.32</literal>
12303 <entry colname="1">
12306 <entry colname="2">
12308 <literal>A</literal>
12311 <entry colname="3">
12313 <literal>10.1.0.52</literal>
12318 <entry colname="1">
12320 <literal>VAXA.ISI.EDU</literal>
12323 <entry colname="2">
12325 <literal>A</literal>
12328 <entry colname="3">
12330 <literal>10.2.0.27</literal>
12335 <entry colname="1">
12338 <entry colname="2">
12340 <literal>A</literal>
12343 <entry colname="3">
12345 <literal>128.9.0.33</literal>
12353 The MX RRs have an RDATA section which consists of a 16-bit
12354 number followed by a domain name. The address RRs use a
12356 IP address format to contain a 32-bit internet address.
12359 The above example shows six RRs, with two RRs at each of three
12363 Similarly we might see:
12365 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12366 <colspec colname="1" colnum="1" colsep="0" colwidth="1.491in"/>
12367 <colspec colname="2" colnum="2" colsep="0" colwidth="1.067in"/>
12368 <colspec colname="3" colnum="3" colsep="0" colwidth="2.067in"/>
12371 <entry colname="1">
12373 <literal>XX.LCS.MIT.EDU.</literal>
12376 <entry colname="2">
12378 <literal>IN A</literal>
12381 <entry colname="3">
12383 <literal>10.0.0.44</literal>
12388 <entry colname="1"/>
12389 <entry colname="2">
12391 <literal>CH A</literal>
12394 <entry colname="3">
12396 <literal>MIT.EDU. 2420</literal>
12404 This example shows two addresses for
12405 <literal>XX.LCS.MIT.EDU</literal>, each of a different class.
12411 <title>Discussion of MX Records</title>
12414 As described above, domain servers store information as a
12415 series of resource records, each of which contains a particular
12416 piece of information about a given domain name (which is usually,
12417 but not always, a host). The simplest way to think of a RR is as
12418 a typed pair of data, a domain name matched with a relevant datum,
12419 and stored with some additional type information to help systems
12420 determine when the RR is relevant.
12424 MX records are used to control delivery of email. The data
12425 specified in the record is a priority and a domain name. The
12427 controls the order in which email delivery is attempted, with the
12428 lowest number first. If two priorities are the same, a server is
12429 chosen randomly. If no servers at a given priority are responding,
12430 the mail transport agent will fall back to the next largest
12432 Priority numbers do not have any absolute meaning — they are
12434 only respective to other MX records for that domain name. The
12436 name given is the machine to which the mail will be delivered.
12437 It <emphasis>must</emphasis> have an associated address record
12438 (A or AAAA) — CNAME is not sufficient.
12441 For a given domain, if there is both a CNAME record and an
12442 MX record, the MX record is in error, and will be ignored.
12444 the mail will be delivered to the server specified in the MX
12446 pointed to by the CNAME.
12449 <informaltable colsep="0" rowsep="0">
12450 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12451 <colspec colname="1" colnum="1" colsep="0" colwidth="1.708in"/>
12452 <colspec colname="2" colnum="2" colsep="0" colwidth="0.444in"/>
12453 <colspec colname="3" colnum="3" colsep="0" colwidth="0.444in"/>
12454 <colspec colname="4" colnum="4" colsep="0" colwidth="0.976in"/>
12455 <colspec colname="5" colnum="5" colsep="0" colwidth="1.553in"/>
12458 <entry colname="1">
12460 <literal>example.com.</literal>
12463 <entry colname="2">
12465 <literal>IN</literal>
12468 <entry colname="3">
12470 <literal>MX</literal>
12473 <entry colname="4">
12475 <literal>10</literal>
12478 <entry colname="5">
12480 <literal>mail.example.com.</literal>
12485 <entry colname="1">
12488 <entry colname="2">
12490 <literal>IN</literal>
12493 <entry colname="3">
12495 <literal>MX</literal>
12498 <entry colname="4">
12500 <literal>10</literal>
12503 <entry colname="5">
12505 <literal>mail2.example.com.</literal>
12510 <entry colname="1">
12513 <entry colname="2">
12515 <literal>IN</literal>
12518 <entry colname="3">
12520 <literal>MX</literal>
12523 <entry colname="4">
12525 <literal>20</literal>
12528 <entry colname="5">
12530 <literal>mail.backup.org.</literal>
12535 <entry colname="1">
12537 <literal>mail.example.com.</literal>
12540 <entry colname="2">
12542 <literal>IN</literal>
12545 <entry colname="3">
12547 <literal>A</literal>
12550 <entry colname="4">
12552 <literal>10.0.0.1</literal>
12555 <entry colname="5">
12560 <entry colname="1">
12562 <literal>mail2.example.com.</literal>
12565 <entry colname="2">
12567 <literal>IN</literal>
12570 <entry colname="3">
12572 <literal>A</literal>
12575 <entry colname="4">
12577 <literal>10.0.0.2</literal>
12580 <entry colname="5">
12586 </informaltable><para>
12587 Mail delivery will be attempted to <literal>mail.example.com</literal> and
12588 <literal>mail2.example.com</literal> (in
12589 any order), and if neither of those succeed, delivery to <literal>mail.backup.org</literal> will
12593 <sect2 id="Setting_TTLs">
12594 <title>Setting TTLs</title>
12596 The time-to-live of the RR field is a 32-bit integer represented
12597 in units of seconds, and is primarily used by resolvers when they
12598 cache RRs. The TTL describes how long a RR can be cached before it
12599 should be discarded. The following three types of TTL are
12601 used in a zone file.
12603 <informaltable colsep="0" rowsep="0">
12604 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12605 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
12606 <colspec colname="2" colnum="2" colsep="0" colwidth="4.375in"/>
12609 <entry colname="1">
12614 <entry colname="2">
12616 The last field in the SOA is the negative
12617 caching TTL. This controls how long other servers will
12618 cache no-such-domain
12619 (NXDOMAIN) responses from you.
12622 The maximum time for
12623 negative caching is 3 hours (3h).
12628 <entry colname="1">
12633 <entry colname="2">
12635 The $TTL directive at the top of the
12636 zone file (before the SOA) gives a default TTL for every
12638 a specific TTL set.
12643 <entry colname="1">
12648 <entry colname="2">
12650 Each RR can have a TTL as the second
12651 field in the RR, which will control how long other
12661 All of these TTLs default to units of seconds, though units
12662 can be explicitly specified, for example, <literal>1h30m</literal>.
12666 <title>Inverse Mapping in IPv4</title>
12668 Reverse name resolution (that is, translation from IP address
12669 to name) is achieved by means of the <emphasis>in-addr.arpa</emphasis> domain
12670 and PTR records. Entries in the in-addr.arpa domain are made in
12671 least-to-most significant order, read left to right. This is the
12672 opposite order to the way IP addresses are usually written. Thus,
12673 a machine with an IP address of 10.1.2.3 would have a
12675 in-addr.arpa name of
12676 3.2.1.10.in-addr.arpa. This name should have a PTR resource record
12677 whose data field is the name of the machine or, optionally,
12679 PTR records if the machine has more than one name. For example,
12680 in the <optional>example.com</optional> domain:
12682 <informaltable colsep="0" rowsep="0">
12683 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12684 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
12685 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
12688 <entry colname="1">
12690 <literal>$ORIGIN</literal>
12693 <entry colname="2">
12695 <literal>2.1.10.in-addr.arpa</literal>
12700 <entry colname="1">
12702 <literal>3</literal>
12705 <entry colname="2">
12707 <literal>IN PTR foo.example.com.</literal>
12716 The <command>$ORIGIN</command> lines in the examples
12717 are for providing context to the examples only — they do not
12719 appear in the actual usage. They are only used here to indicate
12720 that the example is relative to the listed origin.
12725 <title>Other Zone File Directives</title>
12727 The Master File Format was initially defined in RFC 1035 and
12728 has subsequently been extended. While the Master File Format
12730 is class independent all records in a Master File must be of the
12735 Master File Directives include <command>$ORIGIN</command>, <command>$INCLUDE</command>,
12736 and <command>$TTL.</command>
12739 <title>The <command>@</command> (at-sign)</title>
12741 When used in the label (or name) field, the asperand or
12742 at-sign (@) symbol represents the current origin.
12743 At the start of the zone file, it is the
12744 <<varname>zone_name</varname>> (followed by
12749 <title>The <command>$ORIGIN</command> Directive</title>
12751 Syntax: <command>$ORIGIN</command>
12752 <replaceable>domain-name</replaceable>
12753 <optional><replaceable>comment</replaceable></optional>
12755 <para><command>$ORIGIN</command>
12756 sets the domain name that will be appended to any
12757 unqualified records. When a zone is first read in there
12758 is an implicit <command>$ORIGIN</command>
12759 <<varname>zone_name</varname>><command>.</command>
12760 (followed by trailing dot).
12761 The current <command>$ORIGIN</command> is appended to
12762 the domain specified in the <command>$ORIGIN</command>
12763 argument if it is not absolute.
12767 $ORIGIN example.com.
12768 WWW CNAME MAIN-SERVER
12776 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
12781 <title>The <command>$INCLUDE</command> Directive</title>
12783 Syntax: <command>$INCLUDE</command>
12784 <replaceable>filename</replaceable>
12786 <replaceable>origin</replaceable> </optional>
12787 <optional> <replaceable>comment</replaceable> </optional>
12790 Read and process the file <filename>filename</filename> as
12791 if it were included into the file at this point. If <command>origin</command> is
12792 specified the file is processed with <command>$ORIGIN</command> set
12793 to that value, otherwise the current <command>$ORIGIN</command> is
12797 The origin and the current domain name
12798 revert to the values they had prior to the <command>$INCLUDE</command> once
12799 the file has been read.
12803 RFC 1035 specifies that the current origin should be restored
12805 an <command>$INCLUDE</command>, but it is silent
12806 on whether the current
12807 domain name should also be restored. BIND 9 restores both of
12809 This could be construed as a deviation from RFC 1035, a
12815 <title>The <command>$TTL</command> Directive</title>
12817 Syntax: <command>$TTL</command>
12818 <replaceable>default-ttl</replaceable>
12820 <replaceable>comment</replaceable> </optional>
12823 Set the default Time To Live (TTL) for subsequent records
12824 with undefined TTLs. Valid TTLs are of the range 0-2147483647
12827 <para><command>$TTL</command>
12828 is defined in RFC 2308.
12833 <title><acronym>BIND</acronym> Master File Extension: the <command>$GENERATE</command> Directive</title>
12835 Syntax: <command>$GENERATE</command>
12836 <replaceable>range</replaceable>
12837 <replaceable>lhs</replaceable>
12838 <optional><replaceable>ttl</replaceable></optional>
12839 <optional><replaceable>class</replaceable></optional>
12840 <replaceable>type</replaceable>
12841 <replaceable>rhs</replaceable>
12842 <optional><replaceable>comment</replaceable></optional>
12844 <para><command>$GENERATE</command>
12845 is used to create a series of resource records that only
12846 differ from each other by an
12847 iterator. <command>$GENERATE</command> can be used to
12848 easily generate the sets of records required to support
12849 sub /24 reverse delegations described in RFC 2317:
12850 Classless IN-ADDR.ARPA delegation.
12853 <programlisting>$ORIGIN 0.0.192.IN-ADDR.ARPA.
12854 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
12855 $GENERATE 1-127 $ CNAME $.0</programlisting>
12861 <programlisting>0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
12862 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
12863 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
12864 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
12866 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
12870 Generate a set of A and MX records. Note the MX's right hand
12871 side is a quoted string. The quotes will be stripped when the
12872 right hand side is processed.
12877 $GENERATE 1-127 HOST-$ A 1.2.3.$
12878 $GENERATE 1-127 HOST-$ MX "0 ."</programlisting>
12884 <programlisting>HOST-1.EXAMPLE. A 1.2.3.1
12885 HOST-1.EXAMPLE. MX 0 .
12886 HOST-2.EXAMPLE. A 1.2.3.2
12887 HOST-2.EXAMPLE. MX 0 .
12888 HOST-3.EXAMPLE. A 1.2.3.3
12889 HOST-3.EXAMPLE. MX 0 .
12891 HOST-127.EXAMPLE. A 1.2.3.127
12892 HOST-127.EXAMPLE. MX 0 .
12895 <informaltable colsep="0" rowsep="0">
12896 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12897 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
12898 <colspec colname="2" colnum="2" colsep="0" colwidth="4.250in"/>
12901 <entry colname="1">
12902 <para><command>range</command></para>
12904 <entry colname="2">
12906 This can be one of two forms: start-stop
12907 or start-stop/step. If the first form is used, then step
12909 1. All of start, stop and step must be positive.
12914 <entry colname="1">
12915 <para><command>lhs</command></para>
12917 <entry colname="2">
12919 describes the owner name of the resource records
12920 to be created. Any single <command>$</command>
12922 symbols within the <command>lhs</command> string
12923 are replaced by the iterator value.
12925 To get a $ in the output, you need to escape the
12926 <command>$</command> using a backslash
12927 <command>\</command>,
12928 e.g. <command>\$</command>. The
12929 <command>$</command> may optionally be followed
12930 by modifiers which change the offset from the
12931 iterator, field width and base.
12933 Modifiers are introduced by a
12934 <command>{</command> (left brace) immediately following the
12935 <command>$</command> as
12936 <command>${offset[,width[,base]]}</command>.
12937 For example, <command>${-20,3,d}</command>
12938 subtracts 20 from the current value, prints the
12939 result as a decimal in a zero-padded field of
12942 Available output forms are decimal
12943 (<command>d</command>), octal
12944 (<command>o</command>), hexadecimal
12945 (<command>x</command> or <command>X</command>
12946 for uppercase) and nibble
12947 (<command>n</command> or <command>N</command>\
12948 for uppercase). The default modifier is
12949 <command>${0,0,d}</command>. If the
12950 <command>lhs</command> is not absolute, the
12951 current <command>$ORIGIN</command> is appended
12955 In nibble mode the value will be treated as
12956 if it was a reversed hexadecimal string
12957 with each hexadecimal digit as a separate
12958 label. The width field includes the label
12962 For compatibility with earlier versions,
12963 <command>$$</command> is still recognized as
12964 indicating a literal $ in the output.
12969 <entry colname="1">
12970 <para><command>ttl</command></para>
12972 <entry colname="2">
12974 Specifies the time-to-live of the generated records. If
12975 not specified this will be inherited using the
12976 normal TTL inheritance rules.
12978 <para><command>class</command>
12979 and <command>ttl</command> can be
12980 entered in either order.
12985 <entry colname="1">
12986 <para><command>class</command></para>
12988 <entry colname="2">
12990 Specifies the class of the generated records.
12991 This must match the zone class if it is
12994 <para><command>class</command>
12995 and <command>ttl</command> can be
12996 entered in either order.
13001 <entry colname="1">
13002 <para><command>type</command></para>
13004 <entry colname="2">
13011 <entry colname="1">
13012 <para><command>rhs</command></para>
13014 <entry colname="2">
13016 <command>rhs</command>, optionally, quoted string.
13024 The <command>$GENERATE</command> directive is a <acronym>BIND</acronym> extension
13025 and not part of the standard zone file format.
13028 BIND 8 does not support the optional TTL and CLASS fields.
13032 <sect2 id="zonefile_format">
13033 <title>Additional File Formats</title>
13035 In addition to the standard textual format, BIND 9
13036 supports the ability to read or dump to zone files in
13037 other formats. The <constant>raw</constant> format is
13038 currently available as an additional format. It is a
13039 binary format representing BIND 9's internal data
13040 structure directly, thereby remarkably improving the
13044 For a primary server, a zone file in the
13045 <constant>raw</constant> format is expected to be
13046 generated from a textual zone file by the
13047 <command>named-compilezone</command> command. For a
13048 secondary server or for a dynamic zone, it is automatically
13049 generated (if this format is specified by the
13050 <command>masterfile-format</command> option) when
13051 <command>named</command> dumps the zone contents after
13052 zone transfer or when applying prior updates.
13055 If a zone file in a binary format needs manual modification,
13056 it first must be converted to a textual form by the
13057 <command>named-compilezone</command> command. All
13058 necessary modification should go to the text file, which
13059 should then be converted to the binary form by the
13060 <command>named-compilezone</command> command again.
13063 Although the <constant>raw</constant> format uses the
13064 network byte order and avoids architecture-dependent
13065 data alignment so that it is as much portable as
13066 possible, it is primarily expected to be used inside
13067 the same single system. In order to export a zone
13068 file in the <constant>raw</constant> format or make a
13069 portable backup of the file, it is recommended to
13070 convert the file to the standard textual representation.
13075 <sect1 id="statistics">
13076 <title>BIND9 Statistics</title>
13078 <acronym>BIND</acronym> 9 maintains lots of statistics
13079 information and provides several interfaces for users to
13080 get access to the statistics.
13081 The available statistics include all statistics counters
13082 that were available in <acronym>BIND</acronym> 8 and
13083 are meaningful in <acronym>BIND</acronym> 9,
13084 and other information that is considered useful.
13088 The statistics information is categorized into the following
13092 <informaltable frame="all">
13094 <colspec colname="1" colnum="1" colsep="0" colwidth="3.300in"/>
13095 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
13099 <entry colname="1">
13100 <para>Incoming Requests</para>
13102 <entry colname="2">
13104 The number of incoming DNS requests for each OPCODE.
13110 <entry colname="1">
13111 <para>Incoming Queries</para>
13113 <entry colname="2">
13115 The number of incoming queries for each RR type.
13121 <entry colname="1">
13122 <para>Outgoing Queries</para>
13124 <entry colname="2">
13126 The number of outgoing queries for each RR
13127 type sent from the internal resolver.
13128 Maintained per view.
13134 <entry colname="1">
13135 <para>Name Server Statistics</para>
13137 <entry colname="2">
13139 Statistics counters about incoming request processing.
13145 <entry colname="1">
13146 <para>Zone Maintenance Statistics</para>
13148 <entry colname="2">
13150 Statistics counters regarding zone maintenance
13151 operations such as zone transfers.
13157 <entry colname="1">
13158 <para>Resolver Statistics</para>
13160 <entry colname="2">
13162 Statistics counters about name resolution
13163 performed in the internal resolver.
13164 Maintained per view.
13170 <entry colname="1">
13171 <para>Cache DB RRsets</para>
13173 <entry colname="2">
13175 The number of RRsets per RR type and nonexistent
13176 names stored in the cache database.
13177 If the exclamation mark (!) is printed for a RR
13178 type, it means that particular type of RRset is
13179 known to be nonexistent (this is also known as
13181 Maintained per view.
13187 <entry colname="1">
13188 <para>Socket I/O Statistics</para>
13190 <entry colname="2">
13192 Statistics counters about network related events.
13202 A subset of Name Server Statistics is collected and shown
13203 per zone for which the server has the authority when
13204 <command>zone-statistics</command> is set to
13205 <userinput>yes</userinput>.
13206 These statistics counters are shown with their zone and view
13208 In some cases the view names are omitted for the default view.
13212 There are currently two user interfaces to get access to the
13214 One is in the plain text format dumped to the file specified
13215 by the <command>statistics-file</command> configuration option.
13216 The other is remotely accessible via a statistics channel
13217 when the <command>statistics-channels</command> statement
13218 is specified in the configuration file
13219 (see <xref linkend="statschannels"/>.)
13222 <sect3 id="statsfile">
13223 <title>The Statistics File</title>
13225 The text format statistics dump begins with a line, like:
13228 <command>+++ Statistics Dump +++ (973798949)</command>
13231 The number in parentheses is a standard
13232 Unix-style timestamp, measured as seconds since January 1, 1970.
13235 that line is a set of statistics information, which is categorized
13236 as described above.
13237 Each section begins with a line, like:
13241 <command>++ Name Server Statistics ++</command>
13245 Each section consists of lines, each containing the statistics
13246 counter value followed by its textual description.
13247 See below for available counters.
13248 For brevity, counters that have a value of 0 are not shown
13249 in the statistics file.
13253 The statistics dump ends with the line where the
13254 number is identical to the number in the beginning line; for example:
13257 <command>--- Statistics Dump --- (973798949)</command>
13261 <sect2 id="statistics_counters">
13262 <title>Statistics Counters</title>
13264 The following tables summarize statistics counters that
13265 <acronym>BIND</acronym> 9 provides.
13266 For each row of the tables, the leftmost column is the
13267 abbreviated symbol name of that counter.
13268 These symbols are shown in the statistics information
13269 accessed via an HTTP statistics channel.
13270 The rightmost column gives the description of the counter,
13271 which is also shown in the statistics file
13272 (but, in this document, possibly with slight modification
13273 for better readability).
13274 Additional notes may also be provided in this column.
13275 When a middle column exists between these two columns,
13276 it gives the corresponding counter name of the
13277 <acronym>BIND</acronym> 8 statistics, if applicable.
13281 <title>Name Server Statistics Counters</title>
13283 <informaltable colsep="0" rowsep="0">
13284 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13285 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
13286 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
13287 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
13290 <entry colname="1">
13292 <emphasis>Symbol</emphasis>
13295 <entry colname="2">
13297 <emphasis>BIND8 Symbol</emphasis>
13300 <entry colname="3">
13302 <emphasis>Description</emphasis>
13308 <entry colname="1">
13309 <para><command>Requestv4</command></para>
13311 <entry colname="2">
13312 <para><command>RQ</command></para>
13314 <entry colname="3">
13316 IPv4 requests received.
13317 Note: this also counts non query requests.
13322 <entry colname="1">
13323 <para><command>Requestv6</command></para>
13325 <entry colname="2">
13326 <para><command>RQ</command></para>
13328 <entry colname="3">
13330 IPv6 requests received.
13331 Note: this also counts non query requests.
13336 <entry colname="1">
13337 <para><command>ReqEdns0</command></para>
13339 <entry colname="2">
13340 <para><command></command></para>
13342 <entry colname="3">
13344 Requests with EDNS(0) received.
13349 <entry colname="1">
13350 <para><command>ReqBadEDNSVer</command></para>
13352 <entry colname="2">
13353 <para><command></command></para>
13355 <entry colname="3">
13357 Requests with unsupported EDNS version received.
13362 <entry colname="1">
13363 <para><command>ReqTSIG</command></para>
13365 <entry colname="2">
13366 <para><command></command></para>
13368 <entry colname="3">
13370 Requests with TSIG received.
13375 <entry colname="1">
13376 <para><command>ReqSIG0</command></para>
13378 <entry colname="2">
13379 <para><command></command></para>
13381 <entry colname="3">
13383 Requests with SIG(0) received.
13388 <entry colname="1">
13389 <para><command>ReqBadSIG</command></para>
13391 <entry colname="2">
13392 <para><command></command></para>
13394 <entry colname="3">
13396 Requests with invalid (TSIG or SIG(0)) signature.
13401 <entry colname="1">
13402 <para><command>ReqTCP</command></para>
13404 <entry colname="2">
13405 <para><command>RTCP</command></para>
13407 <entry colname="3">
13409 TCP requests received.
13414 <entry colname="1">
13415 <para><command>AuthQryRej</command></para>
13417 <entry colname="2">
13418 <para><command>RUQ</command></para>
13420 <entry colname="3">
13422 Authoritative (non recursive) queries rejected.
13427 <entry colname="1">
13428 <para><command>RecQryRej</command></para>
13430 <entry colname="2">
13431 <para><command>RURQ</command></para>
13433 <entry colname="3">
13435 Recursive queries rejected.
13440 <entry colname="1">
13441 <para><command>XfrRej</command></para>
13443 <entry colname="2">
13444 <para><command>RUXFR</command></para>
13446 <entry colname="3">
13448 Zone transfer requests rejected.
13453 <entry colname="1">
13454 <para><command>UpdateRej</command></para>
13456 <entry colname="2">
13457 <para><command>RUUpd</command></para>
13459 <entry colname="3">
13461 Dynamic update requests rejected.
13466 <entry colname="1">
13467 <para><command>Response</command></para>
13469 <entry colname="2">
13470 <para><command>SAns</command></para>
13472 <entry colname="3">
13479 <entry colname="1">
13480 <para><command>RespTruncated</command></para>
13482 <entry colname="2">
13483 <para><command></command></para>
13485 <entry colname="3">
13487 Truncated responses sent.
13492 <entry colname="1">
13493 <para><command>RespEDNS0</command></para>
13495 <entry colname="2">
13496 <para><command></command></para>
13498 <entry colname="3">
13500 Responses with EDNS(0) sent.
13505 <entry colname="1">
13506 <para><command>RespTSIG</command></para>
13508 <entry colname="2">
13509 <para><command></command></para>
13511 <entry colname="3">
13513 Responses with TSIG sent.
13518 <entry colname="1">
13519 <para><command>RespSIG0</command></para>
13521 <entry colname="2">
13522 <para><command></command></para>
13524 <entry colname="3">
13526 Responses with SIG(0) sent.
13531 <entry colname="1">
13532 <para><command>QrySuccess</command></para>
13534 <entry colname="2">
13535 <para><command></command></para>
13537 <entry colname="3">
13539 Queries resulted in a successful answer.
13540 This means the query which returns a NOERROR response
13541 with at least one answer RR.
13542 This corresponds to the
13543 <command>success</command> counter
13544 of previous versions of
13545 <acronym>BIND</acronym> 9.
13550 <entry colname="1">
13551 <para><command>QryAuthAns</command></para>
13553 <entry colname="2">
13554 <para><command></command></para>
13556 <entry colname="3">
13558 Queries resulted in authoritative answer.
13563 <entry colname="1">
13564 <para><command>QryNoauthAns</command></para>
13566 <entry colname="2">
13567 <para><command>SNaAns</command></para>
13569 <entry colname="3">
13571 Queries resulted in non authoritative answer.
13576 <entry colname="1">
13577 <para><command>QryReferral</command></para>
13579 <entry colname="2">
13580 <para><command></command></para>
13582 <entry colname="3">
13584 Queries resulted in referral answer.
13585 This corresponds to the
13586 <command>referral</command> counter
13587 of previous versions of
13588 <acronym>BIND</acronym> 9.
13593 <entry colname="1">
13594 <para><command>QryNxrrset</command></para>
13596 <entry colname="2">
13597 <para><command></command></para>
13599 <entry colname="3">
13601 Queries resulted in NOERROR responses with no data.
13602 This corresponds to the
13603 <command>nxrrset</command> counter
13604 of previous versions of
13605 <acronym>BIND</acronym> 9.
13610 <entry colname="1">
13611 <para><command>QrySERVFAIL</command></para>
13613 <entry colname="2">
13614 <para><command>SFail</command></para>
13616 <entry colname="3">
13618 Queries resulted in SERVFAIL.
13623 <entry colname="1">
13624 <para><command>QryFORMERR</command></para>
13626 <entry colname="2">
13627 <para><command>SFErr</command></para>
13629 <entry colname="3">
13631 Queries resulted in FORMERR.
13636 <entry colname="1">
13637 <para><command>QryNXDOMAIN</command></para>
13639 <entry colname="2">
13640 <para><command>SNXD</command></para>
13642 <entry colname="3">
13644 Queries resulted in NXDOMAIN.
13645 This corresponds to the
13646 <command>nxdomain</command> counter
13647 of previous versions of
13648 <acronym>BIND</acronym> 9.
13653 <entry colname="1">
13654 <para><command>QryRecursion</command></para>
13656 <entry colname="2">
13657 <para><command>RFwdQ</command></para>
13659 <entry colname="3">
13661 Queries which caused the server
13662 to perform recursion in order to find the final answer.
13663 This corresponds to the
13664 <command>recursion</command> counter
13665 of previous versions of
13666 <acronym>BIND</acronym> 9.
13671 <entry colname="1">
13672 <para><command>QryDuplicate</command></para>
13674 <entry colname="2">
13675 <para><command>RDupQ</command></para>
13677 <entry colname="3">
13679 Queries which the server attempted to
13680 recurse but discovered an existing query with the same
13681 IP address, port, query ID, name, type and class
13682 already being processed.
13683 This corresponds to the
13684 <command>duplicate</command> counter
13685 of previous versions of
13686 <acronym>BIND</acronym> 9.
13691 <entry colname="1">
13692 <para><command>QryDropped</command></para>
13694 <entry colname="2">
13695 <para><command></command></para>
13697 <entry colname="3">
13699 Recursive queries for which the server
13700 discovered an excessive number of existing
13701 recursive queries for the same name, type and
13702 class and were subsequently dropped.
13703 This is the number of dropped queries due to
13704 the reason explained with the
13705 <command>clients-per-query</command>
13707 <command>max-clients-per-query</command>
13709 (see the description about
13710 <xref linkend="clients-per-query"/>.)
13711 This corresponds to the
13712 <command>dropped</command> counter
13713 of previous versions of
13714 <acronym>BIND</acronym> 9.
13719 <entry colname="1">
13720 <para><command>QryFailure</command></para>
13722 <entry colname="2">
13723 <para><command></command></para>
13725 <entry colname="3">
13727 Other query failures.
13728 This corresponds to the
13729 <command>failure</command> counter
13730 of previous versions of
13731 <acronym>BIND</acronym> 9.
13732 Note: this counter is provided mainly for
13733 backward compatibility with the previous versions.
13734 Normally a more fine-grained counters such as
13735 <command>AuthQryRej</command> and
13736 <command>RecQryRej</command>
13737 that would also fall into this counter are provided,
13738 and so this counter would not be of much
13739 interest in practice.
13744 <entry colname="1">
13745 <para><command>XfrReqDone</command></para>
13747 <entry colname="2">
13748 <para><command></command></para>
13750 <entry colname="3">
13752 Requested zone transfers completed.
13757 <entry colname="1">
13758 <para><command>UpdateReqFwd</command></para>
13760 <entry colname="2">
13761 <para><command></command></para>
13763 <entry colname="3">
13765 Update requests forwarded.
13770 <entry colname="1">
13771 <para><command>UpdateRespFwd</command></para>
13773 <entry colname="2">
13774 <para><command></command></para>
13776 <entry colname="3">
13778 Update responses forwarded.
13783 <entry colname="1">
13784 <para><command>UpdateFwdFail</command></para>
13786 <entry colname="2">
13787 <para><command></command></para>
13789 <entry colname="3">
13791 Dynamic update forward failed.
13796 <entry colname="1">
13797 <para><command>UpdateDone</command></para>
13799 <entry colname="2">
13800 <para><command></command></para>
13802 <entry colname="3">
13804 Dynamic updates completed.
13809 <entry colname="1">
13810 <para><command>UpdateFail</command></para>
13812 <entry colname="2">
13813 <para><command></command></para>
13815 <entry colname="3">
13817 Dynamic updates failed.
13822 <entry colname="1">
13823 <para><command>UpdateBadPrereq</command></para>
13825 <entry colname="2">
13826 <para><command></command></para>
13828 <entry colname="3">
13830 Dynamic updates rejected due to prerequisite failure.
13840 <title>Zone Maintenance Statistics Counters</title>
13842 <informaltable colsep="0" rowsep="0">
13843 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13844 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
13845 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
13848 <entry colname="1">
13850 <emphasis>Symbol</emphasis>
13853 <entry colname="2">
13855 <emphasis>Description</emphasis>
13861 <entry colname="1">
13862 <para><command>NotifyOutv4</command></para>
13864 <entry colname="2">
13866 IPv4 notifies sent.
13871 <entry colname="1">
13872 <para><command>NotifyOutv6</command></para>
13874 <entry colname="2">
13876 IPv6 notifies sent.
13881 <entry colname="1">
13882 <para><command>NotifyInv4</command></para>
13884 <entry colname="2">
13886 IPv4 notifies received.
13891 <entry colname="1">
13892 <para><command>NotifyInv6</command></para>
13894 <entry colname="2">
13896 IPv6 notifies received.
13901 <entry colname="1">
13902 <para><command>NotifyRej</command></para>
13904 <entry colname="2">
13906 Incoming notifies rejected.
13911 <entry colname="1">
13912 <para><command>SOAOutv4</command></para>
13914 <entry colname="2">
13916 IPv4 SOA queries sent.
13921 <entry colname="1">
13922 <para><command>SOAOutv6</command></para>
13924 <entry colname="2">
13926 IPv6 SOA queries sent.
13931 <entry colname="1">
13932 <para><command>AXFRReqv4</command></para>
13934 <entry colname="2">
13936 IPv4 AXFR requested.
13941 <entry colname="1">
13942 <para><command>AXFRReqv6</command></para>
13944 <entry colname="2">
13946 IPv6 AXFR requested.
13951 <entry colname="1">
13952 <para><command>IXFRReqv4</command></para>
13954 <entry colname="2">
13956 IPv4 IXFR requested.
13961 <entry colname="1">
13962 <para><command>IXFRReqv6</command></para>
13964 <entry colname="2">
13966 IPv6 IXFR requested.
13971 <entry colname="1">
13972 <para><command>XfrSuccess</command></para>
13974 <entry colname="2">
13976 Zone transfer requests succeeded.
13981 <entry colname="1">
13982 <para><command>XfrFail</command></para>
13984 <entry colname="2">
13986 Zone transfer requests failed.
13996 <title>Resolver Statistics Counters</title>
13998 <informaltable colsep="0" rowsep="0">
13999 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14000 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14001 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
14002 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
14005 <entry colname="1">
14007 <emphasis>Symbol</emphasis>
14010 <entry colname="2">
14012 <emphasis>BIND8 Symbol</emphasis>
14015 <entry colname="3">
14017 <emphasis>Description</emphasis>
14023 <entry colname="1">
14024 <para><command>Queryv4</command></para>
14026 <entry colname="2">
14027 <para><command>SFwdQ</command></para>
14029 <entry colname="3">
14036 <entry colname="1">
14037 <para><command>Queryv6</command></para>
14039 <entry colname="2">
14040 <para><command>SFwdQ</command></para>
14042 <entry colname="3">
14049 <entry colname="1">
14050 <para><command>Responsev4</command></para>
14052 <entry colname="2">
14053 <para><command>RR</command></para>
14055 <entry colname="3">
14057 IPv4 responses received.
14062 <entry colname="1">
14063 <para><command>Responsev6</command></para>
14065 <entry colname="2">
14066 <para><command>RR</command></para>
14068 <entry colname="3">
14070 IPv6 responses received.
14075 <entry colname="1">
14076 <para><command>NXDOMAIN</command></para>
14078 <entry colname="2">
14079 <para><command>RNXD</command></para>
14081 <entry colname="3">
14088 <entry colname="1">
14089 <para><command>SERVFAIL</command></para>
14091 <entry colname="2">
14092 <para><command>RFail</command></para>
14094 <entry colname="3">
14101 <entry colname="1">
14102 <para><command>FORMERR</command></para>
14104 <entry colname="2">
14105 <para><command>RFErr</command></para>
14107 <entry colname="3">
14114 <entry colname="1">
14115 <para><command>OtherError</command></para>
14117 <entry colname="2">
14118 <para><command>RErr</command></para>
14120 <entry colname="3">
14122 Other errors received.
14127 <entry colname="1">
14128 <para><command>EDNS0Fail</command></para>
14130 <entry colname="2">
14131 <para><command></command></para>
14133 <entry colname="3">
14135 EDNS(0) query failures.
14140 <entry colname="1">
14141 <para><command>Mismatch</command></para>
14143 <entry colname="2">
14144 <para><command>RDupR</command></para>
14146 <entry colname="3">
14148 Mismatch responses received.
14149 The DNS ID, response's source address,
14150 and/or the response's source port does not
14151 match what was expected.
14152 (The port must be 53 or as defined by
14153 the <command>port</command> option.)
14154 This may be an indication of a cache
14160 <entry colname="1">
14161 <para><command>Truncated</command></para>
14163 <entry colname="2">
14164 <para><command></command></para>
14166 <entry colname="3">
14168 Truncated responses received.
14173 <entry colname="1">
14174 <para><command>Lame</command></para>
14176 <entry colname="2">
14177 <para><command>RLame</command></para>
14179 <entry colname="3">
14181 Lame delegations received.
14186 <entry colname="1">
14187 <para><command>Retry</command></para>
14189 <entry colname="2">
14190 <para><command>SDupQ</command></para>
14192 <entry colname="3">
14194 Query retries performed.
14199 <entry colname="1">
14200 <para><command>QueryAbort</command></para>
14202 <entry colname="2">
14203 <para><command></command></para>
14205 <entry colname="3">
14207 Queries aborted due to quota control.
14212 <entry colname="1">
14213 <para><command>QuerySockFail</command></para>
14215 <entry colname="2">
14216 <para><command></command></para>
14218 <entry colname="3">
14220 Failures in opening query sockets.
14221 One common reason for such failures is a
14222 failure of opening a new socket due to a
14223 limitation on file descriptors.
14228 <entry colname="1">
14229 <para><command>QueryTimeout</command></para>
14231 <entry colname="2">
14232 <para><command></command></para>
14234 <entry colname="3">
14241 <entry colname="1">
14242 <para><command>GlueFetchv4</command></para>
14244 <entry colname="2">
14245 <para><command>SSysQ</command></para>
14247 <entry colname="3">
14249 IPv4 NS address fetches invoked.
14254 <entry colname="1">
14255 <para><command>GlueFetchv6</command></para>
14257 <entry colname="2">
14258 <para><command>SSysQ</command></para>
14260 <entry colname="3">
14262 IPv6 NS address fetches invoked.
14267 <entry colname="1">
14268 <para><command>GlueFetchv4Fail</command></para>
14270 <entry colname="2">
14271 <para><command></command></para>
14273 <entry colname="3">
14275 IPv4 NS address fetch failed.
14280 <entry colname="1">
14281 <para><command>GlueFetchv6Fail</command></para>
14283 <entry colname="2">
14284 <para><command></command></para>
14286 <entry colname="3">
14288 IPv6 NS address fetch failed.
14293 <entry colname="1">
14294 <para><command>ValAttempt</command></para>
14296 <entry colname="2">
14297 <para><command></command></para>
14299 <entry colname="3">
14301 DNSSEC validation attempted.
14306 <entry colname="1">
14307 <para><command>ValOk</command></para>
14309 <entry colname="2">
14310 <para><command></command></para>
14312 <entry colname="3">
14314 DNSSEC validation succeeded.
14319 <entry colname="1">
14320 <para><command>ValNegOk</command></para>
14322 <entry colname="2">
14323 <para><command></command></para>
14325 <entry colname="3">
14327 DNSSEC validation on negative information succeeded.
14332 <entry colname="1">
14333 <para><command>ValFail</command></para>
14335 <entry colname="2">
14336 <para><command></command></para>
14338 <entry colname="3">
14340 DNSSEC validation failed.
14345 <entry colname="1">
14346 <para><command>QryRTTnn</command></para>
14348 <entry colname="2">
14349 <para><command></command></para>
14351 <entry colname="3">
14353 Frequency table on round trip times (RTTs) of
14355 Each <command>nn</command> specifies the corresponding
14358 <command>nn_1</command>,
14359 <command>nn_2</command>,
14361 <command>nn_m</command>,
14362 the value of <command>nn_i</command> is the
14363 number of queries whose RTTs are between
14364 <command>nn_(i-1)</command> (inclusive) and
14365 <command>nn_i</command> (exclusive) milliseconds.
14366 For the sake of convenience we define
14367 <command>nn_0</command> to be 0.
14368 The last entry should be represented as
14369 <command>nn_m+</command>, which means the
14370 number of queries whose RTTs are equal to or over
14371 <command>nn_m</command> milliseconds.
14382 <title>Socket I/O Statistics Counters</title>
14385 Socket I/O statistics counters are defined per socket
14387 <command>UDP4</command> (UDP/IPv4),
14388 <command>UDP6</command> (UDP/IPv6),
14389 <command>TCP4</command> (TCP/IPv4),
14390 <command>TCP6</command> (TCP/IPv6),
14391 <command>Unix</command> (Unix Domain), and
14392 <command>FDwatch</command> (sockets opened outside the
14394 In the following table <command><TYPE></command>
14395 represents a socket type.
14396 Not all counters are available for all socket types;
14397 exceptions are noted in the description field.
14400 <informaltable colsep="0" rowsep="0">
14401 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14402 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14403 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
14406 <entry colname="1">
14408 <emphasis>Symbol</emphasis>
14411 <entry colname="2">
14413 <emphasis>Description</emphasis>
14419 <entry colname="1">
14420 <para><command><TYPE>Open</command></para>
14422 <entry colname="2">
14424 Sockets opened successfully.
14425 This counter is not applicable to the
14426 <command>FDwatch</command> type.
14431 <entry colname="1">
14432 <para><command><TYPE>OpenFail</command></para>
14434 <entry colname="2">
14436 Failures of opening sockets.
14437 This counter is not applicable to the
14438 <command>FDwatch</command> type.
14443 <entry colname="1">
14444 <para><command><TYPE>Close</command></para>
14446 <entry colname="2">
14453 <entry colname="1">
14454 <para><command><TYPE>BindFail</command></para>
14456 <entry colname="2">
14458 Failures of binding sockets.
14463 <entry colname="1">
14464 <para><command><TYPE>ConnFail</command></para>
14466 <entry colname="2">
14468 Failures of connecting sockets.
14473 <entry colname="1">
14474 <para><command><TYPE>Conn</command></para>
14476 <entry colname="2">
14478 Connections established successfully.
14483 <entry colname="1">
14484 <para><command><TYPE>AcceptFail</command></para>
14486 <entry colname="2">
14488 Failures of accepting incoming connection requests.
14489 This counter is not applicable to the
14490 <command>UDP</command> and
14491 <command>FDwatch</command> types.
14496 <entry colname="1">
14497 <para><command><TYPE>Accept</command></para>
14499 <entry colname="2">
14501 Incoming connections successfully accepted.
14502 This counter is not applicable to the
14503 <command>UDP</command> and
14504 <command>FDwatch</command> types.
14509 <entry colname="1">
14510 <para><command><TYPE>SendErr</command></para>
14512 <entry colname="2">
14514 Errors in socket send operations.
14515 This counter corresponds
14516 to <command>SErr</command> counter of
14517 <command>BIND</command> 8.
14522 <entry colname="1">
14523 <para><command><TYPE>RecvErr</command></para>
14525 <entry colname="2">
14527 Errors in socket receive operations.
14528 This includes errors of send operations on a
14529 connected UDP socket notified by an ICMP error
14539 <title>Compatibility with <emphasis>BIND</emphasis> 8 Counters</title>
14541 Most statistics counters that were available
14542 in <command>BIND</command> 8 are also supported in
14543 <command>BIND</command> 9 as shown in the above tables.
14544 Here are notes about other counters that do not appear
14550 <term><command>RFwdR,SFwdR</command></term>
14553 These counters are not supported
14554 because <command>BIND</command> 9 does not adopt
14555 the notion of <emphasis>forwarding</emphasis>
14556 as <command>BIND</command> 8 did.
14562 <term><command>RAXFR</command></term>
14565 This counter is accessible in the Incoming Queries section.
14571 <term><command>RIQ</command></term>
14574 This counter is accessible in the Incoming Requests section.
14580 <term><command>ROpts</command></term>
14583 This counter is not supported
14584 because <command>BIND</command> 9 does not care
14585 about IP options in the first place.
14595 <chapter id="Bv9ARM.ch07">
14596 <title><acronym>BIND</acronym> 9 Security Considerations</title>
14597 <sect1 id="Access_Control_Lists">
14598 <title>Access Control Lists</title>
14600 Access Control Lists (ACLs) are address match lists that
14601 you can set up and nickname for future use in <command>allow-notify</command>,
14602 <command>allow-query</command>, <command>allow-query-on</command>,
14603 <command>allow-recursion</command>, <command>allow-recursion-on</command>,
14604 <command>blackhole</command>, <command>allow-transfer</command>,
14608 Using ACLs allows you to have finer control over who can access
14609 your name server, without cluttering up your config files with huge
14610 lists of IP addresses.
14613 It is a <emphasis>good idea</emphasis> to use ACLs, and to
14614 control access to your server. Limiting access to your server by
14615 outside parties can help prevent spoofing and denial of service (DoS) attacks against
14619 Here is an example of how to properly apply ACLs:
14623 // Set up an ACL named "bogusnets" that will block
14624 // RFC1918 space and some reserved space, which is
14625 // commonly used in spoofing attacks.
14627 0.0.0.0/8; 1.0.0.0/8; 2.0.0.0/8; 192.0.2.0/24;
14628 224.0.0.0/3; 10.0.0.0/8; 172.16.0.0/12;
14632 // Set up an ACL called our-nets. Replace this with the
14633 // real IP numbers.
14634 acl our-nets { x.x.x.x/24; x.x.x.x/21; };
14638 allow-query { our-nets; };
14639 allow-recursion { our-nets; };
14641 blackhole { bogusnets; };
14645 zone "example.com" {
14647 file "m/example.com";
14648 allow-query { any; };
14653 This allows recursive queries of the server from the outside
14654 unless recursion has been previously disabled.
14657 For more information on how to use ACLs to protect your server,
14658 see the <emphasis>AUSCERT</emphasis> advisory at:
14661 <ulink url="ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos"
14662 >ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos</ulink>
14666 <title><command>Chroot</command> and <command>Setuid</command></title>
14668 On UNIX servers, it is possible to run <acronym>BIND</acronym>
14669 in a <emphasis>chrooted</emphasis> environment (using
14670 the <command>chroot()</command> function) by specifying
14671 the "<option>-t</option>" option for <command>named</command>.
14672 This can help improve system security by placing
14673 <acronym>BIND</acronym> in a "sandbox", which will limit
14674 the damage done if a server is compromised.
14677 Another useful feature in the UNIX version of <acronym>BIND</acronym> is the
14678 ability to run the daemon as an unprivileged user ( <option>-u</option> <replaceable>user</replaceable> ).
14679 We suggest running as an unprivileged user when using the <command>chroot</command> feature.
14682 Here is an example command line to load <acronym>BIND</acronym> in a <command>chroot</command> sandbox,
14683 <command>/var/named</command>, and to run <command>named</command> <command>setuid</command> to
14687 <userinput>/usr/local/sbin/named -u 202 -t /var/named</userinput>
14691 <title>The <command>chroot</command> Environment</title>
14694 In order for a <command>chroot</command> environment
14696 work properly in a particular directory
14697 (for example, <filename>/var/named</filename>),
14698 you will need to set up an environment that includes everything
14699 <acronym>BIND</acronym> needs to run.
14700 From <acronym>BIND</acronym>'s point of view, <filename>/var/named</filename> is
14701 the root of the filesystem. You will need to adjust the values of
14703 like <command>directory</command> and <command>pid-file</command> to account
14707 Unlike with earlier versions of BIND, you typically will
14708 <emphasis>not</emphasis> need to compile <command>named</command>
14709 statically nor install shared libraries under the new root.
14710 However, depending on your operating system, you may need
14711 to set up things like
14712 <filename>/dev/zero</filename>,
14713 <filename>/dev/random</filename>,
14714 <filename>/dev/log</filename>, and
14715 <filename>/etc/localtime</filename>.
14720 <title>Using the <command>setuid</command> Function</title>
14723 Prior to running the <command>named</command> daemon,
14725 the <command>touch</command> utility (to change file
14727 modification times) or the <command>chown</command>
14729 set the user id and/or group id) on files
14730 to which you want <acronym>BIND</acronym>
14734 Note that if the <command>named</command> daemon is running as an
14735 unprivileged user, it will not be able to bind to new restricted
14736 ports if the server is reloaded.
14741 <sect1 id="dynamic_update_security">
14742 <title>Dynamic Update Security</title>
14745 Access to the dynamic
14746 update facility should be strictly limited. In earlier versions of
14747 <acronym>BIND</acronym>, the only way to do this was
14749 address of the host requesting the update, by listing an IP address
14751 network prefix in the <command>allow-update</command>
14753 This method is insecure since the source address of the update UDP
14755 is easily forged. Also note that if the IP addresses allowed by the
14756 <command>allow-update</command> option include the
14758 server which performs forwarding of dynamic updates, the master can
14760 trivially attacked by sending the update to the slave, which will
14761 forward it to the master with its own source IP address causing the
14762 master to approve it without question.
14766 For these reasons, we strongly recommend that updates be
14767 cryptographically authenticated by means of transaction signatures
14768 (TSIG). That is, the <command>allow-update</command>
14770 list only TSIG key names, not IP addresses or network
14771 prefixes. Alternatively, the new <command>update-policy</command>
14772 option can be used.
14776 Some sites choose to keep all dynamically-updated DNS data
14777 in a subdomain and delegate that subdomain to a separate zone. This
14778 way, the top-level zone containing critical data such as the IP
14780 of public web and mail servers need not allow dynamic update at
14787 <chapter id="Bv9ARM.ch08">
14788 <title>Troubleshooting</title>
14790 <title>Common Problems</title>
14792 <title>It's not working; how can I figure out what's wrong?</title>
14795 The best solution to solving installation and
14796 configuration issues is to take preventative measures by setting
14797 up logging files beforehand. The log files provide a
14798 source of hints and information that can be used to figure out
14799 what went wrong and how to fix the problem.
14805 <title>Incrementing and Changing the Serial Number</title>
14808 Zone serial numbers are just numbers — they aren't
14809 date related. A lot of people set them to a number that
14810 represents a date, usually of the form YYYYMMDDRR.
14811 Occasionally they will make a mistake and set them to a
14812 "date in the future" then try to correct them by setting
14813 them to the "current date". This causes problems because
14814 serial numbers are used to indicate that a zone has been
14815 updated. If the serial number on the slave server is
14816 lower than the serial number on the master, the slave
14817 server will attempt to update its copy of the zone.
14821 Setting the serial number to a lower number on the master
14822 server than the slave server means that the slave will not perform
14823 updates to its copy of the zone.
14827 The solution to this is to add 2147483647 (2^31-1) to the
14828 number, reload the zone and make sure all slaves have updated to
14829 the new zone serial number, then reset the number to what you want
14830 it to be, and reload the zone again.
14835 <title>Where Can I Get Help?</title>
14838 The Internet Systems Consortium
14839 (<acronym>ISC</acronym>) offers a wide range
14840 of support and service agreements for <acronym>BIND</acronym> and <acronym>DHCP</acronym> servers. Four
14841 levels of premium support are available and each level includes
14842 support for all <acronym>ISC</acronym> programs,
14843 significant discounts on products
14844 and training, and a recognized priority on bug fixes and
14845 non-funded feature requests. In addition, <acronym>ISC</acronym> offers a standard
14846 support agreement package which includes services ranging from bug
14847 fix announcements to remote support. It also includes training in
14848 <acronym>BIND</acronym> and <acronym>DHCP</acronym>.
14852 To discuss arrangements for support, contact
14853 <ulink url="mailto:info@isc.org">info@isc.org</ulink> or visit the
14854 <acronym>ISC</acronym> web page at
14855 <ulink url="http://www.isc.org/services/support/"
14856 >http://www.isc.org/services/support/</ulink>
14861 <appendix id="Bv9ARM.ch09">
14862 <title>Appendices</title>
14864 <title>Acknowledgments</title>
14865 <sect2 id="historical_dns_information">
14866 <title>A Brief History of the <acronym>DNS</acronym> and <acronym>BIND</acronym></title>
14869 Although the "official" beginning of the Domain Name
14870 System occurred in 1984 with the publication of RFC 920, the
14871 core of the new system was described in 1983 in RFCs 882 and
14872 883. From 1984 to 1987, the ARPAnet (the precursor to today's
14873 Internet) became a testbed of experimentation for developing the
14874 new naming/addressing scheme in a rapidly expanding,
14875 operational network environment. New RFCs were written and
14876 published in 1987 that modified the original documents to
14877 incorporate improvements based on the working model. RFC 1034,
14878 "Domain Names-Concepts and Facilities", and RFC 1035, "Domain
14879 Names-Implementation and Specification" were published and
14880 became the standards upon which all <acronym>DNS</acronym> implementations are
14885 The first working domain name server, called "Jeeves", was
14886 written in 1983-84 by Paul Mockapetris for operation on DEC
14888 machines located at the University of Southern California's
14890 Sciences Institute (USC-ISI) and SRI International's Network
14892 Center (SRI-NIC). A <acronym>DNS</acronym> server for
14893 Unix machines, the Berkeley Internet
14894 Name Domain (<acronym>BIND</acronym>) package, was
14895 written soon after by a group of
14896 graduate students at the University of California at Berkeley
14898 a grant from the US Defense Advanced Research Projects
14903 Versions of <acronym>BIND</acronym> through
14904 4.8.3 were maintained by the Computer
14905 Systems Research Group (CSRG) at UC Berkeley. Douglas Terry, Mark
14906 Painter, David Riggle and Songnian Zhou made up the initial <acronym>BIND</acronym>
14907 project team. After that, additional work on the software package
14908 was done by Ralph Campbell. Kevin Dunlap, a Digital Equipment
14910 employee on loan to the CSRG, worked on <acronym>BIND</acronym> for 2 years, from 1985
14911 to 1987. Many other people also contributed to <acronym>BIND</acronym> development
14912 during that time: Doug Kingston, Craig Partridge, Smoot
14914 Mike Muuss, Jim Bloom and Mike Schwartz. <acronym>BIND</acronym> maintenance was subsequently
14915 handled by Mike Karels and Øivind Kure.
14918 <acronym>BIND</acronym> versions 4.9 and 4.9.1 were
14919 released by Digital Equipment
14920 Corporation (now Compaq Computer Corporation). Paul Vixie, then
14921 a DEC employee, became <acronym>BIND</acronym>'s
14922 primary caretaker. He was assisted
14923 by Phil Almquist, Robert Elz, Alan Barrett, Paul Albitz, Bryan
14925 Partan, Andy Cherenson, Tom Limoncelli, Berthold Paffrath, Fuat
14926 Baran, Anant Kumar, Art Harkin, Win Treese, Don Lewis, Christophe
14927 Wolfhugel, and others.
14930 In 1994, <acronym>BIND</acronym> version 4.9.2 was sponsored by
14931 Vixie Enterprises. Paul
14932 Vixie became <acronym>BIND</acronym>'s principal
14933 architect/programmer.
14936 <acronym>BIND</acronym> versions from 4.9.3 onward
14937 have been developed and maintained
14938 by the Internet Systems Consortium and its predecessor,
14939 the Internet Software Consortium, with support being provided
14943 As co-architects/programmers, Bob Halley and
14944 Paul Vixie released the first production-ready version of
14945 <acronym>BIND</acronym> version 8 in May 1997.
14948 BIND version 9 was released in September 2000 and is a
14949 major rewrite of nearly all aspects of the underlying
14953 BIND versions 4 and 8 are officially deprecated.
14954 No additional development is done
14955 on BIND version 4 or BIND version 8.
14958 <acronym>BIND</acronym> development work is made
14959 possible today by the sponsorship
14960 of several corporations, and by the tireless work efforts of
14961 numerous individuals.
14966 <title>General <acronym>DNS</acronym> Reference Information</title>
14967 <sect2 id="ipv6addresses">
14968 <title>IPv6 addresses (AAAA)</title>
14970 IPv6 addresses are 128-bit identifiers for interfaces and
14971 sets of interfaces which were introduced in the <acronym>DNS</acronym> to facilitate
14972 scalable Internet routing. There are three types of addresses: <emphasis>Unicast</emphasis>,
14973 an identifier for a single interface;
14974 <emphasis>Anycast</emphasis>,
14975 an identifier for a set of interfaces; and <emphasis>Multicast</emphasis>,
14976 an identifier for a set of interfaces. Here we describe the global
14977 Unicast address scheme. For more information, see RFC 3587,
14978 "Global Unicast Address Format."
14981 IPv6 unicast addresses consist of a
14982 <emphasis>global routing prefix</emphasis>, a
14983 <emphasis>subnet identifier</emphasis>, and an
14984 <emphasis>interface identifier</emphasis>.
14987 The global routing prefix is provided by the
14988 upstream provider or ISP, and (roughly) corresponds to the
14989 IPv4 <emphasis>network</emphasis> section
14990 of the address range.
14992 The subnet identifier is for local subnetting, much the
14993 same as subnetting an
14994 IPv4 /16 network into /24 subnets.
14996 The interface identifier is the address of an individual
14997 interface on a given network; in IPv6, addresses belong to
14998 interfaces rather than to machines.
15001 The subnetting capability of IPv6 is much more flexible than
15002 that of IPv4: subnetting can be carried out on bit boundaries,
15003 in much the same way as Classless InterDomain Routing
15004 (CIDR), and the DNS PTR representation ("nibble" format)
15005 makes setting up reverse zones easier.
15008 The Interface Identifier must be unique on the local link,
15009 and is usually generated automatically by the IPv6
15010 implementation, although it is usually possible to
15011 override the default setting if necessary. A typical IPv6
15012 address might look like:
15013 <command>2001:db8:201:9:a00:20ff:fe81:2b32</command>
15016 IPv6 address specifications often contain long strings
15017 of zeros, so the architects have included a shorthand for
15019 them. The double colon (`::') indicates the longest possible
15021 of zeros that can fit, and can be used only once in an address.
15025 <sect1 id="bibliography">
15026 <title>Bibliography (and Suggested Reading)</title>
15028 <title>Request for Comments (RFCs)</title>
15030 Specification documents for the Internet protocol suite, including
15031 the <acronym>DNS</acronym>, are published as part of
15032 the Request for Comments (RFCs)
15033 series of technical notes. The standards themselves are defined
15034 by the Internet Engineering Task Force (IETF) and the Internet
15035 Engineering Steering Group (IESG). RFCs can be obtained online via FTP at:
15038 <ulink url="ftp://www.isi.edu/in-notes/">
15039 ftp://www.isi.edu/in-notes/RFC<replaceable>xxxx</replaceable>.txt
15043 (where <replaceable>xxxx</replaceable> is
15044 the number of the RFC). RFCs are also available via the Web at:
15047 <ulink url="http://www.ietf.org/rfc/"
15048 >http://www.ietf.org/rfc/</ulink>.
15052 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
15053 <title>Standards</title>
15055 <abbrev>RFC974</abbrev>
15057 <surname>Partridge</surname>
15058 <firstname>C.</firstname>
15060 <title>Mail Routing and the Domain System</title>
15061 <pubdate>January 1986</pubdate>
15064 <abbrev>RFC1034</abbrev>
15066 <surname>Mockapetris</surname>
15067 <firstname>P.V.</firstname>
15069 <title>Domain Names — Concepts and Facilities</title>
15070 <pubdate>November 1987</pubdate>
15073 <abbrev>RFC1035</abbrev>
15075 <surname>Mockapetris</surname>
15076 <firstname>P. V.</firstname>
15077 </author> <title>Domain Names — Implementation and
15078 Specification</title>
15079 <pubdate>November 1987</pubdate>
15082 <bibliodiv id="proposed_standards" xreflabel="Proposed Standards">
15084 <title>Proposed Standards</title>
15085 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
15087 <abbrev>RFC2181</abbrev>
15089 <surname>Elz</surname>
15090 <firstname>R., R. Bush</firstname>
15092 <title>Clarifications to the <acronym>DNS</acronym>
15093 Specification</title>
15094 <pubdate>July 1997</pubdate>
15097 <abbrev>RFC2308</abbrev>
15099 <surname>Andrews</surname>
15100 <firstname>M.</firstname>
15102 <title>Negative Caching of <acronym>DNS</acronym>
15104 <pubdate>March 1998</pubdate>
15107 <abbrev>RFC1995</abbrev>
15109 <surname>Ohta</surname>
15110 <firstname>M.</firstname>
15112 <title>Incremental Zone Transfer in <acronym>DNS</acronym></title>
15113 <pubdate>August 1996</pubdate>
15116 <abbrev>RFC1996</abbrev>
15118 <surname>Vixie</surname>
15119 <firstname>P.</firstname>
15121 <title>A Mechanism for Prompt Notification of Zone Changes</title>
15122 <pubdate>August 1996</pubdate>
15125 <abbrev>RFC2136</abbrev>
15128 <surname>Vixie</surname>
15129 <firstname>P.</firstname>
15132 <firstname>S.</firstname>
15133 <surname>Thomson</surname>
15136 <firstname>Y.</firstname>
15137 <surname>Rekhter</surname>
15140 <firstname>J.</firstname>
15141 <surname>Bound</surname>
15144 <title>Dynamic Updates in the Domain Name System</title>
15145 <pubdate>April 1997</pubdate>
15148 <abbrev>RFC2671</abbrev>
15151 <firstname>P.</firstname>
15152 <surname>Vixie</surname>
15155 <title>Extension Mechanisms for DNS (EDNS0)</title>
15156 <pubdate>August 1997</pubdate>
15159 <abbrev>RFC2672</abbrev>
15162 <firstname>M.</firstname>
15163 <surname>Crawford</surname>
15166 <title>Non-Terminal DNS Name Redirection</title>
15167 <pubdate>August 1999</pubdate>
15170 <abbrev>RFC2845</abbrev>
15173 <surname>Vixie</surname>
15174 <firstname>P.</firstname>
15177 <firstname>O.</firstname>
15178 <surname>Gudmundsson</surname>
15181 <firstname>D.</firstname>
15182 <surname>Eastlake</surname>
15183 <lineage>3rd</lineage>
15186 <firstname>B.</firstname>
15187 <surname>Wellington</surname>
15190 <title>Secret Key Transaction Authentication for <acronym>DNS</acronym> (TSIG)</title>
15191 <pubdate>May 2000</pubdate>
15194 <abbrev>RFC2930</abbrev>
15197 <firstname>D.</firstname>
15198 <surname>Eastlake</surname>
15199 <lineage>3rd</lineage>
15202 <title>Secret Key Establishment for DNS (TKEY RR)</title>
15203 <pubdate>September 2000</pubdate>
15206 <abbrev>RFC2931</abbrev>
15209 <firstname>D.</firstname>
15210 <surname>Eastlake</surname>
15211 <lineage>3rd</lineage>
15214 <title>DNS Request and Transaction Signatures (SIG(0)s)</title>
15215 <pubdate>September 2000</pubdate>
15218 <abbrev>RFC3007</abbrev>
15221 <firstname>B.</firstname>
15222 <surname>Wellington</surname>
15225 <title>Secure Domain Name System (DNS) Dynamic Update</title>
15226 <pubdate>November 2000</pubdate>
15229 <abbrev>RFC3645</abbrev>
15232 <firstname>S.</firstname>
15233 <surname>Kwan</surname>
15236 <firstname>P.</firstname>
15237 <surname>Garg</surname>
15240 <firstname>J.</firstname>
15241 <surname>Gilroy</surname>
15244 <firstname>L.</firstname>
15245 <surname>Esibov</surname>
15248 <firstname>J.</firstname>
15249 <surname>Westhead</surname>
15252 <firstname>R.</firstname>
15253 <surname>Hall</surname>
15256 <title>Generic Security Service Algorithm for Secret
15257 Key Transaction Authentication for DNS
15259 <pubdate>October 2003</pubdate>
15263 <title><acronym>DNS</acronym> Security Proposed Standards</title>
15265 <abbrev>RFC3225</abbrev>
15268 <firstname>D.</firstname>
15269 <surname>Conrad</surname>
15272 <title>Indicating Resolver Support of DNSSEC</title>
15273 <pubdate>December 2001</pubdate>
15276 <abbrev>RFC3833</abbrev>
15279 <firstname>D.</firstname>
15280 <surname>Atkins</surname>
15283 <firstname>R.</firstname>
15284 <surname>Austein</surname>
15287 <title>Threat Analysis of the Domain Name System (DNS)</title>
15288 <pubdate>August 2004</pubdate>
15291 <abbrev>RFC4033</abbrev>
15294 <firstname>R.</firstname>
15295 <surname>Arends</surname>
15298 <firstname>R.</firstname>
15299 <surname>Austein</surname>
15302 <firstname>M.</firstname>
15303 <surname>Larson</surname>
15306 <firstname>D.</firstname>
15307 <surname>Massey</surname>
15310 <firstname>S.</firstname>
15311 <surname>Rose</surname>
15314 <title>DNS Security Introduction and Requirements</title>
15315 <pubdate>March 2005</pubdate>
15318 <abbrev>RFC4034</abbrev>
15321 <firstname>R.</firstname>
15322 <surname>Arends</surname>
15325 <firstname>R.</firstname>
15326 <surname>Austein</surname>
15329 <firstname>M.</firstname>
15330 <surname>Larson</surname>
15333 <firstname>D.</firstname>
15334 <surname>Massey</surname>
15337 <firstname>S.</firstname>
15338 <surname>Rose</surname>
15341 <title>Resource Records for the DNS Security Extensions</title>
15342 <pubdate>March 2005</pubdate>
15345 <abbrev>RFC4035</abbrev>
15348 <firstname>R.</firstname>
15349 <surname>Arends</surname>
15352 <firstname>R.</firstname>
15353 <surname>Austein</surname>
15356 <firstname>M.</firstname>
15357 <surname>Larson</surname>
15360 <firstname>D.</firstname>
15361 <surname>Massey</surname>
15364 <firstname>S.</firstname>
15365 <surname>Rose</surname>
15368 <title>Protocol Modifications for the DNS
15369 Security Extensions</title>
15370 <pubdate>March 2005</pubdate>
15374 <title>Other Important RFCs About <acronym>DNS</acronym>
15375 Implementation</title>
15377 <abbrev>RFC1535</abbrev>
15379 <surname>Gavron</surname>
15380 <firstname>E.</firstname>
15382 <title>A Security Problem and Proposed Correction With Widely
15383 Deployed <acronym>DNS</acronym> Software.</title>
15384 <pubdate>October 1993</pubdate>
15387 <abbrev>RFC1536</abbrev>
15390 <surname>Kumar</surname>
15391 <firstname>A.</firstname>
15394 <firstname>J.</firstname>
15395 <surname>Postel</surname>
15398 <firstname>C.</firstname>
15399 <surname>Neuman</surname>
15402 <firstname>P.</firstname>
15403 <surname>Danzig</surname>
15406 <firstname>S.</firstname>
15407 <surname>Miller</surname>
15410 <title>Common <acronym>DNS</acronym> Implementation
15411 Errors and Suggested Fixes</title>
15412 <pubdate>October 1993</pubdate>
15415 <abbrev>RFC1982</abbrev>
15418 <surname>Elz</surname>
15419 <firstname>R.</firstname>
15422 <firstname>R.</firstname>
15423 <surname>Bush</surname>
15426 <title>Serial Number Arithmetic</title>
15427 <pubdate>August 1996</pubdate>
15430 <abbrev>RFC4074</abbrev>
15433 <surname>Morishita</surname>
15434 <firstname>Y.</firstname>
15437 <firstname>T.</firstname>
15438 <surname>Jinmei</surname>
15441 <title>Common Misbehaviour Against <acronym>DNS</acronym>
15442 Queries for IPv6 Addresses</title>
15443 <pubdate>May 2005</pubdate>
15447 <title>Resource Record Types</title>
15449 <abbrev>RFC1183</abbrev>
15452 <surname>Everhart</surname>
15453 <firstname>C.F.</firstname>
15456 <firstname>L. A.</firstname>
15457 <surname>Mamakos</surname>
15460 <firstname>R.</firstname>
15461 <surname>Ullmann</surname>
15464 <firstname>P.</firstname>
15465 <surname>Mockapetris</surname>
15468 <title>New <acronym>DNS</acronym> RR Definitions</title>
15469 <pubdate>October 1990</pubdate>
15472 <abbrev>RFC1706</abbrev>
15475 <surname>Manning</surname>
15476 <firstname>B.</firstname>
15479 <firstname>R.</firstname>
15480 <surname>Colella</surname>
15483 <title><acronym>DNS</acronym> NSAP Resource Records</title>
15484 <pubdate>October 1994</pubdate>
15487 <abbrev>RFC2168</abbrev>
15490 <surname>Daniel</surname>
15491 <firstname>R.</firstname>
15494 <firstname>M.</firstname>
15495 <surname>Mealling</surname>
15498 <title>Resolution of Uniform Resource Identifiers using
15499 the Domain Name System</title>
15500 <pubdate>June 1997</pubdate>
15503 <abbrev>RFC1876</abbrev>
15506 <surname>Davis</surname>
15507 <firstname>C.</firstname>
15510 <firstname>P.</firstname>
15511 <surname>Vixie</surname>
15514 <firstname>T.</firstname>
15515 <firstname>Goodwin</firstname>
15518 <firstname>I.</firstname>
15519 <surname>Dickinson</surname>
15522 <title>A Means for Expressing Location Information in the
15524 Name System</title>
15525 <pubdate>January 1996</pubdate>
15528 <abbrev>RFC2052</abbrev>
15531 <surname>Gulbrandsen</surname>
15532 <firstname>A.</firstname>
15535 <firstname>P.</firstname>
15536 <surname>Vixie</surname>
15539 <title>A <acronym>DNS</acronym> RR for Specifying the
15542 <pubdate>October 1996</pubdate>
15545 <abbrev>RFC2163</abbrev>
15547 <surname>Allocchio</surname>
15548 <firstname>A.</firstname>
15550 <title>Using the Internet <acronym>DNS</acronym> to
15552 Conformant Global Address Mapping</title>
15553 <pubdate>January 1998</pubdate>
15556 <abbrev>RFC2230</abbrev>
15558 <surname>Atkinson</surname>
15559 <firstname>R.</firstname>
15561 <title>Key Exchange Delegation Record for the <acronym>DNS</acronym></title>
15562 <pubdate>October 1997</pubdate>
15565 <abbrev>RFC2536</abbrev>
15567 <surname>Eastlake</surname>
15568 <firstname>D.</firstname>
15569 <lineage>3rd</lineage>
15571 <title>DSA KEYs and SIGs in the Domain Name System (DNS)</title>
15572 <pubdate>March 1999</pubdate>
15575 <abbrev>RFC2537</abbrev>
15577 <surname>Eastlake</surname>
15578 <firstname>D.</firstname>
15579 <lineage>3rd</lineage>
15581 <title>RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)</title>
15582 <pubdate>March 1999</pubdate>
15585 <abbrev>RFC2538</abbrev>
15588 <surname>Eastlake</surname>
15589 <firstname>D.</firstname>
15590 <lineage>3rd</lineage>
15593 <surname>Gudmundsson</surname>
15594 <firstname>O.</firstname>
15597 <title>Storing Certificates in the Domain Name System (DNS)</title>
15598 <pubdate>March 1999</pubdate>
15601 <abbrev>RFC2539</abbrev>
15604 <surname>Eastlake</surname>
15605 <firstname>D.</firstname>
15606 <lineage>3rd</lineage>
15609 <title>Storage of Diffie-Hellman Keys in the Domain Name System (DNS)</title>
15610 <pubdate>March 1999</pubdate>
15613 <abbrev>RFC2540</abbrev>
15616 <surname>Eastlake</surname>
15617 <firstname>D.</firstname>
15618 <lineage>3rd</lineage>
15621 <title>Detached Domain Name System (DNS) Information</title>
15622 <pubdate>March 1999</pubdate>
15625 <abbrev>RFC2782</abbrev>
15627 <surname>Gulbrandsen</surname>
15628 <firstname>A.</firstname>
15631 <surname>Vixie</surname>
15632 <firstname>P.</firstname>
15635 <surname>Esibov</surname>
15636 <firstname>L.</firstname>
15638 <title>A DNS RR for specifying the location of services (DNS SRV)</title>
15639 <pubdate>February 2000</pubdate>
15642 <abbrev>RFC2915</abbrev>
15644 <surname>Mealling</surname>
15645 <firstname>M.</firstname>
15648 <surname>Daniel</surname>
15649 <firstname>R.</firstname>
15651 <title>The Naming Authority Pointer (NAPTR) DNS Resource Record</title>
15652 <pubdate>September 2000</pubdate>
15655 <abbrev>RFC3110</abbrev>
15657 <surname>Eastlake</surname>
15658 <firstname>D.</firstname>
15659 <lineage>3rd</lineage>
15661 <title>RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)</title>
15662 <pubdate>May 2001</pubdate>
15665 <abbrev>RFC3123</abbrev>
15667 <surname>Koch</surname>
15668 <firstname>P.</firstname>
15670 <title>A DNS RR Type for Lists of Address Prefixes (APL RR)</title>
15671 <pubdate>June 2001</pubdate>
15674 <abbrev>RFC3596</abbrev>
15677 <surname>Thomson</surname>
15678 <firstname>S.</firstname>
15681 <firstname>C.</firstname>
15682 <surname>Huitema</surname>
15685 <firstname>V.</firstname>
15686 <surname>Ksinant</surname>
15689 <firstname>M.</firstname>
15690 <surname>Souissi</surname>
15693 <title><acronym>DNS</acronym> Extensions to support IP
15695 <pubdate>October 2003</pubdate>
15698 <abbrev>RFC3597</abbrev>
15700 <surname>Gustafsson</surname>
15701 <firstname>A.</firstname>
15703 <title>Handling of Unknown DNS Resource Record (RR) Types</title>
15704 <pubdate>September 2003</pubdate>
15708 <title><acronym>DNS</acronym> and the Internet</title>
15710 <abbrev>RFC1101</abbrev>
15712 <surname>Mockapetris</surname>
15713 <firstname>P. V.</firstname>
15715 <title><acronym>DNS</acronym> Encoding of Network Names
15716 and Other Types</title>
15717 <pubdate>April 1989</pubdate>
15720 <abbrev>RFC1123</abbrev>
15722 <surname>Braden</surname>
15723 <surname>R.</surname>
15725 <title>Requirements for Internet Hosts - Application and
15727 <pubdate>October 1989</pubdate>
15730 <abbrev>RFC1591</abbrev>
15732 <surname>Postel</surname>
15733 <firstname>J.</firstname>
15735 <title>Domain Name System Structure and Delegation</title>
15736 <pubdate>March 1994</pubdate>
15739 <abbrev>RFC2317</abbrev>
15742 <surname>Eidnes</surname>
15743 <firstname>H.</firstname>
15746 <firstname>G.</firstname>
15747 <surname>de Groot</surname>
15750 <firstname>P.</firstname>
15751 <surname>Vixie</surname>
15754 <title>Classless IN-ADDR.ARPA Delegation</title>
15755 <pubdate>March 1998</pubdate>
15758 <abbrev>RFC2826</abbrev>
15761 <surname>Internet Architecture Board</surname>
15764 <title>IAB Technical Comment on the Unique DNS Root</title>
15765 <pubdate>May 2000</pubdate>
15768 <abbrev>RFC2929</abbrev>
15771 <surname>Eastlake</surname>
15772 <firstname>D.</firstname>
15773 <lineage>3rd</lineage>
15776 <surname>Brunner-Williams</surname>
15777 <firstname>E.</firstname>
15780 <surname>Manning</surname>
15781 <firstname>B.</firstname>
15784 <title>Domain Name System (DNS) IANA Considerations</title>
15785 <pubdate>September 2000</pubdate>
15789 <title><acronym>DNS</acronym> Operations</title>
15791 <abbrev>RFC1033</abbrev>
15793 <surname>Lottor</surname>
15794 <firstname>M.</firstname>
15796 <title>Domain administrators operations guide.</title>
15797 <pubdate>November 1987</pubdate>
15800 <abbrev>RFC1537</abbrev>
15802 <surname>Beertema</surname>
15803 <firstname>P.</firstname>
15805 <title>Common <acronym>DNS</acronym> Data File
15806 Configuration Errors</title>
15807 <pubdate>October 1993</pubdate>
15810 <abbrev>RFC1912</abbrev>
15812 <surname>Barr</surname>
15813 <firstname>D.</firstname>
15815 <title>Common <acronym>DNS</acronym> Operational and
15816 Configuration Errors</title>
15817 <pubdate>February 1996</pubdate>
15820 <abbrev>RFC2010</abbrev>
15823 <surname>Manning</surname>
15824 <firstname>B.</firstname>
15827 <firstname>P.</firstname>
15828 <surname>Vixie</surname>
15831 <title>Operational Criteria for Root Name Servers.</title>
15832 <pubdate>October 1996</pubdate>
15835 <abbrev>RFC2219</abbrev>
15838 <surname>Hamilton</surname>
15839 <firstname>M.</firstname>
15842 <firstname>R.</firstname>
15843 <surname>Wright</surname>
15846 <title>Use of <acronym>DNS</acronym> Aliases for
15847 Network Services.</title>
15848 <pubdate>October 1997</pubdate>
15852 <title>Internationalized Domain Names</title>
15854 <abbrev>RFC2825</abbrev>
15857 <surname>IAB</surname>
15860 <surname>Daigle</surname>
15861 <firstname>R.</firstname>
15864 <title>A Tangled Web: Issues of I18N, Domain Names,
15865 and the Other Internet protocols</title>
15866 <pubdate>May 2000</pubdate>
15869 <abbrev>RFC3490</abbrev>
15872 <surname>Faltstrom</surname>
15873 <firstname>P.</firstname>
15876 <surname>Hoffman</surname>
15877 <firstname>P.</firstname>
15880 <surname>Costello</surname>
15881 <firstname>A.</firstname>
15884 <title>Internationalizing Domain Names in Applications (IDNA)</title>
15885 <pubdate>March 2003</pubdate>
15888 <abbrev>RFC3491</abbrev>
15891 <surname>Hoffman</surname>
15892 <firstname>P.</firstname>
15895 <surname>Blanchet</surname>
15896 <firstname>M.</firstname>
15899 <title>Nameprep: A Stringprep Profile for Internationalized Domain Names</title>
15900 <pubdate>March 2003</pubdate>
15903 <abbrev>RFC3492</abbrev>
15906 <surname>Costello</surname>
15907 <firstname>A.</firstname>
15910 <title>Punycode: A Bootstring encoding of Unicode
15911 for Internationalized Domain Names in
15912 Applications (IDNA)</title>
15913 <pubdate>March 2003</pubdate>
15917 <title>Other <acronym>DNS</acronym>-related RFCs</title>
15920 Note: the following list of RFCs, although
15921 <acronym>DNS</acronym>-related, are not
15922 concerned with implementing software.
15926 <abbrev>RFC1464</abbrev>
15928 <surname>Rosenbaum</surname>
15929 <firstname>R.</firstname>
15931 <title>Using the Domain Name System To Store Arbitrary String
15933 <pubdate>May 1993</pubdate>
15936 <abbrev>RFC1713</abbrev>
15938 <surname>Romao</surname>
15939 <firstname>A.</firstname>
15941 <title>Tools for <acronym>DNS</acronym> Debugging</title>
15942 <pubdate>November 1994</pubdate>
15945 <abbrev>RFC1794</abbrev>
15947 <surname>Brisco</surname>
15948 <firstname>T.</firstname>
15950 <title><acronym>DNS</acronym> Support for Load
15952 <pubdate>April 1995</pubdate>
15955 <abbrev>RFC2240</abbrev>
15957 <surname>Vaughan</surname>
15958 <firstname>O.</firstname>
15960 <title>A Legal Basis for Domain Name Allocation</title>
15961 <pubdate>November 1997</pubdate>
15964 <abbrev>RFC2345</abbrev>
15967 <surname>Klensin</surname>
15968 <firstname>J.</firstname>
15971 <firstname>T.</firstname>
15972 <surname>Wolf</surname>
15975 <firstname>G.</firstname>
15976 <surname>Oglesby</surname>
15979 <title>Domain Names and Company Name Retrieval</title>
15980 <pubdate>May 1998</pubdate>
15983 <abbrev>RFC2352</abbrev>
15985 <surname>Vaughan</surname>
15986 <firstname>O.</firstname>
15988 <title>A Convention For Using Legal Names as Domain Names</title>
15989 <pubdate>May 1998</pubdate>
15992 <abbrev>RFC3071</abbrev>
15995 <surname>Klensin</surname>
15996 <firstname>J.</firstname>
15999 <title>Reflections on the DNS, RFC 1591, and Categories of Domains</title>
16000 <pubdate>February 2001</pubdate>
16003 <abbrev>RFC3258</abbrev>
16006 <surname>Hardie</surname>
16007 <firstname>T.</firstname>
16010 <title>Distributing Authoritative Name Servers via
16011 Shared Unicast Addresses</title>
16012 <pubdate>April 2002</pubdate>
16015 <abbrev>RFC3901</abbrev>
16018 <surname>Durand</surname>
16019 <firstname>A.</firstname>
16022 <firstname>J.</firstname>
16023 <surname>Ihren</surname>
16026 <title>DNS IPv6 Transport Operational Guidelines</title>
16027 <pubdate>September 2004</pubdate>
16031 <title>Obsolete and Unimplemented Experimental RFC</title>
16033 <abbrev>RFC1712</abbrev>
16036 <surname>Farrell</surname>
16037 <firstname>C.</firstname>
16040 <firstname>M.</firstname>
16041 <surname>Schulze</surname>
16044 <firstname>S.</firstname>
16045 <surname>Pleitner</surname>
16048 <firstname>D.</firstname>
16049 <surname>Baldoni</surname>
16052 <title><acronym>DNS</acronym> Encoding of Geographical
16054 <pubdate>November 1994</pubdate>
16057 <abbrev>RFC2673</abbrev>
16060 <surname>Crawford</surname>
16061 <firstname>M.</firstname>
16064 <title>Binary Labels in the Domain Name System</title>
16065 <pubdate>August 1999</pubdate>
16068 <abbrev>RFC2874</abbrev>
16071 <surname>Crawford</surname>
16072 <firstname>M.</firstname>
16075 <surname>Huitema</surname>
16076 <firstname>C.</firstname>
16079 <title>DNS Extensions to Support IPv6 Address Aggregation
16080 and Renumbering</title>
16081 <pubdate>July 2000</pubdate>
16085 <title>Obsoleted DNS Security RFCs</title>
16088 Most of these have been consolidated into RFC4033,
16089 RFC4034 and RFC4035 which collectively describe DNSSECbis.
16093 <abbrev>RFC2065</abbrev>
16096 <surname>Eastlake</surname>
16097 <lineage>3rd</lineage>
16098 <firstname>D.</firstname>
16101 <firstname>C.</firstname>
16102 <surname>Kaufman</surname>
16105 <title>Domain Name System Security Extensions</title>
16106 <pubdate>January 1997</pubdate>
16109 <abbrev>RFC2137</abbrev>
16111 <surname>Eastlake</surname>
16112 <lineage>3rd</lineage>
16113 <firstname>D.</firstname>
16115 <title>Secure Domain Name System Dynamic Update</title>
16116 <pubdate>April 1997</pubdate>
16119 <abbrev>RFC2535</abbrev>
16122 <surname>Eastlake</surname>
16123 <lineage>3rd</lineage>
16124 <firstname>D.</firstname>
16127 <title>Domain Name System Security Extensions</title>
16128 <pubdate>March 1999</pubdate>
16131 <abbrev>RFC3008</abbrev>
16134 <surname>Wellington</surname>
16135 <firstname>B.</firstname>
16138 <title>Domain Name System Security (DNSSEC)
16139 Signing Authority</title>
16140 <pubdate>November 2000</pubdate>
16143 <abbrev>RFC3090</abbrev>
16146 <surname>Lewis</surname>
16147 <firstname>E.</firstname>
16150 <title>DNS Security Extension Clarification on Zone Status</title>
16151 <pubdate>March 2001</pubdate>
16154 <abbrev>RFC3445</abbrev>
16157 <surname>Massey</surname>
16158 <firstname>D.</firstname>
16161 <surname>Rose</surname>
16162 <firstname>S.</firstname>
16165 <title>Limiting the Scope of the KEY Resource Record (RR)</title>
16166 <pubdate>December 2002</pubdate>
16169 <abbrev>RFC3655</abbrev>
16172 <surname>Wellington</surname>
16173 <firstname>B.</firstname>
16176 <surname>Gudmundsson</surname>
16177 <firstname>O.</firstname>
16180 <title>Redefinition of DNS Authenticated Data (AD) bit</title>
16181 <pubdate>November 2003</pubdate>
16184 <abbrev>RFC3658</abbrev>
16187 <surname>Gudmundsson</surname>
16188 <firstname>O.</firstname>
16191 <title>Delegation Signer (DS) Resource Record (RR)</title>
16192 <pubdate>December 2003</pubdate>
16195 <abbrev>RFC3755</abbrev>
16198 <surname>Weiler</surname>
16199 <firstname>S.</firstname>
16202 <title>Legacy Resolver Compatibility for Delegation Signer (DS)</title>
16203 <pubdate>May 2004</pubdate>
16206 <abbrev>RFC3757</abbrev>
16209 <surname>Kolkman</surname>
16210 <firstname>O.</firstname>
16213 <surname>Schlyter</surname>
16214 <firstname>J.</firstname>
16217 <surname>Lewis</surname>
16218 <firstname>E.</firstname>
16221 <title>Domain Name System KEY (DNSKEY) Resource Record
16222 (RR) Secure Entry Point (SEP) Flag</title>
16223 <pubdate>April 2004</pubdate>
16226 <abbrev>RFC3845</abbrev>
16229 <surname>Schlyter</surname>
16230 <firstname>J.</firstname>
16233 <title>DNS Security (DNSSEC) NextSECure (NSEC) RDATA Format</title>
16234 <pubdate>August 2004</pubdate>
16239 <sect2 id="internet_drafts">
16240 <title>Internet Drafts</title>
16242 Internet Drafts (IDs) are rough-draft working documents of
16243 the Internet Engineering Task Force. They are, in essence, RFCs
16244 in the preliminary stages of development. Implementors are
16246 to regard IDs as archival, and they should not be quoted or cited
16247 in any formal documents unless accompanied by the disclaimer that
16248 they are "works in progress." IDs have a lifespan of six months
16249 after which they are deleted unless updated by their authors.
16253 <title>Other Documents About <acronym>BIND</acronym></title>
16259 <surname>Albitz</surname>
16260 <firstname>Paul</firstname>
16263 <firstname>Cricket</firstname>
16264 <surname>Liu</surname>
16267 <title><acronym>DNS</acronym> and <acronym>BIND</acronym></title>
16270 <holder>Sebastopol, CA: O'Reilly and Associates</holder>
16277 <xi:include href="libdns.xml"/>
16282 <reference id="Bv9ARM.ch10">
16283 <title>Manual pages</title>
16284 <xi:include href="../../bin/dig/dig.docbook"/>
16285 <xi:include href="../../bin/dig/host.docbook"/>
16286 <xi:include href="../../bin/dnssec/dnssec-dsfromkey.docbook"/>
16287 <xi:include href="../../bin/dnssec/dnssec-keyfromlabel.docbook"/>
16288 <xi:include href="../../bin/dnssec/dnssec-keygen.docbook"/>
16289 <xi:include href="../../bin/dnssec/dnssec-revoke.docbook"/>
16290 <xi:include href="../../bin/dnssec/dnssec-settime.docbook"/>
16291 <xi:include href="../../bin/dnssec/dnssec-signzone.docbook"/>
16292 <xi:include href="../../bin/check/named-checkconf.docbook"/>
16293 <xi:include href="../../bin/check/named-checkzone.docbook"/>
16294 <xi:include href="../../bin/named/named.docbook"/>
16295 <xi:include href="../../bin/tools/named-journalprint.docbook"/>
16296 <!-- named.conf.docbook and others? -->
16297 <xi:include href="../../bin/nsupdate/nsupdate.docbook"/>
16298 <xi:include href="../../bin/rndc/rndc.docbook"/>
16299 <xi:include href="../../bin/rndc/rndc.conf.docbook"/>
16300 <xi:include href="../../bin/confgen/rndc-confgen.docbook"/>
16301 <xi:include href="../../bin/confgen/ddns-confgen.docbook"/>
16302 <xi:include href="../../bin/tools/arpaname.docbook"/>
16303 <xi:include href="../../bin/tools/genrandom.docbook"/>
16304 <xi:include href="../../bin/tools/isc-hmac-fixup.docbook"/>
16305 <xi:include href="../../bin/tools/nsec3hash.docbook"/>
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