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22 <book xmlns:xi="http://www.w3.org/2001/XInclude">
23 <title>BIND 9 Administrator Reference Manual</title>
36 <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
43 <holder>Internet Software Consortium.</holder>
47 <chapter id="Bv9ARM.ch01">
48 <title>Introduction</title>
50 The Internet Domain Name System (<acronym>DNS</acronym>)
51 consists of the syntax
52 to specify the names of entities in the Internet in a hierarchical
53 manner, the rules used for delegating authority over names, and the
54 system implementation that actually maps names to Internet
55 addresses. <acronym>DNS</acronym> data is maintained in a
57 hierarchical databases.
61 <title>Scope of Document</title>
64 The Berkeley Internet Name Domain
65 (<acronym>BIND</acronym>) implements a
66 domain name server for a number of operating systems. This
67 document provides basic information about the installation and
68 care of the Internet Systems Consortium (<acronym>ISC</acronym>)
69 <acronym>BIND</acronym> version 9 software package for
70 system administrators.
74 This version of the manual corresponds to BIND version 9.8.
79 <title>Organization of This Document</title>
81 In this document, <emphasis>Chapter 1</emphasis> introduces
82 the basic <acronym>DNS</acronym> and <acronym>BIND</acronym> concepts. <emphasis>Chapter 2</emphasis>
83 describes resource requirements for running <acronym>BIND</acronym> in various
84 environments. Information in <emphasis>Chapter 3</emphasis> is
85 <emphasis>task-oriented</emphasis> in its presentation and is
86 organized functionally, to aid in the process of installing the
87 <acronym>BIND</acronym> 9 software. The task-oriented
88 section is followed by
89 <emphasis>Chapter 4</emphasis>, which contains more advanced
90 concepts that the system administrator may need for implementing
91 certain options. <emphasis>Chapter 5</emphasis>
92 describes the <acronym>BIND</acronym> 9 lightweight
93 resolver. The contents of <emphasis>Chapter 6</emphasis> are
94 organized as in a reference manual to aid in the ongoing
95 maintenance of the software. <emphasis>Chapter 7</emphasis> addresses
96 security considerations, and
97 <emphasis>Chapter 8</emphasis> contains troubleshooting help. The
98 main body of the document is followed by several
99 <emphasis>appendices</emphasis> which contain useful reference
100 information, such as a <emphasis>bibliography</emphasis> and
101 historic information related to <acronym>BIND</acronym>
107 <title>Conventions Used in This Document</title>
110 In this document, we use the following general typographic
116 <colspec colname="1" colnum="1" colwidth="3.000in"/>
117 <colspec colname="2" colnum="2" colwidth="2.625in"/>
122 <emphasis>To describe:</emphasis>
127 <emphasis>We use the style:</emphasis>
134 a pathname, filename, URL, hostname,
135 mailing list name, or new term or concept
140 <filename>Fixed width</filename>
153 <userinput>Fixed Width Bold</userinput>
165 <computeroutput>Fixed Width</computeroutput>
174 The following conventions are used in descriptions of the
175 <acronym>BIND</acronym> configuration file:<informaltable colsep="0" frame="all" rowsep="0">
176 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
177 <colspec colname="1" colnum="1" colsep="0" colwidth="3.000in"/>
178 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
181 <entry colname="1" colsep="1" rowsep="1">
183 <emphasis>To describe:</emphasis>
186 <entry colname="2" rowsep="1">
188 <emphasis>We use the style:</emphasis>
193 <entry colname="1" colsep="1" rowsep="1">
198 <entry colname="2" rowsep="1">
200 <literal>Fixed Width</literal>
205 <entry colname="1" colsep="1" rowsep="1">
210 <entry colname="2" rowsep="1">
212 <varname>Fixed Width</varname>
217 <entry colname="1" colsep="1">
224 <optional>Text is enclosed in square brackets</optional>
234 <title>The Domain Name System (<acronym>DNS</acronym>)</title>
236 The purpose of this document is to explain the installation
237 and upkeep of the <acronym>BIND</acronym> (Berkeley Internet
238 Name Domain) software package, and we
239 begin by reviewing the fundamentals of the Domain Name System
240 (<acronym>DNS</acronym>) as they relate to <acronym>BIND</acronym>.
244 <title>DNS Fundamentals</title>
247 The Domain Name System (DNS) is a hierarchical, distributed
248 database. It stores information for mapping Internet host names to
250 addresses and vice versa, mail routing information, and other data
251 used by Internet applications.
255 Clients look up information in the DNS by calling a
256 <emphasis>resolver</emphasis> library, which sends queries to one or
257 more <emphasis>name servers</emphasis> and interprets the responses.
258 The <acronym>BIND</acronym> 9 software distribution
260 name server, <command>named</command>, and a resolver
261 library, <command>liblwres</command>. The older
262 <command>libbind</command> resolver library is also available
263 from ISC as a separate download.
267 <title>Domains and Domain Names</title>
270 The data stored in the DNS is identified by <emphasis>domain names</emphasis> that are organized as a tree according to
271 organizational or administrative boundaries. Each node of the tree,
272 called a <emphasis>domain</emphasis>, is given a label. The domain
274 node is the concatenation of all the labels on the path from the
275 node to the <emphasis>root</emphasis> node. This is represented
276 in written form as a string of labels listed from right to left and
277 separated by dots. A label need only be unique within its parent
282 For example, a domain name for a host at the
283 company <emphasis>Example, Inc.</emphasis> could be
284 <literal>ourhost.example.com</literal>,
285 where <literal>com</literal> is the
286 top level domain to which
287 <literal>ourhost.example.com</literal> belongs,
288 <literal>example</literal> is
289 a subdomain of <literal>com</literal>, and
290 <literal>ourhost</literal> is the
295 For administrative purposes, the name space is partitioned into
296 areas called <emphasis>zones</emphasis>, each starting at a node and
297 extending down to the leaf nodes or to nodes where other zones
299 The data for each zone is stored in a <emphasis>name server</emphasis>, which answers queries about the zone using the
300 <emphasis>DNS protocol</emphasis>.
304 The data associated with each domain name is stored in the
305 form of <emphasis>resource records</emphasis> (<acronym>RR</acronym>s).
306 Some of the supported resource record types are described in
307 <xref linkend="types_of_resource_records_and_when_to_use_them"/>.
311 For more detailed information about the design of the DNS and
312 the DNS protocol, please refer to the standards documents listed in
313 <xref linkend="rfcs"/>.
320 To properly operate a name server, it is important to understand
321 the difference between a <emphasis>zone</emphasis>
322 and a <emphasis>domain</emphasis>.
326 As stated previously, a zone is a point of delegation in
327 the <acronym>DNS</acronym> tree. A zone consists of
328 those contiguous parts of the domain
329 tree for which a name server has complete information and over which
330 it has authority. It contains all domain names from a certain point
331 downward in the domain tree except those which are delegated to
332 other zones. A delegation point is marked by one or more
333 <emphasis>NS records</emphasis> in the
334 parent zone, which should be matched by equivalent NS records at
335 the root of the delegated zone.
339 For instance, consider the <literal>example.com</literal>
340 domain which includes names
341 such as <literal>host.aaa.example.com</literal> and
342 <literal>host.bbb.example.com</literal> even though
343 the <literal>example.com</literal> zone includes
344 only delegations for the <literal>aaa.example.com</literal> and
345 <literal>bbb.example.com</literal> zones. A zone can
347 exactly to a single domain, but could also include only part of a
348 domain, the rest of which could be delegated to other
349 name servers. Every name in the <acronym>DNS</acronym>
351 <emphasis>domain</emphasis>, even if it is
352 <emphasis>terminal</emphasis>, that is, has no
353 <emphasis>subdomains</emphasis>. Every subdomain is a domain and
354 every domain except the root is also a subdomain. The terminology is
355 not intuitive and we suggest that you read RFCs 1033, 1034 and 1035
357 gain a complete understanding of this difficult and subtle
362 Though <acronym>BIND</acronym> is called a "domain name
364 it deals primarily in terms of zones. The master and slave
365 declarations in the <filename>named.conf</filename> file
367 zones, not domains. When you ask some other site if it is willing to
368 be a slave server for your <emphasis>domain</emphasis>, you are
369 actually asking for slave service for some collection of zones.
374 <title>Authoritative Name Servers</title>
377 Each zone is served by at least
378 one <emphasis>authoritative name server</emphasis>,
379 which contains the complete data for the zone.
380 To make the DNS tolerant of server and network failures,
381 most zones have two or more authoritative servers, on
386 Responses from authoritative servers have the "authoritative
387 answer" (AA) bit set in the response packets. This makes them
388 easy to identify when debugging DNS configurations using tools like
389 <command>dig</command> (<xref linkend="diagnostic_tools"/>).
393 <title>The Primary Master</title>
396 The authoritative server where the master copy of the zone
397 data is maintained is called the
398 <emphasis>primary master</emphasis> server, or simply the
399 <emphasis>primary</emphasis>. Typically it loads the zone
400 contents from some local file edited by humans or perhaps
401 generated mechanically from some other local file which is
402 edited by humans. This file is called the
403 <emphasis>zone file</emphasis> or
404 <emphasis>master file</emphasis>.
408 In some cases, however, the master file may not be edited
409 by humans at all, but may instead be the result of
410 <emphasis>dynamic update</emphasis> operations.
415 <title>Slave Servers</title>
417 The other authoritative servers, the <emphasis>slave</emphasis>
418 servers (also known as <emphasis>secondary</emphasis> servers)
420 the zone contents from another server using a replication process
421 known as a <emphasis>zone transfer</emphasis>. Typically the data
423 transferred directly from the primary master, but it is also
425 to transfer it from another slave. In other words, a slave server
426 may itself act as a master to a subordinate slave server.
431 <title>Stealth Servers</title>
434 Usually all of the zone's authoritative servers are listed in
435 NS records in the parent zone. These NS records constitute
436 a <emphasis>delegation</emphasis> of the zone from the parent.
437 The authoritative servers are also listed in the zone file itself,
438 at the <emphasis>top level</emphasis> or <emphasis>apex</emphasis>
439 of the zone. You can list servers in the zone's top-level NS
440 records that are not in the parent's NS delegation, but you cannot
441 list servers in the parent's delegation that are not present at
442 the zone's top level.
446 A <emphasis>stealth server</emphasis> is a server that is
447 authoritative for a zone but is not listed in that zone's NS
448 records. Stealth servers can be used for keeping a local copy of
450 zone to speed up access to the zone's records or to make sure that
452 zone is available even if all the "official" servers for the zone
458 A configuration where the primary master server itself is a
459 stealth server is often referred to as a "hidden primary"
460 configuration. One use for this configuration is when the primary
462 is behind a firewall and therefore unable to communicate directly
463 with the outside world.
471 <title>Caching Name Servers</title>
474 - Terminology here is inconsistent. Probably ought to
475 - convert to using "recursive name server" everywhere
476 - with just a note about "caching" terminology.
480 The resolver libraries provided by most operating systems are
481 <emphasis>stub resolvers</emphasis>, meaning that they are not
483 performing the full DNS resolution process by themselves by talking
484 directly to the authoritative servers. Instead, they rely on a
486 name server to perform the resolution on their behalf. Such a
488 is called a <emphasis>recursive</emphasis> name server; it performs
489 <emphasis>recursive lookups</emphasis> for local clients.
493 To improve performance, recursive servers cache the results of
494 the lookups they perform. Since the processes of recursion and
495 caching are intimately connected, the terms
496 <emphasis>recursive server</emphasis> and
497 <emphasis>caching server</emphasis> are often used synonymously.
501 The length of time for which a record may be retained in
502 the cache of a caching name server is controlled by the
503 Time To Live (TTL) field associated with each resource record.
507 <title>Forwarding</title>
510 Even a caching name server does not necessarily perform
511 the complete recursive lookup itself. Instead, it can
512 <emphasis>forward</emphasis> some or all of the queries
513 that it cannot satisfy from its cache to another caching name
515 commonly referred to as a <emphasis>forwarder</emphasis>.
519 There may be one or more forwarders,
520 and they are queried in turn until the list is exhausted or an
522 is found. Forwarders are typically used when you do not
523 wish all the servers at a given site to interact directly with the
525 the Internet servers. A typical scenario would involve a number
526 of internal <acronym>DNS</acronym> servers and an
527 Internet firewall. Servers unable
528 to pass packets through the firewall would forward to the server
529 that can do it, and that server would query the Internet <acronym>DNS</acronym> servers
530 on the internal server's behalf.
537 <title>Name Servers in Multiple Roles</title>
540 The <acronym>BIND</acronym> name server can
541 simultaneously act as
542 a master for some zones, a slave for other zones, and as a caching
543 (recursive) server for a set of local clients.
547 However, since the functions of authoritative name service
548 and caching/recursive name service are logically separate, it is
549 often advantageous to run them on separate server machines.
551 A server that only provides authoritative name service
552 (an <emphasis>authoritative-only</emphasis> server) can run with
553 recursion disabled, improving reliability and security.
555 A server that is not authoritative for any zones and only provides
556 recursive service to local
557 clients (a <emphasis>caching-only</emphasis> server)
558 does not need to be reachable from the Internet at large and can
559 be placed inside a firewall.
567 <chapter id="Bv9ARM.ch02">
568 <title><acronym>BIND</acronym> Resource Requirements</title>
571 <title>Hardware requirements</title>
574 <acronym>DNS</acronym> hardware requirements have
575 traditionally been quite modest.
576 For many installations, servers that have been pensioned off from
577 active duty have performed admirably as <acronym>DNS</acronym> servers.
580 The DNSSEC features of <acronym>BIND</acronym> 9
581 may prove to be quite
582 CPU intensive however, so organizations that make heavy use of these
583 features may wish to consider larger systems for these applications.
584 <acronym>BIND</acronym> 9 is fully multithreaded, allowing
586 multiprocessor systems for installations that need it.
590 <title>CPU Requirements</title>
592 CPU requirements for <acronym>BIND</acronym> 9 range from
594 for serving of static zones without caching, to enterprise-class
595 machines if you intend to process many dynamic updates and DNSSEC
596 signed zones, serving many thousands of queries per second.
601 <title>Memory Requirements</title>
603 The memory of the server has to be large enough to fit the
604 cache and zones loaded off disk. The <command>max-cache-size</command>
605 option can be used to limit the amount of memory used by the cache,
606 at the expense of reducing cache hit rates and causing more <acronym>DNS</acronym>
608 Additionally, if additional section caching
609 (<xref linkend="acache"/>) is enabled,
610 the <command>max-acache-size</command> option can be used to
612 of memory used by the mechanism.
613 It is still good practice to have enough memory to load
614 all zone and cache data into memory — unfortunately, the best
616 to determine this for a given installation is to watch the name server
617 in operation. After a few weeks the server process should reach
618 a relatively stable size where entries are expiring from the cache as
619 fast as they are being inserted.
622 - Add something here about leaving overhead for attacks?
623 - How much overhead? Percentage?
628 <title>Name Server Intensive Environment Issues</title>
630 For name server intensive environments, there are two alternative
631 configurations that may be used. The first is where clients and
632 any second-level internal name servers query a main name server, which
633 has enough memory to build a large cache. This approach minimizes
634 the bandwidth used by external name lookups. The second alternative
635 is to set up second-level internal name servers to make queries
637 In this configuration, none of the individual machines needs to
638 have as much memory or CPU power as in the first alternative, but
639 this has the disadvantage of making many more external queries,
640 as none of the name servers share their cached data.
645 <title>Supported Operating Systems</title>
647 ISC <acronym>BIND</acronym> 9 compiles and runs on a large
649 of Unix-like operating systems and on
650 Microsoft Windows Server 2003 and 2008, and Windows XP and Vista.
652 list of supported systems, see the README file in the top level
654 of the BIND 9 source distribution.
659 <chapter id="Bv9ARM.ch03">
660 <title>Name Server Configuration</title>
662 In this chapter we provide some suggested configurations along
663 with guidelines for their use. We suggest reasonable values for
664 certain option settings.
667 <sect1 id="sample_configuration">
668 <title>Sample Configurations</title>
670 <title>A Caching-only Name Server</title>
672 The following sample configuration is appropriate for a caching-only
673 name server for use by clients internal to a corporation. All
675 from outside clients are refused using the <command>allow-query</command>
676 option. Alternatively, the same effect could be achieved using
682 // Two corporate subnets we wish to allow queries from.
683 acl corpnets { 192.168.4.0/24; 192.168.7.0/24; };
686 directory "/etc/namedb";
688 allow-query { corpnets; };
690 // Provide a reverse mapping for the loopback
692 zone "0.0.127.in-addr.arpa" {
694 file "localhost.rev";
702 <title>An Authoritative-only Name Server</title>
704 This sample configuration is for an authoritative-only server
705 that is the master server for "<filename>example.com</filename>"
706 and a slave for the subdomain "<filename>eng.example.com</filename>".
712 directory "/etc/namedb";
713 // Do not allow access to cache
714 allow-query-cache { none; };
715 // This is the default
716 allow-query { any; };
717 // Do not provide recursive service
721 // Provide a reverse mapping for the loopback
723 zone "0.0.127.in-addr.arpa" {
725 file "localhost.rev";
728 // We are the master server for example.com
731 file "example.com.db";
732 // IP addresses of slave servers allowed to
733 // transfer example.com
739 // We are a slave server for eng.example.com
740 zone "eng.example.com" {
742 file "eng.example.com.bk";
743 // IP address of eng.example.com master server
744 masters { 192.168.4.12; };
752 <title>Load Balancing</title>
754 - Add explanation of why load balancing is fragile at best
755 - and completely pointless in the general case.
759 A primitive form of load balancing can be achieved in
760 the <acronym>DNS</acronym> by using multiple records
761 (such as multiple A records) for one name.
765 For example, if you have three WWW servers with network addresses
766 of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the
767 following means that clients will connect to each machine one third
771 <informaltable colsep="0" rowsep="0">
772 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="2Level-table">
773 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
774 <colspec colname="2" colnum="2" colsep="0" colwidth="0.500in"/>
775 <colspec colname="3" colnum="3" colsep="0" colwidth="0.750in"/>
776 <colspec colname="4" colnum="4" colsep="0" colwidth="0.750in"/>
777 <colspec colname="5" colnum="5" colsep="0" colwidth="2.028in"/>
802 Resource Record (RR) Data
809 <literal>www</literal>
814 <literal>600</literal>
819 <literal>IN</literal>
829 <literal>10.0.0.1</literal>
839 <literal>600</literal>
844 <literal>IN</literal>
854 <literal>10.0.0.2</literal>
864 <literal>600</literal>
869 <literal>IN</literal>
879 <literal>10.0.0.3</literal>
887 When a resolver queries for these records, <acronym>BIND</acronym> will rotate
888 them and respond to the query with the records in a different
889 order. In the example above, clients will randomly receive
890 records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients
891 will use the first record returned and discard the rest.
894 For more detail on ordering responses, check the
895 <command>rrset-order</command> sub-statement in the
896 <command>options</command> statement, see
897 <xref endterm="rrset_ordering_title" linkend="rrset_ordering"/>.
903 <title>Name Server Operations</title>
906 <title>Tools for Use With the Name Server Daemon</title>
908 This section describes several indispensable diagnostic,
909 administrative and monitoring tools available to the system
910 administrator for controlling and debugging the name server
913 <sect3 id="diagnostic_tools">
914 <title>Diagnostic Tools</title>
916 The <command>dig</command>, <command>host</command>, and
917 <command>nslookup</command> programs are all command
919 for manually querying name servers. They differ in style and
925 <term id="dig"><command>dig</command></term>
928 The domain information groper (<command>dig</command>)
929 is the most versatile and complete of these lookup tools.
930 It has two modes: simple interactive
931 mode for a single query, and batch mode which executes a
933 each in a list of several query lines. All query options are
935 from the command line.
937 <cmdsynopsis label="Usage">
938 <command>dig</command>
939 <arg>@<replaceable>server</replaceable></arg>
940 <arg choice="plain"><replaceable>domain</replaceable></arg>
941 <arg><replaceable>query-type</replaceable></arg>
942 <arg><replaceable>query-class</replaceable></arg>
943 <arg>+<replaceable>query-option</replaceable></arg>
944 <arg>-<replaceable>dig-option</replaceable></arg>
945 <arg>%<replaceable>comment</replaceable></arg>
948 The usual simple use of <command>dig</command> will take the form
951 <command>dig @server domain query-type query-class</command>
954 For more information and a list of available commands and
955 options, see the <command>dig</command> man
962 <term><command>host</command></term>
965 The <command>host</command> utility emphasizes
967 and ease of use. By default, it converts
968 between host names and Internet addresses, but its
970 can be extended with the use of options.
972 <cmdsynopsis label="Usage">
973 <command>host</command>
974 <arg>-aCdlnrsTwv</arg>
975 <arg>-c <replaceable>class</replaceable></arg>
976 <arg>-N <replaceable>ndots</replaceable></arg>
977 <arg>-t <replaceable>type</replaceable></arg>
978 <arg>-W <replaceable>timeout</replaceable></arg>
979 <arg>-R <replaceable>retries</replaceable></arg>
980 <arg>-m <replaceable>flag</replaceable></arg>
983 <arg choice="plain"><replaceable>hostname</replaceable></arg>
984 <arg><replaceable>server</replaceable></arg>
987 For more information and a list of available commands and
988 options, see the <command>host</command> man
995 <term><command>nslookup</command></term>
997 <para><command>nslookup</command>
998 has two modes: interactive and
999 non-interactive. Interactive mode allows the user to
1000 query name servers for information about various
1001 hosts and domains or to print a list of hosts in a
1002 domain. Non-interactive mode is used to print just
1003 the name and requested information for a host or
1006 <cmdsynopsis label="Usage">
1007 <command>nslookup</command>
1008 <arg rep="repeat">-option</arg>
1010 <arg><replaceable>host-to-find</replaceable></arg>
1011 <arg>- <arg>server</arg></arg>
1015 Interactive mode is entered when no arguments are given (the
1016 default name server will be used) or when the first argument
1018 hyphen (`-') and the second argument is the host name or
1023 Non-interactive mode is used when the name or Internet
1025 of the host to be looked up is given as the first argument.
1027 optional second argument specifies the host name or address
1031 Due to its arcane user interface and frequently inconsistent
1032 behavior, we do not recommend the use of <command>nslookup</command>.
1033 Use <command>dig</command> instead.
1041 <sect3 id="admin_tools">
1042 <title>Administrative Tools</title>
1044 Administrative tools play an integral part in the management
1048 <varlistentry id="named-checkconf" xreflabel="Named Configuration Checking application">
1050 <term><command>named-checkconf</command></term>
1053 The <command>named-checkconf</command> program
1054 checks the syntax of a <filename>named.conf</filename> file.
1056 <cmdsynopsis label="Usage">
1057 <command>named-checkconf</command>
1059 <arg>-t <replaceable>directory</replaceable></arg>
1060 <arg><replaceable>filename</replaceable></arg>
1064 <varlistentry id="named-checkzone" xreflabel="Zone Checking application">
1066 <term><command>named-checkzone</command></term>
1069 The <command>named-checkzone</command> program
1070 checks a master file for
1071 syntax and consistency.
1073 <cmdsynopsis label="Usage">
1074 <command>named-checkzone</command>
1076 <arg>-c <replaceable>class</replaceable></arg>
1077 <arg>-o <replaceable>output</replaceable></arg>
1078 <arg>-t <replaceable>directory</replaceable></arg>
1079 <arg>-w <replaceable>directory</replaceable></arg>
1080 <arg>-k <replaceable>(ignore|warn|fail)</replaceable></arg>
1081 <arg>-n <replaceable>(ignore|warn|fail)</replaceable></arg>
1082 <arg>-W <replaceable>(ignore|warn)</replaceable></arg>
1083 <arg choice="plain"><replaceable>zone</replaceable></arg>
1084 <arg><replaceable>filename</replaceable></arg>
1088 <varlistentry id="named-compilezone" xreflabel="Zone Compilation application">
1089 <term><command>named-compilezone</command></term>
1092 Similar to <command>named-checkzone,</command> but
1093 it always dumps the zone content to a specified file
1094 (typically in a different format).
1098 <varlistentry id="rndc" xreflabel="Remote Name Daemon Control application">
1100 <term><command>rndc</command></term>
1103 The remote name daemon control
1104 (<command>rndc</command>) program allows the
1106 administrator to control the operation of a name server.
1107 Since <acronym>BIND</acronym> 9.2, <command>rndc</command>
1108 supports all the commands of the BIND 8 <command>ndc</command>
1109 utility except <command>ndc start</command> and
1110 <command>ndc restart</command>, which were also
1111 not supported in <command>ndc</command>'s
1113 If you run <command>rndc</command> without any
1115 it will display a usage message as follows:
1117 <cmdsynopsis label="Usage">
1118 <command>rndc</command>
1119 <arg>-c <replaceable>config</replaceable></arg>
1120 <arg>-s <replaceable>server</replaceable></arg>
1121 <arg>-p <replaceable>port</replaceable></arg>
1122 <arg>-y <replaceable>key</replaceable></arg>
1123 <arg choice="plain"><replaceable>command</replaceable></arg>
1124 <arg rep="repeat"><replaceable>command</replaceable></arg>
1126 <para>The <command>command</command>
1127 is one of the following:
1133 <term><userinput>reload</userinput></term>
1136 Reload configuration file and zones.
1142 <term><userinput>reload <replaceable>zone</replaceable>
1143 <optional><replaceable>class</replaceable>
1144 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1147 Reload the given zone.
1153 <term><userinput>refresh <replaceable>zone</replaceable>
1154 <optional><replaceable>class</replaceable>
1155 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1158 Schedule zone maintenance for the given zone.
1164 <term><userinput>retransfer <replaceable>zone</replaceable>
1166 <optional><replaceable>class</replaceable>
1167 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1170 Retransfer the given zone from the master.
1176 <term><userinput>sign <replaceable>zone</replaceable>
1177 <optional><replaceable>class</replaceable>
1178 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1181 Fetch all DNSSEC keys for the given zone
1182 from the key directory (see
1183 <command>key-directory</command> in
1184 <xref linkend="options"/>). If they are within
1185 their publication period, merge them into the
1186 zone's DNSKEY RRset. If the DNSKEY RRset
1187 is changed, then the zone is automatically
1188 re-signed with the new key set.
1191 This command requires that the
1192 <command>auto-dnssec</command> zone option be set
1193 to <literal>allow</literal> or
1194 <literal>maintain</literal>,
1195 and also requires the zone to be configured to
1197 See <xref linkend="dynamic_update_policies"/> for
1204 <term><userinput>loadkeys <replaceable>zone</replaceable>
1205 <optional><replaceable>class</replaceable>
1206 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1209 Fetch all DNSSEC keys for the given zone
1210 from the key directory (see
1211 <command>key-directory</command> in
1212 <xref linkend="options"/>). If they are within
1213 their publication period, merge them into the
1214 zone's DNSKEY RRset. Unlike <command>rndc
1215 sign</command>, however, the zone is not
1216 immediately re-signed by the new keys, but is
1217 allowed to incrementally re-sign over time.
1220 This command requires that the
1221 <command>auto-dnssec</command> zone option
1222 be set to <literal>maintain</literal>,
1223 and also requires the zone to be configured to
1225 See <xref linkend="dynamic_update_policies"/> for
1232 <term><userinput>freeze
1233 <optional><replaceable>zone</replaceable>
1234 <optional><replaceable>class</replaceable>
1235 <optional><replaceable>view</replaceable></optional></optional></optional></userinput></term>
1238 Suspend updates to a dynamic zone. If no zone is
1240 then all zones are suspended. This allows manual
1241 edits to be made to a zone normally updated by dynamic
1243 also causes changes in the journal file to be synced
1245 and the journal file to be removed. All dynamic
1246 update attempts will
1247 be refused while the zone is frozen.
1253 <term><userinput>thaw
1254 <optional><replaceable>zone</replaceable>
1255 <optional><replaceable>class</replaceable>
1256 <optional><replaceable>view</replaceable></optional></optional></optional></userinput></term>
1259 Enable updates to a frozen dynamic zone. If no zone
1261 specified, then all frozen zones are enabled. This
1263 the server to reload the zone from disk, and
1264 re-enables dynamic updates
1265 after the load has completed. After a zone is thawed,
1267 will no longer be refused.
1273 <term><userinput>notify <replaceable>zone</replaceable>
1274 <optional><replaceable>class</replaceable>
1275 <optional><replaceable>view</replaceable></optional></optional></userinput></term>
1278 Resend NOTIFY messages for the zone.
1284 <term><userinput>reconfig</userinput></term>
1287 Reload the configuration file and load new zones,
1288 but do not reload existing zone files even if they
1290 This is faster than a full <command>reload</command> when there
1291 is a large number of zones because it avoids the need
1293 modification times of the zones files.
1299 <term><userinput>stats</userinput></term>
1302 Write server statistics to the statistics file.
1308 <term><userinput>querylog</userinput></term>
1311 Toggle query logging. Query logging can also be enabled
1312 by explicitly directing the <command>queries</command>
1313 <command>category</command> to a
1314 <command>channel</command> in the
1315 <command>logging</command> section of
1316 <filename>named.conf</filename> or by specifying
1317 <command>querylog yes;</command> in the
1318 <command>options</command> section of
1319 <filename>named.conf</filename>.
1325 <term><userinput>dumpdb
1326 <optional>-all|-cache|-zone</optional>
1327 <optional><replaceable>view ...</replaceable></optional></userinput></term>
1330 Dump the server's caches (default) and/or zones to
1332 dump file for the specified views. If no view is
1340 <term><userinput>secroots
1341 <optional><replaceable>view ...</replaceable></optional></userinput></term>
1344 Dump the server's security roots to the secroots
1345 file for the specified views. If no view is
1346 specified, security roots for all
1353 <term><userinput>stop <optional>-p</optional></userinput></term>
1356 Stop the server, making sure any recent changes
1357 made through dynamic update or IXFR are first saved to
1358 the master files of the updated zones.
1359 If <option>-p</option> is specified <command>named</command>'s process id is returned.
1360 This allows an external process to determine when <command>named</command>
1361 had completed stopping.
1367 <term><userinput>halt <optional>-p</optional></userinput></term>
1370 Stop the server immediately. Recent changes
1371 made through dynamic update or IXFR are not saved to
1372 the master files, but will be rolled forward from the
1373 journal files when the server is restarted.
1374 If <option>-p</option> is specified <command>named</command>'s process id is returned.
1375 This allows an external process to determine when <command>named</command>
1376 had completed halting.
1382 <term><userinput>trace</userinput></term>
1385 Increment the servers debugging level by one.
1391 <term><userinput>trace <replaceable>level</replaceable></userinput></term>
1394 Sets the server's debugging level to an explicit
1401 <term><userinput>notrace</userinput></term>
1404 Sets the server's debugging level to 0.
1410 <term><userinput>flush</userinput></term>
1413 Flushes the server's cache.
1419 <term><userinput>flushname</userinput> <replaceable>name</replaceable></term>
1422 Flushes the given name from the server's cache.
1428 <term><userinput>status</userinput></term>
1431 Display status of the server.
1432 Note that the number of zones includes the internal <command>bind/CH</command> zone
1433 and the default <command>./IN</command>
1434 hint zone if there is not an
1435 explicit root zone configured.
1441 <term><userinput>recursing</userinput></term>
1444 Dump the list of queries <command>named</command> is currently recursing
1451 <term><userinput>validation
1452 <optional>on|off</optional>
1453 <optional><replaceable>view ...</replaceable></optional>
1457 Enable or disable DNSSEC validation.
1458 Note <command>dnssec-enable</command> also needs to be
1459 set to <userinput>yes</userinput> to be effective.
1460 It defaults to enabled.
1466 <term><userinput>tsig-list</userinput></term>
1469 List the names of all TSIG keys currently configured
1470 for use by <command>named</command> in each view. The
1471 list both statically configured keys and dynamic
1472 TKEY-negotiated keys.
1478 <term><userinput>tsig-delete</userinput>
1479 <replaceable>keyname</replaceable>
1480 <optional><replaceable>view</replaceable></optional></term>
1483 Delete a given TKEY-negotated key from the server.
1484 (This does not apply to statically configured TSIG
1491 <term><userinput>addzone
1492 <replaceable>zone</replaceable>
1493 <optional><replaceable>class</replaceable>
1494 <optional><replaceable>view</replaceable></optional></optional>
1495 <replaceable>configuration</replaceable>
1499 Add a zone while the server is running. This
1500 command requires the
1501 <command>allow-new-zones</command> option to be set
1502 to <userinput>yes</userinput>. The
1503 <replaceable>configuration</replaceable> string
1504 specified on the command line is the zone
1505 configuration text that would ordinarily be
1506 placed in <filename>named.conf</filename>.
1509 The configuration is saved in a file called
1510 <filename><replaceable>hash</replaceable>.nzf</filename>,
1511 where <replaceable>hash</replaceable> is a
1512 cryptographic hash generated from the name of
1513 the view. When <command>named</command> is
1514 restarted, the file will be loaded into the view
1515 configuration, so that zones that were added
1516 can persist after a restart.
1519 This sample <command>addzone</command> command
1520 would add the zone <literal>example.com</literal>
1521 to the default view:
1524 <prompt>$ </prompt><userinput>rndc addzone example.com '{ type master; file "example.com.db"; };'</userinput>
1527 (Note the brackets and semi-colon around the zone
1528 configuration text.)
1534 <term><userinput>delzone
1535 <replaceable>zone</replaceable>
1536 <optional><replaceable>class</replaceable>
1537 <optional><replaceable>view</replaceable></optional></optional>
1541 Delete a zone while the server is running.
1542 Only zones that were originally added via
1543 <command>rndc addzone</command> can be deleted
1552 A configuration file is required, since all
1553 communication with the server is authenticated with
1554 digital signatures that rely on a shared secret, and
1555 there is no way to provide that secret other than with a
1556 configuration file. The default location for the
1557 <command>rndc</command> configuration file is
1558 <filename>/etc/rndc.conf</filename>, but an
1560 location can be specified with the <option>-c</option>
1561 option. If the configuration file is not found,
1562 <command>rndc</command> will also look in
1563 <filename>/etc/rndc.key</filename> (or whatever
1564 <varname>sysconfdir</varname> was defined when
1565 the <acronym>BIND</acronym> build was
1567 The <filename>rndc.key</filename> file is
1569 running <command>rndc-confgen -a</command> as
1571 <xref linkend="controls_statement_definition_and_usage"/>.
1575 The format of the configuration file is similar to
1576 that of <filename>named.conf</filename>, but
1578 only four statements, the <command>options</command>,
1579 <command>key</command>, <command>server</command> and
1580 <command>include</command>
1581 statements. These statements are what associate the
1582 secret keys to the servers with which they are meant to
1583 be shared. The order of statements is not
1588 The <command>options</command> statement has
1590 <command>default-server</command>, <command>default-key</command>,
1591 and <command>default-port</command>.
1592 <command>default-server</command> takes a
1593 host name or address argument and represents the server
1595 be contacted if no <option>-s</option>
1596 option is provided on the command line.
1597 <command>default-key</command> takes
1598 the name of a key as its argument, as defined by a <command>key</command> statement.
1599 <command>default-port</command> specifies the
1601 <command>rndc</command> should connect if no
1602 port is given on the command line or in a
1603 <command>server</command> statement.
1607 The <command>key</command> statement defines a
1609 by <command>rndc</command> when authenticating
1611 <command>named</command>. Its syntax is
1613 <command>key</command> statement in <filename>named.conf</filename>.
1614 The keyword <userinput>key</userinput> is
1615 followed by a key name, which must be a valid
1616 domain name, though it need not actually be hierarchical;
1618 a string like "<userinput>rndc_key</userinput>" is a valid
1620 The <command>key</command> statement has two
1622 <command>algorithm</command> and <command>secret</command>.
1623 While the configuration parser will accept any string as the
1625 to algorithm, currently only the string "<userinput>hmac-md5</userinput>"
1626 has any meaning. The secret is a base-64 encoded string
1627 as specified in RFC 3548.
1631 The <command>server</command> statement
1633 defined using the <command>key</command>
1634 statement with a server.
1635 The keyword <userinput>server</userinput> is followed by a
1636 host name or address. The <command>server</command> statement
1637 has two clauses: <command>key</command> and <command>port</command>.
1638 The <command>key</command> clause specifies the
1640 to be used when communicating with this server, and the
1641 <command>port</command> clause can be used to
1642 specify the port <command>rndc</command> should
1648 A sample minimal configuration file is as follows:
1653 algorithm "hmac-md5";
1655 "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
1658 default-server 127.0.0.1;
1659 default-key rndc_key;
1664 This file, if installed as <filename>/etc/rndc.conf</filename>,
1665 would allow the command:
1669 <prompt>$ </prompt><userinput>rndc reload</userinput>
1673 to connect to 127.0.0.1 port 953 and cause the name server
1674 to reload, if a name server on the local machine were
1676 following controls statements:
1682 allow { localhost; } keys { rndc_key; };
1687 and it had an identical key statement for
1688 <literal>rndc_key</literal>.
1692 Running the <command>rndc-confgen</command>
1694 conveniently create a <filename>rndc.conf</filename>
1695 file for you, and also display the
1696 corresponding <command>controls</command>
1697 statement that you need to
1698 add to <filename>named.conf</filename>.
1700 you can run <command>rndc-confgen -a</command>
1702 a <filename>rndc.key</filename> file and not
1704 <filename>named.conf</filename> at all.
1715 <title>Signals</title>
1717 Certain UNIX signals cause the name server to take specific
1718 actions, as described in the following table. These signals can
1719 be sent using the <command>kill</command> command.
1721 <informaltable frame="all">
1723 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
1724 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
1728 <para><command>SIGHUP</command></para>
1732 Causes the server to read <filename>named.conf</filename> and
1733 reload the database.
1739 <para><command>SIGTERM</command></para>
1743 Causes the server to clean up and exit.
1749 <para><command>SIGINT</command></para>
1753 Causes the server to clean up and exit.
1764 <chapter id="Bv9ARM.ch04">
1765 <title>Advanced DNS Features</title>
1769 <title>Notify</title>
1771 <acronym>DNS</acronym> NOTIFY is a mechanism that allows master
1772 servers to notify their slave servers of changes to a zone's data. In
1773 response to a <command>NOTIFY</command> from a master server, the
1774 slave will check to see that its version of the zone is the
1775 current version and, if not, initiate a zone transfer.
1779 For more information about <acronym>DNS</acronym>
1780 <command>NOTIFY</command>, see the description of the
1781 <command>notify</command> option in <xref linkend="boolean_options"/> and
1782 the description of the zone option <command>also-notify</command> in
1783 <xref linkend="zone_transfers"/>. The <command>NOTIFY</command>
1784 protocol is specified in RFC 1996.
1788 As a slave zone can also be a master to other slaves, <command>named</command>,
1789 by default, sends <command>NOTIFY</command> messages for every zone
1790 it loads. Specifying <command>notify master-only;</command> will
1791 cause <command>named</command> to only send <command>NOTIFY</command> for master
1792 zones that it loads.
1797 <sect1 id="dynamic_update">
1798 <title>Dynamic Update</title>
1801 Dynamic Update is a method for adding, replacing or deleting
1802 records in a master server by sending it a special form of DNS
1803 messages. The format and meaning of these messages is specified
1808 Dynamic update is enabled by including an
1809 <command>allow-update</command> or an <command>update-policy</command>
1810 clause in the <command>zone</command> statement.
1814 If the zone's <command>update-policy</command> is set to
1815 <userinput>local</userinput>, updates to the zone
1816 will be permitted for the key <varname>local-ddns</varname>,
1817 which will be generated by <command>named</command> at startup.
1818 See <xref linkend="dynamic_update_policies"/> for more details.
1822 Dynamic updates using Kerberos signed requests can be made
1823 using the TKEY/GSS protocol by setting either the
1824 <command>tkey-gssapi-keytab</command> option, or alternatively
1825 by setting both the <command>tkey-gssapi-credential</command>
1826 and <command>tkey-domain</command> options. Once enabled,
1827 Kerberos signed requests will be matched against the update
1828 policies for the zone, using the Kerberos principal as the
1829 signer for the request.
1833 Updating of secure zones (zones using DNSSEC) follows RFC
1834 3007: RRSIG, NSEC and NSEC3 records affected by updates are
1835 automatically regenerated by the server using an online
1836 zone key. Update authorization is based on transaction
1837 signatures and an explicit server policy.
1840 <sect2 id="journal">
1841 <title>The journal file</title>
1844 All changes made to a zone using dynamic update are stored
1845 in the zone's journal file. This file is automatically created
1846 by the server when the first dynamic update takes place.
1847 The name of the journal file is formed by appending the extension
1848 <filename>.jnl</filename> to the name of the
1850 file unless specifically overridden. The journal file is in a
1851 binary format and should not be edited manually.
1855 The server will also occasionally write ("dump")
1856 the complete contents of the updated zone to its zone file.
1857 This is not done immediately after
1858 each dynamic update, because that would be too slow when a large
1859 zone is updated frequently. Instead, the dump is delayed by
1860 up to 15 minutes, allowing additional updates to take place.
1861 During the dump process, transient files will be created
1862 with the extensions <filename>.jnw</filename> and
1863 <filename>.jbk</filename>; under ordinary circumstances, these
1864 will be removed when the dump is complete, and can be safely
1869 When a server is restarted after a shutdown or crash, it will replay
1870 the journal file to incorporate into the zone any updates that
1872 place after the last zone dump.
1876 Changes that result from incoming incremental zone transfers are
1878 journalled in a similar way.
1882 The zone files of dynamic zones cannot normally be edited by
1883 hand because they are not guaranteed to contain the most recent
1884 dynamic changes — those are only in the journal file.
1885 The only way to ensure that the zone file of a dynamic zone
1886 is up to date is to run <command>rndc stop</command>.
1890 If you have to make changes to a dynamic zone
1891 manually, the following procedure will work: Disable dynamic updates
1893 <command>rndc freeze <replaceable>zone</replaceable></command>.
1894 This will also remove the zone's <filename>.jnl</filename> file
1895 and update the master file. Edit the zone file. Run
1896 <command>rndc thaw <replaceable>zone</replaceable></command>
1897 to reload the changed zone and re-enable dynamic updates.
1904 <sect1 id="incremental_zone_transfers">
1905 <title>Incremental Zone Transfers (IXFR)</title>
1908 The incremental zone transfer (IXFR) protocol is a way for
1909 slave servers to transfer only changed data, instead of having to
1910 transfer the entire zone. The IXFR protocol is specified in RFC
1911 1995. See <xref linkend="proposed_standards"/>.
1915 When acting as a master, <acronym>BIND</acronym> 9
1916 supports IXFR for those zones
1917 where the necessary change history information is available. These
1918 include master zones maintained by dynamic update and slave zones
1919 whose data was obtained by IXFR. For manually maintained master
1920 zones, and for slave zones obtained by performing a full zone
1921 transfer (AXFR), IXFR is supported only if the option
1922 <command>ixfr-from-differences</command> is set
1923 to <userinput>yes</userinput>.
1927 When acting as a slave, <acronym>BIND</acronym> 9 will attempt
1928 to use IXFR unless it is explicitly disabled via the
1929 <command>request-ixfr</command> option or the use of
1930 <command>ixfr-from-differences</command>. For
1931 more information about disabling IXFR, see the description
1932 of the <command>request-ixfr</command> clause of the
1933 <command>server</command> statement.
1938 <title>Split DNS</title>
1940 Setting up different views, or visibility, of the DNS space to
1941 internal and external resolvers is usually referred to as a
1942 <emphasis>Split DNS</emphasis> setup. There are several
1943 reasons an organization would want to set up its DNS this way.
1946 One common reason for setting up a DNS system this way is
1947 to hide "internal" DNS information from "external" clients on the
1948 Internet. There is some debate as to whether or not this is actually
1950 Internal DNS information leaks out in many ways (via email headers,
1951 for example) and most savvy "attackers" can find the information
1952 they need using other means.
1953 However, since listing addresses of internal servers that
1954 external clients cannot possibly reach can result in
1955 connection delays and other annoyances, an organization may
1956 choose to use a Split DNS to present a consistent view of itself
1957 to the outside world.
1960 Another common reason for setting up a Split DNS system is
1961 to allow internal networks that are behind filters or in RFC 1918
1962 space (reserved IP space, as documented in RFC 1918) to resolve DNS
1963 on the Internet. Split DNS can also be used to allow mail from outside
1964 back in to the internal network.
1967 <title>Example split DNS setup</title>
1969 Let's say a company named <emphasis>Example, Inc.</emphasis>
1970 (<literal>example.com</literal>)
1971 has several corporate sites that have an internal network with
1973 Internet Protocol (IP) space and an external demilitarized zone (DMZ),
1974 or "outside" section of a network, that is available to the public.
1977 <emphasis>Example, Inc.</emphasis> wants its internal clients
1978 to be able to resolve external hostnames and to exchange mail with
1979 people on the outside. The company also wants its internal resolvers
1980 to have access to certain internal-only zones that are not available
1981 at all outside of the internal network.
1984 In order to accomplish this, the company will set up two sets
1985 of name servers. One set will be on the inside network (in the
1987 IP space) and the other set will be on bastion hosts, which are
1989 hosts that can talk to both sides of its network, in the DMZ.
1992 The internal servers will be configured to forward all queries,
1993 except queries for <filename>site1.internal</filename>, <filename>site2.internal</filename>, <filename>site1.example.com</filename>,
1994 and <filename>site2.example.com</filename>, to the servers
1996 DMZ. These internal servers will have complete sets of information
1997 for <filename>site1.example.com</filename>, <filename>site2.example.com</filename>, <filename>site1.internal</filename>,
1998 and <filename>site2.internal</filename>.
2001 To protect the <filename>site1.internal</filename> and <filename>site2.internal</filename> domains,
2002 the internal name servers must be configured to disallow all queries
2003 to these domains from any external hosts, including the bastion
2007 The external servers, which are on the bastion hosts, will
2008 be configured to serve the "public" version of the <filename>site1</filename> and <filename>site2.example.com</filename> zones.
2009 This could include things such as the host records for public servers
2010 (<filename>www.example.com</filename> and <filename>ftp.example.com</filename>),
2011 and mail exchange (MX) records (<filename>a.mx.example.com</filename> and <filename>b.mx.example.com</filename>).
2014 In addition, the public <filename>site1</filename> and <filename>site2.example.com</filename> zones
2015 should have special MX records that contain wildcard (`*') records
2016 pointing to the bastion hosts. This is needed because external mail
2017 servers do not have any other way of looking up how to deliver mail
2018 to those internal hosts. With the wildcard records, the mail will
2019 be delivered to the bastion host, which can then forward it on to
2023 Here's an example of a wildcard MX record:
2025 <programlisting>* IN MX 10 external1.example.com.</programlisting>
2027 Now that they accept mail on behalf of anything in the internal
2028 network, the bastion hosts will need to know how to deliver mail
2029 to internal hosts. In order for this to work properly, the resolvers
2031 the bastion hosts will need to be configured to point to the internal
2032 name servers for DNS resolution.
2035 Queries for internal hostnames will be answered by the internal
2036 servers, and queries for external hostnames will be forwarded back
2037 out to the DNS servers on the bastion hosts.
2040 In order for all this to work properly, internal clients will
2041 need to be configured to query <emphasis>only</emphasis> the internal
2042 name servers for DNS queries. This could also be enforced via
2044 filtering on the network.
2047 If everything has been set properly, <emphasis>Example, Inc.</emphasis>'s
2048 internal clients will now be able to:
2053 Look up any hostnames in the <literal>site1</literal>
2055 <literal>site2.example.com</literal> zones.
2060 Look up any hostnames in the <literal>site1.internal</literal> and
2061 <literal>site2.internal</literal> domains.
2065 <simpara>Look up any hostnames on the Internet.</simpara>
2068 <simpara>Exchange mail with both internal and external people.</simpara>
2072 Hosts on the Internet will be able to:
2077 Look up any hostnames in the <literal>site1</literal>
2079 <literal>site2.example.com</literal> zones.
2084 Exchange mail with anyone in the <literal>site1</literal> and
2085 <literal>site2.example.com</literal> zones.
2091 Here is an example configuration for the setup we just
2092 described above. Note that this is only configuration information;
2093 for information on how to configure your zone files, see <xref linkend="sample_configuration"/>.
2097 Internal DNS server config:
2102 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
2104 acl externals { <varname>bastion-ips-go-here</varname>; };
2110 // forward to external servers
2112 <varname>bastion-ips-go-here</varname>;
2114 // sample allow-transfer (no one)
2115 allow-transfer { none; };
2116 // restrict query access
2117 allow-query { internals; externals; };
2118 // restrict recursion
2119 allow-recursion { internals; };
2124 // sample master zone
2125 zone "site1.example.com" {
2127 file "m/site1.example.com";
2128 // do normal iterative resolution (do not forward)
2130 allow-query { internals; externals; };
2131 allow-transfer { internals; };
2134 // sample slave zone
2135 zone "site2.example.com" {
2137 file "s/site2.example.com";
2138 masters { 172.16.72.3; };
2140 allow-query { internals; externals; };
2141 allow-transfer { internals; };
2144 zone "site1.internal" {
2146 file "m/site1.internal";
2148 allow-query { internals; };
2149 allow-transfer { internals; }
2152 zone "site2.internal" {
2154 file "s/site2.internal";
2155 masters { 172.16.72.3; };
2157 allow-query { internals };
2158 allow-transfer { internals; }
2163 External (bastion host) DNS server config:
2167 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
2169 acl externals { bastion-ips-go-here; };
2174 // sample allow-transfer (no one)
2175 allow-transfer { none; };
2176 // default query access
2177 allow-query { any; };
2178 // restrict cache access
2179 allow-query-cache { internals; externals; };
2180 // restrict recursion
2181 allow-recursion { internals; externals; };
2186 // sample slave zone
2187 zone "site1.example.com" {
2189 file "m/site1.foo.com";
2190 allow-transfer { internals; externals; };
2193 zone "site2.example.com" {
2195 file "s/site2.foo.com";
2196 masters { another_bastion_host_maybe; };
2197 allow-transfer { internals; externals; }
2202 In the <filename>resolv.conf</filename> (or equivalent) on
2203 the bastion host(s):
2208 nameserver 172.16.72.2
2209 nameserver 172.16.72.3
2210 nameserver 172.16.72.4
2218 This is a short guide to setting up Transaction SIGnatures
2219 (TSIG) based transaction security in <acronym>BIND</acronym>. It describes changes
2220 to the configuration file as well as what changes are required for
2221 different features, including the process of creating transaction
2222 keys and using transaction signatures with <acronym>BIND</acronym>.
2225 <acronym>BIND</acronym> primarily supports TSIG for server
2226 to server communication.
2227 This includes zone transfer, notify, and recursive query messages.
2228 Resolvers based on newer versions of <acronym>BIND</acronym> 8 have limited support
2233 TSIG can also be useful for dynamic update. A primary
2234 server for a dynamic zone should control access to the dynamic
2235 update service, but IP-based access control is insufficient.
2236 The cryptographic access control provided by TSIG
2237 is far superior. The <command>nsupdate</command>
2238 program supports TSIG via the <option>-k</option> and
2239 <option>-y</option> command line options or inline by use
2240 of the <command>key</command>.
2244 <title>Generate Shared Keys for Each Pair of Hosts</title>
2246 A shared secret is generated to be shared between <emphasis>host1</emphasis> and <emphasis>host2</emphasis>.
2247 An arbitrary key name is chosen: "host1-host2.". The key name must
2248 be the same on both hosts.
2251 <title>Automatic Generation</title>
2253 The following command will generate a 128-bit (16 byte) HMAC-SHA256
2254 key as described above. Longer keys are better, but shorter keys
2255 are easier to read. Note that the maximum key length is the digest
2256 length, here 256 bits.
2259 <userinput>dnssec-keygen -a hmac-sha256 -b 128 -n HOST host1-host2.</userinput>
2262 The key is in the file <filename>Khost1-host2.+163+00000.private</filename>.
2263 Nothing directly uses this file, but the base-64 encoded string
2264 following "<literal>Key:</literal>"
2265 can be extracted from the file and used as a shared secret:
2267 <programlisting>Key: La/E5CjG9O+os1jq0a2jdA==</programlisting>
2269 The string "<literal>La/E5CjG9O+os1jq0a2jdA==</literal>" can
2270 be used as the shared secret.
2274 <title>Manual Generation</title>
2276 The shared secret is simply a random sequence of bits, encoded
2277 in base-64. Most ASCII strings are valid base-64 strings (assuming
2278 the length is a multiple of 4 and only valid characters are used),
2279 so the shared secret can be manually generated.
2282 Also, a known string can be run through <command>mmencode</command> or
2283 a similar program to generate base-64 encoded data.
2288 <title>Copying the Shared Secret to Both Machines</title>
2290 This is beyond the scope of DNS. A secure transport mechanism
2291 should be used. This could be secure FTP, ssh, telephone, etc.
2295 <title>Informing the Servers of the Key's Existence</title>
2297 Imagine <emphasis>host1</emphasis> and <emphasis>host 2</emphasis>
2299 both servers. The following is added to each server's <filename>named.conf</filename> file:
2304 algorithm hmac-sha256;
2305 secret "La/E5CjG9O+os1jq0a2jdA==";
2310 The secret is the one generated above. Since this is a secret, it
2311 is recommended that either <filename>named.conf</filename> be
2312 non-world readable, or the key directive be added to a non-world
2313 readable file that is included by <filename>named.conf</filename>.
2316 At this point, the key is recognized. This means that if the
2317 server receives a message signed by this key, it can verify the
2318 signature. If the signature is successfully verified, the
2319 response is signed by the same key.
2324 <title>Instructing the Server to Use the Key</title>
2326 Since keys are shared between two hosts only, the server must
2327 be told when keys are to be used. The following is added to the <filename>named.conf</filename> file
2328 for <emphasis>host1</emphasis>, if the IP address of <emphasis>host2</emphasis> is
2334 keys { host1-host2. ;};
2339 Multiple keys may be present, but only the first is used.
2340 This directive does not contain any secrets, so it may be in a
2345 If <emphasis>host1</emphasis> sends a message that is a request
2346 to that address, the message will be signed with the specified key. <emphasis>host1</emphasis> will
2347 expect any responses to signed messages to be signed with the same
2351 A similar statement must be present in <emphasis>host2</emphasis>'s
2352 configuration file (with <emphasis>host1</emphasis>'s address) for <emphasis>host2</emphasis> to
2353 sign request messages to <emphasis>host1</emphasis>.
2357 <title>TSIG Key Based Access Control</title>
2359 <acronym>BIND</acronym> allows IP addresses and ranges
2360 to be specified in ACL
2362 <command>allow-{ query | transfer | update }</command>
2364 This has been extended to allow TSIG keys also. The above key would
2365 be denoted <command>key host1-host2.</command>
2368 An example of an <command>allow-update</command> directive would be:
2372 allow-update { key host1-host2. ;};
2376 This allows dynamic updates to succeed only if the request
2377 was signed by a key named "<command>host1-host2.</command>".
2381 See <xref linkend="dynamic_update_policies"/> for a discussion of
2382 the more flexible <command>update-policy</command> statement.
2387 <title>Errors</title>
2390 The processing of TSIG signed messages can result in
2391 several errors. If a signed message is sent to a non-TSIG aware
2392 server, a FORMERR (format error) will be returned, since the server will not
2393 understand the record. This is a result of misconfiguration,
2394 since the server must be explicitly configured to send a TSIG
2395 signed message to a specific server.
2399 If a TSIG aware server receives a message signed by an
2400 unknown key, the response will be unsigned with the TSIG
2401 extended error code set to BADKEY. If a TSIG aware server
2402 receives a message with a signature that does not validate, the
2403 response will be unsigned with the TSIG extended error code set
2404 to BADSIG. If a TSIG aware server receives a message with a time
2405 outside of the allowed range, the response will be signed with
2406 the TSIG extended error code set to BADTIME, and the time values
2407 will be adjusted so that the response can be successfully
2408 verified. In any of these cases, the message's rcode (response code) is set to
2409 NOTAUTH (not authenticated).
2417 <para><command>TKEY</command>
2418 is a mechanism for automatically generating a shared secret
2419 between two hosts. There are several "modes" of
2420 <command>TKEY</command> that specify how the key is generated
2421 or assigned. <acronym>BIND</acronym> 9 implements only one of
2422 these modes, the Diffie-Hellman key exchange. Both hosts are
2423 required to have a Diffie-Hellman KEY record (although this
2424 record is not required to be present in a zone). The
2425 <command>TKEY</command> process must use signed messages,
2426 signed either by TSIG or SIG(0). The result of
2427 <command>TKEY</command> is a shared secret that can be used to
2428 sign messages with TSIG. <command>TKEY</command> can also be
2429 used to delete shared secrets that it had previously
2434 The <command>TKEY</command> process is initiated by a
2436 or server by sending a signed <command>TKEY</command>
2438 (including any appropriate KEYs) to a TKEY-aware server. The
2439 server response, if it indicates success, will contain a
2440 <command>TKEY</command> record and any appropriate keys.
2442 this exchange, both participants have enough information to
2443 determine the shared secret; the exact process depends on the
2444 <command>TKEY</command> mode. When using the
2446 <command>TKEY</command> mode, Diffie-Hellman keys are
2448 and the shared secret is derived by both participants.
2453 <title>SIG(0)</title>
2456 <acronym>BIND</acronym> 9 partially supports DNSSEC SIG(0)
2457 transaction signatures as specified in RFC 2535 and RFC 2931.
2459 uses public/private keys to authenticate messages. Access control
2460 is performed in the same manner as TSIG keys; privileges can be
2461 granted or denied based on the key name.
2465 When a SIG(0) signed message is received, it will only be
2466 verified if the key is known and trusted by the server; the server
2467 will not attempt to locate and/or validate the key.
2471 SIG(0) signing of multiple-message TCP streams is not
2476 The only tool shipped with <acronym>BIND</acronym> 9 that
2477 generates SIG(0) signed messages is <command>nsupdate</command>.
2482 <title>DNSSEC</title>
2485 Cryptographic authentication of DNS information is possible
2486 through the DNS Security (<emphasis>DNSSEC-bis</emphasis>) extensions,
2487 defined in RFC 4033, RFC 4034, and RFC 4035.
2488 This section describes the creation and use of DNSSEC signed zones.
2492 In order to set up a DNSSEC secure zone, there are a series
2493 of steps which must be followed. <acronym>BIND</acronym>
2496 that are used in this process, which are explained in more detail
2497 below. In all cases, the <option>-h</option> option prints a
2498 full list of parameters. Note that the DNSSEC tools require the
2499 keyset files to be in the working directory or the
2500 directory specified by the <option>-d</option> option, and
2501 that the tools shipped with BIND 9.2.x and earlier are not compatible
2502 with the current ones.
2506 There must also be communication with the administrators of
2507 the parent and/or child zone to transmit keys. A zone's security
2508 status must be indicated by the parent zone for a DNSSEC capable
2509 resolver to trust its data. This is done through the presence
2510 or absence of a <literal>DS</literal> record at the
2516 For other servers to trust data in this zone, they must
2517 either be statically configured with this zone's zone key or the
2518 zone key of another zone above this one in the DNS tree.
2522 <title>Generating Keys</title>
2525 The <command>dnssec-keygen</command> program is used to
2530 A secure zone must contain one or more zone keys. The
2531 zone keys will sign all other records in the zone, as well as
2532 the zone keys of any secure delegated zones. Zone keys must
2533 have the same name as the zone, a name type of
2534 <command>ZONE</command>, and must be usable for
2536 It is recommended that zone keys use a cryptographic algorithm
2537 designated as "mandatory to implement" by the IETF; currently
2538 the only one is RSASHA1.
2542 The following command will generate a 768-bit RSASHA1 key for
2543 the <filename>child.example</filename> zone:
2547 <userinput>dnssec-keygen -a RSASHA1 -b 768 -n ZONE child.example.</userinput>
2551 Two output files will be produced:
2552 <filename>Kchild.example.+005+12345.key</filename> and
2553 <filename>Kchild.example.+005+12345.private</filename>
2555 12345 is an example of a key tag). The key filenames contain
2556 the key name (<filename>child.example.</filename>),
2558 is DSA, 1 is RSAMD5, 5 is RSASHA1, etc.), and the key tag (12345 in
2560 The private key (in the <filename>.private</filename>
2562 used to generate signatures, and the public key (in the
2563 <filename>.key</filename> file) is used for signature
2568 To generate another key with the same properties (but with
2569 a different key tag), repeat the above command.
2573 The <command>dnssec-keyfromlabel</command> program is used
2574 to get a key pair from a crypto hardware and build the key
2575 files. Its usage is similar to <command>dnssec-keygen</command>.
2579 The public keys should be inserted into the zone file by
2580 including the <filename>.key</filename> files using
2581 <command>$INCLUDE</command> statements.
2586 <title>Signing the Zone</title>
2589 The <command>dnssec-signzone</command> program is used
2594 Any <filename>keyset</filename> files corresponding to
2595 secure subzones should be present. The zone signer will
2596 generate <literal>NSEC</literal>, <literal>NSEC3</literal>
2597 and <literal>RRSIG</literal> records for the zone, as
2598 well as <literal>DS</literal> for the child zones if
2599 <literal>'-g'</literal> is specified. If <literal>'-g'</literal>
2600 is not specified, then DS RRsets for the secure child
2601 zones need to be added manually.
2605 The following command signs the zone, assuming it is in a
2606 file called <filename>zone.child.example</filename>. By
2607 default, all zone keys which have an available private key are
2608 used to generate signatures.
2612 <userinput>dnssec-signzone -o child.example zone.child.example</userinput>
2616 One output file is produced:
2617 <filename>zone.child.example.signed</filename>. This
2619 should be referenced by <filename>named.conf</filename>
2621 input file for the zone.
2624 <para><command>dnssec-signzone</command>
2625 will also produce a keyset and dsset files and optionally a
2626 dlvset file. These are used to provide the parent zone
2627 administrators with the <literal>DNSKEYs</literal> (or their
2628 corresponding <literal>DS</literal> records) that are the
2629 secure entry point to the zone.
2635 <title>Configuring Servers</title>
2638 To enable <command>named</command> to respond appropriately
2639 to DNS requests from DNSSEC aware clients,
2640 <command>dnssec-enable</command> must be set to yes.
2641 (This is the default setting.)
2645 To enable <command>named</command> to validate answers from
2646 other servers, the <command>dnssec-enable</command> option
2647 must be set to <userinput>yes</userinput>, and the
2648 <command>dnssec-validation</command> options must be set to
2649 <userinput>yes</userinput> or <userinput>auto</userinput>.
2653 If <command>dnssec-validation</command> is set to
2654 <userinput>auto</userinput>, then a default
2655 trust anchor for the DNS root zone will be used.
2656 If it is set to <userinput>yes</userinput>, however,
2657 then at least one trust anchor must be configured
2658 with a <command>trusted-keys</command> or
2659 <command>managed-keys</command> statement in
2660 <filename>named.conf</filename>, or DNSSEC validation
2661 will not occur. The default setting is
2662 <userinput>yes</userinput>.
2666 <command>trusted-keys</command> are copies of DNSKEY RRs
2667 for zones that are used to form the first link in the
2668 cryptographic chain of trust. All keys listed in
2669 <command>trusted-keys</command> (and corresponding zones)
2670 are deemed to exist and only the listed keys will be used
2671 to validated the DNSKEY RRset that they are from.
2675 <command>managed-keys</command> are trusted keys which are
2676 automatically kept up to date via RFC 5011 trust anchor
2681 <command>trusted-keys</command> and
2682 <command>managed-keys</command> are described in more detail
2683 later in this document.
2687 Unlike <acronym>BIND</acronym> 8, <acronym>BIND</acronym>
2688 9 does not verify signatures on load, so zone keys for
2689 authoritative zones do not need to be specified in the
2694 After DNSSEC gets established, a typical DNSSEC configuration
2695 will look something like the following. It has one or
2696 more public keys for the root. This allows answers from
2697 outside the organization to be validated. It will also
2698 have several keys for parts of the namespace the organization
2699 controls. These are here to ensure that <command>named</command>
2700 is immune to compromises in the DNSSEC components of the security
2707 "." initial-key 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS
2708 JxrGkxJWoZu6I7PzJu/E9gx4UC1zGAHlXKdE4zYIpRh
2709 aBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3zy2Xy
2710 4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYg
2711 hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp
2712 5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M/lUUVRbke
2713 g1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq
2714 66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ
2715 97S+LKUTpQcq27R7AT3/V5hRQxScINqwcz4jYqZD2fQ
2716 dgxbcDTClU0CRBdiieyLMNzXG3";
2720 /* Key for our organization's forward zone */
2721 example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6
2722 5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z
2723 GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb
2724 4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL
2725 kBOUKUf/mC7HvfwYH/Be22GnClrinKJp1O
2726 g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S
2727 TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq
2728 FxmAVZP20igTixin/1LcrgX/KMEGd/biuv
2729 F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm
2730 /oyWR8BW/hWdzOvnSCThlHf3xiYleDbt/o
2733 /* Key for our reverse zone. */
2734 2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwc
2735 xOdNax071L18QqZnQQQAVVr+i
2736 LhGTnNGp3HoWQLUIzKrJVZ3zg
2737 gy3WwNT6kZo6c0tszYqbtvchm
2738 gQC8CzKojM/W16i6MG/eafGU3
2739 siaOdS0yOI6BgPsw+YZdzlYMa
2740 IJGf4M4dyoKIhzdZyQ2bYQrjy
2741 Q4LB0lC7aOnsMyYKHHYeRvPxj
2742 IQXmdqgOJGq+vsevG06zW+1xg
2743 YJh9rCIfnm1GX/KMgxLPG2vXT
2744 D/RnLX+D3T3UL7HJYHJhAZD5L
2745 59VvjSPsZJHeDCUyWYrvPZesZ
2746 DIRvhDD52SKvbheeTJUm6Ehkz
2747 ytNN2SN96QRk8j/iI8ib";
2753 dnssec-validation yes;
2758 None of the keys listed in this example are valid. In particular,
2759 the root key is not valid.
2763 When DNSSEC validation is enabled and properly configured,
2764 the resolver will reject any answers from signed, secure zones
2765 which fail to validate, and will return SERVFAIL to the client.
2769 Responses may fail to validate for any of several reasons,
2770 including missing, expired, or invalid signatures, a key which
2771 does not match the DS RRset in the parent zone, or an insecure
2772 response from a zone which, according to its parent, should have
2778 When the validator receives a response from an unsigned zone
2779 that has a signed parent, it must confirm with the parent
2780 that the zone was intentionally left unsigned. It does
2781 this by verifying, via signed and validated NSEC/NSEC3 records,
2782 that the parent zone contains no DS records for the child.
2785 If the validator <emphasis>can</emphasis> prove that the zone
2786 is insecure, then the response is accepted. However, if it
2787 cannot, then it must assume an insecure response to be a
2788 forgery; it rejects the response and logs an error.
2791 The logged error reads "insecurity proof failed" and
2792 "got insecure response; parent indicates it should be secure".
2793 (Prior to BIND 9.7, the logged error was "not insecure".
2794 This referred to the zone, not the response.)
2801 <xi:include href="dnssec.xml"/>
2803 <xi:include href="managed-keys.xml"/>
2805 <xi:include href="pkcs11.xml"/>
2808 <title>IPv6 Support in <acronym>BIND</acronym> 9</title>
2811 <acronym>BIND</acronym> 9 fully supports all currently
2812 defined forms of IPv6 name to address and address to name
2813 lookups. It will also use IPv6 addresses to make queries when
2814 running on an IPv6 capable system.
2818 For forward lookups, <acronym>BIND</acronym> 9 supports
2819 only AAAA records. RFC 3363 deprecated the use of A6 records,
2820 and client-side support for A6 records was accordingly removed
2821 from <acronym>BIND</acronym> 9.
2822 However, authoritative <acronym>BIND</acronym> 9 name servers still
2823 load zone files containing A6 records correctly, answer queries
2824 for A6 records, and accept zone transfer for a zone containing A6
2829 For IPv6 reverse lookups, <acronym>BIND</acronym> 9 supports
2830 the traditional "nibble" format used in the
2831 <emphasis>ip6.arpa</emphasis> domain, as well as the older, deprecated
2832 <emphasis>ip6.int</emphasis> domain.
2833 Older versions of <acronym>BIND</acronym> 9
2834 supported the "binary label" (also known as "bitstring") format,
2835 but support of binary labels has been completely removed per
2837 Many applications in <acronym>BIND</acronym> 9 do not understand
2838 the binary label format at all any more, and will return an
2840 In particular, an authoritative <acronym>BIND</acronym> 9
2841 name server will not load a zone file containing binary labels.
2845 For an overview of the format and structure of IPv6 addresses,
2846 see <xref linkend="ipv6addresses"/>.
2850 <title>Address Lookups Using AAAA Records</title>
2853 The IPv6 AAAA record is a parallel to the IPv4 A record,
2854 and, unlike the deprecated A6 record, specifies the entire
2855 IPv6 address in a single record. For example,
2859 $ORIGIN example.com.
2860 host 3600 IN AAAA 2001:db8::1
2864 Use of IPv4-in-IPv6 mapped addresses is not recommended.
2865 If a host has an IPv4 address, use an A record, not
2866 a AAAA, with <literal>::ffff:192.168.42.1</literal> as
2871 <title>Address to Name Lookups Using Nibble Format</title>
2874 When looking up an address in nibble format, the address
2875 components are simply reversed, just as in IPv4, and
2876 <literal>ip6.arpa.</literal> is appended to the
2878 For example, the following would provide reverse name lookup for
2880 <literal>2001:db8::1</literal>.
2884 $ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
2885 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR (
2893 <chapter id="Bv9ARM.ch05">
2894 <title>The <acronym>BIND</acronym> 9 Lightweight Resolver</title>
2896 <title>The Lightweight Resolver Library</title>
2898 Traditionally applications have been linked with a stub resolver
2899 library that sends recursive DNS queries to a local caching name
2903 IPv6 once introduced new complexity into the resolution process,
2904 such as following A6 chains and DNAME records, and simultaneous
2905 lookup of IPv4 and IPv6 addresses. Though most of the complexity was
2906 then removed, these are hard or impossible
2907 to implement in a traditional stub resolver.
2910 <acronym>BIND</acronym> 9 therefore can also provide resolution
2911 services to local clients
2912 using a combination of a lightweight resolver library and a resolver
2913 daemon process running on the local host. These communicate using
2914 a simple UDP-based protocol, the "lightweight resolver protocol"
2915 that is distinct from and simpler than the full DNS protocol.
2919 <title>Running a Resolver Daemon</title>
2922 To use the lightweight resolver interface, the system must
2923 run the resolver daemon <command>lwresd</command> or a
2925 name server configured with a <command>lwres</command>
2930 By default, applications using the lightweight resolver library will
2932 UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
2934 address can be overridden by <command>lwserver</command>
2936 <filename>/etc/resolv.conf</filename>.
2940 The daemon currently only looks in the DNS, but in the future
2941 it may use other sources such as <filename>/etc/hosts</filename>,
2946 The <command>lwresd</command> daemon is essentially a
2947 caching-only name server that responds to requests using the
2949 resolver protocol rather than the DNS protocol. Because it needs
2950 to run on each host, it is designed to require no or minimal
2952 Unless configured otherwise, it uses the name servers listed on
2953 <command>nameserver</command> lines in <filename>/etc/resolv.conf</filename>
2954 as forwarders, but is also capable of doing the resolution
2959 The <command>lwresd</command> daemon may also be
2961 <filename>named.conf</filename> style configuration file,
2963 <filename>/etc/lwresd.conf</filename> by default. A name
2965 be configured to act as a lightweight resolver daemon using the
2966 <command>lwres</command> statement in <filename>named.conf</filename>.
2972 <chapter id="Bv9ARM.ch06">
2973 <title><acronym>BIND</acronym> 9 Configuration Reference</title>
2976 <acronym>BIND</acronym> 9 configuration is broadly similar
2977 to <acronym>BIND</acronym> 8; however, there are a few new
2979 of configuration, such as views. <acronym>BIND</acronym>
2980 8 configuration files should work with few alterations in <acronym>BIND</acronym>
2981 9, although more complex configurations should be reviewed to check
2982 if they can be more efficiently implemented using the new features
2983 found in <acronym>BIND</acronym> 9.
2987 <acronym>BIND</acronym> 4 configuration files can be
2988 converted to the new format
2989 using the shell script
2990 <filename>contrib/named-bootconf/named-bootconf.sh</filename>.
2992 <sect1 id="configuration_file_elements">
2993 <title>Configuration File Elements</title>
2995 Following is a list of elements used throughout the <acronym>BIND</acronym> configuration
2998 <informaltable colsep="0" rowsep="0">
2999 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
3000 <colspec colname="1" colnum="1" colsep="0" colwidth="1.855in"/>
3001 <colspec colname="2" colnum="2" colsep="0" colwidth="3.770in"/>
3006 <varname>acl_name</varname>
3011 The name of an <varname>address_match_list</varname> as
3012 defined by the <command>acl</command> statement.
3019 <varname>address_match_list</varname>
3024 A list of one or more
3025 <varname>ip_addr</varname>,
3026 <varname>ip_prefix</varname>, <varname>key_id</varname>,
3027 or <varname>acl_name</varname> elements, see
3028 <xref linkend="address_match_lists"/>.
3035 <varname>masters_list</varname>
3040 A named list of one or more <varname>ip_addr</varname>
3041 with optional <varname>key_id</varname> and/or
3042 <varname>ip_port</varname>.
3043 A <varname>masters_list</varname> may include other
3044 <varname>masters_lists</varname>.
3051 <varname>domain_name</varname>
3056 A quoted string which will be used as
3057 a DNS name, for example "<literal>my.test.domain</literal>".
3064 <varname>namelist</varname>
3069 A list of one or more <varname>domain_name</varname>
3077 <varname>dotted_decimal</varname>
3082 One to four integers valued 0 through
3083 255 separated by dots (`.'), such as <command>123</command>,
3084 <command>45.67</command> or <command>89.123.45.67</command>.
3091 <varname>ip4_addr</varname>
3096 An IPv4 address with exactly four elements
3097 in <varname>dotted_decimal</varname> notation.
3104 <varname>ip6_addr</varname>
3109 An IPv6 address, such as <command>2001:db8::1234</command>.
3110 IPv6 scoped addresses that have ambiguity on their
3111 scope zones must be disambiguated by an appropriate
3112 zone ID with the percent character (`%') as
3113 delimiter. It is strongly recommended to use
3114 string zone names rather than numeric identifiers,
3115 in order to be robust against system configuration
3116 changes. However, since there is no standard
3117 mapping for such names and identifier values,
3118 currently only interface names as link identifiers
3119 are supported, assuming one-to-one mapping between
3120 interfaces and links. For example, a link-local
3121 address <command>fe80::1</command> on the link
3122 attached to the interface <command>ne0</command>
3123 can be specified as <command>fe80::1%ne0</command>.
3124 Note that on most systems link-local addresses
3125 always have the ambiguity, and need to be
3133 <varname>ip_addr</varname>
3138 An <varname>ip4_addr</varname> or <varname>ip6_addr</varname>.
3145 <varname>ip_port</varname>
3150 An IP port <varname>number</varname>.
3151 The <varname>number</varname> is limited to 0
3152 through 65535, with values
3153 below 1024 typically restricted to use by processes running
3155 In some cases, an asterisk (`*') character can be used as a
3157 select a random high-numbered port.
3164 <varname>ip_prefix</varname>
3169 An IP network specified as an <varname>ip_addr</varname>,
3170 followed by a slash (`/') and then the number of bits in the
3172 Trailing zeros in a <varname>ip_addr</varname>
3174 For example, <command>127/8</command> is the
3175 network <command>127.0.0.0</command> with
3176 netmask <command>255.0.0.0</command> and <command>1.2.3.0/28</command> is
3177 network <command>1.2.3.0</command> with netmask <command>255.255.255.240</command>.
3180 When specifying a prefix involving a IPv6 scoped address
3181 the scope may be omitted. In that case the prefix will
3182 match packets from any scope.
3189 <varname>key_id</varname>
3194 A <varname>domain_name</varname> representing
3195 the name of a shared key, to be used for transaction
3203 <varname>key_list</varname>
3208 A list of one or more
3209 <varname>key_id</varname>s,
3210 separated by semicolons and ending with a semicolon.
3217 <varname>number</varname>
3222 A non-negative 32-bit integer
3223 (i.e., a number between 0 and 4294967295, inclusive).
3224 Its acceptable value might further
3225 be limited by the context in which it is used.
3232 <varname>path_name</varname>
3237 A quoted string which will be used as
3238 a pathname, such as <filename>zones/master/my.test.domain</filename>.
3245 <varname>port_list</varname>
3250 A list of an <varname>ip_port</varname> or a port
3252 A port range is specified in the form of
3253 <userinput>range</userinput> followed by
3254 two <varname>ip_port</varname>s,
3255 <varname>port_low</varname> and
3256 <varname>port_high</varname>, which represents
3257 port numbers from <varname>port_low</varname> through
3258 <varname>port_high</varname>, inclusive.
3259 <varname>port_low</varname> must not be larger than
3260 <varname>port_high</varname>.
3262 <userinput>range 1024 65535</userinput> represents
3263 ports from 1024 through 65535.
3264 In either case an asterisk (`*') character is not
3265 allowed as a valid <varname>ip_port</varname>.
3272 <varname>size_spec</varname>
3277 A number, the word <userinput>unlimited</userinput>,
3278 or the word <userinput>default</userinput>.
3281 An <varname>unlimited</varname> <varname>size_spec</varname> requests unlimited
3282 use, or the maximum available amount. A <varname>default size_spec</varname> uses
3283 the limit that was in force when the server was started.
3286 A <varname>number</varname> can optionally be
3287 followed by a scaling factor:
3288 <userinput>K</userinput> or <userinput>k</userinput>
3290 <userinput>M</userinput> or <userinput>m</userinput>
3292 <userinput>G</userinput> or <userinput>g</userinput> for gigabytes,
3293 which scale by 1024, 1024*1024, and 1024*1024*1024
3297 The value must be representable as a 64-bit unsigned integer
3298 (0 to 18446744073709551615, inclusive).
3299 Using <varname>unlimited</varname> is the best
3301 to safely set a really large number.
3308 <varname>yes_or_no</varname>
3313 Either <userinput>yes</userinput> or <userinput>no</userinput>.
3314 The words <userinput>true</userinput> and <userinput>false</userinput> are
3315 also accepted, as are the numbers <userinput>1</userinput>
3316 and <userinput>0</userinput>.
3323 <varname>dialup_option</varname>
3328 One of <userinput>yes</userinput>,
3329 <userinput>no</userinput>, <userinput>notify</userinput>,
3330 <userinput>notify-passive</userinput>, <userinput>refresh</userinput> or
3331 <userinput>passive</userinput>.
3332 When used in a zone, <userinput>notify-passive</userinput>,
3333 <userinput>refresh</userinput>, and <userinput>passive</userinput>
3334 are restricted to slave and stub zones.
3341 <sect2 id="address_match_lists">
3342 <title>Address Match Lists</title>
3344 <title>Syntax</title>
3346 <programlisting><varname>address_match_list</varname> = address_match_list_element ;
3347 <optional> address_match_list_element; ... </optional>
3348 <varname>address_match_list_element</varname> = <optional> ! </optional> (ip_address <optional>/length</optional> |
3349 key key_id | acl_name | { address_match_list } )
3354 <title>Definition and Usage</title>
3356 Address match lists are primarily used to determine access
3357 control for various server operations. They are also used in
3358 the <command>listen-on</command> and <command>sortlist</command>
3359 statements. The elements which constitute an address match
3360 list can be any of the following:
3364 <simpara>an IP address (IPv4 or IPv6)</simpara>
3367 <simpara>an IP prefix (in `/' notation)</simpara>
3371 a key ID, as defined by the <command>key</command>
3376 <simpara>the name of an address match list defined with
3377 the <command>acl</command> statement
3381 <simpara>a nested address match list enclosed in braces</simpara>
3386 Elements can be negated with a leading exclamation mark (`!'),
3387 and the match list names "any", "none", "localhost", and
3388 "localnets" are predefined. More information on those names
3389 can be found in the description of the acl statement.
3393 The addition of the key clause made the name of this syntactic
3394 element something of a misnomer, since security keys can be used
3395 to validate access without regard to a host or network address.
3396 Nonetheless, the term "address match list" is still used
3397 throughout the documentation.
3401 When a given IP address or prefix is compared to an address
3402 match list, the comparison takes place in approximately O(1)
3403 time. However, key comparisons require that the list of keys
3404 be traversed until a matching key is found, and therefore may
3409 The interpretation of a match depends on whether the list is being
3410 used for access control, defining <command>listen-on</command> ports, or in a
3411 <command>sortlist</command>, and whether the element was negated.
3415 When used as an access control list, a non-negated match
3416 allows access and a negated match denies access. If
3417 there is no match, access is denied. The clauses
3418 <command>allow-notify</command>,
3419 <command>allow-recursion</command>,
3420 <command>allow-recursion-on</command>,
3421 <command>allow-query</command>,
3422 <command>allow-query-on</command>,
3423 <command>allow-query-cache</command>,
3424 <command>allow-query-cache-on</command>,
3425 <command>allow-transfer</command>,
3426 <command>allow-update</command>,
3427 <command>allow-update-forwarding</command>, and
3428 <command>blackhole</command> all use address match
3429 lists. Similarly, the <command>listen-on</command> option will cause the
3430 server to refuse queries on any of the machine's
3431 addresses which do not match the list.
3435 Order of insertion is significant. If more than one element
3436 in an ACL is found to match a given IP address or prefix,
3437 preference will be given to the one that came
3438 <emphasis>first</emphasis> in the ACL definition.
3439 Because of this first-match behavior, an element that
3440 defines a subset of another element in the list should
3441 come before the broader element, regardless of whether
3442 either is negated. For example, in
3443 <command>1.2.3/24; ! 1.2.3.13;</command>
3444 the 1.2.3.13 element is completely useless because the
3445 algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
3446 element. Using <command>! 1.2.3.13; 1.2.3/24</command> fixes
3447 that problem by having 1.2.3.13 blocked by the negation, but
3448 all other 1.2.3.* hosts fall through.
3454 <title>Comment Syntax</title>
3457 The <acronym>BIND</acronym> 9 comment syntax allows for
3459 anywhere that whitespace may appear in a <acronym>BIND</acronym> configuration
3460 file. To appeal to programmers of all kinds, they can be written
3461 in the C, C++, or shell/perl style.
3465 <title>Syntax</title>
3468 <programlisting>/* This is a <acronym>BIND</acronym> comment as in C */</programlisting>
3469 <programlisting>// This is a <acronym>BIND</acronym> comment as in C++</programlisting>
3470 <programlisting># This is a <acronym>BIND</acronym> comment as in common UNIX shells
3471 # and perl</programlisting>
3475 <title>Definition and Usage</title>
3477 Comments may appear anywhere that whitespace may appear in
3478 a <acronym>BIND</acronym> configuration file.
3481 C-style comments start with the two characters /* (slash,
3482 star) and end with */ (star, slash). Because they are completely
3483 delimited with these characters, they can be used to comment only
3484 a portion of a line or to span multiple lines.
3487 C-style comments cannot be nested. For example, the following
3488 is not valid because the entire comment ends with the first */:
3492 <programlisting>/* This is the start of a comment.
3493 This is still part of the comment.
3494 /* This is an incorrect attempt at nesting a comment. */
3495 This is no longer in any comment. */
3501 C++-style comments start with the two characters // (slash,
3502 slash) and continue to the end of the physical line. They cannot
3503 be continued across multiple physical lines; to have one logical
3504 comment span multiple lines, each line must use the // pair.
3509 <programlisting>// This is the start of a comment. The next line
3510 // is a new comment, even though it is logically
3511 // part of the previous comment.
3516 Shell-style (or perl-style, if you prefer) comments start
3517 with the character <literal>#</literal> (number sign)
3518 and continue to the end of the
3519 physical line, as in C++ comments.
3525 <programlisting># This is the start of a comment. The next line
3526 # is a new comment, even though it is logically
3527 # part of the previous comment.
3534 You cannot use the semicolon (`;') character
3535 to start a comment such as you would in a zone file. The
3536 semicolon indicates the end of a configuration
3544 <sect1 id="Configuration_File_Grammar">
3545 <title>Configuration File Grammar</title>
3548 A <acronym>BIND</acronym> 9 configuration consists of
3549 statements and comments.
3550 Statements end with a semicolon. Statements and comments are the
3551 only elements that can appear without enclosing braces. Many
3552 statements contain a block of sub-statements, which are also
3553 terminated with a semicolon.
3557 The following statements are supported:
3560 <informaltable colsep="0" rowsep="0">
3561 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
3562 <colspec colname="1" colnum="1" colsep="0" colwidth="1.336in"/>
3563 <colspec colname="2" colnum="2" colsep="0" colwidth="3.778in"/>
3567 <para><command>acl</command></para>
3571 defines a named IP address
3572 matching list, for access control and other uses.
3578 <para><command>controls</command></para>
3582 declares control channels to be used
3583 by the <command>rndc</command> utility.
3589 <para><command>include</command></para>
3599 <para><command>key</command></para>
3603 specifies key information for use in
3604 authentication and authorization using TSIG.
3610 <para><command>logging</command></para>
3614 specifies what the server logs, and where
3615 the log messages are sent.
3621 <para><command>lwres</command></para>
3625 configures <command>named</command> to
3626 also act as a light-weight resolver daemon (<command>lwresd</command>).
3632 <para><command>masters</command></para>
3636 defines a named masters list for
3637 inclusion in stub and slave zone masters clauses.
3643 <para><command>options</command></para>
3647 controls global server configuration
3648 options and sets defaults for other statements.
3654 <para><command>server</command></para>
3658 sets certain configuration options on
3665 <para><command>statistics-channels</command></para>
3669 declares communication channels to get access to
3670 <command>named</command> statistics.
3676 <para><command>trusted-keys</command></para>
3680 defines trusted DNSSEC keys.
3686 <para><command>managed-keys</command></para>
3690 lists DNSSEC keys to be kept up to date
3691 using RFC 5011 trust anchor maintenance.
3697 <para><command>view</command></para>
3707 <para><command>zone</command></para>
3720 The <command>logging</command> and
3721 <command>options</command> statements may only occur once
3727 <title><command>acl</command> Statement Grammar</title>
3729 <programlisting><command>acl</command> acl-name {
3736 <title><command>acl</command> Statement Definition and
3740 The <command>acl</command> statement assigns a symbolic
3741 name to an address match list. It gets its name from a primary
3742 use of address match lists: Access Control Lists (ACLs).
3746 Note that an address match list's name must be defined
3747 with <command>acl</command> before it can be used
3748 elsewhere; no forward references are allowed.
3752 The following ACLs are built-in:
3755 <informaltable colsep="0" rowsep="0">
3756 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
3757 <colspec colname="1" colnum="1" colsep="0" colwidth="1.130in"/>
3758 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
3762 <para><command>any</command></para>
3772 <para><command>none</command></para>
3782 <para><command>localhost</command></para>
3786 Matches the IPv4 and IPv6 addresses of all network
3787 interfaces on the system.
3793 <para><command>localnets</command></para>
3797 Matches any host on an IPv4 or IPv6 network
3798 for which the system has an interface.
3799 Some systems do not provide a way to determine the prefix
3801 local IPv6 addresses.
3802 In such a case, <command>localnets</command>
3803 only matches the local
3804 IPv6 addresses, just like <command>localhost</command>.
3814 <title><command>controls</command> Statement Grammar</title>
3816 <programlisting><command>controls</command> {
3817 [ inet ( ip_addr | * ) [ port ip_port ]
3818 allow { <replaceable> address_match_list </replaceable> }
3819 keys { <replaceable>key_list</replaceable> }; ]
3821 [ unix <replaceable>path</replaceable> perm <replaceable>number</replaceable> owner <replaceable>number</replaceable> group <replaceable>number</replaceable>
3822 keys { <replaceable>key_list</replaceable> }; ]
3829 <sect2 id="controls_statement_definition_and_usage">
3830 <title><command>controls</command> Statement Definition and
3834 The <command>controls</command> statement declares control
3835 channels to be used by system administrators to control the
3836 operation of the name server. These control channels are
3837 used by the <command>rndc</command> utility to send
3838 commands to and retrieve non-DNS results from a name server.
3842 An <command>inet</command> control channel is a TCP socket
3843 listening at the specified <command>ip_port</command> on the
3844 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
3845 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
3846 interpreted as the IPv4 wildcard address; connections will be
3847 accepted on any of the system's IPv4 addresses.
3848 To listen on the IPv6 wildcard address,
3849 use an <command>ip_addr</command> of <literal>::</literal>.
3850 If you will only use <command>rndc</command> on the local host,
3851 using the loopback address (<literal>127.0.0.1</literal>
3852 or <literal>::1</literal>) is recommended for maximum security.
3856 If no port is specified, port 953 is used. The asterisk
3857 "<literal>*</literal>" cannot be used for <command>ip_port</command>.
3861 The ability to issue commands over the control channel is
3862 restricted by the <command>allow</command> and
3863 <command>keys</command> clauses.
3864 Connections to the control channel are permitted based on the
3865 <command>address_match_list</command>. This is for simple
3866 IP address based filtering only; any <command>key_id</command>
3867 elements of the <command>address_match_list</command>
3872 A <command>unix</command> control channel is a UNIX domain
3873 socket listening at the specified path in the file system.
3874 Access to the socket is specified by the <command>perm</command>,
3875 <command>owner</command> and <command>group</command> clauses.
3876 Note on some platforms (SunOS and Solaris) the permissions
3877 (<command>perm</command>) are applied to the parent directory
3878 as the permissions on the socket itself are ignored.
3882 The primary authorization mechanism of the command
3883 channel is the <command>key_list</command>, which
3884 contains a list of <command>key_id</command>s.
3885 Each <command>key_id</command> in the <command>key_list</command>
3886 is authorized to execute commands over the control channel.
3887 See <xref linkend="rndc"/> in <xref linkend="admin_tools"/>)
3888 for information about configuring keys in <command>rndc</command>.
3892 If no <command>controls</command> statement is present,
3893 <command>named</command> will set up a default
3894 control channel listening on the loopback address 127.0.0.1
3895 and its IPv6 counterpart ::1.
3896 In this case, and also when the <command>controls</command> statement
3897 is present but does not have a <command>keys</command> clause,
3898 <command>named</command> will attempt to load the command channel key
3899 from the file <filename>rndc.key</filename> in
3900 <filename>/etc</filename> (or whatever <varname>sysconfdir</varname>
3901 was specified as when <acronym>BIND</acronym> was built).
3902 To create a <filename>rndc.key</filename> file, run
3903 <userinput>rndc-confgen -a</userinput>.
3907 The <filename>rndc.key</filename> feature was created to
3908 ease the transition of systems from <acronym>BIND</acronym> 8,
3909 which did not have digital signatures on its command channel
3910 messages and thus did not have a <command>keys</command> clause.
3912 It makes it possible to use an existing <acronym>BIND</acronym> 8
3913 configuration file in <acronym>BIND</acronym> 9 unchanged,
3914 and still have <command>rndc</command> work the same way
3915 <command>ndc</command> worked in BIND 8, simply by executing the
3916 command <userinput>rndc-confgen -a</userinput> after BIND 9 is
3921 Since the <filename>rndc.key</filename> feature
3922 is only intended to allow the backward-compatible usage of
3923 <acronym>BIND</acronym> 8 configuration files, this
3925 have a high degree of configurability. You cannot easily change
3926 the key name or the size of the secret, so you should make a
3927 <filename>rndc.conf</filename> with your own key if you
3929 those things. The <filename>rndc.key</filename> file
3931 permissions set such that only the owner of the file (the user that
3932 <command>named</command> is running as) can access it.
3934 desire greater flexibility in allowing other users to access
3935 <command>rndc</command> commands, then you need to create
3937 <filename>rndc.conf</filename> file and make it group
3939 that contains the users who should have access.
3943 To disable the command channel, use an empty
3944 <command>controls</command> statement:
3945 <command>controls { };</command>.
3950 <title><command>include</command> Statement Grammar</title>
3951 <programlisting><command>include</command> <replaceable>filename</replaceable>;</programlisting>
3954 <title><command>include</command> Statement Definition and
3958 The <command>include</command> statement inserts the
3959 specified file at the point where the <command>include</command>
3960 statement is encountered. The <command>include</command>
3961 statement facilitates the administration of configuration
3963 by permitting the reading or writing of some things but not
3964 others. For example, the statement could include private keys
3965 that are readable only by the name server.
3970 <title><command>key</command> Statement Grammar</title>
3972 <programlisting><command>key</command> <replaceable>key_id</replaceable> {
3973 algorithm <replaceable>string</replaceable>;
3974 secret <replaceable>string</replaceable>;
3981 <title><command>key</command> Statement Definition and Usage</title>
3984 The <command>key</command> statement defines a shared
3985 secret key for use with TSIG (see <xref linkend="tsig"/>)
3986 or the command channel
3987 (see <xref linkend="controls_statement_definition_and_usage"/>).
3991 The <command>key</command> statement can occur at the
3993 of the configuration file or inside a <command>view</command>
3994 statement. Keys defined in top-level <command>key</command>
3995 statements can be used in all views. Keys intended for use in
3996 a <command>controls</command> statement
3997 (see <xref linkend="controls_statement_definition_and_usage"/>)
3998 must be defined at the top level.
4002 The <replaceable>key_id</replaceable>, also known as the
4003 key name, is a domain name uniquely identifying the key. It can
4004 be used in a <command>server</command>
4005 statement to cause requests sent to that
4006 server to be signed with this key, or in address match lists to
4007 verify that incoming requests have been signed with a key
4008 matching this name, algorithm, and secret.
4012 The <replaceable>algorithm_id</replaceable> is a string
4013 that specifies a security/authentication algorithm. Named
4014 supports <literal>hmac-md5</literal>,
4015 <literal>hmac-sha1</literal>, <literal>hmac-sha224</literal>,
4016 <literal>hmac-sha256</literal>, <literal>hmac-sha384</literal>
4017 and <literal>hmac-sha512</literal> TSIG authentication.
4018 Truncated hashes are supported by appending the minimum
4019 number of required bits preceded by a dash, e.g.
4020 <literal>hmac-sha1-80</literal>. The
4021 <replaceable>secret_string</replaceable> is the secret
4022 to be used by the algorithm, and is treated as a base-64
4028 <title><command>logging</command> Statement Grammar</title>
4030 <programlisting><command>logging</command> {
4031 [ <command>channel</command> <replaceable>channel_name</replaceable> {
4032 ( <command>file</command> <replaceable>path_name</replaceable>
4033 [ <command>versions</command> ( <replaceable>number</replaceable> | <command>unlimited</command> ) ]
4034 [ <command>size</command> <replaceable>size spec</replaceable> ]
4035 | <command>syslog</command> <replaceable>syslog_facility</replaceable>
4036 | <command>stderr</command>
4037 | <command>null</command> );
4038 [ <command>severity</command> (<option>critical</option> | <option>error</option> | <option>warning</option> | <option>notice</option> |
4039 <option>info</option> | <option>debug</option> [ <replaceable>level</replaceable> ] | <option>dynamic</option> ); ]
4040 [ <command>print-category</command> <option>yes</option> or <option>no</option>; ]
4041 [ <command>print-severity</command> <option>yes</option> or <option>no</option>; ]
4042 [ <command>print-time</command> <option>yes</option> or <option>no</option>; ]
4044 [ <command>category</command> <replaceable>category_name</replaceable> {
4045 <replaceable>channel_name</replaceable> ; [ <replaceable>channel_name</replaceable> ; ... ]
4054 <title><command>logging</command> Statement Definition and
4058 The <command>logging</command> statement configures a
4060 variety of logging options for the name server. Its <command>channel</command> phrase
4061 associates output methods, format options and severity levels with
4062 a name that can then be used with the <command>category</command> phrase
4063 to select how various classes of messages are logged.
4066 Only one <command>logging</command> statement is used to
4068 as many channels and categories as are wanted. If there is no <command>logging</command> statement,
4069 the logging configuration will be:
4072 <programlisting>logging {
4073 category default { default_syslog; default_debug; };
4074 category unmatched { null; };
4079 In <acronym>BIND</acronym> 9, the logging configuration
4080 is only established when
4081 the entire configuration file has been parsed. In <acronym>BIND</acronym> 8, it was
4082 established as soon as the <command>logging</command>
4084 was parsed. When the server is starting up, all logging messages
4085 regarding syntax errors in the configuration file go to the default
4086 channels, or to standard error if the "<option>-g</option>" option
4091 <title>The <command>channel</command> Phrase</title>
4094 All log output goes to one or more <emphasis>channels</emphasis>;
4095 you can make as many of them as you want.
4099 Every channel definition must include a destination clause that
4100 says whether messages selected for the channel go to a file, to a
4101 particular syslog facility, to the standard error stream, or are
4102 discarded. It can optionally also limit the message severity level
4103 that will be accepted by the channel (the default is
4104 <command>info</command>), and whether to include a
4105 <command>named</command>-generated time stamp, the
4107 and/or severity level (the default is not to include any).
4111 The <command>null</command> destination clause
4112 causes all messages sent to the channel to be discarded;
4113 in that case, other options for the channel are meaningless.
4117 The <command>file</command> destination clause directs
4119 to a disk file. It can include limitations
4120 both on how large the file is allowed to become, and how many
4122 of the file will be saved each time the file is opened.
4126 If you use the <command>versions</command> log file
4128 <command>named</command> will retain that many backup
4129 versions of the file by
4130 renaming them when opening. For example, if you choose to keep
4132 of the file <filename>lamers.log</filename>, then just
4134 <filename>lamers.log.1</filename> is renamed to
4135 <filename>lamers.log.2</filename>, <filename>lamers.log.0</filename> is renamed
4136 to <filename>lamers.log.1</filename>, and <filename>lamers.log</filename> is
4137 renamed to <filename>lamers.log.0</filename>.
4138 You can say <command>versions unlimited</command> to
4140 the number of versions.
4141 If a <command>size</command> option is associated with
4143 then renaming is only done when the file being opened exceeds the
4144 indicated size. No backup versions are kept by default; any
4146 log file is simply appended.
4150 The <command>size</command> option for files is used
4152 growth. If the file ever exceeds the size, then <command>named</command> will
4153 stop writing to the file unless it has a <command>versions</command> option
4154 associated with it. If backup versions are kept, the files are
4156 described above and a new one begun. If there is no
4157 <command>versions</command> option, no more data will
4158 be written to the log
4159 until some out-of-band mechanism removes or truncates the log to
4161 maximum size. The default behavior is not to limit the size of
4167 Example usage of the <command>size</command> and
4168 <command>versions</command> options:
4171 <programlisting>channel an_example_channel {
4172 file "example.log" versions 3 size 20m;
4179 The <command>syslog</command> destination clause
4181 channel to the system log. Its argument is a
4182 syslog facility as described in the <command>syslog</command> man
4183 page. Known facilities are <command>kern</command>, <command>user</command>,
4184 <command>mail</command>, <command>daemon</command>, <command>auth</command>,
4185 <command>syslog</command>, <command>lpr</command>, <command>news</command>,
4186 <command>uucp</command>, <command>cron</command>, <command>authpriv</command>,
4187 <command>ftp</command>, <command>local0</command>, <command>local1</command>,
4188 <command>local2</command>, <command>local3</command>, <command>local4</command>,
4189 <command>local5</command>, <command>local6</command> and
4190 <command>local7</command>, however not all facilities
4192 all operating systems.
4193 How <command>syslog</command> will handle messages
4195 this facility is described in the <command>syslog.conf</command> man
4196 page. If you have a system which uses a very old version of <command>syslog</command> that
4197 only uses two arguments to the <command>openlog()</command> function,
4198 then this clause is silently ignored.
4201 The <command>severity</command> clause works like <command>syslog</command>'s
4202 "priorities", except that they can also be used if you are writing
4203 straight to a file rather than using <command>syslog</command>.
4204 Messages which are not at least of the severity level given will
4205 not be selected for the channel; messages of higher severity
4210 If you are using <command>syslog</command>, then the <command>syslog.conf</command> priorities
4211 will also determine what eventually passes through. For example,
4212 defining a channel facility and severity as <command>daemon</command> and <command>debug</command> but
4213 only logging <command>daemon.warning</command> via <command>syslog.conf</command> will
4214 cause messages of severity <command>info</command> and
4215 <command>notice</command> to
4216 be dropped. If the situation were reversed, with <command>named</command> writing
4217 messages of only <command>warning</command> or higher,
4218 then <command>syslogd</command> would
4219 print all messages it received from the channel.
4223 The <command>stderr</command> destination clause
4225 channel to the server's standard error stream. This is intended
4227 use when the server is running as a foreground process, for
4229 when debugging a configuration.
4233 The server can supply extensive debugging information when
4234 it is in debugging mode. If the server's global debug level is
4236 than zero, then debugging mode will be active. The global debug
4237 level is set either by starting the <command>named</command> server
4238 with the <option>-d</option> flag followed by a positive integer,
4239 or by running <command>rndc trace</command>.
4240 The global debug level
4241 can be set to zero, and debugging mode turned off, by running <command>rndc
4242 notrace</command>. All debugging messages in the server have a debug
4243 level, and higher debug levels give more detailed output. Channels
4244 that specify a specific debug severity, for example:
4247 <programlisting>channel specific_debug_level {
4254 will get debugging output of level 3 or less any time the
4255 server is in debugging mode, regardless of the global debugging
4256 level. Channels with <command>dynamic</command>
4258 server's global debug level to determine what messages to print.
4261 If <command>print-time</command> has been turned on,
4263 the date and time will be logged. <command>print-time</command> may
4264 be specified for a <command>syslog</command> channel,
4266 pointless since <command>syslog</command> also logs
4268 time. If <command>print-category</command> is
4270 category of the message will be logged as well. Finally, if <command>print-severity</command> is
4271 on, then the severity level of the message will be logged. The <command>print-</command> options may
4272 be used in any combination, and will always be printed in the
4274 order: time, category, severity. Here is an example where all
4275 three <command>print-</command> options
4280 <computeroutput>28-Feb-2000 15:05:32.863 general: notice: running</computeroutput>
4284 There are four predefined channels that are used for
4285 <command>named</command>'s default logging as follows.
4287 used is described in <xref linkend="the_category_phrase"/>.
4290 <programlisting>channel default_syslog {
4291 // send to syslog's daemon facility
4293 // only send priority info and higher
4296 channel default_debug {
4297 // write to named.run in the working directory
4298 // Note: stderr is used instead of "named.run" if
4299 // the server is started with the '-f' option.
4301 // log at the server's current debug level
4305 channel default_stderr {
4308 // only send priority info and higher
4313 // toss anything sent to this channel
4319 The <command>default_debug</command> channel has the
4321 property that it only produces output when the server's debug
4323 nonzero. It normally writes to a file called <filename>named.run</filename>
4324 in the server's working directory.
4328 For security reasons, when the "<option>-u</option>"
4329 command line option is used, the <filename>named.run</filename> file
4330 is created only after <command>named</command> has
4332 new UID, and any debug output generated while <command>named</command> is
4333 starting up and still running as root is discarded. If you need
4334 to capture this output, you must run the server with the "<option>-g</option>"
4335 option and redirect standard error to a file.
4339 Once a channel is defined, it cannot be redefined. Thus you
4340 cannot alter the built-in channels directly, but you can modify
4341 the default logging by pointing categories at channels you have
4346 <sect3 id="the_category_phrase">
4347 <title>The <command>category</command> Phrase</title>
4350 There are many categories, so you can send the logs you want
4351 to see wherever you want, without seeing logs you don't want. If
4352 you don't specify a list of channels for a category, then log
4354 in that category will be sent to the <command>default</command> category
4355 instead. If you don't specify a default category, the following
4356 "default default" is used:
4359 <programlisting>category default { default_syslog; default_debug; };
4363 As an example, let's say you want to log security events to
4364 a file, but you also want keep the default logging behavior. You'd
4365 specify the following:
4368 <programlisting>channel my_security_channel {
4369 file "my_security_file";
4373 my_security_channel;
4379 To discard all messages in a category, specify the <command>null</command> channel:
4382 <programlisting>category xfer-out { null; };
4383 category notify { null; };
4387 Following are the available categories and brief descriptions
4388 of the types of log information they contain. More
4389 categories may be added in future <acronym>BIND</acronym> releases.
4391 <informaltable colsep="0" rowsep="0">
4392 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4393 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4394 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4398 <para><command>default</command></para>
4402 The default category defines the logging
4403 options for those categories where no specific
4404 configuration has been
4411 <para><command>general</command></para>
4415 The catch-all. Many things still aren't
4416 classified into categories, and they all end up here.
4422 <para><command>database</command></para>
4426 Messages relating to the databases used
4427 internally by the name server to store zone and cache
4434 <para><command>security</command></para>
4438 Approval and denial of requests.
4444 <para><command>config</command></para>
4448 Configuration file parsing and processing.
4454 <para><command>resolver</command></para>
4458 DNS resolution, such as the recursive
4459 lookups performed on behalf of clients by a caching name
4466 <para><command>xfer-in</command></para>
4470 Zone transfers the server is receiving.
4476 <para><command>xfer-out</command></para>
4480 Zone transfers the server is sending.
4486 <para><command>notify</command></para>
4490 The NOTIFY protocol.
4496 <para><command>client</command></para>
4500 Processing of client requests.
4506 <para><command>unmatched</command></para>
4510 Messages that <command>named</command> was unable to determine the
4511 class of or for which there was no matching <command>view</command>.
4512 A one line summary is also logged to the <command>client</command> category.
4513 This category is best sent to a file or stderr, by
4514 default it is sent to
4515 the <command>null</command> channel.
4521 <para><command>network</command></para>
4531 <para><command>update</command></para>
4541 <para><command>update-security</command></para>
4545 Approval and denial of update requests.
4551 <para><command>queries</command></para>
4555 Specify where queries should be logged to.
4558 At startup, specifying the category <command>queries</command> will also
4559 enable query logging unless <command>querylog</command> option has been
4564 The query log entry reports the client's IP
4565 address and port number, and the query name,
4566 class and type. Next it reports whether the
4567 Recursion Desired flag was set (+ if set, -
4568 if not set), if the query was signed (S),
4569 EDNS was in use (E), if TCP was used (T), if
4570 DO (DNSSEC Ok) was set (D), or if CD (Checking
4571 Disabled) was set (C). After this the
4572 destination address the query was sent to is
4577 <computeroutput>client 127.0.0.1#62536: query: www.example.com IN AAAA +SE</computeroutput>
4580 <computeroutput>client ::1#62537: query: www.example.net IN AAAA -SE</computeroutput>
4586 <para><command>query-errors</command></para>
4590 Information about queries that resulted in some
4597 <para><command>dispatch</command></para>
4601 Dispatching of incoming packets to the
4602 server modules where they are to be processed.
4608 <para><command>dnssec</command></para>
4612 DNSSEC and TSIG protocol processing.
4618 <para><command>lame-servers</command></para>
4622 Lame servers. These are misconfigurations
4623 in remote servers, discovered by BIND 9 when trying to
4624 query those servers during resolution.
4630 <para><command>delegation-only</command></para>
4634 Delegation only. Logs queries that have been
4635 forced to NXDOMAIN as the result of a
4636 delegation-only zone or a
4637 <command>delegation-only</command> in a hint
4638 or stub zone declaration.
4644 <para><command>edns-disabled</command></para>
4648 Log queries that have been forced to use plain
4649 DNS due to timeouts. This is often due to
4650 the remote servers not being RFC 1034 compliant
4651 (not always returning FORMERR or similar to
4652 EDNS queries and other extensions to the DNS
4653 when they are not understood). In other words, this is
4654 targeted at servers that fail to respond to
4655 DNS queries that they don't understand.
4658 Note: the log message can also be due to
4659 packet loss. Before reporting servers for
4660 non-RFC 1034 compliance they should be re-tested
4661 to determine the nature of the non-compliance.
4662 This testing should prevent or reduce the
4663 number of false-positive reports.
4666 Note: eventually <command>named</command> will have to stop
4667 treating such timeouts as due to RFC 1034 non
4668 compliance and start treating it as plain
4669 packet loss. Falsely classifying packet
4670 loss as due to RFC 1034 non compliance impacts
4671 on DNSSEC validation which requires EDNS for
4672 the DNSSEC records to be returned.
4678 <para><command>RPZ</command></para>
4682 Information about errors in response policy zone files,
4683 rewritten responses, and at the highest
4684 <command>debug</command> levels, mere rewriting
4694 <title>The <command>query-errors</command> Category</title>
4696 The <command>query-errors</command> category is
4697 specifically intended for debugging purposes: To identify
4698 why and how specific queries result in responses which
4700 Messages of this category are therefore only logged
4701 with <command>debug</command> levels.
4705 At the debug levels of 1 or higher, each response with the
4706 rcode of SERVFAIL is logged as follows:
4709 <computeroutput>client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</computeroutput>
4712 This means an error resulting in SERVFAIL was
4713 detected at line 3880 of source file
4714 <filename>query.c</filename>.
4715 Log messages of this level will particularly
4716 help identify the cause of SERVFAIL for an
4717 authoritative server.
4720 At the debug levels of 2 or higher, detailed context
4721 information of recursive resolutions that resulted in
4723 The log message will look like as follows:
4726 <!-- NOTE: newlines and some spaces added so this would fit on page -->
4728 fetch completed at resolver.c:2970 for www.example.com/A
4729 in 30.000183: timed out/success [domain:example.com,
4730 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
4731 badresp:1,adberr:0,findfail:0,valfail:0]
4735 The first part before the colon shows that a recursive
4736 resolution for AAAA records of www.example.com completed
4737 in 30.000183 seconds and the final result that led to the
4738 SERVFAIL was determined at line 2970 of source file
4739 <filename>resolver.c</filename>.
4742 The following part shows the detected final result and the
4743 latest result of DNSSEC validation.
4744 The latter is always success when no validation attempt
4746 In this example, this query resulted in SERVFAIL probably
4747 because all name servers are down or unreachable, leading
4748 to a timeout in 30 seconds.
4749 DNSSEC validation was probably not attempted.
4752 The last part enclosed in square brackets shows statistics
4753 information collected for this particular resolution
4755 The <varname>domain</varname> field shows the deepest zone
4756 that the resolver reached;
4757 it is the zone where the error was finally detected.
4758 The meaning of the other fields is summarized in the
4762 <informaltable colsep="0" rowsep="0">
4763 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4764 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4765 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4769 <para><varname>referral</varname></para>
4773 The number of referrals the resolver received
4774 throughout the resolution process.
4775 In the above example this is 2, which are most
4776 likely com and example.com.
4782 <para><varname>restart</varname></para>
4786 The number of cycles that the resolver tried
4787 remote servers at the <varname>domain</varname>
4789 In each cycle the resolver sends one query
4790 (possibly resending it, depending on the response)
4791 to each known name server of
4792 the <varname>domain</varname> zone.
4798 <para><varname>qrysent</varname></para>
4802 The number of queries the resolver sent at the
4803 <varname>domain</varname> zone.
4809 <para><varname>timeout</varname></para>
4813 The number of timeouts since the resolver
4814 received the last response.
4820 <para><varname>lame</varname></para>
4824 The number of lame servers the resolver detected
4825 at the <varname>domain</varname> zone.
4826 A server is detected to be lame either by an
4827 invalid response or as a result of lookup in
4828 BIND9's address database (ADB), where lame
4835 <para><varname>neterr</varname></para>
4839 The number of erroneous results that the
4840 resolver encountered in sending queries
4841 at the <varname>domain</varname> zone.
4842 One common case is the remote server is
4843 unreachable and the resolver receives an ICMP
4844 unreachable error message.
4850 <para><varname>badresp</varname></para>
4854 The number of unexpected responses (other than
4855 <varname>lame</varname>) to queries sent by the
4856 resolver at the <varname>domain</varname> zone.
4862 <para><varname>adberr</varname></para>
4866 Failures in finding remote server addresses
4867 of the <varname>domain</varname> zone in the ADB.
4868 One common case of this is that the remote
4869 server's name does not have any address records.
4875 <para><varname>findfail</varname></para>
4879 Failures of resolving remote server addresses.
4880 This is a total number of failures throughout
4881 the resolution process.
4887 <para><varname>valfail</varname></para>
4891 Failures of DNSSEC validation.
4892 Validation failures are counted throughout
4893 the resolution process (not limited to
4894 the <varname>domain</varname> zone), but should
4895 only happen in <varname>domain</varname>.
4903 At the debug levels of 3 or higher, the same messages
4904 as those at the debug 1 level are logged for other errors
4906 Note that negative responses such as NXDOMAIN are not
4907 regarded as errors here.
4910 At the debug levels of 4 or higher, the same messages
4911 as those at the debug 2 level are logged for other errors
4913 Unlike the above case of level 3, messages are logged for
4915 This is because any unexpected results can be difficult to
4916 debug in the recursion case.
4922 <title><command>lwres</command> Statement Grammar</title>
4925 This is the grammar of the <command>lwres</command>
4926 statement in the <filename>named.conf</filename> file:
4929 <programlisting><command>lwres</command> {
4930 <optional> listen-on { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
4931 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
4932 <optional> view <replaceable>view_name</replaceable>; </optional>
4933 <optional> search { <replaceable>domain_name</replaceable> ; <optional> <replaceable>domain_name</replaceable> ; ... </optional> }; </optional>
4934 <optional> ndots <replaceable>number</replaceable>; </optional>
4940 <title><command>lwres</command> Statement Definition and Usage</title>
4943 The <command>lwres</command> statement configures the
4945 server to also act as a lightweight resolver server. (See
4946 <xref linkend="lwresd"/>.) There may be multiple
4947 <command>lwres</command> statements configuring
4948 lightweight resolver servers with different properties.
4952 The <command>listen-on</command> statement specifies a
4954 addresses (and ports) that this instance of a lightweight resolver
4956 should accept requests on. If no port is specified, port 921 is
4958 If this statement is omitted, requests will be accepted on
4964 The <command>view</command> statement binds this
4966 lightweight resolver daemon to a view in the DNS namespace, so that
4968 response will be constructed in the same manner as a normal DNS
4970 matching this view. If this statement is omitted, the default view
4972 used, and if there is no default view, an error is triggered.
4976 The <command>search</command> statement is equivalent to
4978 <command>search</command> statement in
4979 <filename>/etc/resolv.conf</filename>. It provides a
4981 which are appended to relative names in queries.
4985 The <command>ndots</command> statement is equivalent to
4987 <command>ndots</command> statement in
4988 <filename>/etc/resolv.conf</filename>. It indicates the
4990 number of dots in a relative domain name that should result in an
4991 exact match lookup before search path elements are appended.
4995 <title><command>masters</command> Statement Grammar</title>
4998 <command>masters</command> <replaceable>name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> |
4999 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> };
5005 <title><command>masters</command> Statement Definition and
5007 <para><command>masters</command>
5008 lists allow for a common set of masters to be easily used by
5009 multiple stub and slave zones.
5014 <title><command>options</command> Statement Grammar</title>
5017 This is the grammar of the <command>options</command>
5018 statement in the <filename>named.conf</filename> file:
5021 <programlisting><command>options</command> {
5022 <optional> attach-cache <replaceable>cache_name</replaceable>; </optional>
5023 <optional> version <replaceable>version_string</replaceable>; </optional>
5024 <optional> hostname <replaceable>hostname_string</replaceable>; </optional>
5025 <optional> server-id <replaceable>server_id_string</replaceable>; </optional>
5026 <optional> directory <replaceable>path_name</replaceable>; </optional>
5027 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
5028 <optional> managed-keys-directory <replaceable>path_name</replaceable>; </optional>
5029 <optional> named-xfer <replaceable>path_name</replaceable>; </optional>
5030 <optional> tkey-gssapi-keytab <replaceable>path_name</replaceable>; </optional>
5031 <optional> tkey-gssapi-credential <replaceable>principal</replaceable>; </optional>
5032 <optional> tkey-domain <replaceable>domainname</replaceable>; </optional>
5033 <optional> tkey-dhkey <replaceable>key_name</replaceable> <replaceable>key_tag</replaceable>; </optional>
5034 <optional> cache-file <replaceable>path_name</replaceable>; </optional>
5035 <optional> dump-file <replaceable>path_name</replaceable>; </optional>
5036 <optional> bindkeys-file <replaceable>path_name</replaceable>; </optional>
5037 <optional> secroots-file <replaceable>path_name</replaceable>; </optional>
5038 <optional> session-keyfile <replaceable>path_name</replaceable>; </optional>
5039 <optional> session-keyname <replaceable>key_name</replaceable>; </optional>
5040 <optional> session-keyalg <replaceable>algorithm_id</replaceable>; </optional>
5041 <optional> memstatistics <replaceable>yes_or_no</replaceable>; </optional>
5042 <optional> memstatistics-file <replaceable>path_name</replaceable>; </optional>
5043 <optional> pid-file <replaceable>path_name</replaceable>; </optional>
5044 <optional> recursing-file <replaceable>path_name</replaceable>; </optional>
5045 <optional> statistics-file <replaceable>path_name</replaceable>; </optional>
5046 <optional> zone-statistics <replaceable>yes_or_no</replaceable>; </optional>
5047 <optional> auth-nxdomain <replaceable>yes_or_no</replaceable>; </optional>
5048 <optional> deallocate-on-exit <replaceable>yes_or_no</replaceable>; </optional>
5049 <optional> dialup <replaceable>dialup_option</replaceable>; </optional>
5050 <optional> fake-iquery <replaceable>yes_or_no</replaceable>; </optional>
5051 <optional> fetch-glue <replaceable>yes_or_no</replaceable>; </optional>
5052 <optional> flush-zones-on-shutdown <replaceable>yes_or_no</replaceable>; </optional>
5053 <optional> has-old-clients <replaceable>yes_or_no</replaceable>; </optional>
5054 <optional> host-statistics <replaceable>yes_or_no</replaceable>; </optional>
5055 <optional> host-statistics-max <replaceable>number</replaceable>; </optional>
5056 <optional> minimal-responses <replaceable>yes_or_no</replaceable>; </optional>
5057 <optional> multiple-cnames <replaceable>yes_or_no</replaceable>; </optional>
5058 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable>; </optional>
5059 <optional> recursion <replaceable>yes_or_no</replaceable>; </optional>
5060 <optional> rfc2308-type1 <replaceable>yes_or_no</replaceable>; </optional>
5061 <optional> use-id-pool <replaceable>yes_or_no</replaceable>; </optional>
5062 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable>; </optional>
5063 <optional> ixfr-from-differences (<replaceable>yes_or_no</replaceable> | <constant>master</constant> | <constant>slave</constant>); </optional>
5064 <optional> dnssec-enable <replaceable>yes_or_no</replaceable>; </optional>
5065 <optional> dnssec-validation (<replaceable>yes_or_no</replaceable> | <constant>auto</constant>); </optional>
5066 <optional> dnssec-lookaside ( <replaceable>auto</replaceable> |
5067 <replaceable>no</replaceable> |
5068 <replaceable>domain</replaceable> trust-anchor <replaceable>domain</replaceable> ); </optional>
5069 <optional> dnssec-must-be-secure <replaceable>domain yes_or_no</replaceable>; </optional>
5070 <optional> dnssec-accept-expired <replaceable>yes_or_no</replaceable>; </optional>
5071 <optional> forward ( <replaceable>only</replaceable> | <replaceable>first</replaceable> ); </optional>
5072 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
5073 <optional> dual-stack-servers <optional>port <replaceable>ip_port</replaceable></optional> {
5074 ( <replaceable>domain_name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> |
5075 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ) ;
5077 <optional> check-names ( <replaceable>master</replaceable> | <replaceable>slave</replaceable> | <replaceable>response</replaceable> )
5078 ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5079 <optional> check-dup-records ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5080 <optional> check-mx ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5081 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
5082 <optional> check-integrity <replaceable>yes_or_no</replaceable>; </optional>
5083 <optional> check-mx-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5084 <optional> check-srv-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
5085 <optional> check-sibling <replaceable>yes_or_no</replaceable>; </optional>
5086 <optional> allow-new-zones { <replaceable>yes_or_no</replaceable> }; </optional>
5087 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
5088 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
5089 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
5090 <optional> allow-query-cache { <replaceable>address_match_list</replaceable> }; </optional>
5091 <optional> allow-query-cache-on { <replaceable>address_match_list</replaceable> }; </optional>
5092 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
5093 <optional> allow-recursion { <replaceable>address_match_list</replaceable> }; </optional>
5094 <optional> allow-recursion-on { <replaceable>address_match_list</replaceable> }; </optional>
5095 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
5096 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
5097 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
5098 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
5099 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ;</optional>
5100 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
5101 <optional> allow-v6-synthesis { <replaceable>address_match_list</replaceable> }; </optional>
5102 <optional> blackhole { <replaceable>address_match_list</replaceable> }; </optional>
5103 <optional> use-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5104 <optional> avoid-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5105 <optional> use-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5106 <optional> avoid-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
5107 <optional> listen-on <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
5108 <optional> listen-on-v6 <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
5109 <optional> query-source ( ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> )
5110 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
5111 <optional> address ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
5112 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
5113 <optional> query-source-v6 ( ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> )
5114 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
5115 <optional> address ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
5116 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
5117 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
5118 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
5119 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
5120 <optional> max-transfer-time-in <replaceable>number</replaceable>; </optional>
5121 <optional> max-transfer-time-out <replaceable>number</replaceable>; </optional>
5122 <optional> max-transfer-idle-in <replaceable>number</replaceable>; </optional>
5123 <optional> max-transfer-idle-out <replaceable>number</replaceable>; </optional>
5124 <optional> tcp-clients <replaceable>number</replaceable>; </optional>
5125 <optional> reserved-sockets <replaceable>number</replaceable>; </optional>
5126 <optional> recursive-clients <replaceable>number</replaceable>; </optional>
5127 <optional> serial-query-rate <replaceable>number</replaceable>; </optional>
5128 <optional> serial-queries <replaceable>number</replaceable>; </optional>
5129 <optional> tcp-listen-queue <replaceable>number</replaceable>; </optional>
5130 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable>; </optional>
5131 <optional> transfers-in <replaceable>number</replaceable>; </optional>
5132 <optional> transfers-out <replaceable>number</replaceable>; </optional>
5133 <optional> transfers-per-ns <replaceable>number</replaceable>; </optional>
5134 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5135 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5136 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5137 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
5138 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5139 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
5140 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
5141 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5142 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
5143 <optional> notify-to-soa <replaceable>yes_or_no</replaceable> ; </optional>
5144 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
5145 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
5146 <optional> max-ixfr-log-size <replaceable>number</replaceable>; </optional>
5147 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
5148 <optional> coresize <replaceable>size_spec</replaceable> ; </optional>
5149 <optional> datasize <replaceable>size_spec</replaceable> ; </optional>
5150 <optional> files <replaceable>size_spec</replaceable> ; </optional>
5151 <optional> stacksize <replaceable>size_spec</replaceable> ; </optional>
5152 <optional> cleaning-interval <replaceable>number</replaceable>; </optional>
5153 <optional> heartbeat-interval <replaceable>number</replaceable>; </optional>
5154 <optional> interface-interval <replaceable>number</replaceable>; </optional>
5155 <optional> statistics-interval <replaceable>number</replaceable>; </optional>
5156 <optional> topology { <replaceable>address_match_list</replaceable> }</optional>;
5157 <optional> sortlist { <replaceable>address_match_list</replaceable> }</optional>;
5158 <optional> rrset-order { <replaceable>order_spec</replaceable> ; <optional> <replaceable>order_spec</replaceable> ; ... </optional> </optional> };
5159 <optional> lame-ttl <replaceable>number</replaceable>; </optional>
5160 <optional> max-ncache-ttl <replaceable>number</replaceable>; </optional>
5161 <optional> max-cache-ttl <replaceable>number</replaceable>; </optional>
5162 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
5163 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
5164 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
5165 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
5166 <optional> min-roots <replaceable>number</replaceable>; </optional>
5167 <optional> use-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
5168 <optional> provide-ixfr <replaceable>yes_or_no</replaceable>; </optional>
5169 <optional> request-ixfr <replaceable>yes_or_no</replaceable>; </optional>
5170 <optional> treat-cr-as-space <replaceable>yes_or_no</replaceable> ; </optional>
5171 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
5172 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
5173 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
5174 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
5175 <optional> port <replaceable>ip_port</replaceable>; </optional>
5176 <optional> additional-from-auth <replaceable>yes_or_no</replaceable> ; </optional>
5177 <optional> additional-from-cache <replaceable>yes_or_no</replaceable> ; </optional>
5178 <optional> random-device <replaceable>path_name</replaceable> ; </optional>
5179 <optional> max-cache-size <replaceable>size_spec</replaceable> ; </optional>
5180 <optional> match-mapped-addresses <replaceable>yes_or_no</replaceable>; </optional>
5181 <optional> filter-aaaa-on-v4 ( <replaceable>yes_or_no</replaceable> | <replaceable>break-dnssec</replaceable> ); </optional>
5182 <optional> filter-aaaa { <replaceable>address_match_list</replaceable> }; </optional>
5183 <optional> dns64 <replaceable>IPv6-prefix</replaceable> {
5184 <optional> clients { <replaceable>address_match_list</replaceable> }; </optional>
5185 <optional> mapped { <replaceable>address_match_list</replaceable> }; </optional>
5186 <optional> exclude { <replaceable>address_match_list</replaceable> }; </optional>
5187 <optional> suffix IPv6-address; </optional>
5188 <optional> recursive-only <replaceable>yes_or_no</replaceable>; </optional>
5189 <optional> break-dnssec <replaceable>yes_or_no</replaceable>; </optional>
5191 <optional> dns64-server <replaceable>name</replaceable> </optional>
5192 <optional> dns64-contact <replaceable>name</replaceable> </optional>
5193 <optional> preferred-glue ( <replaceable>A</replaceable> | <replaceable>AAAA</replaceable> | <replaceable>NONE</replaceable> ); </optional>
5194 <optional> edns-udp-size <replaceable>number</replaceable>; </optional>
5195 <optional> max-udp-size <replaceable>number</replaceable>; </optional>
5196 <optional> root-delegation-only <optional> exclude { <replaceable>namelist</replaceable> } </optional> ; </optional>
5197 <optional> querylog <replaceable>yes_or_no</replaceable> ; </optional>
5198 <optional> disable-algorithms <replaceable>domain</replaceable> { <replaceable>algorithm</replaceable>;
5199 <optional> <replaceable>algorithm</replaceable>; </optional> }; </optional>
5200 <optional> acache-enable <replaceable>yes_or_no</replaceable> ; </optional>
5201 <optional> acache-cleaning-interval <replaceable>number</replaceable>; </optional>
5202 <optional> max-acache-size <replaceable>size_spec</replaceable> ; </optional>
5203 <optional> clients-per-query <replaceable>number</replaceable> ; </optional>
5204 <optional> max-clients-per-query <replaceable>number</replaceable> ; </optional>
5205 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
5206 <optional> empty-server <replaceable>name</replaceable> ; </optional>
5207 <optional> empty-contact <replaceable>name</replaceable> ; </optional>
5208 <optional> empty-zones-enable <replaceable>yes_or_no</replaceable> ; </optional>
5209 <optional> disable-empty-zone <replaceable>zone_name</replaceable> ; </optional>
5210 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
5211 <optional> zero-no-soa-ttl-cache <replaceable>yes_or_no</replaceable> ; </optional>
5212 <optional> resolver-query-timeout <replaceable>number</replaceable> ; </optional>
5213 <optional> deny-answer-addresses { <replaceable>address_match_list</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
5214 <optional> deny-answer-aliases { <replaceable>namelist</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
5215 <optional> response-policy { <replaceable>zone_name</replaceable>
5216 <optional> policy given | disabled | passthru | nxdomain | nodata | cname <replaceable>domain</replaceable> </optional>
5217 <optional> recursive-only <replaceable>yes_or_no</replaceable> </optional> <optional> max-policy-ttl <replaceable>number</replaceable> </optional> ;
5218 } <optional> recursive-only <replaceable>yes_or_no</replaceable> </optional> <optional> max-policy-ttl <replaceable>number</replaceable> </optional>
5219 <optional> break-dnssec <replaceable>yes_or_no</replaceable> </optional> ; </optional>
5225 <sect2 id="options">
5226 <title><command>options</command> Statement Definition and
5230 The <command>options</command> statement sets up global
5232 to be used by <acronym>BIND</acronym>. This statement
5234 once in a configuration file. If there is no <command>options</command>
5235 statement, an options block with each option set to its default will
5242 <term><command>attach-cache</command></term>
5245 Allows multiple views to share a single cache
5247 Each view has its own cache database by default, but
5248 if multiple views have the same operational policy
5249 for name resolution and caching, those views can
5250 share a single cache to save memory and possibly
5251 improve resolution efficiency by using this option.
5255 The <command>attach-cache</command> option
5256 may also be specified in <command>view</command>
5257 statements, in which case it overrides the
5258 global <command>attach-cache</command> option.
5262 The <replaceable>cache_name</replaceable> specifies
5263 the cache to be shared.
5264 When the <command>named</command> server configures
5265 views which are supposed to share a cache, it
5266 creates a cache with the specified name for the
5267 first view of these sharing views.
5268 The rest of the views will simply refer to the
5269 already created cache.
5273 One common configuration to share a cache would be to
5274 allow all views to share a single cache.
5275 This can be done by specifying
5276 the <command>attach-cache</command> as a global
5277 option with an arbitrary name.
5281 Another possible operation is to allow a subset of
5282 all views to share a cache while the others to
5283 retain their own caches.
5284 For example, if there are three views A, B, and C,
5285 and only A and B should share a cache, specify the
5286 <command>attach-cache</command> option as a view A (or
5287 B)'s option, referring to the other view name:
5292 // this view has its own cache
5296 // this view refers to A's cache
5300 // this view has its own cache
5306 Views that share a cache must have the same policy
5307 on configurable parameters that may affect caching.
5308 The current implementation requires the following
5309 configurable options be consistent among these
5311 <command>check-names</command>,
5312 <command>cleaning-interval</command>,
5313 <command>dnssec-accept-expired</command>,
5314 <command>dnssec-validation</command>,
5315 <command>max-cache-ttl</command>,
5316 <command>max-ncache-ttl</command>,
5317 <command>max-cache-size</command>, and
5318 <command>zero-no-soa-ttl</command>.
5322 Note that there may be other parameters that may
5323 cause confusion if they are inconsistent for
5324 different views that share a single cache.
5325 For example, if these views define different sets of
5326 forwarders that can return different answers for the
5327 same question, sharing the answer does not make
5328 sense or could even be harmful.
5329 It is administrator's responsibility to ensure
5330 configuration differences in different views do
5331 not cause disruption with a shared cache.
5338 <term><command>directory</command></term>
5341 The working directory of the server.
5342 Any non-absolute pathnames in the configuration file will be
5344 as relative to this directory. The default location for most
5346 output files (e.g. <filename>named.run</filename>)
5348 If a directory is not specified, the working directory
5349 defaults to `<filename>.</filename>', the directory from
5351 was started. The directory specified should be an absolute
5358 <term><command>key-directory</command></term>
5361 When performing dynamic update of secure zones, the
5362 directory where the public and private DNSSEC key files
5363 should be found, if different than the current working
5364 directory. (Note that this option has no effect on the
5365 paths for files containing non-DNSSEC keys such as
5366 <filename>bind.keys</filename>,
5367 <filename>rndc.key</filename> or
5368 <filename>session.key</filename>.)
5374 <term><command>managed-keys-directory</command></term>
5377 The directory used to hold the files used to track managed keys.
5378 By default it is the working directory. It there are no
5379 views then the file <filename>managed-keys.bind</filename>
5380 otherwise a SHA256 hash of the view name is used with
5381 <filename>.mkeys</filename> extension added.
5387 <term><command>named-xfer</command></term>
5390 <emphasis>This option is obsolete.</emphasis> It
5391 was used in <acronym>BIND</acronym> 8 to specify
5392 the pathname to the <command>named-xfer</command>
5393 program. In <acronym>BIND</acronym> 9, no separate
5394 <command>named-xfer</command> program is needed;
5395 its functionality is built into the name server.
5401 <term><command>tkey-gssapi-keytab</command></term>
5404 The KRB5 keytab file to use for GSS-TSIG updates. If
5405 this option is set and tkey-gssapi-credential is not
5406 set, then updates will be allowed with any key
5407 matching a principal in the specified keytab.
5413 <term><command>tkey-gssapi-credential</command></term>
5416 The security credential with which the server should
5417 authenticate keys requested by the GSS-TSIG protocol.
5418 Currently only Kerberos 5 authentication is available
5419 and the credential is a Kerberos principal which the
5420 server can acquire through the default system key
5421 file, normally <filename>/etc/krb5.keytab</filename>.
5422 The location keytab file can be overridden using the
5423 tkey-gssapi-keytab option. Normally this principal is
5424 of the form "<userinput>DNS/</userinput><varname>server.domain</varname>".
5425 To use GSS-TSIG, <command>tkey-domain</command> must
5426 also be set if a specific keytab is not set with
5433 <term><command>tkey-domain</command></term>
5436 The domain appended to the names of all shared keys
5437 generated with <command>TKEY</command>. When a
5438 client requests a <command>TKEY</command> exchange,
5439 it may or may not specify the desired name for the
5440 key. If present, the name of the shared key will
5441 be <varname>client specified part</varname> +
5442 <varname>tkey-domain</varname>. Otherwise, the
5443 name of the shared key will be <varname>random hex
5444 digits</varname> + <varname>tkey-domain</varname>.
5445 In most cases, the <command>domainname</command>
5446 should be the server's domain name, or an otherwise
5447 non-existent subdomain like
5448 "_tkey.<varname>domainname</varname>". If you are
5449 using GSS-TSIG, this variable must be defined, unless
5450 you specify a specific keytab using tkey-gssapi-keytab.
5456 <term><command>tkey-dhkey</command></term>
5459 The Diffie-Hellman key used by the server
5460 to generate shared keys with clients using the Diffie-Hellman
5462 of <command>TKEY</command>. The server must be
5464 public and private keys from files in the working directory.
5466 most cases, the keyname should be the server's host name.
5472 <term><command>cache-file</command></term>
5475 This is for testing only. Do not use.
5481 <term><command>dump-file</command></term>
5484 The pathname of the file the server dumps
5485 the database to when instructed to do so with
5486 <command>rndc dumpdb</command>.
5487 If not specified, the default is <filename>named_dump.db</filename>.
5493 <term><command>memstatistics-file</command></term>
5496 The pathname of the file the server writes memory
5497 usage statistics to on exit. If not specified,
5498 the default is <filename>named.memstats</filename>.
5504 <term><command>pid-file</command></term>
5507 The pathname of the file the server writes its process ID
5508 in. If not specified, the default is
5509 <filename>/var/run/named/named.pid</filename>.
5510 The PID file is used by programs that want to send signals to
5512 name server. Specifying <command>pid-file none</command> disables the
5513 use of a PID file — no file will be written and any
5514 existing one will be removed. Note that <command>none</command>
5515 is a keyword, not a filename, and therefore is not enclosed
5523 <term><command>recursing-file</command></term>
5526 The pathname of the file the server dumps
5527 the queries that are currently recursing when instructed
5528 to do so with <command>rndc recursing</command>.
5529 If not specified, the default is <filename>named.recursing</filename>.
5535 <term><command>statistics-file</command></term>
5538 The pathname of the file the server appends statistics
5539 to when instructed to do so using <command>rndc stats</command>.
5540 If not specified, the default is <filename>named.stats</filename> in the
5541 server's current directory. The format of the file is
5543 in <xref linkend="statsfile"/>.
5549 <term><command>bindkeys-file</command></term>
5552 The pathname of a file to override the built-in trusted
5553 keys provided by <command>named</command>.
5554 See the discussion of <command>dnssec-lookaside</command>
5555 and <command>dnssec-validation</command> for details.
5556 If not specified, the default is
5557 <filename>/etc/bind.keys</filename>.
5563 <term><command>secroots-file</command></term>
5566 The pathname of the file the server dumps
5567 security roots to when instructed to do so with
5568 <command>rndc secroots</command>.
5569 If not specified, the default is
5570 <filename>named.secroots</filename>.
5576 <term><command>session-keyfile</command></term>
5579 The pathname of the file into which to write a TSIG
5580 session key generated by <command>named</command> for use by
5581 <command>nsupdate -l</command>. If not specified, the
5582 default is <filename>/var/run/named/session.key</filename>.
5583 (See <xref linkend="dynamic_update_policies"/>, and in
5584 particular the discussion of the
5585 <command>update-policy</command> statement's
5586 <userinput>local</userinput> option for more
5587 information about this feature.)
5593 <term><command>session-keyname</command></term>
5596 The key name to use for the TSIG session key.
5597 If not specified, the default is "local-ddns".
5603 <term><command>session-keyalg</command></term>
5606 The algorithm to use for the TSIG session key.
5607 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
5608 hmac-sha384, hmac-sha512 and hmac-md5. If not
5609 specified, the default is hmac-sha256.
5615 <term><command>port</command></term>
5618 The UDP/TCP port number the server uses for
5619 receiving and sending DNS protocol traffic.
5620 The default is 53. This option is mainly intended for server
5622 a server using a port other than 53 will not be able to
5630 <term><command>random-device</command></term>
5633 The source of entropy to be used by the server. Entropy is
5635 for DNSSEC operations, such as TKEY transactions and dynamic
5637 zones. This options specifies the device (or file) from which
5639 entropy. If this is a file, operations requiring entropy will
5641 file has been exhausted. If not specified, the default value
5643 <filename>/dev/random</filename>
5644 (or equivalent) when present, and none otherwise. The
5645 <command>random-device</command> option takes
5647 the initial configuration load at server startup time and
5648 is ignored on subsequent reloads.
5654 <term><command>preferred-glue</command></term>
5657 If specified, the listed type (A or AAAA) will be emitted
5659 in the additional section of a query response.
5660 The default is not to prefer any type (NONE).
5665 <varlistentry id="root_delegation_only">
5666 <term><command>root-delegation-only</command></term>
5669 Turn on enforcement of delegation-only in TLDs
5670 (top level domains) and root zones with an optional
5674 DS queries are expected to be made to and be answered by
5675 delegation only zones. Such queries and responses are
5676 treated as an exception to delegation-only processing
5677 and are not converted to NXDOMAIN responses provided
5678 a CNAME is not discovered at the query name.
5681 If a delegation only zone server also serves a child
5682 zone it is not always possible to determine whether
5683 an answer comes from the delegation only zone or the
5684 child zone. SOA NS and DNSKEY records are apex
5685 only records and a matching response that contains
5686 these records or DS is treated as coming from a
5687 child zone. RRSIG records are also examined to see
5688 if they are signed by a child zone or not. The
5689 authority section is also examined to see if there
5690 is evidence that the answer is from the child zone.
5691 Answers that are determined to be from a child zone
5692 are not converted to NXDOMAIN responses. Despite
5693 all these checks there is still a possibility of
5694 false negatives when a child zone is being served.
5697 Similarly false positives can arise from empty nodes
5698 (no records at the name) in the delegation only zone
5699 when the query type is not ANY.
5702 Note some TLDs are not delegation only (e.g. "DE", "LV",
5703 "US" and "MUSEUM"). This list is not exhaustive.
5708 root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
5716 <term><command>disable-algorithms</command></term>
5719 Disable the specified DNSSEC algorithms at and below the
5721 Multiple <command>disable-algorithms</command>
5722 statements are allowed.
5723 Only the most specific will be applied.
5729 <term><command>dnssec-lookaside</command></term>
5732 When set, <command>dnssec-lookaside</command> provides the
5733 validator with an alternate method to validate DNSKEY
5734 records at the top of a zone. When a DNSKEY is at or
5735 below a domain specified by the deepest
5736 <command>dnssec-lookaside</command>, and the normal DNSSEC
5737 validation has left the key untrusted, the trust-anchor
5738 will be appended to the key name and a DLV record will be
5739 looked up to see if it can validate the key. If the DLV
5740 record validates a DNSKEY (similarly to the way a DS
5741 record does) the DNSKEY RRset is deemed to be trusted.
5744 If <command>dnssec-lookaside</command> is set to
5745 <userinput>auto</userinput>, then built-in default
5746 values for the DLV domain and trust anchor will be
5747 used, along with a built-in key for validation.
5750 If <command>dnssec-lookaside</command> is set to
5751 <userinput>no</userinput>, then dnssec-lookaside
5755 The default DLV key is stored in the file
5756 <filename>bind.keys</filename>;
5757 <command>named</command> will load that key at
5758 startup if <command>dnssec-lookaside</command> is set to
5759 <constant>auto</constant>. A copy of the file is
5760 installed along with <acronym>BIND</acronym> 9, and is
5761 current as of the release date. If the DLV key expires, a
5762 new copy of <filename>bind.keys</filename> can be downloaded
5763 from <ulink>https://www.isc.org/solutions/dlv</ulink>.
5766 (To prevent problems if <filename>bind.keys</filename> is
5767 not found, the current key is also compiled in to
5768 <command>named</command>. Relying on this is not
5769 recommended, however, as it requires <command>named</command>
5770 to be recompiled with a new key when the DLV key expires.)
5773 NOTE: <command>named</command> only loads certain specific
5774 keys from <filename>bind.keys</filename>: those for the
5775 DLV zone and for the DNS root zone. The file cannot be
5776 used to store keys for other zones.
5782 <term><command>dnssec-must-be-secure</command></term>
5785 Specify hierarchies which must be or may not be secure
5786 (signed and validated). If <userinput>yes</userinput>,
5787 then <command>named</command> will only accept answers if
5788 they are secure. If <userinput>no</userinput>, then normal
5789 DNSSEC validation applies allowing for insecure answers to
5790 be accepted. The specified domain must be under a
5791 <command>trusted-keys</command> or
5792 <command>managed-keys</command> statement, or
5793 <command>dnssec-lookaside</command> must be active.
5799 <term><command>dns64</command></term>
5802 This directive instructs <command>named</command> to
5803 return mapped IPv4 addresses to AAAA queries when
5804 there are no AAAA records. It is intended to be
5805 used in conjunction with a NAT64. Each
5806 <command>dns64</command> defines one DNS64 prefix.
5807 Multiple DNS64 prefixes can be defined.
5810 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
5811 64 and 96 as per RFC 6052.
5814 Additionally a reverse IP6.ARPA zone will be created for
5815 the prefix to provide a mapping from the IP6.ARPA names
5816 to the corresponding IN-ADDR.ARPA names using synthesized
5817 CNAMEs. <command>dns64-server</command> and
5818 <command>dns64-contact</command> can be used to specify
5819 the name of the server and contact for the zones. These
5820 are settable at the view / options level. These are
5821 not settable on a per-prefix basis.
5824 Each <command>dns64</command> supports an optional
5825 <command>clients</command> ACL that determines which
5826 clients are affected by this directive. If not defined,
5827 it defaults to <userinput>any;</userinput>.
5830 Each <command>dns64</command> supports an optional
5831 <command>mapped</command> ACL that selects which
5832 IPv4 addresses are to be mapped in the corresponding
5833 A RRset. If not defined it defaults to
5834 <userinput>any;</userinput>.
5837 Normally, DNS64 won't apply to a domain name that
5838 owns one or more AAAA records; these records will
5839 simply be returned. The optional
5840 <command>exclude</command> ACL allows specification
5841 of a list of IPv6 addresses that will be ignored
5842 if they appear in a domain name's AAAA records, and
5843 DNS64 will be applied to any A records the domain
5844 name owns. If not defined, <command>exclude</command>
5848 A optional <command>suffix</command> can also
5849 be defined to set the bits trailing the mapped
5850 IPv4 address bits. By default these bits are
5851 set to <userinput>::</userinput>. The bits
5852 matching the prefix and mapped IPv4 address
5856 If <command>recursive-only</command> is set to
5857 <command>yes</command> the DNS64 synthesis will
5858 only happen for recursive queries. The default
5859 is <command>no</command>.
5862 If <command>break-dnssec</command> is set to
5863 <command>yes</command> the DNS64 synthesis will
5864 happen even if the result, if validated, would
5865 cause a DNSSEC validation failure. If this option
5866 is set to <command>no</command> (the default), the DO
5867 is set on the incoming query, and there are RRSIGs on
5868 the applicable records, then synthesis will not happen.
5871 acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
5873 dns64 64:FF9B::/96 {
5875 mapped { !rfc1918; any; };
5876 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
5885 <sect3 id="boolean_options">
5886 <title>Boolean Options</title>
5891 <term><command>allow-new-zones</command></term>
5894 If <userinput>yes</userinput>, then zones can be
5895 added at runtime via <command>rndc addzone</command>
5896 or deleted via <command>rndc delzone</command>.
5897 The default is <userinput>no</userinput>.
5903 <term><command>auth-nxdomain</command></term>
5906 If <userinput>yes</userinput>, then the <command>AA</command> bit
5907 is always set on NXDOMAIN responses, even if the server is
5909 authoritative. The default is <userinput>no</userinput>;
5911 a change from <acronym>BIND</acronym> 8. If you
5912 are using very old DNS software, you
5913 may need to set it to <userinput>yes</userinput>.
5919 <term><command>deallocate-on-exit</command></term>
5922 This option was used in <acronym>BIND</acronym>
5923 8 to enable checking
5924 for memory leaks on exit. <acronym>BIND</acronym> 9 ignores the option and always performs
5931 <term><command>memstatistics</command></term>
5934 Write memory statistics to the file specified by
5935 <command>memstatistics-file</command> at exit.
5936 The default is <userinput>no</userinput> unless
5937 '-m record' is specified on the command line in
5938 which case it is <userinput>yes</userinput>.
5944 <term><command>dialup</command></term>
5947 If <userinput>yes</userinput>, then the
5948 server treats all zones as if they are doing zone transfers
5950 a dial-on-demand dialup link, which can be brought up by
5952 originating from this server. This has different effects
5954 to zone type and concentrates the zone maintenance so that
5956 happens in a short interval, once every <command>heartbeat-interval</command> and
5957 hopefully during the one call. It also suppresses some of
5959 zone maintenance traffic. The default is <userinput>no</userinput>.
5962 The <command>dialup</command> option
5963 may also be specified in the <command>view</command> and
5964 <command>zone</command> statements,
5965 in which case it overrides the global <command>dialup</command>
5969 If the zone is a master zone, then the server will send out a
5971 request to all the slaves (default). This should trigger the
5973 number check in the slave (providing it supports NOTIFY)
5975 to verify the zone while the connection is active.
5976 The set of servers to which NOTIFY is sent can be controlled
5978 <command>notify</command> and <command>also-notify</command>.
5982 zone is a slave or stub zone, then the server will suppress
5984 "zone up to date" (refresh) queries and only perform them
5986 <command>heartbeat-interval</command> expires in
5991 Finer control can be achieved by using
5992 <userinput>notify</userinput> which only sends NOTIFY
5994 <userinput>notify-passive</userinput> which sends NOTIFY
5996 suppresses the normal refresh queries, <userinput>refresh</userinput>
5997 which suppresses normal refresh processing and sends refresh
5999 when the <command>heartbeat-interval</command>
6001 <userinput>passive</userinput> which just disables normal
6006 <informaltable colsep="0" rowsep="0">
6007 <tgroup cols="4" colsep="0" rowsep="0" tgroupstyle="4Level-table">
6008 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
6009 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
6010 <colspec colname="3" colnum="3" colsep="0" colwidth="1.150in"/>
6011 <colspec colname="4" colnum="4" colsep="0" colwidth="1.150in"/>
6037 <para><command>no</command> (default)</para>
6057 <para><command>yes</command></para>
6077 <para><command>notify</command></para>
6097 <para><command>refresh</command></para>
6117 <para><command>passive</command></para>
6137 <para><command>notify-passive</command></para>
6160 Note that normal NOTIFY processing is not affected by
6161 <command>dialup</command>.
6168 <term><command>fake-iquery</command></term>
6171 In <acronym>BIND</acronym> 8, this option
6172 enabled simulating the obsolete DNS query type
6173 IQUERY. <acronym>BIND</acronym> 9 never does
6180 <term><command>fetch-glue</command></term>
6183 This option is obsolete.
6184 In BIND 8, <userinput>fetch-glue yes</userinput>
6185 caused the server to attempt to fetch glue resource records
6187 didn't have when constructing the additional
6188 data section of a response. This is now considered a bad
6190 and BIND 9 never does it.
6196 <term><command>flush-zones-on-shutdown</command></term>
6199 When the nameserver exits due receiving SIGTERM,
6200 flush or do not flush any pending zone writes. The default
6202 <command>flush-zones-on-shutdown</command> <userinput>no</userinput>.
6208 <term><command>has-old-clients</command></term>
6211 This option was incorrectly implemented
6212 in <acronym>BIND</acronym> 8, and is ignored by <acronym>BIND</acronym> 9.
6213 To achieve the intended effect
6215 <command>has-old-clients</command> <userinput>yes</userinput>, specify
6216 the two separate options <command>auth-nxdomain</command> <userinput>yes</userinput>
6217 and <command>rfc2308-type1</command> <userinput>no</userinput> instead.
6223 <term><command>host-statistics</command></term>
6226 In BIND 8, this enables keeping of
6227 statistics for every host that the name server interacts
6229 Not implemented in BIND 9.
6235 <term><command>maintain-ixfr-base</command></term>
6238 <emphasis>This option is obsolete</emphasis>.
6239 It was used in <acronym>BIND</acronym> 8 to
6240 determine whether a transaction log was
6241 kept for Incremental Zone Transfer. <acronym>BIND</acronym> 9 maintains a transaction
6242 log whenever possible. If you need to disable outgoing
6244 transfers, use <command>provide-ixfr</command> <userinput>no</userinput>.
6250 <term><command>minimal-responses</command></term>
6253 If <userinput>yes</userinput>, then when generating
6254 responses the server will only add records to the authority
6255 and additional data sections when they are required (e.g.
6256 delegations, negative responses). This may improve the
6257 performance of the server.
6258 The default is <userinput>no</userinput>.
6264 <term><command>multiple-cnames</command></term>
6267 This option was used in <acronym>BIND</acronym> 8 to allow
6268 a domain name to have multiple CNAME records in violation of
6269 the DNS standards. <acronym>BIND</acronym> 9.2 onwards
6270 always strictly enforces the CNAME rules both in master
6271 files and dynamic updates.
6277 <term><command>notify</command></term>
6280 If <userinput>yes</userinput> (the default),
6281 DNS NOTIFY messages are sent when a zone the server is
6283 changes, see <xref linkend="notify"/>. The messages are
6285 servers listed in the zone's NS records (except the master
6287 in the SOA MNAME field), and to any servers listed in the
6288 <command>also-notify</command> option.
6291 If <userinput>master-only</userinput>, notifies are only
6294 If <userinput>explicit</userinput>, notifies are sent only
6296 servers explicitly listed using <command>also-notify</command>.
6297 If <userinput>no</userinput>, no notifies are sent.
6300 The <command>notify</command> option may also be
6301 specified in the <command>zone</command>
6303 in which case it overrides the <command>options notify</command> statement.
6304 It would only be necessary to turn off this option if it
6312 <term><command>notify-to-soa</command></term>
6315 If <userinput>yes</userinput> do not check the nameservers
6316 in the NS RRset against the SOA MNAME. Normally a NOTIFY
6317 message is not sent to the SOA MNAME (SOA ORIGIN) as it is
6318 supposed to contain the name of the ultimate master.
6319 Sometimes, however, a slave is listed as the SOA MNAME in
6320 hidden master configurations and in that case you would
6321 want the ultimate master to still send NOTIFY messages to
6322 all the nameservers listed in the NS RRset.
6328 <term><command>recursion</command></term>
6331 If <userinput>yes</userinput>, and a
6332 DNS query requests recursion, then the server will attempt
6334 all the work required to answer the query. If recursion is
6336 and the server does not already know the answer, it will
6338 referral response. The default is
6339 <userinput>yes</userinput>.
6340 Note that setting <command>recursion no</command> does not prevent
6341 clients from getting data from the server's cache; it only
6342 prevents new data from being cached as an effect of client
6344 Caching may still occur as an effect the server's internal
6345 operation, such as NOTIFY address lookups.
6346 See also <command>fetch-glue</command> above.
6352 <term><command>rfc2308-type1</command></term>
6355 Setting this to <userinput>yes</userinput> will
6356 cause the server to send NS records along with the SOA
6358 answers. The default is <userinput>no</userinput>.
6362 Not yet implemented in <acronym>BIND</acronym>
6370 <term><command>use-id-pool</command></term>
6373 <emphasis>This option is obsolete</emphasis>.
6374 <acronym>BIND</acronym> 9 always allocates query
6381 <term><command>zone-statistics</command></term>
6384 If <userinput>yes</userinput>, the server will collect
6385 statistical data on all zones (unless specifically turned
6387 on a per-zone basis by specifying <command>zone-statistics no</command>
6388 in the <command>zone</command> statement).
6389 The default is <userinput>no</userinput>.
6390 These statistics may be accessed
6391 using <command>rndc stats</command>, which will
6392 dump them to the file listed
6393 in the <command>statistics-file</command>. See
6394 also <xref linkend="statsfile"/>.
6400 <term><command>use-ixfr</command></term>
6403 <emphasis>This option is obsolete</emphasis>.
6404 If you need to disable IXFR to a particular server or
6406 the information on the <command>provide-ixfr</command> option
6407 in <xref linkend="server_statement_definition_and_usage"/>.
6409 <xref linkend="incremental_zone_transfers"/>.
6415 <term><command>provide-ixfr</command></term>
6418 See the description of
6419 <command>provide-ixfr</command> in
6420 <xref linkend="server_statement_definition_and_usage"/>.
6426 <term><command>request-ixfr</command></term>
6429 See the description of
6430 <command>request-ixfr</command> in
6431 <xref linkend="server_statement_definition_and_usage"/>.
6437 <term><command>treat-cr-as-space</command></term>
6440 This option was used in <acronym>BIND</acronym>
6442 the server treat carriage return ("<command>\r</command>") characters the same way
6443 as a space or tab character,
6444 to facilitate loading of zone files on a UNIX system that
6446 on an NT or DOS machine. In <acronym>BIND</acronym> 9, both UNIX "<command>\n</command>"
6447 and NT/DOS "<command>\r\n</command>" newlines
6448 are always accepted,
6449 and the option is ignored.
6455 <term><command>additional-from-auth</command></term>
6456 <term><command>additional-from-cache</command></term>
6460 These options control the behavior of an authoritative
6462 answering queries which have additional data, or when
6468 When both of these options are set to <userinput>yes</userinput>
6470 query is being answered from authoritative data (a zone
6471 configured into the server), the additional data section of
6473 reply will be filled in using data from other authoritative
6475 and from the cache. In some situations this is undesirable,
6477 as when there is concern over the correctness of the cache,
6479 in servers where slave zones may be added and modified by
6480 untrusted third parties. Also, avoiding
6481 the search for this additional data will speed up server
6483 at the possible expense of additional queries to resolve
6485 otherwise be provided in the additional section.
6489 For example, if a query asks for an MX record for host <literal>foo.example.com</literal>,
6490 and the record found is "<literal>MX 10 mail.example.net</literal>", normally the address
6491 records (A and AAAA) for <literal>mail.example.net</literal> will be provided as well,
6492 if known, even though they are not in the example.com zone.
6493 Setting these options to <command>no</command>
6494 disables this behavior and makes
6495 the server only search for additional data in the zone it
6500 These options are intended for use in authoritative-only
6501 servers, or in authoritative-only views. Attempts to set
6502 them to <command>no</command> without also
6504 <command>recursion no</command> will cause the
6506 ignore the options and log a warning message.
6510 Specifying <command>additional-from-cache no</command> actually
6511 disables the use of the cache not only for additional data
6513 but also when looking up the answer. This is usually the
6515 behavior in an authoritative-only server where the
6517 the cached data is an issue.
6521 When a name server is non-recursively queried for a name
6523 below the apex of any served zone, it normally answers with
6525 "upwards referral" to the root servers or the servers of
6527 known parent of the query name. Since the data in an
6529 comes from the cache, the server will not be able to provide
6531 referrals when <command>additional-from-cache no</command>
6532 has been specified. Instead, it will respond to such
6534 with REFUSED. This should not cause any problems since
6535 upwards referrals are not required for the resolution
6543 <term><command>match-mapped-addresses</command></term>
6546 If <userinput>yes</userinput>, then an
6547 IPv4-mapped IPv6 address will match any address match
6548 list entries that match the corresponding IPv4 address.
6551 This option was introduced to work around a kernel quirk
6552 in some operating systems that causes IPv4 TCP
6553 connections, such as zone transfers, to be accepted on an
6554 IPv6 socket using mapped addresses. This caused address
6555 match lists designed for IPv4 to fail to match. However,
6556 <command>named</command> now solves this problem
6557 internally. The use of this option is discouraged.
6563 <term><command>filter-aaaa-on-v4</command></term>
6566 This option is only available when
6567 <acronym>BIND</acronym> 9 is compiled with the
6568 <userinput>--enable-filter-aaaa</userinput> option on the
6569 "configure" command line. It is intended to help the
6570 transition from IPv4 to IPv6 by not giving IPv6 addresses
6571 to DNS clients unless they have connections to the IPv6
6572 Internet. This is not recommended unless absolutely
6573 necessary. The default is <userinput>no</userinput>.
6574 The <command>filter-aaaa-on-v4</command> option
6575 may also be specified in <command>view</command> statements
6576 to override the global <command>filter-aaaa-on-v4</command>
6580 If <userinput>yes</userinput>,
6581 the DNS client is at an IPv4 address, in <command>filter-aaaa</command>,
6582 and if the response does not include DNSSEC signatures,
6583 then all AAAA records are deleted from the response.
6584 This filtering applies to all responses and not only
6585 authoritative responses.
6588 If <userinput>break-dnssec</userinput>,
6589 then AAAA records are deleted even when dnssec is enabled.
6590 As suggested by the name, this makes the response not verify,
6591 because the DNSSEC protocol is designed detect deletions.
6594 This mechanism can erroneously cause other servers to
6595 not give AAAA records to their clients.
6596 A recursing server with both IPv6 and IPv4 network connections
6597 that queries an authoritative server using this mechanism
6598 via IPv4 will be denied AAAA records even if its client is
6602 This mechanism is applied to authoritative as well as
6603 non-authoritative records.
6604 A client using IPv4 that is not allowed recursion can
6605 erroneously be given AAAA records because the server is not
6606 allowed to check for A records.
6609 Some AAAA records are given to IPv4 clients in glue records.
6610 IPv4 clients that are servers can then erroneously
6611 answer requests for AAAA records received via IPv4.
6617 <term><command>ixfr-from-differences</command></term>
6620 When <userinput>yes</userinput> and the server loads a new version of a master
6621 zone from its zone file or receives a new version of a slave
6622 file by a non-incremental zone transfer, it will compare
6623 the new version to the previous one and calculate a set
6624 of differences. The differences are then logged in the
6625 zone's journal file such that the changes can be transmitted
6626 to downstream slaves as an incremental zone transfer.
6629 By allowing incremental zone transfers to be used for
6630 non-dynamic zones, this option saves bandwidth at the
6631 expense of increased CPU and memory consumption at the
6633 In particular, if the new version of a zone is completely
6634 different from the previous one, the set of differences
6635 will be of a size comparable to the combined size of the
6636 old and new zone version, and the server will need to
6637 temporarily allocate memory to hold this complete
6640 <para><command>ixfr-from-differences</command>
6641 also accepts <command>master</command> and
6642 <command>slave</command> at the view and options
6644 <command>ixfr-from-differences</command> to be enabled for
6645 all <command>master</command> or
6646 <command>slave</command> zones respectively.
6647 It is off by default.
6653 <term><command>multi-master</command></term>
6656 This should be set when you have multiple masters for a zone
6658 addresses refer to different machines. If <userinput>yes</userinput>, <command>named</command> will
6660 when the serial number on the master is less than what <command>named</command>
6662 has. The default is <userinput>no</userinput>.
6668 <term><command>dnssec-enable</command></term>
6671 Enable DNSSEC support in <command>named</command>. Unless set to <userinput>yes</userinput>,
6672 <command>named</command> behaves as if it does not support DNSSEC.
6673 The default is <userinput>yes</userinput>.
6679 <term><command>dnssec-validation</command></term>
6682 Enable DNSSEC validation in <command>named</command>.
6683 Note <command>dnssec-enable</command> also needs to be
6684 set to <userinput>yes</userinput> to be effective.
6685 If set to <userinput>no</userinput>, DNSSEC validation
6686 is disabled. If set to <userinput>auto</userinput>,
6687 DNSSEC validation is enabled, and a default
6688 trust-anchor for the DNS root zone is used. If set to
6689 <userinput>yes</userinput>, DNSSEC validation is enabled,
6690 but a trust anchor must be manually configured using
6691 a <command>trusted-keys</command> or
6692 <command>managed-keys</command> statement. The default
6693 is <userinput>yes</userinput>.
6699 <term><command>dnssec-accept-expired</command></term>
6702 Accept expired signatures when verifying DNSSEC signatures.
6703 The default is <userinput>no</userinput>.
6704 Setting this option to <userinput>yes</userinput>
6705 leaves <command>named</command> vulnerable to
6712 <term><command>querylog</command></term>
6715 Specify whether query logging should be started when <command>named</command>
6717 If <command>querylog</command> is not specified,
6718 then the query logging
6719 is determined by the presence of the logging category <command>queries</command>.
6725 <term><command>check-names</command></term>
6728 This option is used to restrict the character set and syntax
6730 certain domain names in master files and/or DNS responses
6732 from the network. The default varies according to usage
6734 <command>master</command> zones the default is <command>fail</command>.
6735 For <command>slave</command> zones the default
6736 is <command>warn</command>.
6737 For answers received from the network (<command>response</command>)
6738 the default is <command>ignore</command>.
6741 The rules for legal hostnames and mail domains are derived
6742 from RFC 952 and RFC 821 as modified by RFC 1123.
6744 <para><command>check-names</command>
6745 applies to the owner names of A, AAAA and MX records.
6746 It also applies to the domain names in the RDATA of NS, SOA,
6747 MX, and SRV records.
6748 It also applies to the RDATA of PTR records where the owner
6749 name indicated that it is a reverse lookup of a hostname
6750 (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
6756 <term><command>check-dup-records</command></term>
6759 Check master zones for records that are treated as different
6760 by DNSSEC but are semantically equal in plain DNS. The
6761 default is to <command>warn</command>. Other possible
6762 values are <command>fail</command> and
6763 <command>ignore</command>.
6769 <term><command>check-mx</command></term>
6772 Check whether the MX record appears to refer to a IP address.
6773 The default is to <command>warn</command>. Other possible
6774 values are <command>fail</command> and
6775 <command>ignore</command>.
6781 <term><command>check-wildcard</command></term>
6784 This option is used to check for non-terminal wildcards.
6785 The use of non-terminal wildcards is almost always as a
6787 to understand the wildcard matching algorithm (RFC 1034).
6789 affects master zones. The default (<command>yes</command>) is to check
6790 for non-terminal wildcards and issue a warning.
6796 <term><command>check-integrity</command></term>
6799 Perform post load zone integrity checks on master
6800 zones. This checks that MX and SRV records refer
6801 to address (A or AAAA) records and that glue
6802 address records exist for delegated zones. For
6803 MX and SRV records only in-zone hostnames are
6804 checked (for out-of-zone hostnames use
6805 <command>named-checkzone</command>).
6806 For NS records only names below top of zone are
6807 checked (for out-of-zone names and glue consistency
6808 checks use <command>named-checkzone</command>).
6809 The default is <command>yes</command>.
6815 <term><command>check-mx-cname</command></term>
6818 If <command>check-integrity</command> is set then
6819 fail, warn or ignore MX records that refer
6820 to CNAMES. The default is to <command>warn</command>.
6826 <term><command>check-srv-cname</command></term>
6829 If <command>check-integrity</command> is set then
6830 fail, warn or ignore SRV records that refer
6831 to CNAMES. The default is to <command>warn</command>.
6837 <term><command>check-sibling</command></term>
6840 When performing integrity checks, also check that
6841 sibling glue exists. The default is <command>yes</command>.
6847 <term><command>zero-no-soa-ttl</command></term>
6850 When returning authoritative negative responses to
6851 SOA queries set the TTL of the SOA record returned in
6852 the authority section to zero.
6853 The default is <command>yes</command>.
6859 <term><command>zero-no-soa-ttl-cache</command></term>
6862 When caching a negative response to a SOA query
6863 set the TTL to zero.
6864 The default is <command>no</command>.
6870 <term><command>update-check-ksk</command></term>
6873 When set to the default value of <literal>yes</literal>,
6874 check the KSK bit in each key to determine how the key
6875 should be used when generating RRSIGs for a secure zone.
6878 Ordinarily, zone-signing keys (that is, keys without the
6879 KSK bit set) are used to sign the entire zone, while
6880 key-signing keys (keys with the KSK bit set) are only
6881 used to sign the DNSKEY RRset at the zone apex.
6882 However, if this option is set to <literal>no</literal>,
6883 then the KSK bit is ignored; KSKs are treated as if they
6884 were ZSKs and are used to sign the entire zone. This is
6885 similar to the <command>dnssec-signzone -z</command>
6886 command line option.
6889 When this option is set to <literal>yes</literal>, there
6890 must be at least two active keys for every algorithm
6891 represented in the DNSKEY RRset: at least one KSK and one
6892 ZSK per algorithm. If there is any algorithm for which
6893 this requirement is not met, this option will be ignored
6900 <term><command>dnssec-dnskey-kskonly</command></term>
6903 When this option and <command>update-check-ksk</command>
6904 are both set to <literal>yes</literal>, only key-signing
6905 keys (that is, keys with the KSK bit set) will be used
6906 to sign the DNSKEY RRset at the zone apex. Zone-signing
6907 keys (keys without the KSK bit set) will be used to sign
6908 the remainder of the zone, but not the DNSKEY RRset.
6909 This is similar to the
6910 <command>dnssec-signzone -x</command> command line option.
6913 The default is <command>no</command>. If
6914 <command>update-check-ksk</command> is set to
6915 <literal>no</literal>, this option is ignored.
6921 <term><command>try-tcp-refresh</command></term>
6924 Try to refresh the zone using TCP if UDP queries fail.
6925 For BIND 8 compatibility, the default is
6926 <command>yes</command>.
6932 <term><command>dnssec-secure-to-insecure</command></term>
6935 Allow a dynamic zone to transition from secure to
6936 insecure (i.e., signed to unsigned) by deleting all
6937 of the DNSKEY records. The default is <command>no</command>.
6938 If set to <command>yes</command>, and if the DNSKEY RRset
6939 at the zone apex is deleted, all RRSIG and NSEC records
6940 will be removed from the zone as well.
6943 If the zone uses NSEC3, then it is also necessary to
6944 delete the NSEC3PARAM RRset from the zone apex; this will
6945 cause the removal of all corresponding NSEC3 records.
6946 (It is expected that this requirement will be eliminated
6947 in a future release.)
6950 Note that if a zone has been configured with
6951 <command>auto-dnssec maintain</command> and the
6952 private keys remain accessible in the key repository,
6953 then the zone will be automatically signed again the
6954 next time <command>named</command> is started.
6964 <title>Forwarding</title>
6966 The forwarding facility can be used to create a large site-wide
6967 cache on a few servers, reducing traffic over links to external
6968 name servers. It can also be used to allow queries by servers that
6969 do not have direct access to the Internet, but wish to look up
6971 names anyway. Forwarding occurs only on those queries for which
6972 the server is not authoritative and does not have the answer in
6978 <term><command>forward</command></term>
6981 This option is only meaningful if the
6982 forwarders list is not empty. A value of <varname>first</varname>,
6983 the default, causes the server to query the forwarders
6985 if that doesn't answer the question, the server will then
6987 the answer itself. If <varname>only</varname> is
6989 server will only query the forwarders.
6995 <term><command>forwarders</command></term>
6998 Specifies the IP addresses to be used
6999 for forwarding. The default is the empty list (no
7008 Forwarding can also be configured on a per-domain basis, allowing
7009 for the global forwarding options to be overridden in a variety
7010 of ways. You can set particular domains to use different
7012 or have a different <command>forward only/first</command> behavior,
7013 or not forward at all, see <xref linkend="zone_statement_grammar"/>.
7018 <title>Dual-stack Servers</title>
7020 Dual-stack servers are used as servers of last resort to work
7022 problems in reachability due the lack of support for either IPv4
7024 on the host machine.
7029 <term><command>dual-stack-servers</command></term>
7032 Specifies host names or addresses of machines with access to
7033 both IPv4 and IPv6 transports. If a hostname is used, the
7035 to resolve the name using only the transport it has. If the
7037 stacked, then the <command>dual-stack-servers</command> have no effect unless
7038 access to a transport has been disabled on the command line
7039 (e.g. <command>named -4</command>).
7046 <sect3 id="access_control">
7047 <title>Access Control</title>
7050 Access to the server can be restricted based on the IP address
7051 of the requesting system. See <xref linkend="address_match_lists"/> for
7052 details on how to specify IP address lists.
7058 <term><command>allow-notify</command></term>
7061 Specifies which hosts are allowed to
7062 notify this server, a slave, of zone changes in addition
7063 to the zone masters.
7064 <command>allow-notify</command> may also be
7066 <command>zone</command> statement, in which case
7068 <command>options allow-notify</command>
7069 statement. It is only meaningful
7070 for a slave zone. If not specified, the default is to
7071 process notify messages
7072 only from a zone's master.
7078 <term><command>allow-query</command></term>
7081 Specifies which hosts are allowed to ask ordinary
7082 DNS questions. <command>allow-query</command> may
7083 also be specified in the <command>zone</command>
7084 statement, in which case it overrides the
7085 <command>options allow-query</command> statement.
7086 If not specified, the default is to allow queries
7091 <command>allow-query-cache</command> is now
7092 used to specify access to the cache.
7099 <term><command>allow-query-on</command></term>
7102 Specifies which local addresses can accept ordinary
7103 DNS questions. This makes it possible, for instance,
7104 to allow queries on internal-facing interfaces but
7105 disallow them on external-facing ones, without
7106 necessarily knowing the internal network's addresses.
7109 <command>allow-query-on</command> may
7110 also be specified in the <command>zone</command>
7111 statement, in which case it overrides the
7112 <command>options allow-query-on</command> statement.
7115 If not specified, the default is to allow queries
7120 <command>allow-query-cache</command> is
7121 used to specify access to the cache.
7128 <term><command>allow-query-cache</command></term>
7131 Specifies which hosts are allowed to get answers
7132 from the cache. If <command>allow-query-cache</command>
7133 is not set then <command>allow-recursion</command>
7134 is used if set, otherwise <command>allow-query</command>
7135 is used if set unless <command>recursion no;</command> is
7136 set in which case <command>none;</command> is used,
7137 otherwise the default (<command>localnets;</command>
7138 <command>localhost;</command>) is used.
7144 <term><command>allow-query-cache-on</command></term>
7147 Specifies which local addresses can give answers
7148 from the cache. If not specified, the default is
7149 to allow cache queries on any address,
7150 <command>localnets</command> and
7151 <command>localhost</command>.
7157 <term><command>allow-recursion</command></term>
7160 Specifies which hosts are allowed to make recursive
7161 queries through this server. If
7162 <command>allow-recursion</command> is not set
7163 then <command>allow-query-cache</command> is
7164 used if set, otherwise <command>allow-query</command>
7165 is used if set, otherwise the default
7166 (<command>localnets;</command>
7167 <command>localhost;</command>) is used.
7173 <term><command>allow-recursion-on</command></term>
7176 Specifies which local addresses can accept recursive
7177 queries. If not specified, the default is to allow
7178 recursive queries on all addresses.
7184 <term><command>allow-update</command></term>
7187 Specifies which hosts are allowed to
7188 submit Dynamic DNS updates for master zones. The default is
7190 updates from all hosts. Note that allowing updates based
7191 on the requestor's IP address is insecure; see
7192 <xref linkend="dynamic_update_security"/> for details.
7198 <term><command>allow-update-forwarding</command></term>
7201 Specifies which hosts are allowed to
7202 submit Dynamic DNS updates to slave zones to be forwarded to
7204 master. The default is <userinput>{ none; }</userinput>,
7206 means that no update forwarding will be performed. To
7208 update forwarding, specify
7209 <userinput>allow-update-forwarding { any; };</userinput>.
7210 Specifying values other than <userinput>{ none; }</userinput> or
7211 <userinput>{ any; }</userinput> is usually
7212 counterproductive, since
7213 the responsibility for update access control should rest
7215 master server, not the slaves.
7218 Note that enabling the update forwarding feature on a slave
7220 may expose master servers relying on insecure IP address
7222 access control to attacks; see <xref linkend="dynamic_update_security"/>
7229 <term><command>allow-v6-synthesis</command></term>
7232 This option was introduced for the smooth transition from
7234 to A6 and from "nibble labels" to binary labels.
7235 However, since both A6 and binary labels were then
7237 this option was also deprecated.
7238 It is now ignored with some warning messages.
7244 <term><command>allow-transfer</command></term>
7247 Specifies which hosts are allowed to
7248 receive zone transfers from the server. <command>allow-transfer</command> may
7249 also be specified in the <command>zone</command>
7251 case it overrides the <command>options allow-transfer</command> statement.
7252 If not specified, the default is to allow transfers to all
7259 <term><command>blackhole</command></term>
7262 Specifies a list of addresses that the
7263 server will not accept queries from or use to resolve a
7265 from these addresses will not be responded to. The default
7266 is <userinput>none</userinput>.
7272 <term><command>filter-aaaa</command></term>
7275 Specifies a list of addresses to which
7276 <command>filter-aaaa-on-v4</command>
7277 is applies. The default is <userinput>any</userinput>.
7283 <term><command>resolver-query-timeout</command></term>
7286 The amount of time the resolver will spend attempting
7287 to resolve a recursive query before failing. The default
7288 and minimum is <literal>10</literal> and the maximum is
7289 <literal>30</literal>. Setting it to <literal>0</literal>
7290 will result in the default being used.
7299 <title>Interfaces</title>
7301 The interfaces and ports that the server will answer queries
7302 from may be specified using the <command>listen-on</command> option. <command>listen-on</command> takes
7303 an optional port and an <varname>address_match_list</varname>.
7304 The server will listen on all interfaces allowed by the address
7305 match list. If a port is not specified, port 53 will be used.
7308 Multiple <command>listen-on</command> statements are
7313 <programlisting>listen-on { 5.6.7.8; };
7314 listen-on port 1234 { !1.2.3.4; 1.2/16; };
7318 will enable the name server on port 53 for the IP address
7319 5.6.7.8, and on port 1234 of an address on the machine in net
7320 1.2 that is not 1.2.3.4.
7324 If no <command>listen-on</command> is specified, the
7325 server will listen on port 53 on all IPv4 interfaces.
7329 The <command>listen-on-v6</command> option is used to
7330 specify the interfaces and the ports on which the server will
7332 for incoming queries sent using IPv6.
7336 When <programlisting>{ any; }</programlisting> is
7338 as the <varname>address_match_list</varname> for the
7339 <command>listen-on-v6</command> option,
7340 the server does not bind a separate socket to each IPv6 interface
7341 address as it does for IPv4 if the operating system has enough API
7342 support for IPv6 (specifically if it conforms to RFC 3493 and RFC
7344 Instead, it listens on the IPv6 wildcard address.
7345 If the system only has incomplete API support for IPv6, however,
7346 the behavior is the same as that for IPv4.
7350 A list of particular IPv6 addresses can also be specified, in
7352 the server listens on a separate socket for each specified
7354 regardless of whether the desired API is supported by the system.
7358 Multiple <command>listen-on-v6</command> options can
7363 <programlisting>listen-on-v6 { any; };
7364 listen-on-v6 port 1234 { !2001:db8::/32; any; };
7368 will enable the name server on port 53 for any IPv6 addresses
7369 (with a single wildcard socket),
7370 and on port 1234 of IPv6 addresses that is not in the prefix
7371 2001:db8::/32 (with separate sockets for each matched address.)
7375 To make the server not listen on any IPv6 address, use
7378 <programlisting>listen-on-v6 { none; };
7382 If no <command>listen-on-v6</command> option is
7383 specified, the server will not listen on any IPv6 address
7384 unless <command>-6</command> is specified when <command>named</command> is
7385 invoked. If <command>-6</command> is specified then
7386 <command>named</command> will listen on port 53 on all IPv6 interfaces by default.
7390 <sect3 id="query_address">
7391 <title>Query Address</title>
7393 If the server doesn't know the answer to a question, it will
7394 query other name servers. <command>query-source</command> specifies
7395 the address and port used for such queries. For queries sent over
7396 IPv6, there is a separate <command>query-source-v6</command> option.
7397 If <command>address</command> is <command>*</command> (asterisk) or is omitted,
7398 a wildcard IP address (<command>INADDR_ANY</command>)
7403 If <command>port</command> is <command>*</command> or is omitted,
7404 a random port number from a pre-configured
7405 range is picked up and will be used for each query.
7406 The port range(s) is that specified in
7407 the <command>use-v4-udp-ports</command> (for IPv4)
7408 and <command>use-v6-udp-ports</command> (for IPv6)
7409 options, excluding the ranges specified in
7410 the <command>avoid-v4-udp-ports</command>
7411 and <command>avoid-v6-udp-ports</command> options, respectively.
7415 The defaults of the <command>query-source</command> and
7416 <command>query-source-v6</command> options
7420 <programlisting>query-source address * port *;
7421 query-source-v6 address * port *;
7425 If <command>use-v4-udp-ports</command> or
7426 <command>use-v6-udp-ports</command> is unspecified,
7427 <command>named</command> will check if the operating
7428 system provides a programming interface to retrieve the
7429 system's default range for ephemeral ports.
7430 If such an interface is available,
7431 <command>named</command> will use the corresponding system
7432 default range; otherwise, it will use its own defaults:
7435 <programlisting>use-v4-udp-ports { range 1024 65535; };
7436 use-v6-udp-ports { range 1024 65535; };
7440 Note: make sure the ranges be sufficiently large for
7441 security. A desirable size depends on various parameters,
7442 but we generally recommend it contain at least 16384 ports
7443 (14 bits of entropy).
7444 Note also that the system's default range when used may be
7445 too small for this purpose, and that the range may even be
7446 changed while <command>named</command> is running; the new
7447 range will automatically be applied when <command>named</command>
7450 configure <command>use-v4-udp-ports</command> and
7451 <command>use-v6-udp-ports</command> explicitly so that the
7452 ranges are sufficiently large and are reasonably
7453 independent from the ranges used by other applications.
7457 Note: the operational configuration
7458 where <command>named</command> runs may prohibit the use
7459 of some ports. For example, UNIX systems will not allow
7460 <command>named</command> running without a root privilege
7461 to use ports less than 1024.
7462 If such ports are included in the specified (or detected)
7463 set of query ports, the corresponding query attempts will
7464 fail, resulting in resolution failures or delay.
7465 It is therefore important to configure the set of ports
7466 that can be safely used in the expected operational environment.
7470 The defaults of the <command>avoid-v4-udp-ports</command> and
7471 <command>avoid-v6-udp-ports</command> options
7475 <programlisting>avoid-v4-udp-ports {};
7476 avoid-v6-udp-ports {};
7480 Note: BIND 9.5.0 introduced
7481 the <command>use-queryport-pool</command>
7482 option to support a pool of such random ports, but this
7483 option is now obsolete because reusing the same ports in
7484 the pool may not be sufficiently secure.
7485 For the same reason, it is generally strongly discouraged to
7486 specify a particular port for the
7487 <command>query-source</command> or
7488 <command>query-source-v6</command> options;
7489 it implicitly disables the use of randomized port numbers.
7494 <term><command>use-queryport-pool</command></term>
7497 This option is obsolete.
7503 <term><command>queryport-pool-ports</command></term>
7506 This option is obsolete.
7512 <term><command>queryport-pool-updateinterval</command></term>
7515 This option is obsolete.
7523 The address specified in the <command>query-source</command> option
7524 is used for both UDP and TCP queries, but the port applies only
7525 to UDP queries. TCP queries always use a random
7531 Solaris 2.5.1 and earlier does not support setting the source
7532 address for TCP sockets.
7537 See also <command>transfer-source</command> and
7538 <command>notify-source</command>.
7543 <sect3 id="zone_transfers">
7544 <title>Zone Transfers</title>
7546 <acronym>BIND</acronym> has mechanisms in place to
7547 facilitate zone transfers
7548 and set limits on the amount of load that transfers place on the
7549 system. The following options apply to zone transfers.
7555 <term><command>also-notify</command></term>
7558 Defines a global list of IP addresses of name servers
7559 that are also sent NOTIFY messages whenever a fresh copy of
7561 zone is loaded, in addition to the servers listed in the
7563 This helps to ensure that copies of the zones will
7564 quickly converge on stealth servers.
7565 Optionally, a port may be specified with each
7566 <command>also-notify</command> address to send
7567 the notify messages to a port other than the
7569 If an <command>also-notify</command> list
7570 is given in a <command>zone</command> statement,
7572 the <command>options also-notify</command>
7573 statement. When a <command>zone notify</command>
7575 is set to <command>no</command>, the IP
7576 addresses in the global <command>also-notify</command> list will
7577 not be sent NOTIFY messages for that zone. The default is
7579 list (no global notification list).
7585 <term><command>max-transfer-time-in</command></term>
7588 Inbound zone transfers running longer than
7589 this many minutes will be terminated. The default is 120
7591 (2 hours). The maximum value is 28 days (40320 minutes).
7597 <term><command>max-transfer-idle-in</command></term>
7600 Inbound zone transfers making no progress
7601 in this many minutes will be terminated. The default is 60
7603 (1 hour). The maximum value is 28 days (40320 minutes).
7609 <term><command>max-transfer-time-out</command></term>
7612 Outbound zone transfers running longer than
7613 this many minutes will be terminated. The default is 120
7615 (2 hours). The maximum value is 28 days (40320 minutes).
7621 <term><command>max-transfer-idle-out</command></term>
7624 Outbound zone transfers making no progress
7625 in this many minutes will be terminated. The default is 60
7627 hour). The maximum value is 28 days (40320 minutes).
7633 <term><command>serial-query-rate</command></term>
7636 Slave servers will periodically query master
7637 servers to find out if zone serial numbers have
7638 changed. Each such query uses a minute amount of
7639 the slave server's network bandwidth. To limit
7640 the amount of bandwidth used, BIND 9 limits the
7641 rate at which queries are sent. The value of the
7642 <command>serial-query-rate</command> option, an
7643 integer, is the maximum number of queries sent
7644 per second. The default is 20.
7647 In addition to controlling the rate SOA refresh
7648 queries are issued at
7649 <command>serial-query-rate</command> also controls
7650 the rate at which NOTIFY messages are sent from
7651 both master and slave zones.
7657 <term><command>serial-queries</command></term>
7660 In BIND 8, the <command>serial-queries</command>
7662 set the maximum number of concurrent serial number queries
7663 allowed to be outstanding at any given time.
7664 BIND 9 does not limit the number of outstanding
7665 serial queries and ignores the <command>serial-queries</command> option.
7666 Instead, it limits the rate at which the queries are sent
7667 as defined using the <command>serial-query-rate</command> option.
7673 <term><command>transfer-format</command></term>
7677 Zone transfers can be sent using two different formats,
7678 <command>one-answer</command> and
7679 <command>many-answers</command>.
7680 The <command>transfer-format</command> option is used
7681 on the master server to determine which format it sends.
7682 <command>one-answer</command> uses one DNS message per
7683 resource record transferred.
7684 <command>many-answers</command> packs as many resource
7685 records as possible into a message.
7686 <command>many-answers</command> is more efficient, but is
7687 only supported by relatively new slave servers,
7688 such as <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
7689 8.x and <acronym>BIND</acronym> 4.9.5 onwards.
7690 The <command>many-answers</command> format is also supported by
7691 recent Microsoft Windows nameservers.
7692 The default is <command>many-answers</command>.
7693 <command>transfer-format</command> may be overridden on a
7694 per-server basis by using the <command>server</command>
7702 <term><command>transfers-in</command></term>
7705 The maximum number of inbound zone transfers
7706 that can be running concurrently. The default value is <literal>10</literal>.
7707 Increasing <command>transfers-in</command> may
7708 speed up the convergence
7709 of slave zones, but it also may increase the load on the
7716 <term><command>transfers-out</command></term>
7719 The maximum number of outbound zone transfers
7720 that can be running concurrently. Zone transfer requests in
7722 of the limit will be refused. The default value is <literal>10</literal>.
7728 <term><command>transfers-per-ns</command></term>
7731 The maximum number of inbound zone transfers
7732 that can be concurrently transferring from a given remote
7734 The default value is <literal>2</literal>.
7735 Increasing <command>transfers-per-ns</command>
7737 speed up the convergence of slave zones, but it also may
7739 the load on the remote name server. <command>transfers-per-ns</command> may
7740 be overridden on a per-server basis by using the <command>transfers</command> phrase
7741 of the <command>server</command> statement.
7747 <term><command>transfer-source</command></term>
7749 <para><command>transfer-source</command>
7750 determines which local address will be bound to IPv4
7751 TCP connections used to fetch zones transferred
7752 inbound by the server. It also determines the
7753 source IPv4 address, and optionally the UDP port,
7754 used for the refresh queries and forwarded dynamic
7755 updates. If not set, it defaults to a system
7756 controlled value which will usually be the address
7757 of the interface "closest to" the remote end. This
7758 address must appear in the remote end's
7759 <command>allow-transfer</command> option for the
7760 zone being transferred, if one is specified. This
7762 <command>transfer-source</command> for all zones,
7763 but can be overridden on a per-view or per-zone
7764 basis by including a
7765 <command>transfer-source</command> statement within
7766 the <command>view</command> or
7767 <command>zone</command> block in the configuration
7772 Solaris 2.5.1 and earlier does not support setting the
7773 source address for TCP sockets.
7780 <term><command>transfer-source-v6</command></term>
7783 The same as <command>transfer-source</command>,
7784 except zone transfers are performed using IPv6.
7790 <term><command>alt-transfer-source</command></term>
7793 An alternate transfer source if the one listed in
7794 <command>transfer-source</command> fails and
7795 <command>use-alt-transfer-source</command> is
7799 If you do not wish the alternate transfer source
7800 to be used, you should set
7801 <command>use-alt-transfer-source</command>
7802 appropriately and you should not depend upon
7803 getting an answer back to the first refresh
7810 <term><command>alt-transfer-source-v6</command></term>
7813 An alternate transfer source if the one listed in
7814 <command>transfer-source-v6</command> fails and
7815 <command>use-alt-transfer-source</command> is
7822 <term><command>use-alt-transfer-source</command></term>
7825 Use the alternate transfer sources or not. If views are
7826 specified this defaults to <command>no</command>
7827 otherwise it defaults to
7828 <command>yes</command> (for BIND 8
7835 <term><command>notify-source</command></term>
7837 <para><command>notify-source</command>
7838 determines which local source address, and
7839 optionally UDP port, will be used to send NOTIFY
7840 messages. This address must appear in the slave
7841 server's <command>masters</command> zone clause or
7842 in an <command>allow-notify</command> clause. This
7843 statement sets the <command>notify-source</command>
7844 for all zones, but can be overridden on a per-zone or
7845 per-view basis by including a
7846 <command>notify-source</command> statement within
7847 the <command>zone</command> or
7848 <command>view</command> block in the configuration
7853 Solaris 2.5.1 and earlier does not support setting the
7854 source address for TCP sockets.
7861 <term><command>notify-source-v6</command></term>
7864 Like <command>notify-source</command>,
7865 but applies to notify messages sent to IPv6 addresses.
7875 <title>UDP Port Lists</title>
7877 <command>use-v4-udp-ports</command>,
7878 <command>avoid-v4-udp-ports</command>,
7879 <command>use-v6-udp-ports</command>, and
7880 <command>avoid-v6-udp-ports</command>
7881 specify a list of IPv4 and IPv6 UDP ports that will be
7882 used or not used as source ports for UDP messages.
7883 See <xref linkend="query_address"/> about how the
7884 available ports are determined.
7885 For example, with the following configuration
7889 use-v6-udp-ports { range 32768 65535; };
7890 avoid-v6-udp-ports { 40000; range 50000 60000; };
7894 UDP ports of IPv6 messages sent
7895 from <command>named</command> will be in one
7896 of the following ranges: 32768 to 39999, 40001 to 49999,
7901 <command>avoid-v4-udp-ports</command> and
7902 <command>avoid-v6-udp-ports</command> can be used
7903 to prevent <command>named</command> from choosing as its random source port a
7904 port that is blocked by your firewall or a port that is
7905 used by other applications;
7906 if a query went out with a source port blocked by a
7908 answer would not get by the firewall and the name server would
7909 have to query again.
7910 Note: the desired range can also be represented only with
7911 <command>use-v4-udp-ports</command> and
7912 <command>use-v6-udp-ports</command>, and the
7913 <command>avoid-</command> options are redundant in that
7914 sense; they are provided for backward compatibility and
7915 to possibly simplify the port specification.
7920 <title>Operating System Resource Limits</title>
7923 The server's usage of many system resources can be limited.
7924 Scaled values are allowed when specifying resource limits. For
7925 example, <command>1G</command> can be used instead of
7926 <command>1073741824</command> to specify a limit of
7928 gigabyte. <command>unlimited</command> requests
7929 unlimited use, or the
7930 maximum available amount. <command>default</command>
7932 that was in force when the server was started. See the description
7933 of <command>size_spec</command> in <xref linkend="configuration_file_elements"/>.
7937 The following options set operating system resource limits for
7938 the name server process. Some operating systems don't support
7940 any of the limits. On such systems, a warning will be issued if
7942 unsupported limit is used.
7948 <term><command>coresize</command></term>
7951 The maximum size of a core dump. The default
7952 is <literal>default</literal>.
7958 <term><command>datasize</command></term>
7961 The maximum amount of data memory the server
7962 may use. The default is <literal>default</literal>.
7963 This is a hard limit on server memory usage.
7964 If the server attempts to allocate memory in excess of this
7965 limit, the allocation will fail, which may in turn leave
7966 the server unable to perform DNS service. Therefore,
7967 this option is rarely useful as a way of limiting the
7968 amount of memory used by the server, but it can be used
7969 to raise an operating system data size limit that is
7970 too small by default. If you wish to limit the amount
7971 of memory used by the server, use the
7972 <command>max-cache-size</command> and
7973 <command>recursive-clients</command>
7980 <term><command>files</command></term>
7983 The maximum number of files the server
7984 may have open concurrently. The default is <literal>unlimited</literal>.
7990 <term><command>stacksize</command></term>
7993 The maximum amount of stack memory the server
7994 may use. The default is <literal>default</literal>.
8003 <sect3 id="server_resource_limits">
8004 <title>Server Resource Limits</title>
8007 The following options set limits on the server's
8008 resource consumption that are enforced internally by the
8009 server rather than the operating system.
8015 <term><command>max-ixfr-log-size</command></term>
8018 This option is obsolete; it is accepted
8019 and ignored for BIND 8 compatibility. The option
8020 <command>max-journal-size</command> performs a
8021 similar function in BIND 9.
8027 <term><command>max-journal-size</command></term>
8030 Sets a maximum size for each journal file
8031 (see <xref linkend="journal"/>). When the journal file
8033 the specified size, some of the oldest transactions in the
8035 will be automatically removed. The default is
8036 <literal>unlimited</literal>.
8037 This may also be set on a per-zone basis.
8043 <term><command>host-statistics-max</command></term>
8046 In BIND 8, specifies the maximum number of host statistics
8048 Not implemented in BIND 9.
8054 <term><command>recursive-clients</command></term>
8057 The maximum number of simultaneous recursive lookups
8058 the server will perform on behalf of clients. The default
8060 <literal>1000</literal>. Because each recursing
8062 bit of memory, on the order of 20 kilobytes, the value of
8064 <command>recursive-clients</command> option may
8065 have to be decreased
8066 on hosts with limited memory.
8072 <term><command>tcp-clients</command></term>
8075 The maximum number of simultaneous client TCP
8076 connections that the server will accept.
8077 The default is <literal>100</literal>.
8083 <term><command>reserved-sockets</command></term>
8086 The number of file descriptors reserved for TCP, stdio,
8087 etc. This needs to be big enough to cover the number of
8088 interfaces <command>named</command> listens on, <command>tcp-clients</command> as well as
8089 to provide room for outgoing TCP queries and incoming zone
8090 transfers. The default is <literal>512</literal>.
8091 The minimum value is <literal>128</literal> and the
8092 maximum value is <literal>128</literal> less than
8093 maxsockets (-S). This option may be removed in the future.
8096 This option has little effect on Windows.
8102 <term><command>max-cache-size</command></term>
8105 The maximum amount of memory to use for the
8106 server's cache, in bytes.
8107 When the amount of data in the cache
8108 reaches this limit, the server will cause records to expire
8109 prematurely based on an LRU based strategy so that
8110 the limit is not exceeded.
8111 A value of 0 is special, meaning that
8112 records are purged from the cache only when their
8114 Another special keyword <userinput>unlimited</userinput>
8115 means the maximum value of 32-bit unsigned integers
8116 (0xffffffff), which may not have the same effect as
8117 0 on machines that support more than 32 bits of
8119 Any positive values less than 2MB will be ignored reset
8121 In a server with multiple views, the limit applies
8122 separately to the cache of each view.
8129 <term><command>tcp-listen-queue</command></term>
8132 The listen queue depth. The default and minimum is 3.
8133 If the kernel supports the accept filter "dataready" this
8135 many TCP connections that will be queued in kernel space
8137 some data before being passed to accept. Values less than 3
8149 <title>Periodic Task Intervals</title>
8154 <term><command>cleaning-interval</command></term>
8157 This interval is effectively obsolete. Previously,
8158 the server would remove expired resource records
8159 from the cache every <command>cleaning-interval</command> minutes.
8160 <acronym>BIND</acronym> 9 now manages cache
8161 memory in a more sophisticated manner and does not
8162 rely on the periodic cleaning any more.
8163 Specifying this option therefore has no effect on
8164 the server's behavior.
8170 <term><command>heartbeat-interval</command></term>
8173 The server will perform zone maintenance tasks
8174 for all zones marked as <command>dialup</command> whenever this
8175 interval expires. The default is 60 minutes. Reasonable
8177 to 1 day (1440 minutes). The maximum value is 28 days
8179 If set to 0, no zone maintenance for these zones will occur.
8185 <term><command>interface-interval</command></term>
8188 The server will scan the network interface list
8189 every <command>interface-interval</command>
8190 minutes. The default
8191 is 60 minutes. The maximum value is 28 days (40320 minutes).
8192 If set to 0, interface scanning will only occur when
8193 the configuration file is loaded. After the scan, the
8195 begin listening for queries on any newly discovered
8196 interfaces (provided they are allowed by the
8197 <command>listen-on</command> configuration), and
8199 stop listening on interfaces that have gone away.
8205 <term><command>statistics-interval</command></term>
8208 Name server statistics will be logged
8209 every <command>statistics-interval</command>
8210 minutes. The default is
8211 60. The maximum value is 28 days (40320 minutes).
8212 If set to 0, no statistics will be logged.
8215 Not yet implemented in
8216 <acronym>BIND</acronym> 9.
8226 <sect3 id="topology">
8227 <title>Topology</title>
8230 All other things being equal, when the server chooses a name
8232 to query from a list of name servers, it prefers the one that is
8233 topologically closest to itself. The <command>topology</command> statement
8234 takes an <command>address_match_list</command> and
8236 in a special way. Each top-level list element is assigned a
8238 Non-negated elements get a distance based on their position in the
8239 list, where the closer the match is to the start of the list, the
8240 shorter the distance is between it and the server. A negated match
8241 will be assigned the maximum distance from the server. If there
8242 is no match, the address will get a distance which is further than
8243 any non-negated list element, and closer than any negated element.
8247 <programlisting>topology {
8254 will prefer servers on network 10 the most, followed by hosts
8255 on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
8256 exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
8257 is preferred least of all.
8260 The default topology is
8263 <programlisting> topology { localhost; localnets; };
8268 The <command>topology</command> option
8269 is not implemented in <acronym>BIND</acronym> 9.
8274 <sect3 id="the_sortlist_statement">
8276 <title>The <command>sortlist</command> Statement</title>
8279 The response to a DNS query may consist of multiple resource
8280 records (RRs) forming a resource records set (RRset).
8281 The name server will normally return the
8282 RRs within the RRset in an indeterminate order
8283 (but see the <command>rrset-order</command>
8284 statement in <xref linkend="rrset_ordering"/>).
8285 The client resolver code should rearrange the RRs as appropriate,
8286 that is, using any addresses on the local net in preference to
8288 However, not all resolvers can do this or are correctly
8290 When a client is using a local server, the sorting can be performed
8291 in the server, based on the client's address. This only requires
8292 configuring the name servers, not all the clients.
8296 The <command>sortlist</command> statement (see below)
8298 an <command>address_match_list</command> and
8300 more specifically than the <command>topology</command>
8302 does (<xref linkend="topology"/>).
8303 Each top level statement in the <command>sortlist</command> must
8304 itself be an explicit <command>address_match_list</command> with
8305 one or two elements. The first element (which may be an IP
8307 an IP prefix, an ACL name or a nested <command>address_match_list</command>)
8308 of each top level list is checked against the source address of
8309 the query until a match is found.
8312 Once the source address of the query has been matched, if
8313 the top level statement contains only one element, the actual
8315 element that matched the source address is used to select the
8317 in the response to move to the beginning of the response. If the
8318 statement is a list of two elements, then the second element is
8319 treated the same as the <command>address_match_list</command> in
8320 a <command>topology</command> statement. Each top
8322 is assigned a distance and the address in the response with the
8324 distance is moved to the beginning of the response.
8327 In the following example, any queries received from any of
8328 the addresses of the host itself will get responses preferring
8330 on any of the locally connected networks. Next most preferred are
8332 on the 192.168.1/24 network, and after that either the
8335 192.168.3/24 network with no preference shown between these two
8336 networks. Queries received from a host on the 192.168.1/24 network
8337 will prefer other addresses on that network to the 192.168.2/24
8339 192.168.3/24 networks. Queries received from a host on the
8341 or the 192.168.5/24 network will only prefer other addresses on
8342 their directly connected networks.
8345 <programlisting>sortlist {
8346 // IF the local host
8347 // THEN first fit on the following nets
8351 { 192.168.2/24; 192.168.3/24; }; }; };
8352 // IF on class C 192.168.1 THEN use .1, or .2 or .3
8355 { 192.168.2/24; 192.168.3/24; }; }; };
8356 // IF on class C 192.168.2 THEN use .2, or .1 or .3
8359 { 192.168.1/24; 192.168.3/24; }; }; };
8360 // IF on class C 192.168.3 THEN use .3, or .1 or .2
8363 { 192.168.1/24; 192.168.2/24; }; }; };
8364 // IF .4 or .5 THEN prefer that net
8365 { { 192.168.4/24; 192.168.5/24; };
8370 The following example will give reasonable behavior for the
8371 local host and hosts on directly connected networks. It is similar
8372 to the behavior of the address sort in <acronym>BIND</acronym> 4.9.x. Responses sent
8373 to queries from the local host will favor any of the directly
8375 networks. Responses sent to queries from any other hosts on a
8377 connected network will prefer addresses on that same network.
8379 to other queries will not be sorted.
8382 <programlisting>sortlist {
8383 { localhost; localnets; };
8389 <sect3 id="rrset_ordering">
8390 <title id="rrset_ordering_title">RRset Ordering</title>
8392 When multiple records are returned in an answer it may be
8393 useful to configure the order of the records placed into the
8395 The <command>rrset-order</command> statement permits
8397 of the ordering of the records in a multiple record response.
8398 See also the <command>sortlist</command> statement,
8399 <xref linkend="the_sortlist_statement"/>.
8403 An <command>order_spec</command> is defined as
8407 <optional>class <replaceable>class_name</replaceable></optional>
8408 <optional>type <replaceable>type_name</replaceable></optional>
8409 <optional>name <replaceable>"domain_name"</replaceable></optional>
8410 order <replaceable>ordering</replaceable>
8413 If no class is specified, the default is <command>ANY</command>.
8414 If no type is specified, the default is <command>ANY</command>.
8415 If no name is specified, the default is "<command>*</command>" (asterisk).
8418 The legal values for <command>ordering</command> are:
8420 <informaltable colsep="0" rowsep="0">
8421 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
8422 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
8423 <colspec colname="2" colnum="2" colsep="0" colwidth="3.750in"/>
8427 <para><command>fixed</command></para>
8431 Records are returned in the order they
8432 are defined in the zone file.
8438 <para><command>random</command></para>
8442 Records are returned in some random order.
8448 <para><command>cyclic</command></para>
8452 Records are returned in a cyclic round-robin order.
8455 If <acronym>BIND</acronym> is configured with the
8456 "--enable-fixed-rrset" option at compile time, then
8457 the initial ordering of the RRset will match the
8458 one specified in the zone file.
8469 <programlisting>rrset-order {
8470 class IN type A name "host.example.com" order random;
8476 will cause any responses for type A records in class IN that
8477 have "<literal>host.example.com</literal>" as a
8478 suffix, to always be returned
8479 in random order. All other records are returned in cyclic order.
8482 If multiple <command>rrset-order</command> statements
8484 they are not combined — the last one applies.
8489 In this release of <acronym>BIND</acronym> 9, the
8490 <command>rrset-order</command> statement does not support
8491 "fixed" ordering by default. Fixed ordering can be enabled
8492 at compile time by specifying "--enable-fixed-rrset" on
8493 the "configure" command line.
8499 <title>Tuning</title>
8504 <term><command>lame-ttl</command></term>
8507 Sets the number of seconds to cache a
8508 lame server indication. 0 disables caching. (This is
8509 <emphasis role="bold">NOT</emphasis> recommended.)
8510 The default is <literal>600</literal> (10 minutes) and the
8512 <literal>1800</literal> (30 minutes).
8516 Lame-ttl also controls the amount of time DNSSEC
8517 validation failures are cached. There is a minimum
8518 of 30 seconds applied to bad cache entries if the
8519 lame-ttl is set to less than 30 seconds.
8526 <term><command>max-ncache-ttl</command></term>
8529 To reduce network traffic and increase performance,
8530 the server stores negative answers. <command>max-ncache-ttl</command> is
8531 used to set a maximum retention time for these answers in
8533 in seconds. The default
8534 <command>max-ncache-ttl</command> is <literal>10800</literal> seconds (3 hours).
8535 <command>max-ncache-ttl</command> cannot exceed
8537 be silently truncated to 7 days if set to a greater value.
8543 <term><command>max-cache-ttl</command></term>
8546 Sets the maximum time for which the server will
8547 cache ordinary (positive) answers. The default is
8549 A value of zero may cause all queries to return
8550 SERVFAIL, because of lost caches of intermediate
8551 RRsets (such as NS and glue AAAA/A records) in the
8558 <term><command>min-roots</command></term>
8561 The minimum number of root servers that
8562 is required for a request for the root servers to be
8563 accepted. The default
8564 is <userinput>2</userinput>.
8568 Not implemented in <acronym>BIND</acronym> 9.
8575 <term><command>sig-validity-interval</command></term>
8578 Specifies the number of days into the future when
8579 DNSSEC signatures automatically generated as a
8580 result of dynamic updates (<xref
8581 linkend="dynamic_update"/>) will expire. There
8582 is an optional second field which specifies how
8583 long before expiry that the signatures will be
8584 regenerated. If not specified, the signatures will
8585 be regenerated at 1/4 of base interval. The second
8586 field is specified in days if the base interval is
8587 greater than 7 days otherwise it is specified in hours.
8588 The default base interval is <literal>30</literal> days
8589 giving a re-signing interval of 7 1/2 days. The maximum
8590 values are 10 years (3660 days).
8593 The signature inception time is unconditionally
8594 set to one hour before the current time to allow
8595 for a limited amount of clock skew.
8598 The <command>sig-validity-interval</command>
8599 should be, at least, several multiples of the SOA
8600 expire interval to allow for reasonable interaction
8601 between the various timer and expiry dates.
8607 <term><command>sig-signing-nodes</command></term>
8610 Specify the maximum number of nodes to be
8611 examined in each quantum when signing a zone with
8612 a new DNSKEY. The default is
8613 <literal>100</literal>.
8619 <term><command>sig-signing-signatures</command></term>
8622 Specify a threshold number of signatures that
8623 will terminate processing a quantum when signing
8624 a zone with a new DNSKEY. The default is
8625 <literal>10</literal>.
8631 <term><command>sig-signing-type</command></term>
8634 Specify a private RDATA type to be used when generating
8635 key signing records. The default is
8636 <literal>65534</literal>.
8639 It is expected that this parameter may be removed
8640 in a future version once there is a standard type.
8646 <term><command>min-refresh-time</command></term>
8647 <term><command>max-refresh-time</command></term>
8648 <term><command>min-retry-time</command></term>
8649 <term><command>max-retry-time</command></term>
8652 These options control the server's behavior on refreshing a
8654 (querying for SOA changes) or retrying failed transfers.
8655 Usually the SOA values for the zone are used, but these
8657 are set by the master, giving slave server administrators
8659 control over their contents.
8662 These options allow the administrator to set a minimum and
8664 refresh and retry time either per-zone, per-view, or
8666 These options are valid for slave and stub zones,
8667 and clamp the SOA refresh and retry times to the specified
8671 The following defaults apply.
8672 <command>min-refresh-time</command> 300 seconds,
8673 <command>max-refresh-time</command> 2419200 seconds
8674 (4 weeks), <command>min-retry-time</command> 500 seconds,
8675 and <command>max-retry-time</command> 1209600 seconds
8682 <term><command>edns-udp-size</command></term>
8685 Sets the advertised EDNS UDP buffer size in bytes
8686 to control the size of packets received.
8687 Valid values are 512 to 4096 (values outside this range
8688 will be silently adjusted). The default value
8689 is 4096. The usual reason for setting
8690 <command>edns-udp-size</command> to a non-default
8691 value is to get UDP answers to pass through broken
8692 firewalls that block fragmented packets and/or
8693 block UDP packets that are greater than 512 bytes.
8696 <command>named</command> will fallback to using 512 bytes
8697 if it get a series of timeout at the initial value. 512
8698 bytes is not being offered to encourage sites to fix their
8699 firewalls. Small EDNS UDP sizes will result in the
8700 excessive use of TCP.
8706 <term><command>max-udp-size</command></term>
8709 Sets the maximum EDNS UDP message size
8710 <command>named</command> will send in bytes.
8711 Valid values are 512 to 4096 (values outside this
8712 range will be silently adjusted). The default
8713 value is 4096. The usual reason for setting
8714 <command>max-udp-size</command> to a non-default
8715 value is to get UDP answers to pass through broken
8716 firewalls that block fragmented packets and/or
8717 block UDP packets that are greater than 512 bytes.
8718 This is independent of the advertised receive
8719 buffer (<command>edns-udp-size</command>).
8722 Setting this to a low value will encourage additional
8723 TCP traffic to the nameserver.
8729 <term><command>masterfile-format</command></term>
8732 the file format of zone files (see
8733 <xref linkend="zonefile_format"/>).
8734 The default value is <constant>text</constant>, which is the
8735 standard textual representation. Files in other formats
8736 than <constant>text</constant> are typically expected
8737 to be generated by the <command>named-compilezone</command> tool.
8738 Note that when a zone file in a different format than
8739 <constant>text</constant> is loaded, <command>named</command>
8740 may omit some of the checks which would be performed for a
8741 file in the <constant>text</constant> format. In particular,
8742 <command>check-names</command> checks do not apply
8743 for the <constant>raw</constant> format. This means
8744 a zone file in the <constant>raw</constant> format
8745 must be generated with the same check level as that
8746 specified in the <command>named</command> configuration
8747 file. This statement sets the
8748 <command>masterfile-format</command> for all zones,
8749 but can be overridden on a per-zone or per-view basis
8750 by including a <command>masterfile-format</command>
8751 statement within the <command>zone</command> or
8752 <command>view</command> block in the configuration
8758 <varlistentry id="clients-per-query">
8759 <term><command>clients-per-query</command></term>
8760 <term><command>max-clients-per-query</command></term>
8763 initial value (minimum) and maximum number of recursive
8764 simultaneous clients for any given query
8765 (<qname,qtype,qclass>) that the server will accept
8766 before dropping additional clients. <command>named</command> will attempt to
8767 self tune this value and changes will be logged. The
8768 default values are 10 and 100.
8771 This value should reflect how many queries come in for
8772 a given name in the time it takes to resolve that name.
8773 If the number of queries exceed this value, <command>named</command> will
8774 assume that it is dealing with a non-responsive zone
8775 and will drop additional queries. If it gets a response
8776 after dropping queries, it will raise the estimate. The
8777 estimate will then be lowered in 20 minutes if it has
8781 If <command>clients-per-query</command> is set to zero,
8782 then there is no limit on the number of clients per query
8783 and no queries will be dropped.
8786 If <command>max-clients-per-query</command> is set to zero,
8787 then there is no upper bound other than imposed by
8788 <command>recursive-clients</command>.
8794 <term><command>notify-delay</command></term>
8797 The delay, in seconds, between sending sets of notify
8798 messages for a zone. The default is five (5) seconds.
8801 The overall rate that NOTIFY messages are sent for all
8802 zones is controlled by <command>serial-query-rate</command>.
8810 <sect3 id="builtin">
8811 <title>Built-in server information zones</title>
8814 The server provides some helpful diagnostic information
8815 through a number of built-in zones under the
8816 pseudo-top-level-domain <literal>bind</literal> in the
8817 <command>CHAOS</command> class. These zones are part
8819 built-in view (see <xref linkend="view_statement_grammar"/>) of
8821 <command>CHAOS</command> which is separate from the
8823 class <command>IN</command>; therefore, any global
8825 such as <command>allow-query</command> do not apply
8827 If you feel the need to disable these zones, use the options
8828 below, or hide the built-in <command>CHAOS</command>
8830 defining an explicit view of class <command>CHAOS</command>
8831 that matches all clients.
8837 <term><command>version</command></term>
8840 The version the server should report
8841 via a query of the name <literal>version.bind</literal>
8842 with type <command>TXT</command>, class <command>CHAOS</command>.
8843 The default is the real version number of this server.
8844 Specifying <command>version none</command>
8845 disables processing of the queries.
8851 <term><command>hostname</command></term>
8854 The hostname the server should report via a query of
8855 the name <filename>hostname.bind</filename>
8856 with type <command>TXT</command>, class <command>CHAOS</command>.
8857 This defaults to the hostname of the machine hosting the
8859 found by the gethostname() function. The primary purpose of such queries
8861 identify which of a group of anycast servers is actually
8862 answering your queries. Specifying <command>hostname none;</command>
8863 disables processing of the queries.
8869 <term><command>server-id</command></term>
8872 The ID the server should report when receiving a Name
8873 Server Identifier (NSID) query, or a query of the name
8874 <filename>ID.SERVER</filename> with type
8875 <command>TXT</command>, class <command>CHAOS</command>.
8876 The primary purpose of such queries is to
8877 identify which of a group of anycast servers is actually
8878 answering your queries. Specifying <command>server-id none;</command>
8879 disables processing of the queries.
8880 Specifying <command>server-id hostname;</command> will cause <command>named</command> to
8881 use the hostname as found by the gethostname() function.
8882 The default <command>server-id</command> is <command>none</command>.
8892 <title>Built-in Empty Zones</title>
8894 Named has some built-in empty zones (SOA and NS records only).
8895 These are for zones that should normally be answered locally
8896 and which queries should not be sent to the Internet's root
8897 servers. The official servers which cover these namespaces
8898 return NXDOMAIN responses to these queries. In particular,
8899 these cover the reverse namespaces for addresses from
8900 RFC 1918, RFC 4193, and RFC 5737. They also include the
8901 reverse namespace for IPv6 local address (locally assigned),
8902 IPv6 link local addresses, the IPv6 loopback address and the
8903 IPv6 unknown address.
8906 Named will attempt to determine if a built-in zone already exists
8907 or is active (covered by a forward-only forwarding declaration)
8908 and will not create an empty zone in that case.
8911 The current list of empty zones is:
8913 <listitem>10.IN-ADDR.ARPA</listitem>
8914 <listitem>16.172.IN-ADDR.ARPA</listitem>
8915 <listitem>17.172.IN-ADDR.ARPA</listitem>
8916 <listitem>18.172.IN-ADDR.ARPA</listitem>
8917 <listitem>19.172.IN-ADDR.ARPA</listitem>
8918 <listitem>20.172.IN-ADDR.ARPA</listitem>
8919 <listitem>21.172.IN-ADDR.ARPA</listitem>
8920 <listitem>22.172.IN-ADDR.ARPA</listitem>
8921 <listitem>23.172.IN-ADDR.ARPA</listitem>
8922 <listitem>24.172.IN-ADDR.ARPA</listitem>
8923 <listitem>25.172.IN-ADDR.ARPA</listitem>
8924 <listitem>26.172.IN-ADDR.ARPA</listitem>
8925 <listitem>27.172.IN-ADDR.ARPA</listitem>
8926 <listitem>28.172.IN-ADDR.ARPA</listitem>
8927 <listitem>29.172.IN-ADDR.ARPA</listitem>
8928 <listitem>30.172.IN-ADDR.ARPA</listitem>
8929 <listitem>31.172.IN-ADDR.ARPA</listitem>
8930 <listitem>168.192.IN-ADDR.ARPA</listitem>
8931 <listitem>0.IN-ADDR.ARPA</listitem>
8932 <listitem>127.IN-ADDR.ARPA</listitem>
8933 <listitem>254.169.IN-ADDR.ARPA</listitem>
8934 <listitem>2.0.192.IN-ADDR.ARPA</listitem>
8935 <listitem>100.51.198.IN-ADDR.ARPA</listitem>
8936 <listitem>113.0.203.IN-ADDR.ARPA</listitem>
8937 <listitem>255.255.255.255.IN-ADDR.ARPA</listitem>
8938 <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>
8939 <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>
8940 <listitem>8.B.D.0.1.0.0.2.IP6.ARPA</listitem>
8941 <listitem>D.F.IP6.ARPA</listitem>
8942 <listitem>8.E.F.IP6.ARPA</listitem>
8943 <listitem>9.E.F.IP6.ARPA</listitem>
8944 <listitem>A.E.F.IP6.ARPA</listitem>
8945 <listitem>B.E.F.IP6.ARPA</listitem>
8949 Empty zones are settable at the view level and only apply to
8950 views of class IN. Disabled empty zones are only inherited
8951 from options if there are no disabled empty zones specified
8952 at the view level. To override the options list of disabled
8953 zones, you can disable the root zone at the view level, for example:
8955 disable-empty-zone ".";
8959 If you are using the address ranges covered here, you should
8960 already have reverse zones covering the addresses you use.
8961 In practice this appears to not be the case with many queries
8962 being made to the infrastructure servers for names in these
8963 spaces. So many in fact that sacrificial servers were needed
8964 to be deployed to channel the query load away from the
8965 infrastructure servers.
8968 The real parent servers for these zones should disable all
8969 empty zone under the parent zone they serve. For the real
8970 root servers, this is all built-in empty zones. This will
8971 enable them to return referrals to deeper in the tree.
8975 <term><command>empty-server</command></term>
8978 Specify what server name will appear in the returned
8979 SOA record for empty zones. If none is specified, then
8980 the zone's name will be used.
8986 <term><command>empty-contact</command></term>
8989 Specify what contact name will appear in the returned
8990 SOA record for empty zones. If none is specified, then
8997 <term><command>empty-zones-enable</command></term>
9000 Enable or disable all empty zones. By default, they
9007 <term><command>disable-empty-zone</command></term>
9010 Disable individual empty zones. By default, none are
9011 disabled. This option can be specified multiple times.
9019 <title>Additional Section Caching</title>
9022 The additional section cache, also called <command>acache</command>,
9023 is an internal cache to improve the response performance of BIND 9.
9024 When additional section caching is enabled, BIND 9 will
9025 cache an internal short-cut to the additional section content for
9027 Note that <command>acache</command> is an internal caching
9028 mechanism of BIND 9, and is not related to the DNS caching
9033 Additional section caching does not change the
9034 response content (except the RRsets ordering of the additional
9035 section, see below), but can improve the response performance
9037 It is particularly effective when BIND 9 acts as an authoritative
9038 server for a zone that has many delegations with many glue RRs.
9042 In order to obtain the maximum performance improvement
9043 from additional section caching, setting
9044 <command>additional-from-cache</command>
9045 to <command>no</command> is recommended, since the current
9046 implementation of <command>acache</command>
9047 does not short-cut of additional section information from the
9052 One obvious disadvantage of <command>acache</command> is
9053 that it requires much more
9054 memory for the internal cached data.
9055 Thus, if the response performance does not matter and memory
9056 consumption is much more critical, the
9057 <command>acache</command> mechanism can be
9058 disabled by setting <command>acache-enable</command> to
9059 <command>no</command>.
9060 It is also possible to specify the upper limit of memory
9062 for acache by using <command>max-acache-size</command>.
9066 Additional section caching also has a minor effect on the
9067 RRset ordering in the additional section.
9068 Without <command>acache</command>,
9069 <command>cyclic</command> order is effective for the additional
9070 section as well as the answer and authority sections.
9071 However, additional section caching fixes the ordering when it
9072 first caches an RRset for the additional section, and the same
9073 ordering will be kept in succeeding responses, regardless of the
9074 setting of <command>rrset-order</command>.
9075 The effect of this should be minor, however, since an
9076 RRset in the additional section
9077 typically only contains a small number of RRs (and in many cases
9078 it only contains a single RR), in which case the
9079 ordering does not matter much.
9083 The following is a summary of options related to
9084 <command>acache</command>.
9090 <term><command>acache-enable</command></term>
9093 If <command>yes</command>, additional section caching is
9094 enabled. The default value is <command>no</command>.
9100 <term><command>acache-cleaning-interval</command></term>
9103 The server will remove stale cache entries, based on an LRU
9105 algorithm, every <command>acache-cleaning-interval</command> minutes.
9106 The default is 60 minutes.
9107 If set to 0, no periodic cleaning will occur.
9113 <term><command>max-acache-size</command></term>
9116 The maximum amount of memory in bytes to use for the server's acache.
9117 When the amount of data in the acache reaches this limit,
9119 will clean more aggressively so that the limit is not
9121 In a server with multiple views, the limit applies
9123 acache of each view.
9124 The default is <literal>16M</literal>.
9134 <title>Content Filtering</title>
9136 <acronym>BIND</acronym> 9 provides the ability to filter
9137 out DNS responses from external DNS servers containing
9138 certain types of data in the answer section.
9139 Specifically, it can reject address (A or AAAA) records if
9140 the corresponding IPv4 or IPv6 addresses match the given
9141 <varname>address_match_list</varname> of the
9142 <command>deny-answer-addresses</command> option.
9143 It can also reject CNAME or DNAME records if the "alias"
9144 name (i.e., the CNAME alias or the substituted query name
9145 due to DNAME) matches the
9146 given <varname>namelist</varname> of the
9147 <command>deny-answer-aliases</command> option, where
9148 "match" means the alias name is a subdomain of one of
9149 the <varname>name_list</varname> elements.
9150 If the optional <varname>namelist</varname> is specified
9151 with <command>except-from</command>, records whose query name
9152 matches the list will be accepted regardless of the filter
9154 Likewise, if the alias name is a subdomain of the
9155 corresponding zone, the <command>deny-answer-aliases</command>
9156 filter will not apply;
9157 for example, even if "example.com" is specified for
9158 <command>deny-answer-aliases</command>,
9160 <programlisting>www.example.com. CNAME xxx.example.com.</programlisting>
9163 returned by an "example.com" server will be accepted.
9167 In the <varname>address_match_list</varname> of the
9168 <command>deny-answer-addresses</command> option, only
9169 <varname>ip_addr</varname>
9170 and <varname>ip_prefix</varname>
9172 any <varname>key_id</varname> will be silently ignored.
9176 If a response message is rejected due to the filtering,
9177 the entire message is discarded without being cached, and
9178 a SERVFAIL error will be returned to the client.
9182 This filtering is intended to prevent "DNS rebinding attacks," in
9183 which an attacker, in response to a query for a domain name the
9184 attacker controls, returns an IP address within your own network or
9185 an alias name within your own domain.
9186 A naive web browser or script could then serve as an
9187 unintended proxy, allowing the attacker
9188 to get access to an internal node of your local network
9189 that couldn't be externally accessed otherwise.
9190 See the paper available at
9192 http://portal.acm.org/citation.cfm?id=1315245.1315298
9194 for more details about the attacks.
9198 For example, if you own a domain named "example.net" and
9199 your internal network uses an IPv4 prefix 192.0.2.0/24,
9200 you might specify the following rules:
9203 <programlisting>deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
9204 deny-answer-aliases { "example.net"; };
9208 If an external attacker lets a web browser in your local
9209 network look up an IPv4 address of "attacker.example.com",
9210 the attacker's DNS server would return a response like this:
9213 <programlisting>attacker.example.com. A 192.0.2.1</programlisting>
9216 in the answer section.
9217 Since the rdata of this record (the IPv4 address) matches
9218 the specified prefix 192.0.2.0/24, this response will be
9223 On the other hand, if the browser looks up a legitimate
9224 internal web server "www.example.net" and the
9225 following response is returned to
9226 the <acronym>BIND</acronym> 9 server
9229 <programlisting>www.example.net. A 192.0.2.2</programlisting>
9232 it will be accepted since the owner name "www.example.net"
9233 matches the <command>except-from</command> element,
9238 Note that this is not really an attack on the DNS per se.
9239 In fact, there is nothing wrong for an "external" name to
9240 be mapped to your "internal" IP address or domain name
9241 from the DNS point of view.
9242 It might actually be provided for a legitimate purpose,
9243 such as for debugging.
9244 As long as the mapping is provided by the correct owner,
9245 it is not possible or does not make sense to detect
9246 whether the intent of the mapping is legitimate or not
9248 The "rebinding" attack must primarily be protected at the
9249 application that uses the DNS.
9250 For a large site, however, it may be difficult to protect
9251 all possible applications at once.
9252 This filtering feature is provided only to help such an
9253 operational environment;
9254 it is generally discouraged to turn it on unless you are
9255 very sure you have no other choice and the attack is a
9256 real threat for your applications.
9260 Care should be particularly taken if you want to use this
9261 option for addresses within 127.0.0.0/8.
9262 These addresses are obviously "internal", but many
9263 applications conventionally rely on a DNS mapping from
9264 some name to such an address.
9265 Filtering out DNS records containing this address
9266 spuriously can break such applications.
9271 <title>Response Policy Zone (RPZ) Rewriting</title>
9273 <acronym>BIND</acronym> 9 includes a limited
9274 mechanism to modify DNS responses for requests
9275 analogous to email anti-spam DNS blacklists.
9276 Responses can be changed to deny the existence of domains(NXDOMAIN),
9277 deny the existence of IP addresses for domains (NODATA),
9278 or contain other IP addresses or data.
9282 Response policy zones are named in the
9283 <command>response-policy</command> option for the view or among the
9284 global options if there is no response-policy option for the view.
9285 RPZs are ordinary DNS zones containing RRsets
9286 that can be queried normally if allowed.
9287 It is usually best to restrict those queries with something like
9288 <command>allow-query { localhost; };</command>.
9292 Four policy triggers are encoded in RPZ records, QNAME, IP, NSIP,
9294 QNAME RPZ records triggered by query names of requests and targets
9295 of CNAME records resolved to generate the response.
9296 The owner name of a QNAME RPZ record is the query name relativized
9301 The second kind of RPZ trigger is an IP address in an A and AAAA
9302 record in the ANSWER section of a response.
9303 IP address triggers are encoded in records that have owner names
9304 that are subdomains of <userinput>rpz-ip</userinput> relativized
9305 to the RPZ origin name and encode an IP address or address block.
9306 IPv4 trigger addresses are represented as
9307 <userinput>prefixlength.B4.B3.B2.B1.rpz-ip</userinput>.
9308 The prefix length must be between 1 and 32.
9309 All four bytes, B4, B3, B2, and B1, must be present.
9310 B4 is the decimal value of the least significant byte of the
9311 IPv4 address as in IN-ADDR.ARPA.
9312 IPv6 addresses are encoded in a format similar to the standard
9313 IPv6 text representation,
9314 <userinput>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</userinput>.
9315 Each of W8,...,W1 is a one to four digit hexadecimal number
9316 representing 16 bits of the IPv6 address as in the standard text
9317 representation of IPv6 addresses, but reversed as in IN-ADDR.ARPA.
9318 All 8 words must be present except when consecutive
9319 zero words are replaced with <userinput>.zz.</userinput>
9320 analogous to double colons (::) in standard IPv6 text encodings.
9321 The prefix length must be between 1 and 128.
9325 NSDNAME triggers match names of authoritative servers
9326 for the query name, a parent of the query name, a CNAME for
9327 query name, or a parent of a CNAME.
9328 They are encoded as subdomains of
9329 <userinput>rpz-nsdomain</userinput> relativized
9330 to the RPZ origin name.
9334 NSIP triggers match IP addresses in A and
9335 AAAA RRsets for domains that can be checked against NSDNAME
9337 NSIP triggers are encoded like IP triggers except as subdomains of
9338 <userinput>rpz-nsip</userinput>.
9342 The query response is checked against all RPZs, so
9343 two or more policy records can be triggered by a response.
9344 Because DNS responses can be rewritten according to at most one
9345 policy record, a single record encoding an action (other than
9346 <command>DISABLED</command> actions) must be chosen.
9347 Triggers or the records that encode them are chosen in
9348 the following order:
9350 <listitem>Choose the triggered record in the zone that appears
9351 first in the response-policy option.
9353 <listitem>Prefer QNAME to IP to NSDNAME to NSIP triggers
9356 <listitem>Among NSDNAME triggers, prefer the
9357 trigger that matches the smallest name under the DNSSEC ordering.
9359 <listitem>Among IP or NSIP triggers, prefer the trigger
9360 with the longest prefix.
9362 <listitem>Among triggers with the same prefex length,
9363 prefer the IP or NSIP trigger that matches
9364 the smallest IP address.
9370 When the processing of a response is restarted to resolve
9371 DNAME or CNAME records and a policy record set has
9373 all RPZs are again consulted for the DNAME or CNAME names
9378 Authority verification issues and variations in authority data
9379 can cause inconsistent results for NSIP and NSDNAME policy records.
9380 Glue NS records often differ from authoritative NS records.
9381 So they are available
9382 only when <acronym>BIND</acronym> is built with the
9383 <userinput>--enable-rpz-nsip</userinput> or
9384 <userinput>--enable-rpz-nsdname</userinput> options
9385 on the "configure" command line.
9389 RPZ record sets are sets of any types of DNS record except
9390 DNAME or DNSSEC that encode actions or responses to queries.
9392 <listitem>The <command>NXDOMAIN</command> response is encoded
9393 by a CNAME whose target is the root domain (.)
9395 <listitem>A CNAME whose target is the wildcard top-level
9396 domain (*.) specifies the <command>NODATA</command> action,
9397 which rewrites the response to NODATA or ANCOUNT=1.
9399 <listitem>The <command>Local Data</command> action is
9400 represented by a set ordinary DNS records that are used
9401 to answer queries. Queries for record types not the
9402 set are answered with NODATA.
9404 A special form of local data is a CNAME whose target is a
9405 wildcard such as *.example.com.
9406 It is used as if were an ordinary CNAME after the astrisk (*)
9407 has been replaced with the query name.
9408 The purpose for this special form is query logging in the
9409 walled garden's authority DNS server.
9411 <listitem>The <command>PASSTHRU</command> policy is specified
9412 by a CNAME whose target is <command>rpz_passthru.</command>
9413 It causes the response to not be rewritten
9414 and is most often used to "poke holes" in policies for
9416 (A CNAME whose target is the variable part of its owner name
9417 is an obsolete specification of the PASSTHRU policy.)
9423 The actions specified in an RPZ can be overridden with a
9424 <command>policy</command> clause in the
9425 <command>response-policy</command> option.
9426 An organization using an RPZ provided by another organization might
9427 use this mechanism to redirect domains to its own walled garden.
9429 <listitem><command>GIVEN</command> says "do not override but
9430 perform the action specified in the zone."
9432 <listitem><command>DISABLED</command> causes policy records to do
9433 nothing but log what they might have done.
9434 The response to the DNS query will be written according to
9435 any triggered policy records that are not disabled.
9436 Disabled policy zones should appear first,
9437 because they will often not be logged
9438 if a higher precedence trigger is found first.
9440 <listitem><command>PASSTHRU</command> causes all policy records
9441 to act as if they were CNAME records with targets the variable
9442 part of their owner name. They protect the response from
9445 <listitem><command>NXDOMAIN</command> causes all RPZ records
9446 to specify NXDOMAIN policies.
9448 <listitem><command>NODATA</command> overrides with the
9451 <listitem><command>CNAME domain</command> causes all RPZ
9452 policy records to act as if they were "cname domain" records.
9458 By default, the actions encoded in an RPZ are applied
9459 only to queries that ask for recursion (RD=1).
9460 That default can be changed for a single RPZ or all RPZs in a view
9461 with a <command>recursive-only no</command> clause.
9462 This feature is useful for serving the same zone files
9463 both inside and outside an RFC 1918 cloud and using RPZ to
9464 delete answers that would otherwise contain RFC 1918 values
9465 on the externally visible name server or view.
9469 Also by default, RPZ actions are applied only to DNS requests that
9470 either do not request DNSSEC metadata (DO=0) or when no DNSSEC
9471 records are available for request name in the original zone (not
9472 the response policy zone).
9473 This default can be changed for all RPZs in a view with a
9474 <command>break-dnssec yes</command> clause.
9475 In that case, RPZ actions are applied regardless of DNSSEC.
9476 The name of the clause option reflects the fact that results
9477 rewritten by RPZ actions cannot verify.
9481 The TTL of a record modified by RPZ policies is set from the
9482 TTL of the relevant record in policy zone. It is then limited
9484 The <command>max-policy-ttl</command> clause changes that
9485 maximum from its default of 5.
9489 For example, you might use this option statement
9491 <programlisting> response-policy { zone "badlist"; };</programlisting>
9493 and this zone statement
9495 <programlisting> zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</programlisting>
9499 <programlisting>$TTL 1H
9500 @ SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
9503 ; QNAME policy records. There are no periods (.) after the owner names.
9504 nxdomain.domain.com CNAME . ; NXDOMAIN policy
9505 nodata.domain.com CNAME *. ; NODATA policy
9506 bad.domain.com A 10.0.0.1 ; redirect to a walled garden
9509 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
9510 ok.domain.com CNAME rpz-passthru.
9512 bzone.domain.com CNAME garden.example.com.
9514 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
9515 *.bzone.domain.com CNAME *.garden.example.com.
9518 ; IP policy records that rewrite all answers for 127/8 except 127.0.0.1
9519 8.0.0.0.127.rpz-ip CNAME .
9520 32.1.0.0.127.rpz-ip CNAME rpz-passthru.
9522 ; NSDNAME and NSIP policy records
9523 ns.domain.com.rpz-nsdname CNAME .
9524 48.zz.2.2001.rpz-nsip CNAME .
9529 <sect2 id="server_statement_grammar">
9530 <title><command>server</command> Statement Grammar</title>
9532 <programlisting><command>server</command> <replaceable>ip_addr[/prefixlen]</replaceable> {
9533 <optional> bogus <replaceable>yes_or_no</replaceable> ; </optional>
9534 <optional> provide-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9535 <optional> request-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9536 <optional> edns <replaceable>yes_or_no</replaceable> ; </optional>
9537 <optional> edns-udp-size <replaceable>number</replaceable> ; </optional>
9538 <optional> max-udp-size <replaceable>number</replaceable> ; </optional>
9539 <optional> transfers <replaceable>number</replaceable> ; </optional>
9540 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable> ; ]</optional>
9541 <optional> keys <replaceable>{ string ; <optional> string ; <optional>...</optional></optional> }</replaceable> ; </optional>
9542 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9543 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9544 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9545 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9546 <optional> query-source <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9547 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9548 <optional> query-source-v6 <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9549 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9550 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
9551 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
9552 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
9558 <sect2 id="server_statement_definition_and_usage">
9559 <title><command>server</command> Statement Definition and
9563 The <command>server</command> statement defines
9565 to be associated with a remote name server. If a prefix length is
9566 specified, then a range of servers is covered. Only the most
9568 server clause applies regardless of the order in
9569 <filename>named.conf</filename>.
9573 The <command>server</command> statement can occur at
9574 the top level of the
9575 configuration file or inside a <command>view</command>
9577 If a <command>view</command> statement contains
9578 one or more <command>server</command> statements, only
9580 apply to the view and any top-level ones are ignored.
9581 If a view contains no <command>server</command>
9583 any top-level <command>server</command> statements are
9589 If you discover that a remote server is giving out bad data,
9590 marking it as bogus will prevent further queries to it. The
9592 value of <command>bogus</command> is <command>no</command>.
9595 The <command>provide-ixfr</command> clause determines
9597 the local server, acting as master, will respond with an
9599 zone transfer when the given remote server, a slave, requests it.
9600 If set to <command>yes</command>, incremental transfer
9602 whenever possible. If set to <command>no</command>,
9604 to the remote server will be non-incremental. If not set, the
9606 of the <command>provide-ixfr</command> option in the
9608 global options block is used as a default.
9612 The <command>request-ixfr</command> clause determines
9614 the local server, acting as a slave, will request incremental zone
9615 transfers from the given remote server, a master. If not set, the
9616 value of the <command>request-ixfr</command> option in
9618 global options block is used as a default.
9622 IXFR requests to servers that do not support IXFR will
9624 fall back to AXFR. Therefore, there is no need to manually list
9625 which servers support IXFR and which ones do not; the global
9627 of <command>yes</command> should always work.
9628 The purpose of the <command>provide-ixfr</command> and
9629 <command>request-ixfr</command> clauses is
9630 to make it possible to disable the use of IXFR even when both
9632 and slave claim to support it, for example if one of the servers
9633 is buggy and crashes or corrupts data when IXFR is used.
9637 The <command>edns</command> clause determines whether
9638 the local server will attempt to use EDNS when communicating
9639 with the remote server. The default is <command>yes</command>.
9643 The <command>edns-udp-size</command> option sets the EDNS UDP size
9644 that is advertised by <command>named</command> when querying the remote server.
9645 Valid values are 512 to 4096 bytes (values outside this range will be
9646 silently adjusted). This option is useful when you wish to
9647 advertises a different value to this server than the value you
9648 advertise globally, for example, when there is a firewall at the
9649 remote site that is blocking large replies.
9653 The <command>max-udp-size</command> option sets the
9654 maximum EDNS UDP message size <command>named</command> will send. Valid
9655 values are 512 to 4096 bytes (values outside this range will
9656 be silently adjusted). This option is useful when you
9657 know that there is a firewall that is blocking large
9658 replies from <command>named</command>.
9662 The server supports two zone transfer methods. The first, <command>one-answer</command>,
9663 uses one DNS message per resource record transferred. <command>many-answers</command> packs
9664 as many resource records as possible into a message. <command>many-answers</command> is
9665 more efficient, but is only known to be understood by <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
9666 8.x, and patched versions of <acronym>BIND</acronym>
9667 4.9.5. You can specify which method
9668 to use for a server with the <command>transfer-format</command> option.
9669 If <command>transfer-format</command> is not
9670 specified, the <command>transfer-format</command>
9672 by the <command>options</command> statement will be
9676 <para><command>transfers</command>
9677 is used to limit the number of concurrent inbound zone
9678 transfers from the specified server. If no
9679 <command>transfers</command> clause is specified, the
9680 limit is set according to the
9681 <command>transfers-per-ns</command> option.
9685 The <command>keys</command> clause identifies a
9686 <command>key_id</command> defined by the <command>key</command> statement,
9687 to be used for transaction security (TSIG, <xref linkend="tsig"/>)
9688 when talking to the remote server.
9689 When a request is sent to the remote server, a request signature
9690 will be generated using the key specified here and appended to the
9691 message. A request originating from the remote server is not
9693 to be signed by this key.
9697 Although the grammar of the <command>keys</command>
9699 allows for multiple keys, only a single key per server is
9705 The <command>transfer-source</command> and
9706 <command>transfer-source-v6</command> clauses specify
9707 the IPv4 and IPv6 source
9708 address to be used for zone transfer with the remote server,
9710 For an IPv4 remote server, only <command>transfer-source</command> can
9712 Similarly, for an IPv6 remote server, only
9713 <command>transfer-source-v6</command> can be
9715 For more details, see the description of
9716 <command>transfer-source</command> and
9717 <command>transfer-source-v6</command> in
9718 <xref linkend="zone_transfers"/>.
9722 The <command>notify-source</command> and
9723 <command>notify-source-v6</command> clauses specify the
9724 IPv4 and IPv6 source address to be used for notify
9725 messages sent to remote servers, respectively. For an
9726 IPv4 remote server, only <command>notify-source</command>
9727 can be specified. Similarly, for an IPv6 remote server,
9728 only <command>notify-source-v6</command> can be specified.
9732 The <command>query-source</command> and
9733 <command>query-source-v6</command> clauses specify the
9734 IPv4 and IPv6 source address to be used for queries
9735 sent to remote servers, respectively. For an IPv4
9736 remote server, only <command>query-source</command> can
9737 be specified. Similarly, for an IPv6 remote server,
9738 only <command>query-source-v6</command> can be specified.
9743 <sect2 id="statschannels">
9744 <title><command>statistics-channels</command> Statement Grammar</title>
9746 <programlisting><command>statistics-channels</command> {
9747 [ inet ( ip_addr | * ) [ port ip_port ]
9748 [ allow { <replaceable> address_match_list </replaceable> } ]; ]
9755 <title><command>statistics-channels</command> Statement Definition and
9759 The <command>statistics-channels</command> statement
9760 declares communication channels to be used by system
9761 administrators to get access to statistics information of
9766 This statement intends to be flexible to support multiple
9767 communication protocols in the future, but currently only
9768 HTTP access is supported.
9769 It requires that BIND 9 be compiled with libxml2;
9770 the <command>statistics-channels</command> statement is
9771 still accepted even if it is built without the library,
9772 but any HTTP access will fail with an error.
9776 An <command>inet</command> control channel is a TCP socket
9777 listening at the specified <command>ip_port</command> on the
9778 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
9779 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
9780 interpreted as the IPv4 wildcard address; connections will be
9781 accepted on any of the system's IPv4 addresses.
9782 To listen on the IPv6 wildcard address,
9783 use an <command>ip_addr</command> of <literal>::</literal>.
9787 If no port is specified, port 80 is used for HTTP channels.
9788 The asterisk "<literal>*</literal>" cannot be used for
9789 <command>ip_port</command>.
9793 The attempt of opening a statistics channel is
9794 restricted by the optional <command>allow</command> clause.
9795 Connections to the statistics channel are permitted based on the
9796 <command>address_match_list</command>.
9797 If no <command>allow</command> clause is present,
9798 <command>named</command> accepts connection
9799 attempts from any address; since the statistics may
9800 contain sensitive internal information, it is highly
9801 recommended to restrict the source of connection requests
9806 If no <command>statistics-channels</command> statement is present,
9807 <command>named</command> will not open any communication channels.
9812 <sect2 id="trusted-keys">
9813 <title><command>trusted-keys</command> Statement Grammar</title>
9815 <programlisting><command>trusted-keys</command> {
9816 <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9817 <optional> <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9823 <title><command>trusted-keys</command> Statement Definition
9826 The <command>trusted-keys</command> statement defines
9827 DNSSEC security roots. DNSSEC is described in <xref
9828 linkend="DNSSEC"/>. A security root is defined when the
9829 public key for a non-authoritative zone is known, but
9830 cannot be securely obtained through DNS, either because
9831 it is the DNS root zone or because its parent zone is
9832 unsigned. Once a key has been configured as a trusted
9833 key, it is treated as if it had been validated and
9834 proven secure. The resolver attempts DNSSEC validation
9835 on all DNS data in subdomains of a security root.
9838 All keys (and corresponding zones) listed in
9839 <command>trusted-keys</command> are deemed to exist regardless
9840 of what parent zones say. Similarly for all keys listed in
9841 <command>trusted-keys</command> only those keys are
9842 used to validate the DNSKEY RRset. The parent's DS RRset
9846 The <command>trusted-keys</command> statement can contain
9847 multiple key entries, each consisting of the key's
9848 domain name, flags, protocol, algorithm, and the Base-64
9849 representation of the key data.
9850 Spaces, tabs, newlines and carriage returns are ignored
9851 in the key data, so the configuration may be split up into
9855 <command>trusted-keys</command> may be set at the top level
9856 of <filename>named.conf</filename> or within a view. If it is
9857 set in both places, they are additive: keys defined at the top
9858 level are inherited by all views, but keys defined in a view
9859 are only used within that view.
9864 <title><command>managed-keys</command> Statement Grammar</title>
9866 <programlisting><command>managed-keys</command> {
9867 <replaceable>string</replaceable> initial-key <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9868 <optional> <replaceable>string</replaceable> initial-key <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9873 <sect2 id="managed-keys">
9874 <title><command>managed-keys</command> Statement Definition
9877 The <command>managed-keys</command> statement, like
9878 <command>trusted-keys</command>, defines DNSSEC
9879 security roots. The difference is that
9880 <command>managed-keys</command> can be kept up to date
9881 automatically, without intervention from the resolver
9885 Suppose, for example, that a zone's key-signing
9886 key was compromised, and the zone owner had to revoke and
9887 replace the key. A resolver which had the old key in a
9888 <command>trusted-keys</command> statement would be
9889 unable to validate this zone any longer; it would
9890 reply with a SERVFAIL response code. This would
9891 continue until the resolver operator had updated the
9892 <command>trusted-keys</command> statement with the new key.
9895 If, however, the zone were listed in a
9896 <command>managed-keys</command> statement instead, then the
9897 zone owner could add a "stand-by" key to the zone in advance.
9898 <command>named</command> would store the stand-by key, and
9899 when the original key was revoked, <command>named</command>
9900 would be able to transition smoothly to the new key. It would
9901 also recognize that the old key had been revoked, and cease
9902 using that key to validate answers, minimizing the damage that
9903 the compromised key could do.
9906 A <command>managed-keys</command> statement contains a list of
9907 the keys to be managed, along with information about how the
9908 keys are to be initialized for the first time. The only
9909 initialization method currently supported (as of
9910 <acronym>BIND</acronym> 9.7.0) is <literal>initial-key</literal>.
9911 This means the <command>managed-keys</command> statement must
9912 contain a copy of the initializing key. (Future releases may
9913 allow keys to be initialized by other methods, eliminating this
9917 Consequently, a <command>managed-keys</command> statement
9918 appears similar to a <command>trusted-keys</command>, differing
9919 in the presence of the second field, containing the keyword
9920 <literal>initial-key</literal>. The difference is, whereas the
9921 keys listed in a <command>trusted-keys</command> continue to be
9922 trusted until they are removed from
9923 <filename>named.conf</filename>, an initializing key listed
9924 in a <command>managed-keys</command> statement is only trusted
9925 <emphasis>once</emphasis>: for as long as it takes to load the
9926 managed key database and start the RFC 5011 key maintenance
9930 The first time <command>named</command> runs with a managed key
9931 configured in <filename>named.conf</filename>, it fetches the
9932 DNSKEY RRset directly from the zone apex, and validates it
9933 using the key specified in the <command>managed-keys</command>
9934 statement. If the DNSKEY RRset is validly signed, then it is
9935 used as the basis for a new managed keys database.
9938 From that point on, whenever <command>named</command> runs, it
9939 sees the <command>managed-keys</command> statement, checks to
9940 make sure RFC 5011 key maintenance has already been initialized
9941 for the specified domain, and if so, it simply moves on. The
9942 key specified in the <command>managed-keys</command> is not
9943 used to validate answers; it has been superseded by the key or
9944 keys stored in the managed keys database.
9947 The next time <command>named</command> runs after a name
9948 has been <emphasis>removed</emphasis> from the
9949 <command>managed-keys</command> statement, the corresponding
9950 zone will be removed from the managed keys database,
9951 and RFC 5011 key maintenance will no longer be used for that
9955 <command>named</command> only maintains a single managed keys
9956 database; consequently, unlike <command>trusted-keys</command>,
9957 <command>managed-keys</command> may only be set at the top
9958 level of <filename>named.conf</filename>, not within a view.
9961 In the current implementation, the managed keys database is
9962 stored as a master-format zone file called
9963 <filename>managed-keys.bind</filename>. When the key database
9964 is changed, the zone is updated. As with any other dynamic
9965 zone, changes will be written into a journal file,
9966 <filename>managed-keys.bind.jnl</filename>. They are committed
9967 to the master file as soon as possible afterward; in the case
9968 of the managed key database, this will usually occur within 30
9969 seconds. So, whenever <command>named</command> is using
9970 automatic key maintenance, those two files can be expected to
9971 exist in the working directory. (For this reason among others,
9972 the working directory should be always be writable by
9973 <command>named</command>.)
9976 If the <command>dnssec-lookaside</command> option is
9977 set to <userinput>auto</userinput>, <command>named</command>
9978 will automatically initialize a managed key for the
9979 zone <literal>dlv.isc.org</literal>. The key that is
9980 used to initialize the key maintenance process is built
9981 into <command>named</command>, and can be overridden
9982 from <command>bindkeys-file</command>.
9986 <sect2 id="view_statement_grammar">
9987 <title><command>view</command> Statement Grammar</title>
9989 <programlisting><command>view</command> <replaceable>view_name</replaceable>
9990 <optional><replaceable>class</replaceable></optional> {
9991 match-clients { <replaceable>address_match_list</replaceable> };
9992 match-destinations { <replaceable>address_match_list</replaceable> };
9993 match-recursive-only <replaceable>yes_or_no</replaceable> ;
9994 <optional> <replaceable>view_option</replaceable>; ...</optional>
9995 <optional> <replaceable>zone_statement</replaceable>; ...</optional>
10001 <title><command>view</command> Statement Definition and Usage</title>
10004 The <command>view</command> statement is a powerful
10006 of <acronym>BIND</acronym> 9 that lets a name server
10007 answer a DNS query differently
10008 depending on who is asking. It is particularly useful for
10010 split DNS setups without having to run multiple servers.
10014 Each <command>view</command> statement defines a view
10016 DNS namespace that will be seen by a subset of clients. A client
10018 a view if its source IP address matches the
10019 <varname>address_match_list</varname> of the view's
10020 <command>match-clients</command> clause and its
10021 destination IP address matches
10022 the <varname>address_match_list</varname> of the
10024 <command>match-destinations</command> clause. If not
10026 <command>match-clients</command> and <command>match-destinations</command>
10027 default to matching all addresses. In addition to checking IP
10029 <command>match-clients</command> and <command>match-destinations</command>
10030 can also take <command>keys</command> which provide an
10032 client to select the view. A view can also be specified
10033 as <command>match-recursive-only</command>, which
10034 means that only recursive
10035 requests from matching clients will match that view.
10036 The order of the <command>view</command> statements is
10037 significant —
10038 a client request will be resolved in the context of the first
10039 <command>view</command> that it matches.
10043 Zones defined within a <command>view</command>
10045 only be accessible to clients that match the <command>view</command>.
10046 By defining a zone of the same name in multiple views, different
10047 zone data can be given to different clients, for example,
10049 and "external" clients in a split DNS setup.
10053 Many of the options given in the <command>options</command> statement
10054 can also be used within a <command>view</command>
10055 statement, and then
10056 apply only when resolving queries with that view. When no
10058 value is given, the value in the <command>options</command> statement
10059 is used as a default. Also, zone options can have default values
10061 in the <command>view</command> statement; these
10062 view-specific defaults
10063 take precedence over those in the <command>options</command> statement.
10067 Views are class specific. If no class is given, class IN
10068 is assumed. Note that all non-IN views must contain a hint zone,
10069 since only the IN class has compiled-in default hints.
10073 If there are no <command>view</command> statements in
10075 file, a default view that matches any client is automatically
10077 in class IN. Any <command>zone</command> statements
10079 the top level of the configuration file are considered to be part
10081 this default view, and the <command>options</command>
10083 apply to the default view. If any explicit <command>view</command>
10084 statements are present, all <command>zone</command>
10086 occur inside <command>view</command> statements.
10090 Here is an example of a typical split DNS setup implemented
10091 using <command>view</command> statements:
10094 <programlisting>view "internal" {
10095 // This should match our internal networks.
10096 match-clients { 10.0.0.0/8; };
10098 // Provide recursive service to internal
10102 // Provide a complete view of the example.com
10103 // zone including addresses of internal hosts.
10104 zone "example.com" {
10106 file "example-internal.db";
10111 // Match all clients not matched by the
10113 match-clients { any; };
10115 // Refuse recursive service to external clients.
10118 // Provide a restricted view of the example.com
10119 // zone containing only publicly accessible hosts.
10120 zone "example.com" {
10122 file "example-external.db";
10128 <sect2 id="zone_statement_grammar">
10129 <title><command>zone</command>
10130 Statement Grammar</title>
10132 <programlisting><command>zone</command> <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10134 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10135 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10136 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
10137 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
10138 <optional> update-policy <replaceable>local</replaceable> | { <replaceable>update_policy_rule</replaceable> <optional>...</optional> }; </optional>
10139 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
10140 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10141 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10142 <optional> check-mx (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10143 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
10144 <optional> check-integrity <replaceable>yes_or_no</replaceable> ; </optional>
10145 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10146 <optional> file <replaceable>string</replaceable> ; </optional>
10147 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10148 <optional> journal <replaceable>string</replaceable> ; </optional>
10149 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
10150 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10151 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10152 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
10153 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
10154 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
10155 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
10156 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
10157 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
10158 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
10159 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
10160 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
10161 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
10162 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10163 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10164 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10165 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10166 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
10167 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
10168 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
10169 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
10170 <optional> database <replaceable>string</replaceable> ; </optional>
10171 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10172 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10173 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10174 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10175 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
10176 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>off</constant>; </optional>
10177 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
10180 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10182 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
10183 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10184 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10185 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
10186 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
10187 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
10188 <optional> dnssec-update-mode ( <replaceable>maintain</replaceable> | <replaceable>no-resign</replaceable> ); </optional>
10189 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
10190 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ; </optional>
10191 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
10192 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
10193 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10194 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10195 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10196 <optional> file <replaceable>string</replaceable> ; </optional>
10197 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10198 <optional> journal <replaceable>string</replaceable> ; </optional>
10199 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
10200 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10201 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10202 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
10203 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
10204 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
10205 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
10206 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10207 <optional>port <replaceable>ip_port</replaceable></optional>
10208 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10209 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
10210 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10211 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
10212 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10213 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
10214 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
10215 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
10216 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
10217 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10218 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10219 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10220 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10221 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10222 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10223 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10224 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10225 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10226 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10227 <optional> database <replaceable>string</replaceable> ; </optional>
10228 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10229 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10230 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10231 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10232 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10233 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
10236 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10238 file <replaceable>string</replaceable> ;
10239 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10240 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional> // Not Implemented.
10243 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10245 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10246 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10247 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10248 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10249 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10250 <optional> file <replaceable>string</replaceable> ; </optional>
10251 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10252 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10253 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10254 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10255 <optional>port <replaceable>ip_port</replaceable></optional>
10256 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10257 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10258 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10259 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10260 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10261 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10262 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10263 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10264 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10265 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10266 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10267 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10268 <optional> database <replaceable>string</replaceable> ; </optional>
10269 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10270 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10271 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10272 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10273 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10276 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10278 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10279 <optional> server-addresses { <optional> <replaceable>ip_addr</replaceable> ; ... </optional> }; </optional>
10280 <optional> server-names { <optional> <replaceable>namelist</replaceable> </optional> }; </optional>
10281 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10284 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10286 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10287 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10288 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10291 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10292 type delegation-only;
10299 <title><command>zone</command> Statement Definition and Usage</title>
10301 <title>Zone Types</title>
10302 <informaltable colsep="0" rowsep="0">
10303 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
10304 <!--colspec colname="1" colnum="1" colsep="0" colwidth="1.108in"/-->
10305 <!--colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/-->
10306 <colspec colname="1" colnum="1" colsep="0"/>
10307 <colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/>
10310 <entry colname="1">
10312 <varname>master</varname>
10315 <entry colname="2">
10317 The server has a master copy of the data
10318 for the zone and will be able to provide authoritative
10325 <entry colname="1">
10327 <varname>slave</varname>
10330 <entry colname="2">
10332 A slave zone is a replica of a master
10333 zone. The <command>masters</command> list
10334 specifies one or more IP addresses
10335 of master servers that the slave contacts to update
10336 its copy of the zone.
10337 Masters list elements can also be names of other
10339 By default, transfers are made from port 53 on the
10341 be changed for all servers by specifying a port number
10343 list of IP addresses, or on a per-server basis after
10345 Authentication to the master can also be done with
10346 per-server TSIG keys.
10347 If a file is specified, then the
10348 replica will be written to this file whenever the zone
10350 and reloaded from this file on a server restart. Use
10352 recommended, since it often speeds server startup and
10354 a needless waste of bandwidth. Note that for large
10356 tens or hundreds of thousands) of zones per server, it
10358 use a two-level naming scheme for zone filenames. For
10360 a slave server for the zone <literal>example.com</literal> might place
10361 the zone contents into a file called
10362 <filename>ex/example.com</filename> where <filename>ex/</filename> is
10363 just the first two letters of the zone name. (Most
10365 behave very slowly if you put 100000 files into
10366 a single directory.)
10371 <entry colname="1">
10373 <varname>stub</varname>
10376 <entry colname="2">
10378 A stub zone is similar to a slave zone,
10379 except that it replicates only the NS records of a
10380 master zone instead
10381 of the entire zone. Stub zones are not a standard part
10383 they are a feature specific to the <acronym>BIND</acronym> implementation.
10387 Stub zones can be used to eliminate the need for glue
10389 in a parent zone at the expense of maintaining a stub
10391 a set of name server addresses in <filename>named.conf</filename>.
10392 This usage is not recommended for new configurations,
10394 supports it only in a limited way.
10395 In <acronym>BIND</acronym> 4/8, zone
10396 transfers of a parent zone
10397 included the NS records from stub children of that
10399 that, in some cases, users could get away with
10400 configuring child stubs
10401 only in the master server for the parent zone. <acronym>BIND</acronym>
10402 9 never mixes together zone data from different zones
10404 way. Therefore, if a <acronym>BIND</acronym> 9 master serving a parent
10405 zone has child stub zones configured, all the slave
10407 parent zone also need to have the same child stub
10413 Stub zones can also be used as a way of forcing the
10415 of a given domain to use a particular set of
10416 authoritative servers.
10417 For example, the caching name servers on a private
10419 RFC1918 addressing may be configured with stub zones
10421 <literal>10.in-addr.arpa</literal>
10422 to use a set of internal name servers as the
10424 servers for that domain.
10429 <entry colname="1">
10431 <varname>static-stub</varname>
10434 <entry colname="2">
10436 A static-stub zone is similar to a stub zone
10437 with the following exceptions:
10438 the zone data is statically configured, rather
10439 than transferred from a master server;
10440 when recursion is necessary for a query that
10441 matches a static-stub zone, the locally
10442 configured data (nameserver names and glue addresses)
10443 is always used even if different authoritative
10444 information is cached.
10447 Zone data is configured via the
10448 <command>server-addresses</command> and
10449 <command>server-names</command> zone options.
10452 The zone data is maintained in the form of NS
10453 and (if necessary) glue A or AAAA RRs
10454 internally, which can be seen by dumping zone
10455 databases by <command>rndc dumpdb -all</command>.
10456 The configured RRs are considered local configuration
10457 parameters rather than public data.
10458 Non recursive queries (i.e., those with the RD
10459 bit off) to a static-stub zone are therefore
10460 prohibited and will be responded with REFUSED.
10463 Since the data is statically configured, no
10464 zone maintenance action takes place for a static-stub
10466 For example, there is no periodic refresh
10467 attempt, and an incoming notify message
10468 will be rejected with an rcode of NOTAUTH.
10471 Each static-stub zone is configured with
10472 internally generated NS and (if necessary)
10478 <entry colname="1">
10480 <varname>forward</varname>
10483 <entry colname="2">
10485 A "forward zone" is a way to configure
10486 forwarding on a per-domain basis. A <command>zone</command> statement
10487 of type <command>forward</command> can
10488 contain a <command>forward</command>
10489 and/or <command>forwarders</command>
10491 which will apply to queries within the domain given by
10493 name. If no <command>forwarders</command>
10494 statement is present or
10495 an empty list for <command>forwarders</command> is given, then no
10496 forwarding will be done for the domain, canceling the
10498 any forwarders in the <command>options</command> statement. Thus
10499 if you want to use this type of zone to change the
10501 global <command>forward</command> option
10502 (that is, "forward first"
10503 to, then "forward only", or vice versa, but want to
10505 servers as set globally) you need to re-specify the
10511 <entry colname="1">
10513 <varname>hint</varname>
10516 <entry colname="2">
10518 The initial set of root name servers is
10519 specified using a "hint zone". When the server starts
10521 the root hints to find a root name server and get the
10523 list of root name servers. If no hint zone is
10524 specified for class
10525 IN, the server uses a compiled-in default set of root
10527 Classes other than IN have no built-in defaults hints.
10532 <entry colname="1">
10534 <varname>delegation-only</varname>
10537 <entry colname="2">
10539 This is used to enforce the delegation-only
10540 status of infrastructure zones (e.g. COM,
10541 NET, ORG). Any answer that is received
10542 without an explicit or implicit delegation
10543 in the authority section will be treated
10544 as NXDOMAIN. This does not apply to the
10545 zone apex. This should not be applied to
10549 <varname>delegation-only</varname> has no
10550 effect on answers received from forwarders.
10553 See caveats in <xref linkend="root_delegation_only"/>.
10563 <title>Class</title>
10565 The zone's name may optionally be followed by a class. If
10566 a class is not specified, class <literal>IN</literal> (for <varname>Internet</varname>),
10567 is assumed. This is correct for the vast majority of cases.
10570 The <literal>hesiod</literal> class is
10571 named for an information service from MIT's Project Athena. It
10573 used to share information about various systems databases, such
10574 as users, groups, printers and so on. The keyword
10575 <literal>HS</literal> is
10576 a synonym for hesiod.
10579 Another MIT development is Chaosnet, a LAN protocol created
10580 in the mid-1970s. Zone data for it can be specified with the <literal>CHAOS</literal> class.
10585 <title>Zone Options</title>
10590 <term><command>allow-notify</command></term>
10593 See the description of
10594 <command>allow-notify</command> in <xref linkend="access_control"/>.
10600 <term><command>allow-query</command></term>
10603 See the description of
10604 <command>allow-query</command> in <xref linkend="access_control"/>.
10610 <term><command>allow-query-on</command></term>
10613 See the description of
10614 <command>allow-query-on</command> in <xref linkend="access_control"/>.
10620 <term><command>allow-transfer</command></term>
10623 See the description of <command>allow-transfer</command>
10624 in <xref linkend="access_control"/>.
10630 <term><command>allow-update</command></term>
10633 See the description of <command>allow-update</command>
10634 in <xref linkend="access_control"/>.
10640 <term><command>update-policy</command></term>
10643 Specifies a "Simple Secure Update" policy. See
10644 <xref linkend="dynamic_update_policies"/>.
10650 <term><command>allow-update-forwarding</command></term>
10653 See the description of <command>allow-update-forwarding</command>
10654 in <xref linkend="access_control"/>.
10660 <term><command>also-notify</command></term>
10663 Only meaningful if <command>notify</command>
10665 active for this zone. The set of machines that will
10667 <literal>DNS NOTIFY</literal> message
10668 for this zone is made up of all the listed name servers
10670 the primary master) for the zone plus any IP addresses
10672 with <command>also-notify</command>. A port
10674 with each <command>also-notify</command>
10675 address to send the notify
10676 messages to a port other than the default of 53.
10677 <command>also-notify</command> is not
10678 meaningful for stub zones.
10679 The default is the empty list.
10685 <term><command>check-names</command></term>
10688 This option is used to restrict the character set and
10690 certain domain names in master files and/or DNS responses
10692 network. The default varies according to zone type. For <command>master</command> zones the default is <command>fail</command>. For <command>slave</command>
10693 zones the default is <command>warn</command>.
10694 It is not implemented for <command>hint</command> zones.
10700 <term><command>check-mx</command></term>
10703 See the description of
10704 <command>check-mx</command> in <xref linkend="boolean_options"/>.
10710 <term><command>check-wildcard</command></term>
10713 See the description of
10714 <command>check-wildcard</command> in <xref linkend="boolean_options"/>.
10720 <term><command>check-integrity</command></term>
10723 See the description of
10724 <command>check-integrity</command> in <xref linkend="boolean_options"/>.
10730 <term><command>check-sibling</command></term>
10733 See the description of
10734 <command>check-sibling</command> in <xref linkend="boolean_options"/>.
10740 <term><command>zero-no-soa-ttl</command></term>
10743 See the description of
10744 <command>zero-no-soa-ttl</command> in <xref linkend="boolean_options"/>.
10750 <term><command>update-check-ksk</command></term>
10753 See the description of
10754 <command>update-check-ksk</command> in <xref linkend="boolean_options"/>.
10760 <term><command>dnssec-dnskey-kskonly</command></term>
10763 See the description of
10764 <command>dnssec-dnskey-kskonly</command> in <xref linkend="boolean_options"/>.
10770 <term><command>try-tcp-refresh</command></term>
10773 See the description of
10774 <command>try-tcp-refresh</command> in <xref linkend="boolean_options"/>.
10780 <term><command>database</command></term>
10783 Specify the type of database to be used for storing the
10784 zone data. The string following the <command>database</command> keyword
10785 is interpreted as a list of whitespace-delimited words.
10787 identifies the database type, and any subsequent words are
10789 as arguments to the database to be interpreted in a way
10791 to the database type.
10794 The default is <userinput>"rbt"</userinput>, BIND 9's
10796 red-black-tree database. This database does not take
10800 Other values are possible if additional database drivers
10801 have been linked into the server. Some sample drivers are
10803 with the distribution but none are linked in by default.
10809 <term><command>dialup</command></term>
10812 See the description of
10813 <command>dialup</command> in <xref linkend="boolean_options"/>.
10819 <term><command>delegation-only</command></term>
10822 The flag only applies to hint and stub zones. If set
10823 to <userinput>yes</userinput>, then the zone will also be
10824 treated as if it is also a delegation-only type zone.
10827 See caveats in <xref linkend="root_delegation_only"/>.
10833 <term><command>forward</command></term>
10836 Only meaningful if the zone has a forwarders
10837 list. The <command>only</command> value causes
10839 after trying the forwarders and getting no answer, while <command>first</command> would
10840 allow a normal lookup to be tried.
10846 <term><command>forwarders</command></term>
10849 Used to override the list of global forwarders.
10850 If it is not specified in a zone of type <command>forward</command>,
10851 no forwarding is done for the zone and the global options are
10858 <term><command>ixfr-base</command></term>
10861 Was used in <acronym>BIND</acronym> 8 to
10863 of the transaction log (journal) file for dynamic update
10865 <acronym>BIND</acronym> 9 ignores the option
10866 and constructs the name of the journal
10867 file by appending "<filename>.jnl</filename>"
10875 <term><command>ixfr-tmp-file</command></term>
10878 Was an undocumented option in <acronym>BIND</acronym> 8.
10879 Ignored in <acronym>BIND</acronym> 9.
10885 <term><command>journal</command></term>
10888 Allow the default journal's filename to be overridden.
10889 The default is the zone's filename with "<filename>.jnl</filename>" appended.
10890 This is applicable to <command>master</command> and <command>slave</command> zones.
10896 <term><command>max-journal-size</command></term>
10899 See the description of
10900 <command>max-journal-size</command> in <xref linkend="server_resource_limits"/>.
10906 <term><command>max-transfer-time-in</command></term>
10909 See the description of
10910 <command>max-transfer-time-in</command> in <xref linkend="zone_transfers"/>.
10916 <term><command>max-transfer-idle-in</command></term>
10919 See the description of
10920 <command>max-transfer-idle-in</command> in <xref linkend="zone_transfers"/>.
10926 <term><command>max-transfer-time-out</command></term>
10929 See the description of
10930 <command>max-transfer-time-out</command> in <xref linkend="zone_transfers"/>.
10936 <term><command>max-transfer-idle-out</command></term>
10939 See the description of
10940 <command>max-transfer-idle-out</command> in <xref linkend="zone_transfers"/>.
10946 <term><command>notify</command></term>
10949 See the description of
10950 <command>notify</command> in <xref linkend="boolean_options"/>.
10956 <term><command>notify-delay</command></term>
10959 See the description of
10960 <command>notify-delay</command> in <xref linkend="tuning"/>.
10966 <term><command>notify-to-soa</command></term>
10969 See the description of
10970 <command>notify-to-soa</command> in
10971 <xref linkend="boolean_options"/>.
10977 <term><command>pubkey</command></term>
10980 In <acronym>BIND</acronym> 8, this option was
10981 intended for specifying
10982 a public zone key for verification of signatures in DNSSEC
10984 zones when they are loaded from disk. <acronym>BIND</acronym> 9 does not verify signatures
10985 on load and ignores the option.
10991 <term><command>zone-statistics</command></term>
10994 If <userinput>yes</userinput>, the server will keep
10996 information for this zone, which can be dumped to the
10997 <command>statistics-file</command> defined in
10998 the server options.
11004 <term><command>server-addresses</command></term>
11007 Only meaningful for static-stub zones.
11008 This is a list of IP addresses to which queries
11009 should be sent in recursive resolution for the
11011 A non empty list for this option will internally
11012 configure the apex NS RR with associated glue A or
11016 For example, if "example.com" is configured as a
11017 static-stub zone with 192.0.2.1 and 2001:db8::1234
11018 in a <command>server-addresses</command> option,
11019 the following RRs will be internally configured.
11021 <programlisting>example.com. NS example.com.
11022 example.com. A 192.0.2.1
11023 example.com. AAAA 2001:db8::1234</programlisting>
11025 These records are internally used to resolve
11026 names under the static-stub zone.
11027 For instance, if the server receives a query for
11028 "www.example.com" with the RD bit on, the server
11029 will initiate recursive resolution and send
11030 queries to 192.0.2.1 and/or 2001:db8::1234.
11036 <term><command>server-names</command></term>
11039 Only meaningful for static-stub zones.
11040 This is a list of domain names of nameservers that
11041 act as authoritative servers of the static-stub
11043 These names will be resolved to IP addresses when
11044 <command>named</command> needs to send queries to
11046 To make this supplemental resolution successful,
11047 these names must not be a subdomain of the origin
11048 name of static-stub zone.
11049 That is, when "example.net" is the origin of a
11050 static-stub zone, "ns.example" and
11051 "master.example.com" can be specified in the
11052 <command>server-names</command> option, but
11053 "ns.example.net" cannot, and will be rejected by
11054 the configuration parser.
11057 A non empty list for this option will internally
11058 configure the apex NS RR with the specified names.
11059 For example, if "example.com" is configured as a
11060 static-stub zone with "ns1.example.net" and
11062 in a <command>server-names</command> option,
11063 the following RRs will be internally configured.
11065 <programlisting>example.com. NS ns1.example.net.
11066 example.com. NS ns2.example.net.
11069 These records are internally used to resolve
11070 names under the static-stub zone.
11071 For instance, if the server receives a query for
11072 "www.example.com" with the RD bit on, the server
11073 initiate recursive resolution,
11074 resolve "ns1.example.net" and/or
11075 "ns2.example.net" to IP addresses, and then send
11076 queries to (one or more of) these addresses.
11082 <term><command>sig-validity-interval</command></term>
11085 See the description of
11086 <command>sig-validity-interval</command> in <xref linkend="tuning"/>.
11092 <term><command>sig-signing-nodes</command></term>
11095 See the description of
11096 <command>sig-signing-nodes</command> in <xref linkend="tuning"/>.
11102 <term><command>sig-signing-signatures</command></term>
11105 See the description of
11106 <command>sig-signing-signatures</command> in <xref linkend="tuning"/>.
11112 <term><command>sig-signing-type</command></term>
11115 See the description of
11116 <command>sig-signing-type</command> in <xref linkend="tuning"/>.
11122 <term><command>transfer-source</command></term>
11125 See the description of
11126 <command>transfer-source</command> in <xref linkend="zone_transfers"/>.
11132 <term><command>transfer-source-v6</command></term>
11135 See the description of
11136 <command>transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
11142 <term><command>alt-transfer-source</command></term>
11145 See the description of
11146 <command>alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
11152 <term><command>alt-transfer-source-v6</command></term>
11155 See the description of
11156 <command>alt-transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
11162 <term><command>use-alt-transfer-source</command></term>
11165 See the description of
11166 <command>use-alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
11173 <term><command>notify-source</command></term>
11176 See the description of
11177 <command>notify-source</command> in <xref linkend="zone_transfers"/>.
11183 <term><command>notify-source-v6</command></term>
11186 See the description of
11187 <command>notify-source-v6</command> in <xref linkend="zone_transfers"/>.
11193 <term><command>min-refresh-time</command></term>
11194 <term><command>max-refresh-time</command></term>
11195 <term><command>min-retry-time</command></term>
11196 <term><command>max-retry-time</command></term>
11199 See the description in <xref linkend="tuning"/>.
11205 <term><command>ixfr-from-differences</command></term>
11208 See the description of
11209 <command>ixfr-from-differences</command> in <xref linkend="boolean_options"/>.
11210 (Note that the <command>ixfr-from-differences</command>
11211 <userinput>master</userinput> and
11212 <userinput>slave</userinput> choices are not
11213 available at the zone level.)
11219 <term><command>key-directory</command></term>
11222 See the description of
11223 <command>key-directory</command> in <xref linkend="options"/>.
11229 <term><command>auto-dnssec</command></term>
11232 Zones configured for dynamic DNS may also use this
11233 option to allow varying levels of automatic DNSSEC key
11234 management. There are three possible settings:
11237 <command>auto-dnssec allow;</command> permits
11238 keys to be updated and the zone fully re-signed
11239 whenever the user issues the command <command>rndc sign
11240 <replaceable>zonename</replaceable></command>.
11243 <command>auto-dnssec maintain;</command> includes the
11244 above, but also automatically adjusts the zone's DNSSEC
11245 keys on schedule, according to the keys' timing metadata
11246 (see <xref linkend="man.dnssec-keygen"/> and
11247 <xref linkend="man.dnssec-settime"/>). The command
11249 <replaceable>zonename</replaceable></command> causes
11250 <command>named</command> to load keys from the key
11251 repository and sign the zone with all keys that are
11253 <command>rndc loadkeys
11254 <replaceable>zonename</replaceable></command> causes
11255 <command>named</command> to load keys from the key
11256 repository and schedule key maintenance events to occur
11257 in the future, but it does not sign the full zone
11258 immediately. Note: once keys have been loaded for a
11259 zone the first time, the repository will be searched
11260 for changes periodically, regardless of whether
11261 <command>rndc loadkeys</command> is used. The recheck
11262 interval is hard-coded to
11266 <command>auto-dnssec create;</command> includes the
11267 above, but also allows <command>named</command>
11268 to create new keys in the key repository when needed.
11269 (NOTE: This option is not yet implemented; the syntax is
11270 being reserved for future use.)
11273 The default setting is <command>auto-dnssec off</command>.
11279 <term><command>multi-master</command></term>
11282 See the description of <command>multi-master</command> in
11283 <xref linkend="boolean_options"/>.
11289 <term><command>masterfile-format</command></term>
11292 See the description of <command>masterfile-format</command>
11293 in <xref linkend="tuning"/>.
11299 <term><command>dnssec-secure-to-insecure</command></term>
11302 See the description of
11303 <command>dnssec-secure-to-insecure</command> in <xref linkend="boolean_options"/>.
11311 <sect3 id="dynamic_update_policies">
11312 <title>Dynamic Update Policies</title>
11313 <para><acronym>BIND</acronym> 9 supports two alternative
11314 methods of granting clients the right to perform
11315 dynamic updates to a zone, configured by the
11316 <command>allow-update</command> and
11317 <command>update-policy</command> option, respectively.
11320 The <command>allow-update</command> clause works the
11321 same way as in previous versions of <acronym>BIND</acronym>.
11322 It grants given clients the permission to update any
11323 record of any name in the zone.
11326 The <command>update-policy</command> clause
11327 allows more fine-grained control over what updates are
11328 allowed. A set of rules is specified, where each rule
11329 either grants or denies permissions for one or more
11330 names to be updated by one or more identities. If
11331 the dynamic update request message is signed (that is,
11332 it includes either a TSIG or SIG(0) record), the
11333 identity of the signer can be determined.
11336 Rules are specified in the <command>update-policy</command>
11337 zone option, and are only meaningful for master zones.
11338 When the <command>update-policy</command> statement
11339 is present, it is a configuration error for the
11340 <command>allow-update</command> statement to be
11341 present. The <command>update-policy</command> statement
11342 only examines the signer of a message; the source
11343 address is not relevant.
11346 There is a pre-defined <command>update-policy</command>
11347 rule which can be switched on with the command
11348 <command>update-policy local;</command>.
11349 Switching on this rule in a zone causes
11350 <command>named</command> to generate a TSIG session
11351 key and place it in a file, and to allow that key
11352 to update the zone. (By default, the file is
11353 <filename>/var/run/named/session.key</filename>, the key
11354 name is "local-ddns" and the key algorithm is HMAC-SHA256,
11355 but these values are configurable with the
11356 <command>session-keyfile</command>,
11357 <command>session-keyname</command> and
11358 <command>session-keyalg</command> options, respectively).
11361 A client running on the local system, and with appropriate
11362 permissions, may read that file and use the key to sign update
11363 requests. The zone's update policy will be set to allow that
11364 key to change any record within the zone. Assuming the
11365 key name is "local-ddns", this policy is equivalent to:
11368 <programlisting>update-policy { grant local-ddns zonesub any; };
11372 The command <command>nsupdate -l</command> sends update
11373 requests to localhost, and signs them using the session key.
11377 Other rule definitions look like this:
11381 ( <command>grant</command> | <command>deny</command> ) <replaceable>identity</replaceable> <replaceable>nametype</replaceable> <optional> <replaceable>name</replaceable> </optional> <optional> <replaceable>types</replaceable> </optional>
11385 Each rule grants or denies privileges. Once a message has
11386 successfully matched a rule, the operation is immediately
11387 granted or denied and no further rules are examined. A rule
11388 is matched when the signer matches the identity field, the
11389 name matches the name field in accordance with the nametype
11390 field, and the type matches the types specified in the type
11394 No signer is required for <replaceable>tcp-self</replaceable>
11395 or <replaceable>6to4-self</replaceable> however the standard
11396 reverse mapping / prefix conversion must match the identity
11400 The identity field specifies a name or a wildcard
11401 name. Normally, this is the name of the TSIG or
11402 SIG(0) key used to sign the update request. When a
11403 TKEY exchange has been used to create a shared secret,
11404 the identity of the shared secret is the same as the
11405 identity of the key used to authenticate the TKEY
11406 exchange. TKEY is also the negotiation method used
11407 by GSS-TSIG, which establishes an identity that is
11408 the Kerberos principal of the client, such as
11409 <userinput>"user@host.domain"</userinput>. When the
11410 <replaceable>identity</replaceable> field specifies
11411 a wildcard name, it is subject to DNS wildcard
11412 expansion, so the rule will apply to multiple identities.
11413 The <replaceable>identity</replaceable> field must
11414 contain a fully-qualified domain name.
11417 For nametypes <varname>krb5-self</varname>,
11418 <varname>ms-self</varname>, <varname>krb5-subdomain</varname>,
11419 and <varname>ms-subdomain</varname> the
11420 <replaceable>identity</replaceable> field specifies
11421 the Windows or Kerberos realm of the machine belongs to.
11424 The <replaceable>nametype</replaceable> field has 13
11426 <varname>name</varname>, <varname>subdomain</varname>,
11427 <varname>wildcard</varname>, <varname>self</varname>,
11428 <varname>selfsub</varname>, <varname>selfwild</varname>,
11429 <varname>krb5-self</varname>, <varname>ms-self</varname>,
11430 <varname>krb5-subdomain</varname>,
11431 <varname>ms-subdomain</varname>,
11432 <varname>tcp-self</varname>, <varname>6to4-self</varname>,
11433 <varname>zonesub</varname>, and <varname>external</varname>.
11436 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11437 <colspec colname="1" colnum="1" colsep="0" colwidth="0.819in"/>
11438 <colspec colname="2" colnum="2" colsep="0" colwidth="3.681in"/>
11441 <entry colname="1">
11443 <varname>name</varname>
11445 </entry> <entry colname="2">
11447 Exact-match semantics. This rule matches
11448 when the name being updated is identical
11449 to the contents of the
11450 <replaceable>name</replaceable> field.
11455 <entry colname="1">
11457 <varname>subdomain</varname>
11459 </entry> <entry colname="2">
11461 This rule matches when the name being updated
11462 is a subdomain of, or identical to, the
11463 contents of the <replaceable>name</replaceable>
11469 <entry colname="1">
11471 <varname>zonesub</varname>
11473 </entry> <entry colname="2">
11475 This rule is similar to subdomain, except that
11476 it matches when the name being updated is a
11477 subdomain of the zone in which the
11478 <command>update-policy</command> statement
11479 appears. This obviates the need to type the zone
11480 name twice, and enables the use of a standard
11481 <command>update-policy</command> statement in
11482 multiple zones without modification.
11485 When this rule is used, the
11486 <replaceable>name</replaceable> field is omitted.
11491 <entry colname="1">
11493 <varname>wildcard</varname>
11495 </entry> <entry colname="2">
11497 The <replaceable>name</replaceable> field
11498 is subject to DNS wildcard expansion, and
11499 this rule matches when the name being updated
11500 name is a valid expansion of the wildcard.
11505 <entry colname="1">
11507 <varname>self</varname>
11510 <entry colname="2">
11512 This rule matches when the name being updated
11513 matches the contents of the
11514 <replaceable>identity</replaceable> field.
11515 The <replaceable>name</replaceable> field
11516 is ignored, but should be the same as the
11517 <replaceable>identity</replaceable> field.
11518 The <varname>self</varname> nametype is
11519 most useful when allowing using one key per
11520 name to update, where the key has the same
11521 name as the name to be updated. The
11522 <replaceable>identity</replaceable> would
11523 be specified as <constant>*</constant> (an asterisk) in
11529 <entry colname="1">
11531 <varname>selfsub</varname>
11533 </entry> <entry colname="2">
11535 This rule is similar to <varname>self</varname>
11536 except that subdomains of <varname>self</varname>
11537 can also be updated.
11542 <entry colname="1">
11544 <varname>selfwild</varname>
11546 </entry> <entry colname="2">
11548 This rule is similar to <varname>self</varname>
11549 except that only subdomains of
11550 <varname>self</varname> can be updated.
11555 <entry colname="1">
11557 <varname>ms-self</varname>
11559 </entry> <entry colname="2">
11561 This rule takes a Windows machine principal
11562 (machine$@REALM) for machine in REALM and
11563 and converts it machine.realm allowing the machine
11564 to update machine.realm. The REALM to be matched
11565 is specified in the <replaceable>identity</replaceable>
11571 <entry colname="1">
11573 <varname>ms-subdomain</varname>
11575 </entry> <entry colname="2">
11577 This rule takes a Windows machine principal
11578 (machine$@REALM) for machine in REALM and
11579 converts it to machine.realm allowing the machine
11580 to update subdomains of machine.realm. The REALM
11581 to be matched is specified in the
11582 <replaceable>identity</replaceable> field.
11587 <entry colname="1">
11589 <varname>krb5-self</varname>
11591 </entry> <entry colname="2">
11593 This rule takes a Kerberos machine principal
11594 (host/machine@REALM) for machine in REALM and
11595 and converts it machine.realm allowing the machine
11596 to update machine.realm. The REALM to be matched
11597 is specified in the <replaceable>identity</replaceable>
11603 <entry colname="1">
11605 <varname>krb5-subdomain</varname>
11607 </entry> <entry colname="2">
11609 This rule takes a Kerberos machine principal
11610 (host/machine@REALM) for machine in REALM and
11611 converts it to machine.realm allowing the machine
11612 to update subdomains of machine.realm. The REALM
11613 to be matched is specified in the
11614 <replaceable>identity</replaceable> field.
11619 <entry colname="1">
11621 <varname>tcp-self</varname>
11623 </entry> <entry colname="2">
11625 Allow updates that have been sent via TCP and
11626 for which the standard mapping from the initiating
11627 IP address into the IN-ADDR.ARPA and IP6.ARPA
11628 namespaces match the name to be updated.
11631 It is theoretically possible to spoof these TCP
11637 <entry colname="1">
11639 <varname>6to4-self</varname>
11641 </entry> <entry colname="2">
11643 Allow the 6to4 prefix to be update by any TCP
11644 connection from the 6to4 network or from the
11645 corresponding IPv4 address. This is intended
11646 to allow NS or DNAME RRsets to be added to the
11650 It is theoretically possible to spoof these TCP
11656 <entry colname="1">
11658 <varname>external</varname>
11660 </entry> <entry colname="2">
11662 This rule allows <command>named</command>
11663 to defer the decision of whether to allow a
11664 given update to an external daemon.
11667 The method of communicating with the daemon is
11668 specified in the <replaceable>identity</replaceable>
11669 field, the format of which is
11670 "<constant>local:</constant><replaceable>path</replaceable>",
11671 where <replaceable>path</replaceable> is the location
11672 of a UNIX-domain socket. (Currently, "local" is the
11673 only supported mechanism.)
11676 Requests to the external daemon are sent over the
11677 UNIX-domain socket as datagrams with the following
11681 Protocol version number (4 bytes, network byte order, currently 1)
11682 Request length (4 bytes, network byte order)
11683 Signer (null-terminated string)
11684 Name (null-terminated string)
11685 TCP source address (null-terminated string)
11686 Rdata type (null-terminated string)
11687 Key (null-terminated string)
11688 TKEY token length (4 bytes, network byte order)
11689 TKEY token (remainder of packet)</programlisting>
11691 The daemon replies with a four-byte value in
11692 network byte order, containing either 0 or 1; 0
11693 indicates that the specified update is not
11694 permitted, and 1 indicates that it is.
11703 In all cases, the <replaceable>name</replaceable>
11704 field must specify a fully-qualified domain name.
11708 If no types are explicitly specified, this rule matches
11709 all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
11710 may be specified by name, including "ANY" (ANY matches
11711 all types except NSEC and NSEC3, which can never be
11712 updated). Note that when an attempt is made to delete
11713 all records associated with a name, the rules are
11714 checked for each existing record type.
11720 <title>Zone File</title>
11721 <sect2 id="types_of_resource_records_and_when_to_use_them">
11722 <title>Types of Resource Records and When to Use Them</title>
11724 This section, largely borrowed from RFC 1034, describes the
11725 concept of a Resource Record (RR) and explains when each is used.
11726 Since the publication of RFC 1034, several new RRs have been
11728 and implemented in the DNS. These are also included.
11731 <title>Resource Records</title>
11734 A domain name identifies a node. Each node has a set of
11735 resource information, which may be empty. The set of resource
11736 information associated with a particular name is composed of
11737 separate RRs. The order of RRs in a set is not significant and
11738 need not be preserved by name servers, resolvers, or other
11739 parts of the DNS. However, sorting of multiple RRs is
11740 permitted for optimization purposes, for example, to specify
11741 that a particular nearby server be tried first. See <xref linkend="the_sortlist_statement"/> and <xref linkend="rrset_ordering"/>.
11745 The components of a Resource Record are:
11747 <informaltable colsep="0" rowsep="0">
11748 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11749 <colspec colname="1" colnum="1" colsep="0" colwidth="1.000in"/>
11750 <colspec colname="2" colnum="2" colsep="0" colwidth="3.500in"/>
11753 <entry colname="1">
11758 <entry colname="2">
11760 The domain name where the RR is found.
11765 <entry colname="1">
11770 <entry colname="2">
11772 An encoded 16-bit value that specifies
11773 the type of the resource record.
11778 <entry colname="1">
11783 <entry colname="2">
11785 The time-to-live of the RR. This field
11786 is a 32-bit integer in units of seconds, and is
11788 resolvers when they cache RRs. The TTL describes how
11790 be cached before it should be discarded.
11795 <entry colname="1">
11800 <entry colname="2">
11802 An encoded 16-bit value that identifies
11803 a protocol family or instance of a protocol.
11808 <entry colname="1">
11813 <entry colname="2">
11815 The resource data. The format of the
11816 data is type (and sometimes class) specific.
11824 The following are <emphasis>types</emphasis> of valid RRs:
11826 <informaltable colsep="0" rowsep="0">
11827 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11828 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
11829 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
11832 <entry colname="1">
11837 <entry colname="2">
11839 A host address. In the IN class, this is a
11840 32-bit IP address. Described in RFC 1035.
11845 <entry colname="1">
11850 <entry colname="2">
11852 IPv6 address. Described in RFC 1886.
11857 <entry colname="1">
11862 <entry colname="2">
11864 IPv6 address. This can be a partial
11865 address (a suffix) and an indirection to the name
11866 where the rest of the
11867 address (the prefix) can be found. Experimental.
11868 Described in RFC 2874.
11873 <entry colname="1">
11878 <entry colname="2">
11880 Location of AFS database servers.
11881 Experimental. Described in RFC 1183.
11886 <entry colname="1">
11891 <entry colname="2">
11893 Address prefix list. Experimental.
11894 Described in RFC 3123.
11899 <entry colname="1">
11904 <entry colname="2">
11906 Holds a digital certificate.
11907 Described in RFC 2538.
11912 <entry colname="1">
11917 <entry colname="2">
11919 Identifies the canonical name of an alias.
11920 Described in RFC 1035.
11925 <entry colname="1">
11930 <entry colname="2">
11932 Is used for identifying which DHCP client is
11933 associated with this name. Described in RFC 4701.
11938 <entry colname="1">
11943 <entry colname="2">
11945 Replaces the domain name specified with
11946 another name to be looked up, effectively aliasing an
11948 subtree of the domain name space rather than a single
11950 as in the case of the CNAME RR.
11951 Described in RFC 2672.
11956 <entry colname="1">
11961 <entry colname="2">
11963 Stores a public key associated with a signed
11964 DNS zone. Described in RFC 4034.
11969 <entry colname="1">
11974 <entry colname="2">
11976 Stores the hash of a public key associated with a
11977 signed DNS zone. Described in RFC 4034.
11982 <entry colname="1">
11987 <entry colname="2">
11989 Specifies the global position. Superseded by LOC.
11994 <entry colname="1">
11999 <entry colname="2">
12001 Identifies the CPU and OS used by a host.
12002 Described in RFC 1035.
12007 <entry colname="1">
12012 <entry colname="2">
12014 Provides a method for storing IPsec keying material in
12015 DNS. Described in RFC 4025.
12020 <entry colname="1">
12025 <entry colname="2">
12027 Representation of ISDN addresses.
12028 Experimental. Described in RFC 1183.
12033 <entry colname="1">
12038 <entry colname="2">
12040 Stores a public key associated with a
12041 DNS name. Used in original DNSSEC; replaced
12042 by DNSKEY in DNSSECbis, but still used with
12043 SIG(0). Described in RFCs 2535 and 2931.
12048 <entry colname="1">
12053 <entry colname="2">
12055 Identifies a key exchanger for this
12056 DNS name. Described in RFC 2230.
12061 <entry colname="1">
12066 <entry colname="2">
12068 For storing GPS info. Described in RFC 1876.
12074 <entry colname="1">
12079 <entry colname="2">
12081 Identifies a mail exchange for the domain with
12082 a 16-bit preference value (lower is better)
12083 followed by the host name of the mail exchange.
12084 Described in RFC 974, RFC 1035.
12089 <entry colname="1">
12094 <entry colname="2">
12096 Name authority pointer. Described in RFC 2915.
12101 <entry colname="1">
12106 <entry colname="2">
12108 A network service access point.
12109 Described in RFC 1706.
12114 <entry colname="1">
12119 <entry colname="2">
12121 The authoritative name server for the
12122 domain. Described in RFC 1035.
12127 <entry colname="1">
12132 <entry colname="2">
12134 Used in DNSSECbis to securely indicate that
12135 RRs with an owner name in a certain name interval do
12137 a zone and indicate what RR types are present for an
12139 Described in RFC 4034.
12144 <entry colname="1">
12149 <entry colname="2">
12151 Used in DNSSECbis to securely indicate that
12152 RRs with an owner name in a certain name
12153 interval do not exist in a zone and indicate
12154 what RR types are present for an existing
12155 name. NSEC3 differs from NSEC in that it
12156 prevents zone enumeration but is more
12157 computationally expensive on both the server
12158 and the client than NSEC. Described in RFC
12164 <entry colname="1">
12169 <entry colname="2">
12171 Used in DNSSECbis to tell the authoritative
12172 server which NSEC3 chains are available to use.
12173 Described in RFC 5155.
12178 <entry colname="1">
12183 <entry colname="2">
12185 Used in DNSSEC to securely indicate that
12186 RRs with an owner name in a certain name interval do
12188 a zone and indicate what RR types are present for an
12190 Used in original DNSSEC; replaced by NSEC in
12192 Described in RFC 2535.
12197 <entry colname="1">
12202 <entry colname="2">
12204 A pointer to another part of the domain
12205 name space. Described in RFC 1035.
12210 <entry colname="1">
12215 <entry colname="2">
12217 Provides mappings between RFC 822 and X.400
12218 addresses. Described in RFC 2163.
12223 <entry colname="1">
12228 <entry colname="2">
12230 Information on persons responsible
12231 for the domain. Experimental. Described in RFC 1183.
12236 <entry colname="1">
12241 <entry colname="2">
12243 Contains DNSSECbis signature data. Described
12249 <entry colname="1">
12254 <entry colname="2">
12256 Route-through binding for hosts that
12257 do not have their own direct wide area network
12259 Experimental. Described in RFC 1183.
12264 <entry colname="1">
12269 <entry colname="2">
12271 Contains DNSSEC signature data. Used in
12272 original DNSSEC; replaced by RRSIG in
12273 DNSSECbis, but still used for SIG(0).
12274 Described in RFCs 2535 and 2931.
12279 <entry colname="1">
12284 <entry colname="2">
12286 Identifies the start of a zone of authority.
12287 Described in RFC 1035.
12292 <entry colname="1">
12297 <entry colname="2">
12299 Contains the Sender Policy Framework information
12300 for a given email domain. Described in RFC 4408.
12305 <entry colname="1">
12310 <entry colname="2">
12312 Information about well known network
12313 services (replaces WKS). Described in RFC 2782.
12318 <entry colname="1">
12323 <entry colname="2">
12325 Provides a way to securely publish a secure shell key's
12326 fingerprint. Described in RFC 4255.
12331 <entry colname="1">
12336 <entry colname="2">
12338 Text records. Described in RFC 1035.
12343 <entry colname="1">
12348 <entry colname="2">
12350 Information about which well known
12351 network services, such as SMTP, that a domain
12352 supports. Historical.
12357 <entry colname="1">
12362 <entry colname="2">
12364 Representation of X.25 network addresses.
12365 Experimental. Described in RFC 1183.
12373 The following <emphasis>classes</emphasis> of resource records
12374 are currently valid in the DNS:
12376 <informaltable colsep="0" rowsep="0"><tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12377 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
12378 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
12382 <entry colname="1">
12387 <entry colname="2">
12395 <entry colname="1">
12400 <entry colname="2">
12402 Chaosnet, a LAN protocol created at MIT in the
12404 Rarely used for its historical purpose, but reused for
12406 built-in server information zones, e.g.,
12407 <literal>version.bind</literal>.
12413 <entry colname="1">
12418 <entry colname="2">
12420 Hesiod, an information service
12421 developed by MIT's Project Athena. It is used to share
12423 about various systems databases, such as users,
12435 The owner name is often implicit, rather than forming an
12437 part of the RR. For example, many name servers internally form
12439 or hash structures for the name space, and chain RRs off nodes.
12440 The remaining RR parts are the fixed header (type, class, TTL)
12441 which is consistent for all RRs, and a variable part (RDATA)
12443 fits the needs of the resource being described.
12446 The meaning of the TTL field is a time limit on how long an
12447 RR can be kept in a cache. This limit does not apply to
12449 data in zones; it is also timed out, but by the refreshing
12451 for the zone. The TTL is assigned by the administrator for the
12452 zone where the data originates. While short TTLs can be used to
12453 minimize caching, and a zero TTL prohibits caching, the
12455 of Internet performance suggest that these times should be on
12457 order of days for the typical host. If a change can be
12459 the TTL can be reduced prior to the change to minimize
12461 during the change, and then increased back to its former value
12466 The data in the RDATA section of RRs is carried as a combination
12467 of binary strings and domain names. The domain names are
12469 used as "pointers" to other data in the DNS.
12473 <title>Textual expression of RRs</title>
12475 RRs are represented in binary form in the packets of the DNS
12476 protocol, and are usually represented in highly encoded form
12478 stored in a name server or resolver. In the examples provided
12480 RFC 1034, a style similar to that used in master files was
12482 in order to show the contents of RRs. In this format, most RRs
12483 are shown on a single line, although continuation lines are
12488 The start of the line gives the owner of the RR. If a line
12489 begins with a blank, then the owner is assumed to be the same as
12490 that of the previous RR. Blank lines are often included for
12494 Following the owner, we list the TTL, type, and class of the
12495 RR. Class and type use the mnemonics defined above, and TTL is
12496 an integer before the type field. In order to avoid ambiguity
12498 parsing, type and class mnemonics are disjoint, TTLs are
12500 and the type mnemonic is always last. The IN class and TTL
12502 are often omitted from examples in the interests of clarity.
12505 The resource data or RDATA section of the RR are given using
12506 knowledge of the typical representation for the data.
12509 For example, we might show the RRs carried in a message as:
12511 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12512 <colspec colname="1" colnum="1" colsep="0" colwidth="1.381in"/>
12513 <colspec colname="2" colnum="2" colsep="0" colwidth="1.020in"/>
12514 <colspec colname="3" colnum="3" colsep="0" colwidth="2.099in"/>
12517 <entry colname="1">
12519 <literal>ISI.EDU.</literal>
12522 <entry colname="2">
12524 <literal>MX</literal>
12527 <entry colname="3">
12529 <literal>10 VENERA.ISI.EDU.</literal>
12534 <entry colname="1">
12537 <entry colname="2">
12539 <literal>MX</literal>
12542 <entry colname="3">
12544 <literal>10 VAXA.ISI.EDU</literal>
12549 <entry colname="1">
12551 <literal>VENERA.ISI.EDU</literal>
12554 <entry colname="2">
12556 <literal>A</literal>
12559 <entry colname="3">
12561 <literal>128.9.0.32</literal>
12566 <entry colname="1">
12569 <entry colname="2">
12571 <literal>A</literal>
12574 <entry colname="3">
12576 <literal>10.1.0.52</literal>
12581 <entry colname="1">
12583 <literal>VAXA.ISI.EDU</literal>
12586 <entry colname="2">
12588 <literal>A</literal>
12591 <entry colname="3">
12593 <literal>10.2.0.27</literal>
12598 <entry colname="1">
12601 <entry colname="2">
12603 <literal>A</literal>
12606 <entry colname="3">
12608 <literal>128.9.0.33</literal>
12616 The MX RRs have an RDATA section which consists of a 16-bit
12617 number followed by a domain name. The address RRs use a
12619 IP address format to contain a 32-bit internet address.
12622 The above example shows six RRs, with two RRs at each of three
12626 Similarly we might see:
12628 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12629 <colspec colname="1" colnum="1" colsep="0" colwidth="1.491in"/>
12630 <colspec colname="2" colnum="2" colsep="0" colwidth="1.067in"/>
12631 <colspec colname="3" colnum="3" colsep="0" colwidth="2.067in"/>
12634 <entry colname="1">
12636 <literal>XX.LCS.MIT.EDU.</literal>
12639 <entry colname="2">
12641 <literal>IN A</literal>
12644 <entry colname="3">
12646 <literal>10.0.0.44</literal>
12651 <entry colname="1"/>
12652 <entry colname="2">
12654 <literal>CH A</literal>
12657 <entry colname="3">
12659 <literal>MIT.EDU. 2420</literal>
12667 This example shows two addresses for
12668 <literal>XX.LCS.MIT.EDU</literal>, each of a different class.
12674 <title>Discussion of MX Records</title>
12677 As described above, domain servers store information as a
12678 series of resource records, each of which contains a particular
12679 piece of information about a given domain name (which is usually,
12680 but not always, a host). The simplest way to think of a RR is as
12681 a typed pair of data, a domain name matched with a relevant datum,
12682 and stored with some additional type information to help systems
12683 determine when the RR is relevant.
12687 MX records are used to control delivery of email. The data
12688 specified in the record is a priority and a domain name. The
12690 controls the order in which email delivery is attempted, with the
12691 lowest number first. If two priorities are the same, a server is
12692 chosen randomly. If no servers at a given priority are responding,
12693 the mail transport agent will fall back to the next largest
12695 Priority numbers do not have any absolute meaning — they are
12697 only respective to other MX records for that domain name. The
12699 name given is the machine to which the mail will be delivered.
12700 It <emphasis>must</emphasis> have an associated address record
12701 (A or AAAA) — CNAME is not sufficient.
12704 For a given domain, if there is both a CNAME record and an
12705 MX record, the MX record is in error, and will be ignored.
12707 the mail will be delivered to the server specified in the MX
12709 pointed to by the CNAME.
12712 <informaltable colsep="0" rowsep="0">
12713 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12714 <colspec colname="1" colnum="1" colsep="0" colwidth="1.708in"/>
12715 <colspec colname="2" colnum="2" colsep="0" colwidth="0.444in"/>
12716 <colspec colname="3" colnum="3" colsep="0" colwidth="0.444in"/>
12717 <colspec colname="4" colnum="4" colsep="0" colwidth="0.976in"/>
12718 <colspec colname="5" colnum="5" colsep="0" colwidth="1.553in"/>
12721 <entry colname="1">
12723 <literal>example.com.</literal>
12726 <entry colname="2">
12728 <literal>IN</literal>
12731 <entry colname="3">
12733 <literal>MX</literal>
12736 <entry colname="4">
12738 <literal>10</literal>
12741 <entry colname="5">
12743 <literal>mail.example.com.</literal>
12748 <entry colname="1">
12751 <entry colname="2">
12753 <literal>IN</literal>
12756 <entry colname="3">
12758 <literal>MX</literal>
12761 <entry colname="4">
12763 <literal>10</literal>
12766 <entry colname="5">
12768 <literal>mail2.example.com.</literal>
12773 <entry colname="1">
12776 <entry colname="2">
12778 <literal>IN</literal>
12781 <entry colname="3">
12783 <literal>MX</literal>
12786 <entry colname="4">
12788 <literal>20</literal>
12791 <entry colname="5">
12793 <literal>mail.backup.org.</literal>
12798 <entry colname="1">
12800 <literal>mail.example.com.</literal>
12803 <entry colname="2">
12805 <literal>IN</literal>
12808 <entry colname="3">
12810 <literal>A</literal>
12813 <entry colname="4">
12815 <literal>10.0.0.1</literal>
12818 <entry colname="5">
12823 <entry colname="1">
12825 <literal>mail2.example.com.</literal>
12828 <entry colname="2">
12830 <literal>IN</literal>
12833 <entry colname="3">
12835 <literal>A</literal>
12838 <entry colname="4">
12840 <literal>10.0.0.2</literal>
12843 <entry colname="5">
12849 </informaltable><para>
12850 Mail delivery will be attempted to <literal>mail.example.com</literal> and
12851 <literal>mail2.example.com</literal> (in
12852 any order), and if neither of those succeed, delivery to <literal>mail.backup.org</literal> will
12856 <sect2 id="Setting_TTLs">
12857 <title>Setting TTLs</title>
12859 The time-to-live of the RR field is a 32-bit integer represented
12860 in units of seconds, and is primarily used by resolvers when they
12861 cache RRs. The TTL describes how long a RR can be cached before it
12862 should be discarded. The following three types of TTL are
12864 used in a zone file.
12866 <informaltable colsep="0" rowsep="0">
12867 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12868 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
12869 <colspec colname="2" colnum="2" colsep="0" colwidth="4.375in"/>
12872 <entry colname="1">
12877 <entry colname="2">
12879 The last field in the SOA is the negative
12880 caching TTL. This controls how long other servers will
12881 cache no-such-domain
12882 (NXDOMAIN) responses from you.
12885 The maximum time for
12886 negative caching is 3 hours (3h).
12891 <entry colname="1">
12896 <entry colname="2">
12898 The $TTL directive at the top of the
12899 zone file (before the SOA) gives a default TTL for every
12901 a specific TTL set.
12906 <entry colname="1">
12911 <entry colname="2">
12913 Each RR can have a TTL as the second
12914 field in the RR, which will control how long other
12924 All of these TTLs default to units of seconds, though units
12925 can be explicitly specified, for example, <literal>1h30m</literal>.
12929 <title>Inverse Mapping in IPv4</title>
12931 Reverse name resolution (that is, translation from IP address
12932 to name) is achieved by means of the <emphasis>in-addr.arpa</emphasis> domain
12933 and PTR records. Entries in the in-addr.arpa domain are made in
12934 least-to-most significant order, read left to right. This is the
12935 opposite order to the way IP addresses are usually written. Thus,
12936 a machine with an IP address of 10.1.2.3 would have a
12938 in-addr.arpa name of
12939 3.2.1.10.in-addr.arpa. This name should have a PTR resource record
12940 whose data field is the name of the machine or, optionally,
12942 PTR records if the machine has more than one name. For example,
12943 in the <optional>example.com</optional> domain:
12945 <informaltable colsep="0" rowsep="0">
12946 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
12947 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
12948 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
12951 <entry colname="1">
12953 <literal>$ORIGIN</literal>
12956 <entry colname="2">
12958 <literal>2.1.10.in-addr.arpa</literal>
12963 <entry colname="1">
12965 <literal>3</literal>
12968 <entry colname="2">
12970 <literal>IN PTR foo.example.com.</literal>
12979 The <command>$ORIGIN</command> lines in the examples
12980 are for providing context to the examples only — they do not
12982 appear in the actual usage. They are only used here to indicate
12983 that the example is relative to the listed origin.
12988 <title>Other Zone File Directives</title>
12990 The Master File Format was initially defined in RFC 1035 and
12991 has subsequently been extended. While the Master File Format
12993 is class independent all records in a Master File must be of the
12998 Master File Directives include <command>$ORIGIN</command>, <command>$INCLUDE</command>,
12999 and <command>$TTL.</command>
13002 <title>The <command>@</command> (at-sign)</title>
13004 When used in the label (or name) field, the asperand or
13005 at-sign (@) symbol represents the current origin.
13006 At the start of the zone file, it is the
13007 <<varname>zone_name</varname>> (followed by
13012 <title>The <command>$ORIGIN</command> Directive</title>
13014 Syntax: <command>$ORIGIN</command>
13015 <replaceable>domain-name</replaceable>
13016 <optional><replaceable>comment</replaceable></optional>
13018 <para><command>$ORIGIN</command>
13019 sets the domain name that will be appended to any
13020 unqualified records. When a zone is first read in there
13021 is an implicit <command>$ORIGIN</command>
13022 <<varname>zone_name</varname>><command>.</command>
13023 (followed by trailing dot).
13024 The current <command>$ORIGIN</command> is appended to
13025 the domain specified in the <command>$ORIGIN</command>
13026 argument if it is not absolute.
13030 $ORIGIN example.com.
13031 WWW CNAME MAIN-SERVER
13039 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
13044 <title>The <command>$INCLUDE</command> Directive</title>
13046 Syntax: <command>$INCLUDE</command>
13047 <replaceable>filename</replaceable>
13049 <replaceable>origin</replaceable> </optional>
13050 <optional> <replaceable>comment</replaceable> </optional>
13053 Read and process the file <filename>filename</filename> as
13054 if it were included into the file at this point. If <command>origin</command> is
13055 specified the file is processed with <command>$ORIGIN</command> set
13056 to that value, otherwise the current <command>$ORIGIN</command> is
13060 The origin and the current domain name
13061 revert to the values they had prior to the <command>$INCLUDE</command> once
13062 the file has been read.
13066 RFC 1035 specifies that the current origin should be restored
13068 an <command>$INCLUDE</command>, but it is silent
13069 on whether the current
13070 domain name should also be restored. BIND 9 restores both of
13072 This could be construed as a deviation from RFC 1035, a
13078 <title>The <command>$TTL</command> Directive</title>
13080 Syntax: <command>$TTL</command>
13081 <replaceable>default-ttl</replaceable>
13083 <replaceable>comment</replaceable> </optional>
13086 Set the default Time To Live (TTL) for subsequent records
13087 with undefined TTLs. Valid TTLs are of the range 0-2147483647
13090 <para><command>$TTL</command>
13091 is defined in RFC 2308.
13096 <title><acronym>BIND</acronym> Master File Extension: the <command>$GENERATE</command> Directive</title>
13098 Syntax: <command>$GENERATE</command>
13099 <replaceable>range</replaceable>
13100 <replaceable>lhs</replaceable>
13101 <optional><replaceable>ttl</replaceable></optional>
13102 <optional><replaceable>class</replaceable></optional>
13103 <replaceable>type</replaceable>
13104 <replaceable>rhs</replaceable>
13105 <optional><replaceable>comment</replaceable></optional>
13107 <para><command>$GENERATE</command>
13108 is used to create a series of resource records that only
13109 differ from each other by an
13110 iterator. <command>$GENERATE</command> can be used to
13111 easily generate the sets of records required to support
13112 sub /24 reverse delegations described in RFC 2317:
13113 Classless IN-ADDR.ARPA delegation.
13116 <programlisting>$ORIGIN 0.0.192.IN-ADDR.ARPA.
13117 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
13118 $GENERATE 1-127 $ CNAME $.0</programlisting>
13124 <programlisting>0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
13125 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
13126 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
13127 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
13129 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
13133 Generate a set of A and MX records. Note the MX's right hand
13134 side is a quoted string. The quotes will be stripped when the
13135 right hand side is processed.
13140 $GENERATE 1-127 HOST-$ A 1.2.3.$
13141 $GENERATE 1-127 HOST-$ MX "0 ."</programlisting>
13147 <programlisting>HOST-1.EXAMPLE. A 1.2.3.1
13148 HOST-1.EXAMPLE. MX 0 .
13149 HOST-2.EXAMPLE. A 1.2.3.2
13150 HOST-2.EXAMPLE. MX 0 .
13151 HOST-3.EXAMPLE. A 1.2.3.3
13152 HOST-3.EXAMPLE. MX 0 .
13154 HOST-127.EXAMPLE. A 1.2.3.127
13155 HOST-127.EXAMPLE. MX 0 .
13158 <informaltable colsep="0" rowsep="0">
13159 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13160 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
13161 <colspec colname="2" colnum="2" colsep="0" colwidth="4.250in"/>
13164 <entry colname="1">
13165 <para><command>range</command></para>
13167 <entry colname="2">
13169 This can be one of two forms: start-stop
13170 or start-stop/step. If the first form is used, then step
13172 1. All of start, stop and step must be positive.
13177 <entry colname="1">
13178 <para><command>lhs</command></para>
13180 <entry colname="2">
13182 describes the owner name of the resource records
13183 to be created. Any single <command>$</command>
13185 symbols within the <command>lhs</command> string
13186 are replaced by the iterator value.
13188 To get a $ in the output, you need to escape the
13189 <command>$</command> using a backslash
13190 <command>\</command>,
13191 e.g. <command>\$</command>. The
13192 <command>$</command> may optionally be followed
13193 by modifiers which change the offset from the
13194 iterator, field width and base.
13196 Modifiers are introduced by a
13197 <command>{</command> (left brace) immediately following the
13198 <command>$</command> as
13199 <command>${offset[,width[,base]]}</command>.
13200 For example, <command>${-20,3,d}</command>
13201 subtracts 20 from the current value, prints the
13202 result as a decimal in a zero-padded field of
13205 Available output forms are decimal
13206 (<command>d</command>), octal
13207 (<command>o</command>), hexadecimal
13208 (<command>x</command> or <command>X</command>
13209 for uppercase) and nibble
13210 (<command>n</command> or <command>N</command>\
13211 for uppercase). The default modifier is
13212 <command>${0,0,d}</command>. If the
13213 <command>lhs</command> is not absolute, the
13214 current <command>$ORIGIN</command> is appended
13218 In nibble mode the value will be treated as
13219 if it was a reversed hexadecimal string
13220 with each hexadecimal digit as a separate
13221 label. The width field includes the label
13225 For compatibility with earlier versions,
13226 <command>$$</command> is still recognized as
13227 indicating a literal $ in the output.
13232 <entry colname="1">
13233 <para><command>ttl</command></para>
13235 <entry colname="2">
13237 Specifies the time-to-live of the generated records. If
13238 not specified this will be inherited using the
13239 normal TTL inheritance rules.
13241 <para><command>class</command>
13242 and <command>ttl</command> can be
13243 entered in either order.
13248 <entry colname="1">
13249 <para><command>class</command></para>
13251 <entry colname="2">
13253 Specifies the class of the generated records.
13254 This must match the zone class if it is
13257 <para><command>class</command>
13258 and <command>ttl</command> can be
13259 entered in either order.
13264 <entry colname="1">
13265 <para><command>type</command></para>
13267 <entry colname="2">
13274 <entry colname="1">
13275 <para><command>rhs</command></para>
13277 <entry colname="2">
13279 <command>rhs</command>, optionally, quoted string.
13287 The <command>$GENERATE</command> directive is a <acronym>BIND</acronym> extension
13288 and not part of the standard zone file format.
13291 BIND 8 does not support the optional TTL and CLASS fields.
13295 <sect2 id="zonefile_format">
13296 <title>Additional File Formats</title>
13298 In addition to the standard textual format, BIND 9
13299 supports the ability to read or dump to zone files in
13300 other formats. The <constant>raw</constant> format is
13301 currently available as an additional format. It is a
13302 binary format representing BIND 9's internal data
13303 structure directly, thereby remarkably improving the
13307 For a primary server, a zone file in the
13308 <constant>raw</constant> format is expected to be
13309 generated from a textual zone file by the
13310 <command>named-compilezone</command> command. For a
13311 secondary server or for a dynamic zone, it is automatically
13312 generated (if this format is specified by the
13313 <command>masterfile-format</command> option) when
13314 <command>named</command> dumps the zone contents after
13315 zone transfer or when applying prior updates.
13318 If a zone file in a binary format needs manual modification,
13319 it first must be converted to a textual form by the
13320 <command>named-compilezone</command> command. All
13321 necessary modification should go to the text file, which
13322 should then be converted to the binary form by the
13323 <command>named-compilezone</command> command again.
13326 Although the <constant>raw</constant> format uses the
13327 network byte order and avoids architecture-dependent
13328 data alignment so that it is as much portable as
13329 possible, it is primarily expected to be used inside
13330 the same single system. In order to export a zone
13331 file in the <constant>raw</constant> format or make a
13332 portable backup of the file, it is recommended to
13333 convert the file to the standard textual representation.
13338 <sect1 id="statistics">
13339 <title>BIND9 Statistics</title>
13341 <acronym>BIND</acronym> 9 maintains lots of statistics
13342 information and provides several interfaces for users to
13343 get access to the statistics.
13344 The available statistics include all statistics counters
13345 that were available in <acronym>BIND</acronym> 8 and
13346 are meaningful in <acronym>BIND</acronym> 9,
13347 and other information that is considered useful.
13351 The statistics information is categorized into the following
13355 <informaltable frame="all">
13357 <colspec colname="1" colnum="1" colsep="0" colwidth="3.300in"/>
13358 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
13362 <entry colname="1">
13363 <para>Incoming Requests</para>
13365 <entry colname="2">
13367 The number of incoming DNS requests for each OPCODE.
13373 <entry colname="1">
13374 <para>Incoming Queries</para>
13376 <entry colname="2">
13378 The number of incoming queries for each RR type.
13384 <entry colname="1">
13385 <para>Outgoing Queries</para>
13387 <entry colname="2">
13389 The number of outgoing queries for each RR
13390 type sent from the internal resolver.
13391 Maintained per view.
13397 <entry colname="1">
13398 <para>Name Server Statistics</para>
13400 <entry colname="2">
13402 Statistics counters about incoming request processing.
13408 <entry colname="1">
13409 <para>Zone Maintenance Statistics</para>
13411 <entry colname="2">
13413 Statistics counters regarding zone maintenance
13414 operations such as zone transfers.
13420 <entry colname="1">
13421 <para>Resolver Statistics</para>
13423 <entry colname="2">
13425 Statistics counters about name resolution
13426 performed in the internal resolver.
13427 Maintained per view.
13433 <entry colname="1">
13434 <para>Cache DB RRsets</para>
13436 <entry colname="2">
13438 The number of RRsets per RR type and nonexistent
13439 names stored in the cache database.
13440 If the exclamation mark (!) is printed for a RR
13441 type, it means that particular type of RRset is
13442 known to be nonexistent (this is also known as
13444 Maintained per view.
13450 <entry colname="1">
13451 <para>Socket I/O Statistics</para>
13453 <entry colname="2">
13455 Statistics counters about network related events.
13465 A subset of Name Server Statistics is collected and shown
13466 per zone for which the server has the authority when
13467 <command>zone-statistics</command> is set to
13468 <userinput>yes</userinput>.
13469 These statistics counters are shown with their zone and view
13471 In some cases the view names are omitted for the default view.
13475 There are currently two user interfaces to get access to the
13477 One is in the plain text format dumped to the file specified
13478 by the <command>statistics-file</command> configuration option.
13479 The other is remotely accessible via a statistics channel
13480 when the <command>statistics-channels</command> statement
13481 is specified in the configuration file
13482 (see <xref linkend="statschannels"/>.)
13485 <sect3 id="statsfile">
13486 <title>The Statistics File</title>
13488 The text format statistics dump begins with a line, like:
13491 <command>+++ Statistics Dump +++ (973798949)</command>
13494 The number in parentheses is a standard
13495 Unix-style timestamp, measured as seconds since January 1, 1970.
13498 that line is a set of statistics information, which is categorized
13499 as described above.
13500 Each section begins with a line, like:
13504 <command>++ Name Server Statistics ++</command>
13508 Each section consists of lines, each containing the statistics
13509 counter value followed by its textual description.
13510 See below for available counters.
13511 For brevity, counters that have a value of 0 are not shown
13512 in the statistics file.
13516 The statistics dump ends with the line where the
13517 number is identical to the number in the beginning line; for example:
13520 <command>--- Statistics Dump --- (973798949)</command>
13524 <sect2 id="statistics_counters">
13525 <title>Statistics Counters</title>
13527 The following tables summarize statistics counters that
13528 <acronym>BIND</acronym> 9 provides.
13529 For each row of the tables, the leftmost column is the
13530 abbreviated symbol name of that counter.
13531 These symbols are shown in the statistics information
13532 accessed via an HTTP statistics channel.
13533 The rightmost column gives the description of the counter,
13534 which is also shown in the statistics file
13535 (but, in this document, possibly with slight modification
13536 for better readability).
13537 Additional notes may also be provided in this column.
13538 When a middle column exists between these two columns,
13539 it gives the corresponding counter name of the
13540 <acronym>BIND</acronym> 8 statistics, if applicable.
13544 <title>Name Server Statistics Counters</title>
13546 <informaltable colsep="0" rowsep="0">
13547 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13548 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
13549 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
13550 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
13553 <entry colname="1">
13555 <emphasis>Symbol</emphasis>
13558 <entry colname="2">
13560 <emphasis>BIND8 Symbol</emphasis>
13563 <entry colname="3">
13565 <emphasis>Description</emphasis>
13571 <entry colname="1">
13572 <para><command>Requestv4</command></para>
13574 <entry colname="2">
13575 <para><command>RQ</command></para>
13577 <entry colname="3">
13579 IPv4 requests received.
13580 Note: this also counts non query requests.
13585 <entry colname="1">
13586 <para><command>Requestv6</command></para>
13588 <entry colname="2">
13589 <para><command>RQ</command></para>
13591 <entry colname="3">
13593 IPv6 requests received.
13594 Note: this also counts non query requests.
13599 <entry colname="1">
13600 <para><command>ReqEdns0</command></para>
13602 <entry colname="2">
13603 <para><command></command></para>
13605 <entry colname="3">
13607 Requests with EDNS(0) received.
13612 <entry colname="1">
13613 <para><command>ReqBadEDNSVer</command></para>
13615 <entry colname="2">
13616 <para><command></command></para>
13618 <entry colname="3">
13620 Requests with unsupported EDNS version received.
13625 <entry colname="1">
13626 <para><command>ReqTSIG</command></para>
13628 <entry colname="2">
13629 <para><command></command></para>
13631 <entry colname="3">
13633 Requests with TSIG received.
13638 <entry colname="1">
13639 <para><command>ReqSIG0</command></para>
13641 <entry colname="2">
13642 <para><command></command></para>
13644 <entry colname="3">
13646 Requests with SIG(0) received.
13651 <entry colname="1">
13652 <para><command>ReqBadSIG</command></para>
13654 <entry colname="2">
13655 <para><command></command></para>
13657 <entry colname="3">
13659 Requests with invalid (TSIG or SIG(0)) signature.
13664 <entry colname="1">
13665 <para><command>ReqTCP</command></para>
13667 <entry colname="2">
13668 <para><command>RTCP</command></para>
13670 <entry colname="3">
13672 TCP requests received.
13677 <entry colname="1">
13678 <para><command>AuthQryRej</command></para>
13680 <entry colname="2">
13681 <para><command>RUQ</command></para>
13683 <entry colname="3">
13685 Authoritative (non recursive) queries rejected.
13690 <entry colname="1">
13691 <para><command>RecQryRej</command></para>
13693 <entry colname="2">
13694 <para><command>RURQ</command></para>
13696 <entry colname="3">
13698 Recursive queries rejected.
13703 <entry colname="1">
13704 <para><command>XfrRej</command></para>
13706 <entry colname="2">
13707 <para><command>RUXFR</command></para>
13709 <entry colname="3">
13711 Zone transfer requests rejected.
13716 <entry colname="1">
13717 <para><command>UpdateRej</command></para>
13719 <entry colname="2">
13720 <para><command>RUUpd</command></para>
13722 <entry colname="3">
13724 Dynamic update requests rejected.
13729 <entry colname="1">
13730 <para><command>Response</command></para>
13732 <entry colname="2">
13733 <para><command>SAns</command></para>
13735 <entry colname="3">
13742 <entry colname="1">
13743 <para><command>RespTruncated</command></para>
13745 <entry colname="2">
13746 <para><command></command></para>
13748 <entry colname="3">
13750 Truncated responses sent.
13755 <entry colname="1">
13756 <para><command>RespEDNS0</command></para>
13758 <entry colname="2">
13759 <para><command></command></para>
13761 <entry colname="3">
13763 Responses with EDNS(0) sent.
13768 <entry colname="1">
13769 <para><command>RespTSIG</command></para>
13771 <entry colname="2">
13772 <para><command></command></para>
13774 <entry colname="3">
13776 Responses with TSIG sent.
13781 <entry colname="1">
13782 <para><command>RespSIG0</command></para>
13784 <entry colname="2">
13785 <para><command></command></para>
13787 <entry colname="3">
13789 Responses with SIG(0) sent.
13794 <entry colname="1">
13795 <para><command>QrySuccess</command></para>
13797 <entry colname="2">
13798 <para><command></command></para>
13800 <entry colname="3">
13802 Queries resulted in a successful answer.
13803 This means the query which returns a NOERROR response
13804 with at least one answer RR.
13805 This corresponds to the
13806 <command>success</command> counter
13807 of previous versions of
13808 <acronym>BIND</acronym> 9.
13813 <entry colname="1">
13814 <para><command>QryAuthAns</command></para>
13816 <entry colname="2">
13817 <para><command></command></para>
13819 <entry colname="3">
13821 Queries resulted in authoritative answer.
13826 <entry colname="1">
13827 <para><command>QryNoauthAns</command></para>
13829 <entry colname="2">
13830 <para><command>SNaAns</command></para>
13832 <entry colname="3">
13834 Queries resulted in non authoritative answer.
13839 <entry colname="1">
13840 <para><command>QryReferral</command></para>
13842 <entry colname="2">
13843 <para><command></command></para>
13845 <entry colname="3">
13847 Queries resulted in referral answer.
13848 This corresponds to the
13849 <command>referral</command> counter
13850 of previous versions of
13851 <acronym>BIND</acronym> 9.
13856 <entry colname="1">
13857 <para><command>QryNxrrset</command></para>
13859 <entry colname="2">
13860 <para><command></command></para>
13862 <entry colname="3">
13864 Queries resulted in NOERROR responses with no data.
13865 This corresponds to the
13866 <command>nxrrset</command> counter
13867 of previous versions of
13868 <acronym>BIND</acronym> 9.
13873 <entry colname="1">
13874 <para><command>QrySERVFAIL</command></para>
13876 <entry colname="2">
13877 <para><command>SFail</command></para>
13879 <entry colname="3">
13881 Queries resulted in SERVFAIL.
13886 <entry colname="1">
13887 <para><command>QryFORMERR</command></para>
13889 <entry colname="2">
13890 <para><command>SFErr</command></para>
13892 <entry colname="3">
13894 Queries resulted in FORMERR.
13899 <entry colname="1">
13900 <para><command>QryNXDOMAIN</command></para>
13902 <entry colname="2">
13903 <para><command>SNXD</command></para>
13905 <entry colname="3">
13907 Queries resulted in NXDOMAIN.
13908 This corresponds to the
13909 <command>nxdomain</command> counter
13910 of previous versions of
13911 <acronym>BIND</acronym> 9.
13916 <entry colname="1">
13917 <para><command>QryRecursion</command></para>
13919 <entry colname="2">
13920 <para><command>RFwdQ</command></para>
13922 <entry colname="3">
13924 Queries which caused the server
13925 to perform recursion in order to find the final answer.
13926 This corresponds to the
13927 <command>recursion</command> counter
13928 of previous versions of
13929 <acronym>BIND</acronym> 9.
13934 <entry colname="1">
13935 <para><command>QryDuplicate</command></para>
13937 <entry colname="2">
13938 <para><command>RDupQ</command></para>
13940 <entry colname="3">
13942 Queries which the server attempted to
13943 recurse but discovered an existing query with the same
13944 IP address, port, query ID, name, type and class
13945 already being processed.
13946 This corresponds to the
13947 <command>duplicate</command> counter
13948 of previous versions of
13949 <acronym>BIND</acronym> 9.
13954 <entry colname="1">
13955 <para><command>QryDropped</command></para>
13957 <entry colname="2">
13958 <para><command></command></para>
13960 <entry colname="3">
13962 Recursive queries for which the server
13963 discovered an excessive number of existing
13964 recursive queries for the same name, type and
13965 class and were subsequently dropped.
13966 This is the number of dropped queries due to
13967 the reason explained with the
13968 <command>clients-per-query</command>
13970 <command>max-clients-per-query</command>
13972 (see the description about
13973 <xref linkend="clients-per-query"/>.)
13974 This corresponds to the
13975 <command>dropped</command> counter
13976 of previous versions of
13977 <acronym>BIND</acronym> 9.
13982 <entry colname="1">
13983 <para><command>QryFailure</command></para>
13985 <entry colname="2">
13986 <para><command></command></para>
13988 <entry colname="3">
13990 Other query failures.
13991 This corresponds to the
13992 <command>failure</command> counter
13993 of previous versions of
13994 <acronym>BIND</acronym> 9.
13995 Note: this counter is provided mainly for
13996 backward compatibility with the previous versions.
13997 Normally a more fine-grained counters such as
13998 <command>AuthQryRej</command> and
13999 <command>RecQryRej</command>
14000 that would also fall into this counter are provided,
14001 and so this counter would not be of much
14002 interest in practice.
14007 <entry colname="1">
14008 <para><command>XfrReqDone</command></para>
14010 <entry colname="2">
14011 <para><command></command></para>
14013 <entry colname="3">
14015 Requested zone transfers completed.
14020 <entry colname="1">
14021 <para><command>UpdateReqFwd</command></para>
14023 <entry colname="2">
14024 <para><command></command></para>
14026 <entry colname="3">
14028 Update requests forwarded.
14033 <entry colname="1">
14034 <para><command>UpdateRespFwd</command></para>
14036 <entry colname="2">
14037 <para><command></command></para>
14039 <entry colname="3">
14041 Update responses forwarded.
14046 <entry colname="1">
14047 <para><command>UpdateFwdFail</command></para>
14049 <entry colname="2">
14050 <para><command></command></para>
14052 <entry colname="3">
14054 Dynamic update forward failed.
14059 <entry colname="1">
14060 <para><command>UpdateDone</command></para>
14062 <entry colname="2">
14063 <para><command></command></para>
14065 <entry colname="3">
14067 Dynamic updates completed.
14072 <entry colname="1">
14073 <para><command>UpdateFail</command></para>
14075 <entry colname="2">
14076 <para><command></command></para>
14078 <entry colname="3">
14080 Dynamic updates failed.
14085 <entry colname="1">
14086 <para><command>UpdateBadPrereq</command></para>
14088 <entry colname="2">
14089 <para><command></command></para>
14091 <entry colname="3">
14093 Dynamic updates rejected due to prerequisite failure.
14103 <title>Zone Maintenance Statistics Counters</title>
14105 <informaltable colsep="0" rowsep="0">
14106 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14107 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14108 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
14111 <entry colname="1">
14113 <emphasis>Symbol</emphasis>
14116 <entry colname="2">
14118 <emphasis>Description</emphasis>
14124 <entry colname="1">
14125 <para><command>NotifyOutv4</command></para>
14127 <entry colname="2">
14129 IPv4 notifies sent.
14134 <entry colname="1">
14135 <para><command>NotifyOutv6</command></para>
14137 <entry colname="2">
14139 IPv6 notifies sent.
14144 <entry colname="1">
14145 <para><command>NotifyInv4</command></para>
14147 <entry colname="2">
14149 IPv4 notifies received.
14154 <entry colname="1">
14155 <para><command>NotifyInv6</command></para>
14157 <entry colname="2">
14159 IPv6 notifies received.
14164 <entry colname="1">
14165 <para><command>NotifyRej</command></para>
14167 <entry colname="2">
14169 Incoming notifies rejected.
14174 <entry colname="1">
14175 <para><command>SOAOutv4</command></para>
14177 <entry colname="2">
14179 IPv4 SOA queries sent.
14184 <entry colname="1">
14185 <para><command>SOAOutv6</command></para>
14187 <entry colname="2">
14189 IPv6 SOA queries sent.
14194 <entry colname="1">
14195 <para><command>AXFRReqv4</command></para>
14197 <entry colname="2">
14199 IPv4 AXFR requested.
14204 <entry colname="1">
14205 <para><command>AXFRReqv6</command></para>
14207 <entry colname="2">
14209 IPv6 AXFR requested.
14214 <entry colname="1">
14215 <para><command>IXFRReqv4</command></para>
14217 <entry colname="2">
14219 IPv4 IXFR requested.
14224 <entry colname="1">
14225 <para><command>IXFRReqv6</command></para>
14227 <entry colname="2">
14229 IPv6 IXFR requested.
14234 <entry colname="1">
14235 <para><command>XfrSuccess</command></para>
14237 <entry colname="2">
14239 Zone transfer requests succeeded.
14244 <entry colname="1">
14245 <para><command>XfrFail</command></para>
14247 <entry colname="2">
14249 Zone transfer requests failed.
14259 <title>Resolver Statistics Counters</title>
14261 <informaltable colsep="0" rowsep="0">
14262 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14263 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14264 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
14265 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
14268 <entry colname="1">
14270 <emphasis>Symbol</emphasis>
14273 <entry colname="2">
14275 <emphasis>BIND8 Symbol</emphasis>
14278 <entry colname="3">
14280 <emphasis>Description</emphasis>
14286 <entry colname="1">
14287 <para><command>Queryv4</command></para>
14289 <entry colname="2">
14290 <para><command>SFwdQ</command></para>
14292 <entry colname="3">
14299 <entry colname="1">
14300 <para><command>Queryv6</command></para>
14302 <entry colname="2">
14303 <para><command>SFwdQ</command></para>
14305 <entry colname="3">
14312 <entry colname="1">
14313 <para><command>Responsev4</command></para>
14315 <entry colname="2">
14316 <para><command>RR</command></para>
14318 <entry colname="3">
14320 IPv4 responses received.
14325 <entry colname="1">
14326 <para><command>Responsev6</command></para>
14328 <entry colname="2">
14329 <para><command>RR</command></para>
14331 <entry colname="3">
14333 IPv6 responses received.
14338 <entry colname="1">
14339 <para><command>NXDOMAIN</command></para>
14341 <entry colname="2">
14342 <para><command>RNXD</command></para>
14344 <entry colname="3">
14351 <entry colname="1">
14352 <para><command>SERVFAIL</command></para>
14354 <entry colname="2">
14355 <para><command>RFail</command></para>
14357 <entry colname="3">
14364 <entry colname="1">
14365 <para><command>FORMERR</command></para>
14367 <entry colname="2">
14368 <para><command>RFErr</command></para>
14370 <entry colname="3">
14377 <entry colname="1">
14378 <para><command>OtherError</command></para>
14380 <entry colname="2">
14381 <para><command>RErr</command></para>
14383 <entry colname="3">
14385 Other errors received.
14390 <entry colname="1">
14391 <para><command>EDNS0Fail</command></para>
14393 <entry colname="2">
14394 <para><command></command></para>
14396 <entry colname="3">
14398 EDNS(0) query failures.
14403 <entry colname="1">
14404 <para><command>Mismatch</command></para>
14406 <entry colname="2">
14407 <para><command>RDupR</command></para>
14409 <entry colname="3">
14411 Mismatch responses received.
14412 The DNS ID, response's source address,
14413 and/or the response's source port does not
14414 match what was expected.
14415 (The port must be 53 or as defined by
14416 the <command>port</command> option.)
14417 This may be an indication of a cache
14423 <entry colname="1">
14424 <para><command>Truncated</command></para>
14426 <entry colname="2">
14427 <para><command></command></para>
14429 <entry colname="3">
14431 Truncated responses received.
14436 <entry colname="1">
14437 <para><command>Lame</command></para>
14439 <entry colname="2">
14440 <para><command>RLame</command></para>
14442 <entry colname="3">
14444 Lame delegations received.
14449 <entry colname="1">
14450 <para><command>Retry</command></para>
14452 <entry colname="2">
14453 <para><command>SDupQ</command></para>
14455 <entry colname="3">
14457 Query retries performed.
14462 <entry colname="1">
14463 <para><command>QueryAbort</command></para>
14465 <entry colname="2">
14466 <para><command></command></para>
14468 <entry colname="3">
14470 Queries aborted due to quota control.
14475 <entry colname="1">
14476 <para><command>QuerySockFail</command></para>
14478 <entry colname="2">
14479 <para><command></command></para>
14481 <entry colname="3">
14483 Failures in opening query sockets.
14484 One common reason for such failures is a
14485 failure of opening a new socket due to a
14486 limitation on file descriptors.
14491 <entry colname="1">
14492 <para><command>QueryTimeout</command></para>
14494 <entry colname="2">
14495 <para><command></command></para>
14497 <entry colname="3">
14504 <entry colname="1">
14505 <para><command>GlueFetchv4</command></para>
14507 <entry colname="2">
14508 <para><command>SSysQ</command></para>
14510 <entry colname="3">
14512 IPv4 NS address fetches invoked.
14517 <entry colname="1">
14518 <para><command>GlueFetchv6</command></para>
14520 <entry colname="2">
14521 <para><command>SSysQ</command></para>
14523 <entry colname="3">
14525 IPv6 NS address fetches invoked.
14530 <entry colname="1">
14531 <para><command>GlueFetchv4Fail</command></para>
14533 <entry colname="2">
14534 <para><command></command></para>
14536 <entry colname="3">
14538 IPv4 NS address fetch failed.
14543 <entry colname="1">
14544 <para><command>GlueFetchv6Fail</command></para>
14546 <entry colname="2">
14547 <para><command></command></para>
14549 <entry colname="3">
14551 IPv6 NS address fetch failed.
14556 <entry colname="1">
14557 <para><command>ValAttempt</command></para>
14559 <entry colname="2">
14560 <para><command></command></para>
14562 <entry colname="3">
14564 DNSSEC validation attempted.
14569 <entry colname="1">
14570 <para><command>ValOk</command></para>
14572 <entry colname="2">
14573 <para><command></command></para>
14575 <entry colname="3">
14577 DNSSEC validation succeeded.
14582 <entry colname="1">
14583 <para><command>ValNegOk</command></para>
14585 <entry colname="2">
14586 <para><command></command></para>
14588 <entry colname="3">
14590 DNSSEC validation on negative information succeeded.
14595 <entry colname="1">
14596 <para><command>ValFail</command></para>
14598 <entry colname="2">
14599 <para><command></command></para>
14601 <entry colname="3">
14603 DNSSEC validation failed.
14608 <entry colname="1">
14609 <para><command>QryRTTnn</command></para>
14611 <entry colname="2">
14612 <para><command></command></para>
14614 <entry colname="3">
14616 Frequency table on round trip times (RTTs) of
14618 Each <command>nn</command> specifies the corresponding
14621 <command>nn_1</command>,
14622 <command>nn_2</command>,
14624 <command>nn_m</command>,
14625 the value of <command>nn_i</command> is the
14626 number of queries whose RTTs are between
14627 <command>nn_(i-1)</command> (inclusive) and
14628 <command>nn_i</command> (exclusive) milliseconds.
14629 For the sake of convenience we define
14630 <command>nn_0</command> to be 0.
14631 The last entry should be represented as
14632 <command>nn_m+</command>, which means the
14633 number of queries whose RTTs are equal to or over
14634 <command>nn_m</command> milliseconds.
14645 <title>Socket I/O Statistics Counters</title>
14648 Socket I/O statistics counters are defined per socket
14650 <command>UDP4</command> (UDP/IPv4),
14651 <command>UDP6</command> (UDP/IPv6),
14652 <command>TCP4</command> (TCP/IPv4),
14653 <command>TCP6</command> (TCP/IPv6),
14654 <command>Unix</command> (Unix Domain), and
14655 <command>FDwatch</command> (sockets opened outside the
14657 In the following table <command><TYPE></command>
14658 represents a socket type.
14659 Not all counters are available for all socket types;
14660 exceptions are noted in the description field.
14663 <informaltable colsep="0" rowsep="0">
14664 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14665 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14666 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
14669 <entry colname="1">
14671 <emphasis>Symbol</emphasis>
14674 <entry colname="2">
14676 <emphasis>Description</emphasis>
14682 <entry colname="1">
14683 <para><command><TYPE>Open</command></para>
14685 <entry colname="2">
14687 Sockets opened successfully.
14688 This counter is not applicable to the
14689 <command>FDwatch</command> type.
14694 <entry colname="1">
14695 <para><command><TYPE>OpenFail</command></para>
14697 <entry colname="2">
14699 Failures of opening sockets.
14700 This counter is not applicable to the
14701 <command>FDwatch</command> type.
14706 <entry colname="1">
14707 <para><command><TYPE>Close</command></para>
14709 <entry colname="2">
14716 <entry colname="1">
14717 <para><command><TYPE>BindFail</command></para>
14719 <entry colname="2">
14721 Failures of binding sockets.
14726 <entry colname="1">
14727 <para><command><TYPE>ConnFail</command></para>
14729 <entry colname="2">
14731 Failures of connecting sockets.
14736 <entry colname="1">
14737 <para><command><TYPE>Conn</command></para>
14739 <entry colname="2">
14741 Connections established successfully.
14746 <entry colname="1">
14747 <para><command><TYPE>AcceptFail</command></para>
14749 <entry colname="2">
14751 Failures of accepting incoming connection requests.
14752 This counter is not applicable to the
14753 <command>UDP</command> and
14754 <command>FDwatch</command> types.
14759 <entry colname="1">
14760 <para><command><TYPE>Accept</command></para>
14762 <entry colname="2">
14764 Incoming connections successfully accepted.
14765 This counter is not applicable to the
14766 <command>UDP</command> and
14767 <command>FDwatch</command> types.
14772 <entry colname="1">
14773 <para><command><TYPE>SendErr</command></para>
14775 <entry colname="2">
14777 Errors in socket send operations.
14778 This counter corresponds
14779 to <command>SErr</command> counter of
14780 <command>BIND</command> 8.
14785 <entry colname="1">
14786 <para><command><TYPE>RecvErr</command></para>
14788 <entry colname="2">
14790 Errors in socket receive operations.
14791 This includes errors of send operations on a
14792 connected UDP socket notified by an ICMP error
14802 <title>Compatibility with <emphasis>BIND</emphasis> 8 Counters</title>
14804 Most statistics counters that were available
14805 in <command>BIND</command> 8 are also supported in
14806 <command>BIND</command> 9 as shown in the above tables.
14807 Here are notes about other counters that do not appear
14813 <term><command>RFwdR,SFwdR</command></term>
14816 These counters are not supported
14817 because <command>BIND</command> 9 does not adopt
14818 the notion of <emphasis>forwarding</emphasis>
14819 as <command>BIND</command> 8 did.
14825 <term><command>RAXFR</command></term>
14828 This counter is accessible in the Incoming Queries section.
14834 <term><command>RIQ</command></term>
14837 This counter is accessible in the Incoming Requests section.
14843 <term><command>ROpts</command></term>
14846 This counter is not supported
14847 because <command>BIND</command> 9 does not care
14848 about IP options in the first place.
14858 <chapter id="Bv9ARM.ch07">
14859 <title><acronym>BIND</acronym> 9 Security Considerations</title>
14860 <sect1 id="Access_Control_Lists">
14861 <title>Access Control Lists</title>
14863 Access Control Lists (ACLs) are address match lists that
14864 you can set up and nickname for future use in <command>allow-notify</command>,
14865 <command>allow-query</command>, <command>allow-query-on</command>,
14866 <command>allow-recursion</command>, <command>allow-recursion-on</command>,
14867 <command>blackhole</command>, <command>allow-transfer</command>,
14871 Using ACLs allows you to have finer control over who can access
14872 your name server, without cluttering up your config files with huge
14873 lists of IP addresses.
14876 It is a <emphasis>good idea</emphasis> to use ACLs, and to
14877 control access to your server. Limiting access to your server by
14878 outside parties can help prevent spoofing and denial of service (DoS) attacks against
14882 Here is an example of how to properly apply ACLs:
14886 // Set up an ACL named "bogusnets" that will block
14887 // RFC1918 space and some reserved space, which is
14888 // commonly used in spoofing attacks.
14890 0.0.0.0/8; 192.0.2.0/24; 224.0.0.0/3;
14891 10.0.0.0/8; 172.16.0.0/12; 192.168.0.0/16;
14894 // Set up an ACL called our-nets. Replace this with the
14895 // real IP numbers.
14896 acl our-nets { x.x.x.x/24; x.x.x.x/21; };
14900 allow-query { our-nets; };
14901 allow-recursion { our-nets; };
14903 blackhole { bogusnets; };
14907 zone "example.com" {
14909 file "m/example.com";
14910 allow-query { any; };
14915 This allows recursive queries of the server from the outside
14916 unless recursion has been previously disabled.
14919 For more information on how to use ACLs to protect your server,
14920 see the <emphasis>AUSCERT</emphasis> advisory at:
14923 <ulink url="ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos"
14924 >ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos</ulink>
14928 <title><command>Chroot</command> and <command>Setuid</command></title>
14930 On UNIX servers, it is possible to run <acronym>BIND</acronym>
14931 in a <emphasis>chrooted</emphasis> environment (using
14932 the <command>chroot()</command> function) by specifying
14933 the "<option>-t</option>" option for <command>named</command>.
14934 This can help improve system security by placing
14935 <acronym>BIND</acronym> in a "sandbox", which will limit
14936 the damage done if a server is compromised.
14939 Another useful feature in the UNIX version of <acronym>BIND</acronym> is the
14940 ability to run the daemon as an unprivileged user ( <option>-u</option> <replaceable>user</replaceable> ).
14941 We suggest running as an unprivileged user when using the <command>chroot</command> feature.
14944 Here is an example command line to load <acronym>BIND</acronym> in a <command>chroot</command> sandbox,
14945 <command>/var/named</command>, and to run <command>named</command> <command>setuid</command> to
14949 <userinput>/usr/local/sbin/named -u 202 -t /var/named</userinput>
14953 <title>The <command>chroot</command> Environment</title>
14956 In order for a <command>chroot</command> environment
14958 work properly in a particular directory
14959 (for example, <filename>/var/named</filename>),
14960 you will need to set up an environment that includes everything
14961 <acronym>BIND</acronym> needs to run.
14962 From <acronym>BIND</acronym>'s point of view, <filename>/var/named</filename> is
14963 the root of the filesystem. You will need to adjust the values of
14965 like <command>directory</command> and <command>pid-file</command> to account
14969 Unlike with earlier versions of BIND, you typically will
14970 <emphasis>not</emphasis> need to compile <command>named</command>
14971 statically nor install shared libraries under the new root.
14972 However, depending on your operating system, you may need
14973 to set up things like
14974 <filename>/dev/zero</filename>,
14975 <filename>/dev/random</filename>,
14976 <filename>/dev/log</filename>, and
14977 <filename>/etc/localtime</filename>.
14982 <title>Using the <command>setuid</command> Function</title>
14985 Prior to running the <command>named</command> daemon,
14987 the <command>touch</command> utility (to change file
14989 modification times) or the <command>chown</command>
14991 set the user id and/or group id) on files
14992 to which you want <acronym>BIND</acronym>
14996 Note that if the <command>named</command> daemon is running as an
14997 unprivileged user, it will not be able to bind to new restricted
14998 ports if the server is reloaded.
15003 <sect1 id="dynamic_update_security">
15004 <title>Dynamic Update Security</title>
15007 Access to the dynamic
15008 update facility should be strictly limited. In earlier versions of
15009 <acronym>BIND</acronym>, the only way to do this was
15011 address of the host requesting the update, by listing an IP address
15013 network prefix in the <command>allow-update</command>
15015 This method is insecure since the source address of the update UDP
15017 is easily forged. Also note that if the IP addresses allowed by the
15018 <command>allow-update</command> option include the
15020 server which performs forwarding of dynamic updates, the master can
15022 trivially attacked by sending the update to the slave, which will
15023 forward it to the master with its own source IP address causing the
15024 master to approve it without question.
15028 For these reasons, we strongly recommend that updates be
15029 cryptographically authenticated by means of transaction signatures
15030 (TSIG). That is, the <command>allow-update</command>
15032 list only TSIG key names, not IP addresses or network
15033 prefixes. Alternatively, the new <command>update-policy</command>
15034 option can be used.
15038 Some sites choose to keep all dynamically-updated DNS data
15039 in a subdomain and delegate that subdomain to a separate zone. This
15040 way, the top-level zone containing critical data such as the IP
15042 of public web and mail servers need not allow dynamic update at
15049 <chapter id="Bv9ARM.ch08">
15050 <title>Troubleshooting</title>
15052 <title>Common Problems</title>
15054 <title>It's not working; how can I figure out what's wrong?</title>
15057 The best solution to solving installation and
15058 configuration issues is to take preventative measures by setting
15059 up logging files beforehand. The log files provide a
15060 source of hints and information that can be used to figure out
15061 what went wrong and how to fix the problem.
15067 <title>Incrementing and Changing the Serial Number</title>
15070 Zone serial numbers are just numbers — they aren't
15071 date related. A lot of people set them to a number that
15072 represents a date, usually of the form YYYYMMDDRR.
15073 Occasionally they will make a mistake and set them to a
15074 "date in the future" then try to correct them by setting
15075 them to the "current date". This causes problems because
15076 serial numbers are used to indicate that a zone has been
15077 updated. If the serial number on the slave server is
15078 lower than the serial number on the master, the slave
15079 server will attempt to update its copy of the zone.
15083 Setting the serial number to a lower number on the master
15084 server than the slave server means that the slave will not perform
15085 updates to its copy of the zone.
15089 The solution to this is to add 2147483647 (2^31-1) to the
15090 number, reload the zone and make sure all slaves have updated to
15091 the new zone serial number, then reset the number to what you want
15092 it to be, and reload the zone again.
15097 <title>Where Can I Get Help?</title>
15100 The Internet Systems Consortium
15101 (<acronym>ISC</acronym>) offers a wide range
15102 of support and service agreements for <acronym>BIND</acronym> and <acronym>DHCP</acronym> servers. Four
15103 levels of premium support are available and each level includes
15104 support for all <acronym>ISC</acronym> programs,
15105 significant discounts on products
15106 and training, and a recognized priority on bug fixes and
15107 non-funded feature requests. In addition, <acronym>ISC</acronym> offers a standard
15108 support agreement package which includes services ranging from bug
15109 fix announcements to remote support. It also includes training in
15110 <acronym>BIND</acronym> and <acronym>DHCP</acronym>.
15114 To discuss arrangements for support, contact
15115 <ulink url="mailto:info@isc.org">info@isc.org</ulink> or visit the
15116 <acronym>ISC</acronym> web page at
15117 <ulink url="http://www.isc.org/services/support/"
15118 >http://www.isc.org/services/support/</ulink>
15123 <appendix id="Bv9ARM.ch09">
15124 <title>Appendices</title>
15126 <title>Acknowledgments</title>
15127 <sect2 id="historical_dns_information">
15128 <title>A Brief History of the <acronym>DNS</acronym> and <acronym>BIND</acronym></title>
15131 Although the "official" beginning of the Domain Name
15132 System occurred in 1984 with the publication of RFC 920, the
15133 core of the new system was described in 1983 in RFCs 882 and
15134 883. From 1984 to 1987, the ARPAnet (the precursor to today's
15135 Internet) became a testbed of experimentation for developing the
15136 new naming/addressing scheme in a rapidly expanding,
15137 operational network environment. New RFCs were written and
15138 published in 1987 that modified the original documents to
15139 incorporate improvements based on the working model. RFC 1034,
15140 "Domain Names-Concepts and Facilities", and RFC 1035, "Domain
15141 Names-Implementation and Specification" were published and
15142 became the standards upon which all <acronym>DNS</acronym> implementations are
15147 The first working domain name server, called "Jeeves", was
15148 written in 1983-84 by Paul Mockapetris for operation on DEC
15150 machines located at the University of Southern California's
15152 Sciences Institute (USC-ISI) and SRI International's Network
15154 Center (SRI-NIC). A <acronym>DNS</acronym> server for
15155 Unix machines, the Berkeley Internet
15156 Name Domain (<acronym>BIND</acronym>) package, was
15157 written soon after by a group of
15158 graduate students at the University of California at Berkeley
15160 a grant from the US Defense Advanced Research Projects
15165 Versions of <acronym>BIND</acronym> through
15166 4.8.3 were maintained by the Computer
15167 Systems Research Group (CSRG) at UC Berkeley. Douglas Terry, Mark
15168 Painter, David Riggle and Songnian Zhou made up the initial <acronym>BIND</acronym>
15169 project team. After that, additional work on the software package
15170 was done by Ralph Campbell. Kevin Dunlap, a Digital Equipment
15172 employee on loan to the CSRG, worked on <acronym>BIND</acronym> for 2 years, from 1985
15173 to 1987. Many other people also contributed to <acronym>BIND</acronym> development
15174 during that time: Doug Kingston, Craig Partridge, Smoot
15176 Mike Muuss, Jim Bloom and Mike Schwartz. <acronym>BIND</acronym> maintenance was subsequently
15177 handled by Mike Karels and Øivind Kure.
15180 <acronym>BIND</acronym> versions 4.9 and 4.9.1 were
15181 released by Digital Equipment
15182 Corporation (now Compaq Computer Corporation). Paul Vixie, then
15183 a DEC employee, became <acronym>BIND</acronym>'s
15184 primary caretaker. He was assisted
15185 by Phil Almquist, Robert Elz, Alan Barrett, Paul Albitz, Bryan
15187 Partan, Andy Cherenson, Tom Limoncelli, Berthold Paffrath, Fuat
15188 Baran, Anant Kumar, Art Harkin, Win Treese, Don Lewis, Christophe
15189 Wolfhugel, and others.
15192 In 1994, <acronym>BIND</acronym> version 4.9.2 was sponsored by
15193 Vixie Enterprises. Paul
15194 Vixie became <acronym>BIND</acronym>'s principal
15195 architect/programmer.
15198 <acronym>BIND</acronym> versions from 4.9.3 onward
15199 have been developed and maintained
15200 by the Internet Systems Consortium and its predecessor,
15201 the Internet Software Consortium, with support being provided
15205 As co-architects/programmers, Bob Halley and
15206 Paul Vixie released the first production-ready version of
15207 <acronym>BIND</acronym> version 8 in May 1997.
15210 BIND version 9 was released in September 2000 and is a
15211 major rewrite of nearly all aspects of the underlying
15215 BIND versions 4 and 8 are officially deprecated.
15216 No additional development is done
15217 on BIND version 4 or BIND version 8.
15220 <acronym>BIND</acronym> development work is made
15221 possible today by the sponsorship
15222 of several corporations, and by the tireless work efforts of
15223 numerous individuals.
15228 <title>General <acronym>DNS</acronym> Reference Information</title>
15229 <sect2 id="ipv6addresses">
15230 <title>IPv6 addresses (AAAA)</title>
15232 IPv6 addresses are 128-bit identifiers for interfaces and
15233 sets of interfaces which were introduced in the <acronym>DNS</acronym> to facilitate
15234 scalable Internet routing. There are three types of addresses: <emphasis>Unicast</emphasis>,
15235 an identifier for a single interface;
15236 <emphasis>Anycast</emphasis>,
15237 an identifier for a set of interfaces; and <emphasis>Multicast</emphasis>,
15238 an identifier for a set of interfaces. Here we describe the global
15239 Unicast address scheme. For more information, see RFC 3587,
15240 "Global Unicast Address Format."
15243 IPv6 unicast addresses consist of a
15244 <emphasis>global routing prefix</emphasis>, a
15245 <emphasis>subnet identifier</emphasis>, and an
15246 <emphasis>interface identifier</emphasis>.
15249 The global routing prefix is provided by the
15250 upstream provider or ISP, and (roughly) corresponds to the
15251 IPv4 <emphasis>network</emphasis> section
15252 of the address range.
15254 The subnet identifier is for local subnetting, much the
15255 same as subnetting an
15256 IPv4 /16 network into /24 subnets.
15258 The interface identifier is the address of an individual
15259 interface on a given network; in IPv6, addresses belong to
15260 interfaces rather than to machines.
15263 The subnetting capability of IPv6 is much more flexible than
15264 that of IPv4: subnetting can be carried out on bit boundaries,
15265 in much the same way as Classless InterDomain Routing
15266 (CIDR), and the DNS PTR representation ("nibble" format)
15267 makes setting up reverse zones easier.
15270 The Interface Identifier must be unique on the local link,
15271 and is usually generated automatically by the IPv6
15272 implementation, although it is usually possible to
15273 override the default setting if necessary. A typical IPv6
15274 address might look like:
15275 <command>2001:db8:201:9:a00:20ff:fe81:2b32</command>
15278 IPv6 address specifications often contain long strings
15279 of zeros, so the architects have included a shorthand for
15281 them. The double colon (`::') indicates the longest possible
15283 of zeros that can fit, and can be used only once in an address.
15287 <sect1 id="bibliography">
15288 <title>Bibliography (and Suggested Reading)</title>
15290 <title>Request for Comments (RFCs)</title>
15292 Specification documents for the Internet protocol suite, including
15293 the <acronym>DNS</acronym>, are published as part of
15294 the Request for Comments (RFCs)
15295 series of technical notes. The standards themselves are defined
15296 by the Internet Engineering Task Force (IETF) and the Internet
15297 Engineering Steering Group (IESG). RFCs can be obtained online via FTP at:
15300 <ulink url="ftp://www.isi.edu/in-notes/">
15301 ftp://www.isi.edu/in-notes/RFC<replaceable>xxxx</replaceable>.txt
15305 (where <replaceable>xxxx</replaceable> is
15306 the number of the RFC). RFCs are also available via the Web at:
15309 <ulink url="http://www.ietf.org/rfc/"
15310 >http://www.ietf.org/rfc/</ulink>.
15314 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
15315 <title>Standards</title>
15317 <abbrev>RFC974</abbrev>
15319 <surname>Partridge</surname>
15320 <firstname>C.</firstname>
15322 <title>Mail Routing and the Domain System</title>
15323 <pubdate>January 1986</pubdate>
15326 <abbrev>RFC1034</abbrev>
15328 <surname>Mockapetris</surname>
15329 <firstname>P.V.</firstname>
15331 <title>Domain Names — Concepts and Facilities</title>
15332 <pubdate>November 1987</pubdate>
15335 <abbrev>RFC1035</abbrev>
15337 <surname>Mockapetris</surname>
15338 <firstname>P. V.</firstname>
15339 </author> <title>Domain Names — Implementation and
15340 Specification</title>
15341 <pubdate>November 1987</pubdate>
15344 <bibliodiv id="proposed_standards" xreflabel="Proposed Standards">
15346 <title>Proposed Standards</title>
15347 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
15349 <abbrev>RFC2181</abbrev>
15351 <surname>Elz</surname>
15352 <firstname>R., R. Bush</firstname>
15354 <title>Clarifications to the <acronym>DNS</acronym>
15355 Specification</title>
15356 <pubdate>July 1997</pubdate>
15359 <abbrev>RFC2308</abbrev>
15361 <surname>Andrews</surname>
15362 <firstname>M.</firstname>
15364 <title>Negative Caching of <acronym>DNS</acronym>
15366 <pubdate>March 1998</pubdate>
15369 <abbrev>RFC1995</abbrev>
15371 <surname>Ohta</surname>
15372 <firstname>M.</firstname>
15374 <title>Incremental Zone Transfer in <acronym>DNS</acronym></title>
15375 <pubdate>August 1996</pubdate>
15378 <abbrev>RFC1996</abbrev>
15380 <surname>Vixie</surname>
15381 <firstname>P.</firstname>
15383 <title>A Mechanism for Prompt Notification of Zone Changes</title>
15384 <pubdate>August 1996</pubdate>
15387 <abbrev>RFC2136</abbrev>
15390 <surname>Vixie</surname>
15391 <firstname>P.</firstname>
15394 <firstname>S.</firstname>
15395 <surname>Thomson</surname>
15398 <firstname>Y.</firstname>
15399 <surname>Rekhter</surname>
15402 <firstname>J.</firstname>
15403 <surname>Bound</surname>
15406 <title>Dynamic Updates in the Domain Name System</title>
15407 <pubdate>April 1997</pubdate>
15410 <abbrev>RFC2671</abbrev>
15413 <firstname>P.</firstname>
15414 <surname>Vixie</surname>
15417 <title>Extension Mechanisms for DNS (EDNS0)</title>
15418 <pubdate>August 1997</pubdate>
15421 <abbrev>RFC2672</abbrev>
15424 <firstname>M.</firstname>
15425 <surname>Crawford</surname>
15428 <title>Non-Terminal DNS Name Redirection</title>
15429 <pubdate>August 1999</pubdate>
15432 <abbrev>RFC2845</abbrev>
15435 <surname>Vixie</surname>
15436 <firstname>P.</firstname>
15439 <firstname>O.</firstname>
15440 <surname>Gudmundsson</surname>
15443 <firstname>D.</firstname>
15444 <surname>Eastlake</surname>
15445 <lineage>3rd</lineage>
15448 <firstname>B.</firstname>
15449 <surname>Wellington</surname>
15452 <title>Secret Key Transaction Authentication for <acronym>DNS</acronym> (TSIG)</title>
15453 <pubdate>May 2000</pubdate>
15456 <abbrev>RFC2930</abbrev>
15459 <firstname>D.</firstname>
15460 <surname>Eastlake</surname>
15461 <lineage>3rd</lineage>
15464 <title>Secret Key Establishment for DNS (TKEY RR)</title>
15465 <pubdate>September 2000</pubdate>
15468 <abbrev>RFC2931</abbrev>
15471 <firstname>D.</firstname>
15472 <surname>Eastlake</surname>
15473 <lineage>3rd</lineage>
15476 <title>DNS Request and Transaction Signatures (SIG(0)s)</title>
15477 <pubdate>September 2000</pubdate>
15480 <abbrev>RFC3007</abbrev>
15483 <firstname>B.</firstname>
15484 <surname>Wellington</surname>
15487 <title>Secure Domain Name System (DNS) Dynamic Update</title>
15488 <pubdate>November 2000</pubdate>
15491 <abbrev>RFC3645</abbrev>
15494 <firstname>S.</firstname>
15495 <surname>Kwan</surname>
15498 <firstname>P.</firstname>
15499 <surname>Garg</surname>
15502 <firstname>J.</firstname>
15503 <surname>Gilroy</surname>
15506 <firstname>L.</firstname>
15507 <surname>Esibov</surname>
15510 <firstname>J.</firstname>
15511 <surname>Westhead</surname>
15514 <firstname>R.</firstname>
15515 <surname>Hall</surname>
15518 <title>Generic Security Service Algorithm for Secret
15519 Key Transaction Authentication for DNS
15521 <pubdate>October 2003</pubdate>
15525 <title><acronym>DNS</acronym> Security Proposed Standards</title>
15527 <abbrev>RFC3225</abbrev>
15530 <firstname>D.</firstname>
15531 <surname>Conrad</surname>
15534 <title>Indicating Resolver Support of DNSSEC</title>
15535 <pubdate>December 2001</pubdate>
15538 <abbrev>RFC3833</abbrev>
15541 <firstname>D.</firstname>
15542 <surname>Atkins</surname>
15545 <firstname>R.</firstname>
15546 <surname>Austein</surname>
15549 <title>Threat Analysis of the Domain Name System (DNS)</title>
15550 <pubdate>August 2004</pubdate>
15553 <abbrev>RFC4033</abbrev>
15556 <firstname>R.</firstname>
15557 <surname>Arends</surname>
15560 <firstname>R.</firstname>
15561 <surname>Austein</surname>
15564 <firstname>M.</firstname>
15565 <surname>Larson</surname>
15568 <firstname>D.</firstname>
15569 <surname>Massey</surname>
15572 <firstname>S.</firstname>
15573 <surname>Rose</surname>
15576 <title>DNS Security Introduction and Requirements</title>
15577 <pubdate>March 2005</pubdate>
15580 <abbrev>RFC4034</abbrev>
15583 <firstname>R.</firstname>
15584 <surname>Arends</surname>
15587 <firstname>R.</firstname>
15588 <surname>Austein</surname>
15591 <firstname>M.</firstname>
15592 <surname>Larson</surname>
15595 <firstname>D.</firstname>
15596 <surname>Massey</surname>
15599 <firstname>S.</firstname>
15600 <surname>Rose</surname>
15603 <title>Resource Records for the DNS Security Extensions</title>
15604 <pubdate>March 2005</pubdate>
15607 <abbrev>RFC4035</abbrev>
15610 <firstname>R.</firstname>
15611 <surname>Arends</surname>
15614 <firstname>R.</firstname>
15615 <surname>Austein</surname>
15618 <firstname>M.</firstname>
15619 <surname>Larson</surname>
15622 <firstname>D.</firstname>
15623 <surname>Massey</surname>
15626 <firstname>S.</firstname>
15627 <surname>Rose</surname>
15630 <title>Protocol Modifications for the DNS
15631 Security Extensions</title>
15632 <pubdate>March 2005</pubdate>
15636 <title>Other Important RFCs About <acronym>DNS</acronym>
15637 Implementation</title>
15639 <abbrev>RFC1535</abbrev>
15641 <surname>Gavron</surname>
15642 <firstname>E.</firstname>
15644 <title>A Security Problem and Proposed Correction With Widely
15645 Deployed <acronym>DNS</acronym> Software.</title>
15646 <pubdate>October 1993</pubdate>
15649 <abbrev>RFC1536</abbrev>
15652 <surname>Kumar</surname>
15653 <firstname>A.</firstname>
15656 <firstname>J.</firstname>
15657 <surname>Postel</surname>
15660 <firstname>C.</firstname>
15661 <surname>Neuman</surname>
15664 <firstname>P.</firstname>
15665 <surname>Danzig</surname>
15668 <firstname>S.</firstname>
15669 <surname>Miller</surname>
15672 <title>Common <acronym>DNS</acronym> Implementation
15673 Errors and Suggested Fixes</title>
15674 <pubdate>October 1993</pubdate>
15677 <abbrev>RFC1982</abbrev>
15680 <surname>Elz</surname>
15681 <firstname>R.</firstname>
15684 <firstname>R.</firstname>
15685 <surname>Bush</surname>
15688 <title>Serial Number Arithmetic</title>
15689 <pubdate>August 1996</pubdate>
15692 <abbrev>RFC4074</abbrev>
15695 <surname>Morishita</surname>
15696 <firstname>Y.</firstname>
15699 <firstname>T.</firstname>
15700 <surname>Jinmei</surname>
15703 <title>Common Misbehaviour Against <acronym>DNS</acronym>
15704 Queries for IPv6 Addresses</title>
15705 <pubdate>May 2005</pubdate>
15709 <title>Resource Record Types</title>
15711 <abbrev>RFC1183</abbrev>
15714 <surname>Everhart</surname>
15715 <firstname>C.F.</firstname>
15718 <firstname>L. A.</firstname>
15719 <surname>Mamakos</surname>
15722 <firstname>R.</firstname>
15723 <surname>Ullmann</surname>
15726 <firstname>P.</firstname>
15727 <surname>Mockapetris</surname>
15730 <title>New <acronym>DNS</acronym> RR Definitions</title>
15731 <pubdate>October 1990</pubdate>
15734 <abbrev>RFC1706</abbrev>
15737 <surname>Manning</surname>
15738 <firstname>B.</firstname>
15741 <firstname>R.</firstname>
15742 <surname>Colella</surname>
15745 <title><acronym>DNS</acronym> NSAP Resource Records</title>
15746 <pubdate>October 1994</pubdate>
15749 <abbrev>RFC2168</abbrev>
15752 <surname>Daniel</surname>
15753 <firstname>R.</firstname>
15756 <firstname>M.</firstname>
15757 <surname>Mealling</surname>
15760 <title>Resolution of Uniform Resource Identifiers using
15761 the Domain Name System</title>
15762 <pubdate>June 1997</pubdate>
15765 <abbrev>RFC1876</abbrev>
15768 <surname>Davis</surname>
15769 <firstname>C.</firstname>
15772 <firstname>P.</firstname>
15773 <surname>Vixie</surname>
15776 <firstname>T.</firstname>
15777 <firstname>Goodwin</firstname>
15780 <firstname>I.</firstname>
15781 <surname>Dickinson</surname>
15784 <title>A Means for Expressing Location Information in the
15786 Name System</title>
15787 <pubdate>January 1996</pubdate>
15790 <abbrev>RFC2052</abbrev>
15793 <surname>Gulbrandsen</surname>
15794 <firstname>A.</firstname>
15797 <firstname>P.</firstname>
15798 <surname>Vixie</surname>
15801 <title>A <acronym>DNS</acronym> RR for Specifying the
15804 <pubdate>October 1996</pubdate>
15807 <abbrev>RFC2163</abbrev>
15809 <surname>Allocchio</surname>
15810 <firstname>A.</firstname>
15812 <title>Using the Internet <acronym>DNS</acronym> to
15814 Conformant Global Address Mapping</title>
15815 <pubdate>January 1998</pubdate>
15818 <abbrev>RFC2230</abbrev>
15820 <surname>Atkinson</surname>
15821 <firstname>R.</firstname>
15823 <title>Key Exchange Delegation Record for the <acronym>DNS</acronym></title>
15824 <pubdate>October 1997</pubdate>
15827 <abbrev>RFC2536</abbrev>
15829 <surname>Eastlake</surname>
15830 <firstname>D.</firstname>
15831 <lineage>3rd</lineage>
15833 <title>DSA KEYs and SIGs in the Domain Name System (DNS)</title>
15834 <pubdate>March 1999</pubdate>
15837 <abbrev>RFC2537</abbrev>
15839 <surname>Eastlake</surname>
15840 <firstname>D.</firstname>
15841 <lineage>3rd</lineage>
15843 <title>RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)</title>
15844 <pubdate>March 1999</pubdate>
15847 <abbrev>RFC2538</abbrev>
15850 <surname>Eastlake</surname>
15851 <firstname>D.</firstname>
15852 <lineage>3rd</lineage>
15855 <surname>Gudmundsson</surname>
15856 <firstname>O.</firstname>
15859 <title>Storing Certificates in the Domain Name System (DNS)</title>
15860 <pubdate>March 1999</pubdate>
15863 <abbrev>RFC2539</abbrev>
15866 <surname>Eastlake</surname>
15867 <firstname>D.</firstname>
15868 <lineage>3rd</lineage>
15871 <title>Storage of Diffie-Hellman Keys in the Domain Name System (DNS)</title>
15872 <pubdate>March 1999</pubdate>
15875 <abbrev>RFC2540</abbrev>
15878 <surname>Eastlake</surname>
15879 <firstname>D.</firstname>
15880 <lineage>3rd</lineage>
15883 <title>Detached Domain Name System (DNS) Information</title>
15884 <pubdate>March 1999</pubdate>
15887 <abbrev>RFC2782</abbrev>
15889 <surname>Gulbrandsen</surname>
15890 <firstname>A.</firstname>
15893 <surname>Vixie</surname>
15894 <firstname>P.</firstname>
15897 <surname>Esibov</surname>
15898 <firstname>L.</firstname>
15900 <title>A DNS RR for specifying the location of services (DNS SRV)</title>
15901 <pubdate>February 2000</pubdate>
15904 <abbrev>RFC2915</abbrev>
15906 <surname>Mealling</surname>
15907 <firstname>M.</firstname>
15910 <surname>Daniel</surname>
15911 <firstname>R.</firstname>
15913 <title>The Naming Authority Pointer (NAPTR) DNS Resource Record</title>
15914 <pubdate>September 2000</pubdate>
15917 <abbrev>RFC3110</abbrev>
15919 <surname>Eastlake</surname>
15920 <firstname>D.</firstname>
15921 <lineage>3rd</lineage>
15923 <title>RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)</title>
15924 <pubdate>May 2001</pubdate>
15927 <abbrev>RFC3123</abbrev>
15929 <surname>Koch</surname>
15930 <firstname>P.</firstname>
15932 <title>A DNS RR Type for Lists of Address Prefixes (APL RR)</title>
15933 <pubdate>June 2001</pubdate>
15936 <abbrev>RFC3596</abbrev>
15939 <surname>Thomson</surname>
15940 <firstname>S.</firstname>
15943 <firstname>C.</firstname>
15944 <surname>Huitema</surname>
15947 <firstname>V.</firstname>
15948 <surname>Ksinant</surname>
15951 <firstname>M.</firstname>
15952 <surname>Souissi</surname>
15955 <title><acronym>DNS</acronym> Extensions to support IP
15957 <pubdate>October 2003</pubdate>
15960 <abbrev>RFC3597</abbrev>
15962 <surname>Gustafsson</surname>
15963 <firstname>A.</firstname>
15965 <title>Handling of Unknown DNS Resource Record (RR) Types</title>
15966 <pubdate>September 2003</pubdate>
15970 <title><acronym>DNS</acronym> and the Internet</title>
15972 <abbrev>RFC1101</abbrev>
15974 <surname>Mockapetris</surname>
15975 <firstname>P. V.</firstname>
15977 <title><acronym>DNS</acronym> Encoding of Network Names
15978 and Other Types</title>
15979 <pubdate>April 1989</pubdate>
15982 <abbrev>RFC1123</abbrev>
15984 <surname>Braden</surname>
15985 <surname>R.</surname>
15987 <title>Requirements for Internet Hosts - Application and
15989 <pubdate>October 1989</pubdate>
15992 <abbrev>RFC1591</abbrev>
15994 <surname>Postel</surname>
15995 <firstname>J.</firstname>
15997 <title>Domain Name System Structure and Delegation</title>
15998 <pubdate>March 1994</pubdate>
16001 <abbrev>RFC2317</abbrev>
16004 <surname>Eidnes</surname>
16005 <firstname>H.</firstname>
16008 <firstname>G.</firstname>
16009 <surname>de Groot</surname>
16012 <firstname>P.</firstname>
16013 <surname>Vixie</surname>
16016 <title>Classless IN-ADDR.ARPA Delegation</title>
16017 <pubdate>March 1998</pubdate>
16020 <abbrev>RFC2826</abbrev>
16023 <surname>Internet Architecture Board</surname>
16026 <title>IAB Technical Comment on the Unique DNS Root</title>
16027 <pubdate>May 2000</pubdate>
16030 <abbrev>RFC2929</abbrev>
16033 <surname>Eastlake</surname>
16034 <firstname>D.</firstname>
16035 <lineage>3rd</lineage>
16038 <surname>Brunner-Williams</surname>
16039 <firstname>E.</firstname>
16042 <surname>Manning</surname>
16043 <firstname>B.</firstname>
16046 <title>Domain Name System (DNS) IANA Considerations</title>
16047 <pubdate>September 2000</pubdate>
16051 <title><acronym>DNS</acronym> Operations</title>
16053 <abbrev>RFC1033</abbrev>
16055 <surname>Lottor</surname>
16056 <firstname>M.</firstname>
16058 <title>Domain administrators operations guide.</title>
16059 <pubdate>November 1987</pubdate>
16062 <abbrev>RFC1537</abbrev>
16064 <surname>Beertema</surname>
16065 <firstname>P.</firstname>
16067 <title>Common <acronym>DNS</acronym> Data File
16068 Configuration Errors</title>
16069 <pubdate>October 1993</pubdate>
16072 <abbrev>RFC1912</abbrev>
16074 <surname>Barr</surname>
16075 <firstname>D.</firstname>
16077 <title>Common <acronym>DNS</acronym> Operational and
16078 Configuration Errors</title>
16079 <pubdate>February 1996</pubdate>
16082 <abbrev>RFC2010</abbrev>
16085 <surname>Manning</surname>
16086 <firstname>B.</firstname>
16089 <firstname>P.</firstname>
16090 <surname>Vixie</surname>
16093 <title>Operational Criteria for Root Name Servers.</title>
16094 <pubdate>October 1996</pubdate>
16097 <abbrev>RFC2219</abbrev>
16100 <surname>Hamilton</surname>
16101 <firstname>M.</firstname>
16104 <firstname>R.</firstname>
16105 <surname>Wright</surname>
16108 <title>Use of <acronym>DNS</acronym> Aliases for
16109 Network Services.</title>
16110 <pubdate>October 1997</pubdate>
16114 <title>Internationalized Domain Names</title>
16116 <abbrev>RFC2825</abbrev>
16119 <surname>IAB</surname>
16122 <surname>Daigle</surname>
16123 <firstname>R.</firstname>
16126 <title>A Tangled Web: Issues of I18N, Domain Names,
16127 and the Other Internet protocols</title>
16128 <pubdate>May 2000</pubdate>
16131 <abbrev>RFC3490</abbrev>
16134 <surname>Faltstrom</surname>
16135 <firstname>P.</firstname>
16138 <surname>Hoffman</surname>
16139 <firstname>P.</firstname>
16142 <surname>Costello</surname>
16143 <firstname>A.</firstname>
16146 <title>Internationalizing Domain Names in Applications (IDNA)</title>
16147 <pubdate>March 2003</pubdate>
16150 <abbrev>RFC3491</abbrev>
16153 <surname>Hoffman</surname>
16154 <firstname>P.</firstname>
16157 <surname>Blanchet</surname>
16158 <firstname>M.</firstname>
16161 <title>Nameprep: A Stringprep Profile for Internationalized Domain Names</title>
16162 <pubdate>March 2003</pubdate>
16165 <abbrev>RFC3492</abbrev>
16168 <surname>Costello</surname>
16169 <firstname>A.</firstname>
16172 <title>Punycode: A Bootstring encoding of Unicode
16173 for Internationalized Domain Names in
16174 Applications (IDNA)</title>
16175 <pubdate>March 2003</pubdate>
16179 <title>Other <acronym>DNS</acronym>-related RFCs</title>
16182 Note: the following list of RFCs, although
16183 <acronym>DNS</acronym>-related, are not
16184 concerned with implementing software.
16188 <abbrev>RFC1464</abbrev>
16190 <surname>Rosenbaum</surname>
16191 <firstname>R.</firstname>
16193 <title>Using the Domain Name System To Store Arbitrary String
16195 <pubdate>May 1993</pubdate>
16198 <abbrev>RFC1713</abbrev>
16200 <surname>Romao</surname>
16201 <firstname>A.</firstname>
16203 <title>Tools for <acronym>DNS</acronym> Debugging</title>
16204 <pubdate>November 1994</pubdate>
16207 <abbrev>RFC1794</abbrev>
16209 <surname>Brisco</surname>
16210 <firstname>T.</firstname>
16212 <title><acronym>DNS</acronym> Support for Load
16214 <pubdate>April 1995</pubdate>
16217 <abbrev>RFC2240</abbrev>
16219 <surname>Vaughan</surname>
16220 <firstname>O.</firstname>
16222 <title>A Legal Basis for Domain Name Allocation</title>
16223 <pubdate>November 1997</pubdate>
16226 <abbrev>RFC2345</abbrev>
16229 <surname>Klensin</surname>
16230 <firstname>J.</firstname>
16233 <firstname>T.</firstname>
16234 <surname>Wolf</surname>
16237 <firstname>G.</firstname>
16238 <surname>Oglesby</surname>
16241 <title>Domain Names and Company Name Retrieval</title>
16242 <pubdate>May 1998</pubdate>
16245 <abbrev>RFC2352</abbrev>
16247 <surname>Vaughan</surname>
16248 <firstname>O.</firstname>
16250 <title>A Convention For Using Legal Names as Domain Names</title>
16251 <pubdate>May 1998</pubdate>
16254 <abbrev>RFC3071</abbrev>
16257 <surname>Klensin</surname>
16258 <firstname>J.</firstname>
16261 <title>Reflections on the DNS, RFC 1591, and Categories of Domains</title>
16262 <pubdate>February 2001</pubdate>
16265 <abbrev>RFC3258</abbrev>
16268 <surname>Hardie</surname>
16269 <firstname>T.</firstname>
16272 <title>Distributing Authoritative Name Servers via
16273 Shared Unicast Addresses</title>
16274 <pubdate>April 2002</pubdate>
16277 <abbrev>RFC3901</abbrev>
16280 <surname>Durand</surname>
16281 <firstname>A.</firstname>
16284 <firstname>J.</firstname>
16285 <surname>Ihren</surname>
16288 <title>DNS IPv6 Transport Operational Guidelines</title>
16289 <pubdate>September 2004</pubdate>
16293 <title>Obsolete and Unimplemented Experimental RFC</title>
16295 <abbrev>RFC1712</abbrev>
16298 <surname>Farrell</surname>
16299 <firstname>C.</firstname>
16302 <firstname>M.</firstname>
16303 <surname>Schulze</surname>
16306 <firstname>S.</firstname>
16307 <surname>Pleitner</surname>
16310 <firstname>D.</firstname>
16311 <surname>Baldoni</surname>
16314 <title><acronym>DNS</acronym> Encoding of Geographical
16316 <pubdate>November 1994</pubdate>
16319 <abbrev>RFC2673</abbrev>
16322 <surname>Crawford</surname>
16323 <firstname>M.</firstname>
16326 <title>Binary Labels in the Domain Name System</title>
16327 <pubdate>August 1999</pubdate>
16330 <abbrev>RFC2874</abbrev>
16333 <surname>Crawford</surname>
16334 <firstname>M.</firstname>
16337 <surname>Huitema</surname>
16338 <firstname>C.</firstname>
16341 <title>DNS Extensions to Support IPv6 Address Aggregation
16342 and Renumbering</title>
16343 <pubdate>July 2000</pubdate>
16347 <title>Obsoleted DNS Security RFCs</title>
16350 Most of these have been consolidated into RFC4033,
16351 RFC4034 and RFC4035 which collectively describe DNSSECbis.
16355 <abbrev>RFC2065</abbrev>
16358 <surname>Eastlake</surname>
16359 <lineage>3rd</lineage>
16360 <firstname>D.</firstname>
16363 <firstname>C.</firstname>
16364 <surname>Kaufman</surname>
16367 <title>Domain Name System Security Extensions</title>
16368 <pubdate>January 1997</pubdate>
16371 <abbrev>RFC2137</abbrev>
16373 <surname>Eastlake</surname>
16374 <lineage>3rd</lineage>
16375 <firstname>D.</firstname>
16377 <title>Secure Domain Name System Dynamic Update</title>
16378 <pubdate>April 1997</pubdate>
16381 <abbrev>RFC2535</abbrev>
16384 <surname>Eastlake</surname>
16385 <lineage>3rd</lineage>
16386 <firstname>D.</firstname>
16389 <title>Domain Name System Security Extensions</title>
16390 <pubdate>March 1999</pubdate>
16393 <abbrev>RFC3008</abbrev>
16396 <surname>Wellington</surname>
16397 <firstname>B.</firstname>
16400 <title>Domain Name System Security (DNSSEC)
16401 Signing Authority</title>
16402 <pubdate>November 2000</pubdate>
16405 <abbrev>RFC3090</abbrev>
16408 <surname>Lewis</surname>
16409 <firstname>E.</firstname>
16412 <title>DNS Security Extension Clarification on Zone Status</title>
16413 <pubdate>March 2001</pubdate>
16416 <abbrev>RFC3445</abbrev>
16419 <surname>Massey</surname>
16420 <firstname>D.</firstname>
16423 <surname>Rose</surname>
16424 <firstname>S.</firstname>
16427 <title>Limiting the Scope of the KEY Resource Record (RR)</title>
16428 <pubdate>December 2002</pubdate>
16431 <abbrev>RFC3655</abbrev>
16434 <surname>Wellington</surname>
16435 <firstname>B.</firstname>
16438 <surname>Gudmundsson</surname>
16439 <firstname>O.</firstname>
16442 <title>Redefinition of DNS Authenticated Data (AD) bit</title>
16443 <pubdate>November 2003</pubdate>
16446 <abbrev>RFC3658</abbrev>
16449 <surname>Gudmundsson</surname>
16450 <firstname>O.</firstname>
16453 <title>Delegation Signer (DS) Resource Record (RR)</title>
16454 <pubdate>December 2003</pubdate>
16457 <abbrev>RFC3755</abbrev>
16460 <surname>Weiler</surname>
16461 <firstname>S.</firstname>
16464 <title>Legacy Resolver Compatibility for Delegation Signer (DS)</title>
16465 <pubdate>May 2004</pubdate>
16468 <abbrev>RFC3757</abbrev>
16471 <surname>Kolkman</surname>
16472 <firstname>O.</firstname>
16475 <surname>Schlyter</surname>
16476 <firstname>J.</firstname>
16479 <surname>Lewis</surname>
16480 <firstname>E.</firstname>
16483 <title>Domain Name System KEY (DNSKEY) Resource Record
16484 (RR) Secure Entry Point (SEP) Flag</title>
16485 <pubdate>April 2004</pubdate>
16488 <abbrev>RFC3845</abbrev>
16491 <surname>Schlyter</surname>
16492 <firstname>J.</firstname>
16495 <title>DNS Security (DNSSEC) NextSECure (NSEC) RDATA Format</title>
16496 <pubdate>August 2004</pubdate>
16501 <sect2 id="internet_drafts">
16502 <title>Internet Drafts</title>
16504 Internet Drafts (IDs) are rough-draft working documents of
16505 the Internet Engineering Task Force. They are, in essence, RFCs
16506 in the preliminary stages of development. Implementors are
16508 to regard IDs as archival, and they should not be quoted or cited
16509 in any formal documents unless accompanied by the disclaimer that
16510 they are "works in progress." IDs have a lifespan of six months
16511 after which they are deleted unless updated by their authors.
16515 <title>Other Documents About <acronym>BIND</acronym></title>
16521 <surname>Albitz</surname>
16522 <firstname>Paul</firstname>
16525 <firstname>Cricket</firstname>
16526 <surname>Liu</surname>
16529 <title><acronym>DNS</acronym> and <acronym>BIND</acronym></title>
16532 <holder>Sebastopol, CA: O'Reilly and Associates</holder>
16539 <xi:include href="libdns.xml"/>
16544 <reference id="Bv9ARM.ch10">
16545 <title>Manual pages</title>
16546 <xi:include href="../../bin/dig/dig.docbook"/>
16547 <xi:include href="../../bin/dig/host.docbook"/>
16548 <xi:include href="../../bin/dnssec/dnssec-dsfromkey.docbook"/>
16549 <xi:include href="../../bin/dnssec/dnssec-keyfromlabel.docbook"/>
16550 <xi:include href="../../bin/dnssec/dnssec-keygen.docbook"/>
16551 <xi:include href="../../bin/dnssec/dnssec-revoke.docbook"/>
16552 <xi:include href="../../bin/dnssec/dnssec-settime.docbook"/>
16553 <xi:include href="../../bin/dnssec/dnssec-signzone.docbook"/>
16554 <xi:include href="../../bin/check/named-checkconf.docbook"/>
16555 <xi:include href="../../bin/check/named-checkzone.docbook"/>
16556 <xi:include href="../../bin/named/named.docbook"/>
16557 <xi:include href="../../bin/tools/named-journalprint.docbook"/>
16558 <!-- named.conf.docbook and others? -->
16559 <xi:include href="../../bin/nsupdate/nsupdate.docbook"/>
16560 <xi:include href="../../bin/rndc/rndc.docbook"/>
16561 <xi:include href="../../bin/rndc/rndc.conf.docbook"/>
16562 <xi:include href="../../bin/confgen/rndc-confgen.docbook"/>
16563 <xi:include href="../../bin/confgen/ddns-confgen.docbook"/>
16564 <xi:include href="../../bin/tools/arpaname.docbook"/>
16565 <xi:include href="../../bin/tools/genrandom.docbook"/>
16566 <xi:include href="../../bin/tools/isc-hmac-fixup.docbook"/>
16567 <xi:include href="../../bin/tools/nsec3hash.docbook"/>