1 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
2 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
3 [<!ENTITY mdash "—">]>
5 - Copyright (C) 2004-2013 Internet Systems Consortium, Inc. ("ISC")
6 - Copyright (C) 2000-2003 Internet Software Consortium.
8 - Permission to use, copy, modify, and/or distribute this software for any
9 - purpose with or without fee is hereby granted, provided that the above
10 - copyright notice and this permission notice appear in all copies.
12 - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
13 - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
14 - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
15 - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
16 - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
17 - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
18 - PERFORMANCE OF THIS SOFTWARE.
22 <book xmlns:xi="http://www.w3.org/2001/XInclude">
23 <title>BIND 9 Administrator Reference Manual</title>
37 <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
44 <holder>Internet Software Consortium.</holder>
48 <chapter id="Bv9ARM.ch01">
49 <title>Introduction</title>
51 The Internet Domain Name System (<acronym>DNS</acronym>)
52 consists of the syntax
53 to specify the names of entities in the Internet in a hierarchical
54 manner, the rules used for delegating authority over names, and the
55 system implementation that actually maps names to Internet
56 addresses. <acronym>DNS</acronym> data is maintained in a
58 hierarchical databases.
62 <title>Scope of Document</title>
65 The Berkeley Internet Name Domain
66 (<acronym>BIND</acronym>) implements a
67 domain name server for a number of operating systems. This
68 document provides basic information about the installation and
69 care of the Internet Systems Consortium (<acronym>ISC</acronym>)
70 <acronym>BIND</acronym> version 9 software package for
71 system administrators.
75 This version of the manual corresponds to BIND version 9.9.
80 <title>Organization of This Document</title>
82 In this document, <emphasis>Chapter 1</emphasis> introduces
83 the basic <acronym>DNS</acronym> and <acronym>BIND</acronym> concepts. <emphasis>Chapter 2</emphasis>
84 describes resource requirements for running <acronym>BIND</acronym> in various
85 environments. Information in <emphasis>Chapter 3</emphasis> is
86 <emphasis>task-oriented</emphasis> in its presentation and is
87 organized functionally, to aid in the process of installing the
88 <acronym>BIND</acronym> 9 software. The task-oriented
89 section is followed by
90 <emphasis>Chapter 4</emphasis>, which contains more advanced
91 concepts that the system administrator may need for implementing
92 certain options. <emphasis>Chapter 5</emphasis>
93 describes the <acronym>BIND</acronym> 9 lightweight
94 resolver. The contents of <emphasis>Chapter 6</emphasis> are
95 organized as in a reference manual to aid in the ongoing
96 maintenance of the software. <emphasis>Chapter 7</emphasis> addresses
97 security considerations, and
98 <emphasis>Chapter 8</emphasis> contains troubleshooting help. The
99 main body of the document is followed by several
100 <emphasis>appendices</emphasis> which contain useful reference
101 information, such as a <emphasis>bibliography</emphasis> and
102 historic information related to <acronym>BIND</acronym>
108 <title>Conventions Used in This Document</title>
111 In this document, we use the following general typographic
117 <colspec colname="1" colnum="1" colwidth="3.000in"/>
118 <colspec colname="2" colnum="2" colwidth="2.625in"/>
123 <emphasis>To describe:</emphasis>
128 <emphasis>We use the style:</emphasis>
135 a pathname, filename, URL, hostname,
136 mailing list name, or new term or concept
141 <filename>Fixed width</filename>
154 <userinput>Fixed Width Bold</userinput>
166 <computeroutput>Fixed Width</computeroutput>
175 The following conventions are used in descriptions of the
176 <acronym>BIND</acronym> configuration file:<informaltable colsep="0" frame="all" rowsep="0">
177 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
178 <colspec colname="1" colnum="1" colsep="0" colwidth="3.000in"/>
179 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
182 <entry colname="1" colsep="1" rowsep="1">
184 <emphasis>To describe:</emphasis>
187 <entry colname="2" rowsep="1">
189 <emphasis>We use the style:</emphasis>
194 <entry colname="1" colsep="1" rowsep="1">
199 <entry colname="2" rowsep="1">
201 <literal>Fixed Width</literal>
206 <entry colname="1" colsep="1" rowsep="1">
211 <entry colname="2" rowsep="1">
213 <varname>Fixed Width</varname>
218 <entry colname="1" colsep="1">
225 <optional>Text is enclosed in square brackets</optional>
235 <title>The Domain Name System (<acronym>DNS</acronym>)</title>
237 The purpose of this document is to explain the installation
238 and upkeep of the <acronym>BIND</acronym> (Berkeley Internet
239 Name Domain) software package, and we
240 begin by reviewing the fundamentals of the Domain Name System
241 (<acronym>DNS</acronym>) as they relate to <acronym>BIND</acronym>.
245 <title>DNS Fundamentals</title>
248 The Domain Name System (DNS) is a hierarchical, distributed
249 database. It stores information for mapping Internet host names to
251 addresses and vice versa, mail routing information, and other data
252 used by Internet applications.
256 Clients look up information in the DNS by calling a
257 <emphasis>resolver</emphasis> library, which sends queries to one or
258 more <emphasis>name servers</emphasis> and interprets the responses.
259 The <acronym>BIND</acronym> 9 software distribution
261 name server, <command>named</command>, and a resolver
262 library, <command>liblwres</command>. The older
263 <command>libbind</command> resolver library is also available
264 from ISC as a separate download.
268 <title>Domains and Domain Names</title>
271 The data stored in the DNS is identified by <emphasis>domain names</emphasis> that are organized as a tree according to
272 organizational or administrative boundaries. Each node of the tree,
273 called a <emphasis>domain</emphasis>, is given a label. The domain
275 node is the concatenation of all the labels on the path from the
276 node to the <emphasis>root</emphasis> node. This is represented
277 in written form as a string of labels listed from right to left and
278 separated by dots. A label need only be unique within its parent
283 For example, a domain name for a host at the
284 company <emphasis>Example, Inc.</emphasis> could be
285 <literal>ourhost.example.com</literal>,
286 where <literal>com</literal> is the
287 top level domain to which
288 <literal>ourhost.example.com</literal> belongs,
289 <literal>example</literal> is
290 a subdomain of <literal>com</literal>, and
291 <literal>ourhost</literal> is the
296 For administrative purposes, the name space is partitioned into
297 areas called <emphasis>zones</emphasis>, each starting at a node and
298 extending down to the leaf nodes or to nodes where other zones
300 The data for each zone is stored in a <emphasis>name server</emphasis>, which answers queries about the zone using the
301 <emphasis>DNS protocol</emphasis>.
305 The data associated with each domain name is stored in the
306 form of <emphasis>resource records</emphasis> (<acronym>RR</acronym>s).
307 Some of the supported resource record types are described in
308 <xref linkend="types_of_resource_records_and_when_to_use_them"/>.
312 For more detailed information about the design of the DNS and
313 the DNS protocol, please refer to the standards documents listed in
314 <xref linkend="rfcs"/>.
321 To properly operate a name server, it is important to understand
322 the difference between a <emphasis>zone</emphasis>
323 and a <emphasis>domain</emphasis>.
327 As stated previously, a zone is a point of delegation in
328 the <acronym>DNS</acronym> tree. A zone consists of
329 those contiguous parts of the domain
330 tree for which a name server has complete information and over which
331 it has authority. It contains all domain names from a certain point
332 downward in the domain tree except those which are delegated to
333 other zones. A delegation point is marked by one or more
334 <emphasis>NS records</emphasis> in the
335 parent zone, which should be matched by equivalent NS records at
336 the root of the delegated zone.
340 For instance, consider the <literal>example.com</literal>
341 domain which includes names
342 such as <literal>host.aaa.example.com</literal> and
343 <literal>host.bbb.example.com</literal> even though
344 the <literal>example.com</literal> zone includes
345 only delegations for the <literal>aaa.example.com</literal> and
346 <literal>bbb.example.com</literal> zones. A zone can
348 exactly to a single domain, but could also include only part of a
349 domain, the rest of which could be delegated to other
350 name servers. Every name in the <acronym>DNS</acronym>
352 <emphasis>domain</emphasis>, even if it is
353 <emphasis>terminal</emphasis>, that is, has no
354 <emphasis>subdomains</emphasis>. Every subdomain is a domain and
355 every domain except the root is also a subdomain. The terminology is
356 not intuitive and we suggest that you read RFCs 1033, 1034 and 1035
358 gain a complete understanding of this difficult and subtle
363 Though <acronym>BIND</acronym> is called a "domain name
365 it deals primarily in terms of zones. The master and slave
366 declarations in the <filename>named.conf</filename> file
368 zones, not domains. When you ask some other site if it is willing to
369 be a slave server for your <emphasis>domain</emphasis>, you are
370 actually asking for slave service for some collection of zones.
375 <title>Authoritative Name Servers</title>
378 Each zone is served by at least
379 one <emphasis>authoritative name server</emphasis>,
380 which contains the complete data for the zone.
381 To make the DNS tolerant of server and network failures,
382 most zones have two or more authoritative servers, on
387 Responses from authoritative servers have the "authoritative
388 answer" (AA) bit set in the response packets. This makes them
389 easy to identify when debugging DNS configurations using tools like
390 <command>dig</command> (<xref linkend="diagnostic_tools"/>).
394 <title>The Primary Master</title>
397 The authoritative server where the master copy of the zone
398 data is maintained is called the
399 <emphasis>primary master</emphasis> server, or simply the
400 <emphasis>primary</emphasis>. Typically it loads the zone
401 contents from some local file edited by humans or perhaps
402 generated mechanically from some other local file which is
403 edited by humans. This file is called the
404 <emphasis>zone file</emphasis> or
405 <emphasis>master file</emphasis>.
409 In some cases, however, the master file may not be edited
410 by humans at all, but may instead be the result of
411 <emphasis>dynamic update</emphasis> operations.
416 <title>Slave Servers</title>
418 The other authoritative servers, the <emphasis>slave</emphasis>
419 servers (also known as <emphasis>secondary</emphasis> servers)
421 the zone contents from another server using a replication process
422 known as a <emphasis>zone transfer</emphasis>. Typically the data
424 transferred directly from the primary master, but it is also
426 to transfer it from another slave. In other words, a slave server
427 may itself act as a master to a subordinate slave server.
432 <title>Stealth Servers</title>
435 Usually all of the zone's authoritative servers are listed in
436 NS records in the parent zone. These NS records constitute
437 a <emphasis>delegation</emphasis> of the zone from the parent.
438 The authoritative servers are also listed in the zone file itself,
439 at the <emphasis>top level</emphasis> or <emphasis>apex</emphasis>
440 of the zone. You can list servers in the zone's top-level NS
441 records that are not in the parent's NS delegation, but you cannot
442 list servers in the parent's delegation that are not present at
443 the zone's top level.
447 A <emphasis>stealth server</emphasis> is a server that is
448 authoritative for a zone but is not listed in that zone's NS
449 records. Stealth servers can be used for keeping a local copy of
451 zone to speed up access to the zone's records or to make sure that
453 zone is available even if all the "official" servers for the zone
459 A configuration where the primary master server itself is a
460 stealth server is often referred to as a "hidden primary"
461 configuration. One use for this configuration is when the primary
463 is behind a firewall and therefore unable to communicate directly
464 with the outside world.
472 <title>Caching Name Servers</title>
475 - Terminology here is inconsistent. Probably ought to
476 - convert to using "recursive name server" everywhere
477 - with just a note about "caching" terminology.
481 The resolver libraries provided by most operating systems are
482 <emphasis>stub resolvers</emphasis>, meaning that they are not
484 performing the full DNS resolution process by themselves by talking
485 directly to the authoritative servers. Instead, they rely on a
487 name server to perform the resolution on their behalf. Such a
489 is called a <emphasis>recursive</emphasis> name server; it performs
490 <emphasis>recursive lookups</emphasis> for local clients.
494 To improve performance, recursive servers cache the results of
495 the lookups they perform. Since the processes of recursion and
496 caching are intimately connected, the terms
497 <emphasis>recursive server</emphasis> and
498 <emphasis>caching server</emphasis> are often used synonymously.
502 The length of time for which a record may be retained in
503 the cache of a caching name server is controlled by the
504 Time To Live (TTL) field associated with each resource record.
508 <title>Forwarding</title>
511 Even a caching name server does not necessarily perform
512 the complete recursive lookup itself. Instead, it can
513 <emphasis>forward</emphasis> some or all of the queries
514 that it cannot satisfy from its cache to another caching name
516 commonly referred to as a <emphasis>forwarder</emphasis>.
520 There may be one or more forwarders,
521 and they are queried in turn until the list is exhausted or an
523 is found. Forwarders are typically used when you do not
524 wish all the servers at a given site to interact directly with the
526 the Internet servers. A typical scenario would involve a number
527 of internal <acronym>DNS</acronym> servers and an
528 Internet firewall. Servers unable
529 to pass packets through the firewall would forward to the server
530 that can do it, and that server would query the Internet <acronym>DNS</acronym> servers
531 on the internal server's behalf.
538 <title>Name Servers in Multiple Roles</title>
541 The <acronym>BIND</acronym> name server can
542 simultaneously act as
543 a master for some zones, a slave for other zones, and as a caching
544 (recursive) server for a set of local clients.
548 However, since the functions of authoritative name service
549 and caching/recursive name service are logically separate, it is
550 often advantageous to run them on separate server machines.
552 A server that only provides authoritative name service
553 (an <emphasis>authoritative-only</emphasis> server) can run with
554 recursion disabled, improving reliability and security.
556 A server that is not authoritative for any zones and only provides
557 recursive service to local
558 clients (a <emphasis>caching-only</emphasis> server)
559 does not need to be reachable from the Internet at large and can
560 be placed inside a firewall.
568 <chapter id="Bv9ARM.ch02">
569 <title><acronym>BIND</acronym> Resource Requirements</title>
572 <title>Hardware requirements</title>
575 <acronym>DNS</acronym> hardware requirements have
576 traditionally been quite modest.
577 For many installations, servers that have been pensioned off from
578 active duty have performed admirably as <acronym>DNS</acronym> servers.
581 The DNSSEC features of <acronym>BIND</acronym> 9
582 may prove to be quite
583 CPU intensive however, so organizations that make heavy use of these
584 features may wish to consider larger systems for these applications.
585 <acronym>BIND</acronym> 9 is fully multithreaded, allowing
587 multiprocessor systems for installations that need it.
591 <title>CPU Requirements</title>
593 CPU requirements for <acronym>BIND</acronym> 9 range from
595 for serving of static zones without caching, to enterprise-class
596 machines if you intend to process many dynamic updates and DNSSEC
597 signed zones, serving many thousands of queries per second.
602 <title>Memory Requirements</title>
604 The memory of the server has to be large enough to fit the
605 cache and zones loaded off disk. The <command>max-cache-size</command>
606 option can be used to limit the amount of memory used by the cache,
607 at the expense of reducing cache hit rates and causing more <acronym>DNS</acronym>
609 Additionally, if additional section caching
610 (<xref linkend="acache"/>) is enabled,
611 the <command>max-acache-size</command> option can be used to
613 of memory used by the mechanism.
614 It is still good practice to have enough memory to load
615 all zone and cache data into memory — unfortunately, the best
617 to determine this for a given installation is to watch the name server
618 in operation. After a few weeks the server process should reach
619 a relatively stable size where entries are expiring from the cache as
620 fast as they are being inserted.
623 - Add something here about leaving overhead for attacks?
624 - How much overhead? Percentage?
629 <title>Name Server Intensive Environment Issues</title>
631 For name server intensive environments, there are two alternative
632 configurations that may be used. The first is where clients and
633 any second-level internal name servers query a main name server, which
634 has enough memory to build a large cache. This approach minimizes
635 the bandwidth used by external name lookups. The second alternative
636 is to set up second-level internal name servers to make queries
638 In this configuration, none of the individual machines needs to
639 have as much memory or CPU power as in the first alternative, but
640 this has the disadvantage of making many more external queries,
641 as none of the name servers share their cached data.
646 <title>Supported Operating Systems</title>
648 ISC <acronym>BIND</acronym> 9 compiles and runs on a large
650 of Unix-like operating systems and on
651 Microsoft Windows Server 2003 and 2008, and Windows XP and Vista.
653 list of supported systems, see the README file in the top level
655 of the BIND 9 source distribution.
660 <chapter id="Bv9ARM.ch03">
661 <title>Name Server Configuration</title>
663 In this chapter we provide some suggested configurations along
664 with guidelines for their use. We suggest reasonable values for
665 certain option settings.
668 <sect1 id="sample_configuration">
669 <title>Sample Configurations</title>
671 <title>A Caching-only Name Server</title>
673 The following sample configuration is appropriate for a caching-only
674 name server for use by clients internal to a corporation. All
676 from outside clients are refused using the <command>allow-query</command>
677 option. Alternatively, the same effect could be achieved using
683 // Two corporate subnets we wish to allow queries from.
684 acl corpnets { 192.168.4.0/24; 192.168.7.0/24; };
687 directory "/etc/namedb";
689 allow-query { corpnets; };
691 // Provide a reverse mapping for the loopback
693 zone "0.0.127.in-addr.arpa" {
695 file "localhost.rev";
703 <title>An Authoritative-only Name Server</title>
705 This sample configuration is for an authoritative-only server
706 that is the master server for "<filename>example.com</filename>"
707 and a slave for the subdomain "<filename>eng.example.com</filename>".
713 directory "/etc/namedb";
714 // Do not allow access to cache
715 allow-query-cache { none; };
716 // This is the default
717 allow-query { any; };
718 // Do not provide recursive service
722 // Provide a reverse mapping for the loopback
724 zone "0.0.127.in-addr.arpa" {
726 file "localhost.rev";
729 // We are the master server for example.com
732 file "example.com.db";
733 // IP addresses of slave servers allowed to
734 // transfer example.com
740 // We are a slave server for eng.example.com
741 zone "eng.example.com" {
743 file "eng.example.com.bk";
744 // IP address of eng.example.com master server
745 masters { 192.168.4.12; };
753 <title>Load Balancing</title>
755 - Add explanation of why load balancing is fragile at best
756 - and completely pointless in the general case.
760 A primitive form of load balancing can be achieved in
761 the <acronym>DNS</acronym> by using multiple records
762 (such as multiple A records) for one name.
766 For example, if you have three WWW servers with network addresses
767 of 10.0.0.1, 10.0.0.2 and 10.0.0.3, a set of records such as the
768 following means that clients will connect to each machine one third
772 <informaltable colsep="0" rowsep="0">
773 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="2Level-table">
774 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
775 <colspec colname="2" colnum="2" colsep="0" colwidth="0.500in"/>
776 <colspec colname="3" colnum="3" colsep="0" colwidth="0.750in"/>
777 <colspec colname="4" colnum="4" colsep="0" colwidth="0.750in"/>
778 <colspec colname="5" colnum="5" colsep="0" colwidth="2.028in"/>
803 Resource Record (RR) Data
810 <literal>www</literal>
815 <literal>600</literal>
820 <literal>IN</literal>
830 <literal>10.0.0.1</literal>
840 <literal>600</literal>
845 <literal>IN</literal>
855 <literal>10.0.0.2</literal>
865 <literal>600</literal>
870 <literal>IN</literal>
880 <literal>10.0.0.3</literal>
888 When a resolver queries for these records, <acronym>BIND</acronym> will rotate
889 them and respond to the query with the records in a different
890 order. In the example above, clients will randomly receive
891 records in the order 1, 2, 3; 2, 3, 1; and 3, 1, 2. Most clients
892 will use the first record returned and discard the rest.
895 For more detail on ordering responses, check the
896 <command>rrset-order</command> sub-statement in the
897 <command>options</command> statement, see
898 <xref endterm="rrset_ordering_title" linkend="rrset_ordering"/>.
904 <title>Name Server Operations</title>
907 <title>Tools for Use With the Name Server Daemon</title>
909 This section describes several indispensable diagnostic,
910 administrative and monitoring tools available to the system
911 administrator for controlling and debugging the name server
914 <sect3 id="diagnostic_tools">
915 <title>Diagnostic Tools</title>
917 The <command>dig</command>, <command>host</command>, and
918 <command>nslookup</command> programs are all command
920 for manually querying name servers. They differ in style and
926 <term id="dig"><command>dig</command></term>
929 The domain information groper (<command>dig</command>)
930 is the most versatile and complete of these lookup tools.
931 It has two modes: simple interactive
932 mode for a single query, and batch mode which executes a
934 each in a list of several query lines. All query options are
936 from the command line.
938 <cmdsynopsis label="Usage">
939 <command>dig</command>
940 <arg>@<replaceable>server</replaceable></arg>
941 <arg choice="plain"><replaceable>domain</replaceable></arg>
942 <arg><replaceable>query-type</replaceable></arg>
943 <arg><replaceable>query-class</replaceable></arg>
944 <arg>+<replaceable>query-option</replaceable></arg>
945 <arg>-<replaceable>dig-option</replaceable></arg>
946 <arg>%<replaceable>comment</replaceable></arg>
949 The usual simple use of <command>dig</command> will take the form
952 <command>dig @server domain query-type query-class</command>
955 For more information and a list of available commands and
956 options, see the <command>dig</command> man
963 <term><command>host</command></term>
966 The <command>host</command> utility emphasizes
968 and ease of use. By default, it converts
969 between host names and Internet addresses, but its
971 can be extended with the use of options.
973 <cmdsynopsis label="Usage">
974 <command>host</command>
975 <arg>-aCdlnrsTwv</arg>
976 <arg>-c <replaceable>class</replaceable></arg>
977 <arg>-N <replaceable>ndots</replaceable></arg>
978 <arg>-t <replaceable>type</replaceable></arg>
979 <arg>-W <replaceable>timeout</replaceable></arg>
980 <arg>-R <replaceable>retries</replaceable></arg>
981 <arg>-m <replaceable>flag</replaceable></arg>
984 <arg choice="plain"><replaceable>hostname</replaceable></arg>
985 <arg><replaceable>server</replaceable></arg>
988 For more information and a list of available commands and
989 options, see the <command>host</command> man
996 <term><command>nslookup</command></term>
998 <para><command>nslookup</command>
999 has two modes: interactive and
1000 non-interactive. Interactive mode allows the user to
1001 query name servers for information about various
1002 hosts and domains or to print a list of hosts in a
1003 domain. Non-interactive mode is used to print just
1004 the name and requested information for a host or
1007 <cmdsynopsis label="Usage">
1008 <command>nslookup</command>
1009 <arg rep="repeat">-option</arg>
1011 <arg><replaceable>host-to-find</replaceable></arg>
1012 <arg>- <arg>server</arg></arg>
1016 Interactive mode is entered when no arguments are given (the
1017 default name server will be used) or when the first argument
1019 hyphen (`-') and the second argument is the host name or
1024 Non-interactive mode is used when the name or Internet
1026 of the host to be looked up is given as the first argument.
1028 optional second argument specifies the host name or address
1032 Due to its arcane user interface and frequently inconsistent
1033 behavior, we do not recommend the use of <command>nslookup</command>.
1034 Use <command>dig</command> instead.
1042 <sect3 id="admin_tools">
1043 <title>Administrative Tools</title>
1045 Administrative tools play an integral part in the management
1049 <varlistentry id="named-checkconf" xreflabel="Named Configuration Checking application">
1051 <term><command>named-checkconf</command></term>
1054 The <command>named-checkconf</command> program
1055 checks the syntax of a <filename>named.conf</filename> file.
1057 <cmdsynopsis label="Usage">
1058 <command>named-checkconf</command>
1060 <arg>-t <replaceable>directory</replaceable></arg>
1061 <arg><replaceable>filename</replaceable></arg>
1065 <varlistentry id="named-checkzone" xreflabel="Zone Checking application">
1067 <term><command>named-checkzone</command></term>
1070 The <command>named-checkzone</command> program
1071 checks a master file for
1072 syntax and consistency.
1074 <cmdsynopsis label="Usage">
1075 <command>named-checkzone</command>
1077 <arg>-c <replaceable>class</replaceable></arg>
1078 <arg>-o <replaceable>output</replaceable></arg>
1079 <arg>-t <replaceable>directory</replaceable></arg>
1080 <arg>-w <replaceable>directory</replaceable></arg>
1081 <arg>-k <replaceable>(ignore|warn|fail)</replaceable></arg>
1082 <arg>-n <replaceable>(ignore|warn|fail)</replaceable></arg>
1083 <arg>-W <replaceable>(ignore|warn)</replaceable></arg>
1084 <arg choice="plain"><replaceable>zone</replaceable></arg>
1085 <arg><replaceable>filename</replaceable></arg>
1089 <varlistentry id="named-compilezone" xreflabel="Zone Compilation application">
1090 <term><command>named-compilezone</command></term>
1093 Similar to <command>named-checkzone,</command> but
1094 it always dumps the zone content to a specified file
1095 (typically in a different format).
1099 <varlistentry id="rndc" xreflabel="Remote Name Daemon Control application">
1101 <term><command>rndc</command></term>
1104 The remote name daemon control
1105 (<command>rndc</command>) program allows the
1107 administrator to control the operation of a name server.
1108 Since <acronym>BIND</acronym> 9.2, <command>rndc</command>
1109 supports all the commands of the BIND 8 <command>ndc</command>
1110 utility except <command>ndc start</command> and
1111 <command>ndc restart</command>, which were also
1112 not supported in <command>ndc</command>'s
1114 If you run <command>rndc</command> without any
1116 it will display a usage message as follows:
1118 <cmdsynopsis label="Usage">
1119 <command>rndc</command>
1120 <arg>-c <replaceable>config</replaceable></arg>
1121 <arg>-s <replaceable>server</replaceable></arg>
1122 <arg>-p <replaceable>port</replaceable></arg>
1123 <arg>-y <replaceable>key</replaceable></arg>
1124 <arg choice="plain"><replaceable>command</replaceable></arg>
1125 <arg rep="repeat"><replaceable>command</replaceable></arg>
1128 <para>See <xref linkend="man.rndc"/> for details of
1129 the available <command>rndc</command> commands.
1133 <command>rndc</command> requires a configuration file,
1135 communication with the server is authenticated with
1136 digital signatures that rely on a shared secret, and
1137 there is no way to provide that secret other than with a
1138 configuration file. The default location for the
1139 <command>rndc</command> configuration file is
1140 <filename>/etc/rndc.conf</filename>, but an
1142 location can be specified with the <option>-c</option>
1143 option. If the configuration file is not found,
1144 <command>rndc</command> will also look in
1145 <filename>/etc/rndc.key</filename> (or whatever
1146 <varname>sysconfdir</varname> was defined when
1147 the <acronym>BIND</acronym> build was
1149 The <filename>rndc.key</filename> file is
1151 running <command>rndc-confgen -a</command> as
1153 <xref linkend="controls_statement_definition_and_usage"/>.
1157 The format of the configuration file is similar to
1158 that of <filename>named.conf</filename>, but
1160 only four statements, the <command>options</command>,
1161 <command>key</command>, <command>server</command> and
1162 <command>include</command>
1163 statements. These statements are what associate the
1164 secret keys to the servers with which they are meant to
1165 be shared. The order of statements is not
1170 The <command>options</command> statement has
1172 <command>default-server</command>, <command>default-key</command>,
1173 and <command>default-port</command>.
1174 <command>default-server</command> takes a
1175 host name or address argument and represents the server
1177 be contacted if no <option>-s</option>
1178 option is provided on the command line.
1179 <command>default-key</command> takes
1180 the name of a key as its argument, as defined by a <command>key</command> statement.
1181 <command>default-port</command> specifies the
1183 <command>rndc</command> should connect if no
1184 port is given on the command line or in a
1185 <command>server</command> statement.
1189 The <command>key</command> statement defines a
1191 by <command>rndc</command> when authenticating
1193 <command>named</command>. Its syntax is
1195 <command>key</command> statement in <filename>named.conf</filename>.
1196 The keyword <userinput>key</userinput> is
1197 followed by a key name, which must be a valid
1198 domain name, though it need not actually be hierarchical;
1200 a string like "<userinput>rndc_key</userinput>" is a valid
1202 The <command>key</command> statement has two
1204 <command>algorithm</command> and <command>secret</command>.
1205 While the configuration parser will accept any string as the
1207 to algorithm, currently only the string "<userinput>hmac-md5</userinput>"
1208 has any meaning. The secret is a base-64 encoded string
1209 as specified in RFC 3548.
1213 The <command>server</command> statement
1215 defined using the <command>key</command>
1216 statement with a server.
1217 The keyword <userinput>server</userinput> is followed by a
1218 host name or address. The <command>server</command> statement
1219 has two clauses: <command>key</command> and <command>port</command>.
1220 The <command>key</command> clause specifies the
1222 to be used when communicating with this server, and the
1223 <command>port</command> clause can be used to
1224 specify the port <command>rndc</command> should
1230 A sample minimal configuration file is as follows:
1235 algorithm "hmac-md5";
1237 "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
1240 default-server 127.0.0.1;
1241 default-key rndc_key;
1246 This file, if installed as <filename>/etc/rndc.conf</filename>,
1247 would allow the command:
1251 <prompt>$ </prompt><userinput>rndc reload</userinput>
1255 to connect to 127.0.0.1 port 953 and cause the name server
1256 to reload, if a name server on the local machine were
1258 following controls statements:
1264 allow { localhost; } keys { rndc_key; };
1269 and it had an identical key statement for
1270 <literal>rndc_key</literal>.
1274 Running the <command>rndc-confgen</command>
1276 conveniently create a <filename>rndc.conf</filename>
1277 file for you, and also display the
1278 corresponding <command>controls</command>
1279 statement that you need to
1280 add to <filename>named.conf</filename>.
1282 you can run <command>rndc-confgen -a</command>
1284 a <filename>rndc.key</filename> file and not
1286 <filename>named.conf</filename> at all.
1297 <title>Signals</title>
1299 Certain UNIX signals cause the name server to take specific
1300 actions, as described in the following table. These signals can
1301 be sent using the <command>kill</command> command.
1303 <informaltable frame="all">
1305 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
1306 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
1310 <para><command>SIGHUP</command></para>
1314 Causes the server to read <filename>named.conf</filename> and
1315 reload the database.
1321 <para><command>SIGTERM</command></para>
1325 Causes the server to clean up and exit.
1331 <para><command>SIGINT</command></para>
1335 Causes the server to clean up and exit.
1346 <chapter id="Bv9ARM.ch04">
1347 <title>Advanced DNS Features</title>
1351 <title>Notify</title>
1353 <acronym>DNS</acronym> NOTIFY is a mechanism that allows master
1354 servers to notify their slave servers of changes to a zone's data. In
1355 response to a <command>NOTIFY</command> from a master server, the
1356 slave will check to see that its version of the zone is the
1357 current version and, if not, initiate a zone transfer.
1361 For more information about <acronym>DNS</acronym>
1362 <command>NOTIFY</command>, see the description of the
1363 <command>notify</command> option in <xref linkend="boolean_options"/> and
1364 the description of the zone option <command>also-notify</command> in
1365 <xref linkend="zone_transfers"/>. The <command>NOTIFY</command>
1366 protocol is specified in RFC 1996.
1370 As a slave zone can also be a master to other slaves, <command>named</command>,
1371 by default, sends <command>NOTIFY</command> messages for every zone
1372 it loads. Specifying <command>notify master-only;</command> will
1373 cause <command>named</command> to only send <command>NOTIFY</command> for master
1374 zones that it loads.
1379 <sect1 id="dynamic_update">
1380 <title>Dynamic Update</title>
1383 Dynamic Update is a method for adding, replacing or deleting
1384 records in a master server by sending it a special form of DNS
1385 messages. The format and meaning of these messages is specified
1390 Dynamic update is enabled by including an
1391 <command>allow-update</command> or an <command>update-policy</command>
1392 clause in the <command>zone</command> statement.
1396 If the zone's <command>update-policy</command> is set to
1397 <userinput>local</userinput>, updates to the zone
1398 will be permitted for the key <varname>local-ddns</varname>,
1399 which will be generated by <command>named</command> at startup.
1400 See <xref linkend="dynamic_update_policies"/> for more details.
1404 Dynamic updates using Kerberos signed requests can be made
1405 using the TKEY/GSS protocol by setting either the
1406 <command>tkey-gssapi-keytab</command> option, or alternatively
1407 by setting both the <command>tkey-gssapi-credential</command>
1408 and <command>tkey-domain</command> options. Once enabled,
1409 Kerberos signed requests will be matched against the update
1410 policies for the zone, using the Kerberos principal as the
1411 signer for the request.
1415 Updating of secure zones (zones using DNSSEC) follows RFC
1416 3007: RRSIG, NSEC and NSEC3 records affected by updates are
1417 automatically regenerated by the server using an online
1418 zone key. Update authorization is based on transaction
1419 signatures and an explicit server policy.
1422 <sect2 id="journal">
1423 <title>The journal file</title>
1426 All changes made to a zone using dynamic update are stored
1427 in the zone's journal file. This file is automatically created
1428 by the server when the first dynamic update takes place.
1429 The name of the journal file is formed by appending the extension
1430 <filename>.jnl</filename> to the name of the
1432 file unless specifically overridden. The journal file is in a
1433 binary format and should not be edited manually.
1437 The server will also occasionally write ("dump")
1438 the complete contents of the updated zone to its zone file.
1439 This is not done immediately after
1440 each dynamic update, because that would be too slow when a large
1441 zone is updated frequently. Instead, the dump is delayed by
1442 up to 15 minutes, allowing additional updates to take place.
1443 During the dump process, transient files will be created
1444 with the extensions <filename>.jnw</filename> and
1445 <filename>.jbk</filename>; under ordinary circumstances, these
1446 will be removed when the dump is complete, and can be safely
1451 When a server is restarted after a shutdown or crash, it will replay
1452 the journal file to incorporate into the zone any updates that
1454 place after the last zone dump.
1458 Changes that result from incoming incremental zone transfers are
1460 journalled in a similar way.
1464 The zone files of dynamic zones cannot normally be edited by
1465 hand because they are not guaranteed to contain the most recent
1466 dynamic changes — those are only in the journal file.
1467 The only way to ensure that the zone file of a dynamic zone
1468 is up to date is to run <command>rndc stop</command>.
1472 If you have to make changes to a dynamic zone
1473 manually, the following procedure will work: Disable dynamic updates
1475 <command>rndc freeze <replaceable>zone</replaceable></command>.
1476 This will also remove the zone's <filename>.jnl</filename> file
1477 and update the master file. Edit the zone file. Run
1478 <command>rndc thaw <replaceable>zone</replaceable></command>
1479 to reload the changed zone and re-enable dynamic updates.
1486 <sect1 id="incremental_zone_transfers">
1487 <title>Incremental Zone Transfers (IXFR)</title>
1490 The incremental zone transfer (IXFR) protocol is a way for
1491 slave servers to transfer only changed data, instead of having to
1492 transfer the entire zone. The IXFR protocol is specified in RFC
1493 1995. See <xref linkend="proposed_standards"/>.
1497 When acting as a master, <acronym>BIND</acronym> 9
1498 supports IXFR for those zones
1499 where the necessary change history information is available. These
1500 include master zones maintained by dynamic update and slave zones
1501 whose data was obtained by IXFR. For manually maintained master
1502 zones, and for slave zones obtained by performing a full zone
1503 transfer (AXFR), IXFR is supported only if the option
1504 <command>ixfr-from-differences</command> is set
1505 to <userinput>yes</userinput>.
1509 When acting as a slave, <acronym>BIND</acronym> 9 will
1510 attempt to use IXFR unless
1511 it is explicitly disabled. For more information about disabling
1512 IXFR, see the description of the <command>request-ixfr</command> clause
1513 of the <command>server</command> statement.
1518 <title>Split DNS</title>
1520 Setting up different views, or visibility, of the DNS space to
1521 internal and external resolvers is usually referred to as a
1522 <emphasis>Split DNS</emphasis> setup. There are several
1523 reasons an organization would want to set up its DNS this way.
1526 One common reason for setting up a DNS system this way is
1527 to hide "internal" DNS information from "external" clients on the
1528 Internet. There is some debate as to whether or not this is actually
1530 Internal DNS information leaks out in many ways (via email headers,
1531 for example) and most savvy "attackers" can find the information
1532 they need using other means.
1533 However, since listing addresses of internal servers that
1534 external clients cannot possibly reach can result in
1535 connection delays and other annoyances, an organization may
1536 choose to use a Split DNS to present a consistent view of itself
1537 to the outside world.
1540 Another common reason for setting up a Split DNS system is
1541 to allow internal networks that are behind filters or in RFC 1918
1542 space (reserved IP space, as documented in RFC 1918) to resolve DNS
1543 on the Internet. Split DNS can also be used to allow mail from outside
1544 back in to the internal network.
1547 <title>Example split DNS setup</title>
1549 Let's say a company named <emphasis>Example, Inc.</emphasis>
1550 (<literal>example.com</literal>)
1551 has several corporate sites that have an internal network with
1553 Internet Protocol (IP) space and an external demilitarized zone (DMZ),
1554 or "outside" section of a network, that is available to the public.
1557 <emphasis>Example, Inc.</emphasis> wants its internal clients
1558 to be able to resolve external hostnames and to exchange mail with
1559 people on the outside. The company also wants its internal resolvers
1560 to have access to certain internal-only zones that are not available
1561 at all outside of the internal network.
1564 In order to accomplish this, the company will set up two sets
1565 of name servers. One set will be on the inside network (in the
1567 IP space) and the other set will be on bastion hosts, which are
1569 hosts that can talk to both sides of its network, in the DMZ.
1572 The internal servers will be configured to forward all queries,
1573 except queries for <filename>site1.internal</filename>, <filename>site2.internal</filename>, <filename>site1.example.com</filename>,
1574 and <filename>site2.example.com</filename>, to the servers
1576 DMZ. These internal servers will have complete sets of information
1577 for <filename>site1.example.com</filename>, <filename>site2.example.com</filename>, <filename>site1.internal</filename>,
1578 and <filename>site2.internal</filename>.
1581 To protect the <filename>site1.internal</filename> and <filename>site2.internal</filename> domains,
1582 the internal name servers must be configured to disallow all queries
1583 to these domains from any external hosts, including the bastion
1587 The external servers, which are on the bastion hosts, will
1588 be configured to serve the "public" version of the <filename>site1</filename> and <filename>site2.example.com</filename> zones.
1589 This could include things such as the host records for public servers
1590 (<filename>www.example.com</filename> and <filename>ftp.example.com</filename>),
1591 and mail exchange (MX) records (<filename>a.mx.example.com</filename> and <filename>b.mx.example.com</filename>).
1594 In addition, the public <filename>site1</filename> and <filename>site2.example.com</filename> zones
1595 should have special MX records that contain wildcard (`*') records
1596 pointing to the bastion hosts. This is needed because external mail
1597 servers do not have any other way of looking up how to deliver mail
1598 to those internal hosts. With the wildcard records, the mail will
1599 be delivered to the bastion host, which can then forward it on to
1603 Here's an example of a wildcard MX record:
1605 <programlisting>* IN MX 10 external1.example.com.</programlisting>
1607 Now that they accept mail on behalf of anything in the internal
1608 network, the bastion hosts will need to know how to deliver mail
1609 to internal hosts. In order for this to work properly, the resolvers
1611 the bastion hosts will need to be configured to point to the internal
1612 name servers for DNS resolution.
1615 Queries for internal hostnames will be answered by the internal
1616 servers, and queries for external hostnames will be forwarded back
1617 out to the DNS servers on the bastion hosts.
1620 In order for all this to work properly, internal clients will
1621 need to be configured to query <emphasis>only</emphasis> the internal
1622 name servers for DNS queries. This could also be enforced via
1624 filtering on the network.
1627 If everything has been set properly, <emphasis>Example, Inc.</emphasis>'s
1628 internal clients will now be able to:
1633 Look up any hostnames in the <literal>site1</literal>
1635 <literal>site2.example.com</literal> zones.
1640 Look up any hostnames in the <literal>site1.internal</literal> and
1641 <literal>site2.internal</literal> domains.
1645 <simpara>Look up any hostnames on the Internet.</simpara>
1648 <simpara>Exchange mail with both internal and external people.</simpara>
1652 Hosts on the Internet will be able to:
1657 Look up any hostnames in the <literal>site1</literal>
1659 <literal>site2.example.com</literal> zones.
1664 Exchange mail with anyone in the <literal>site1</literal> and
1665 <literal>site2.example.com</literal> zones.
1671 Here is an example configuration for the setup we just
1672 described above. Note that this is only configuration information;
1673 for information on how to configure your zone files, see <xref linkend="sample_configuration"/>.
1677 Internal DNS server config:
1682 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
1684 acl externals { <varname>bastion-ips-go-here</varname>; };
1690 // forward to external servers
1692 <varname>bastion-ips-go-here</varname>;
1694 // sample allow-transfer (no one)
1695 allow-transfer { none; };
1696 // restrict query access
1697 allow-query { internals; externals; };
1698 // restrict recursion
1699 allow-recursion { internals; };
1704 // sample master zone
1705 zone "site1.example.com" {
1707 file "m/site1.example.com";
1708 // do normal iterative resolution (do not forward)
1710 allow-query { internals; externals; };
1711 allow-transfer { internals; };
1714 // sample slave zone
1715 zone "site2.example.com" {
1717 file "s/site2.example.com";
1718 masters { 172.16.72.3; };
1720 allow-query { internals; externals; };
1721 allow-transfer { internals; };
1724 zone "site1.internal" {
1726 file "m/site1.internal";
1728 allow-query { internals; };
1729 allow-transfer { internals; }
1732 zone "site2.internal" {
1734 file "s/site2.internal";
1735 masters { 172.16.72.3; };
1737 allow-query { internals };
1738 allow-transfer { internals; }
1743 External (bastion host) DNS server config:
1747 acl internals { 172.16.72.0/24; 192.168.1.0/24; };
1749 acl externals { bastion-ips-go-here; };
1754 // sample allow-transfer (no one)
1755 allow-transfer { none; };
1756 // default query access
1757 allow-query { any; };
1758 // restrict cache access
1759 allow-query-cache { internals; externals; };
1760 // restrict recursion
1761 allow-recursion { internals; externals; };
1766 // sample slave zone
1767 zone "site1.example.com" {
1769 file "m/site1.foo.com";
1770 allow-transfer { internals; externals; };
1773 zone "site2.example.com" {
1775 file "s/site2.foo.com";
1776 masters { another_bastion_host_maybe; };
1777 allow-transfer { internals; externals; }
1782 In the <filename>resolv.conf</filename> (or equivalent) on
1783 the bastion host(s):
1788 nameserver 172.16.72.2
1789 nameserver 172.16.72.3
1790 nameserver 172.16.72.4
1798 This is a short guide to setting up Transaction SIGnatures
1799 (TSIG) based transaction security in <acronym>BIND</acronym>. It describes changes
1800 to the configuration file as well as what changes are required for
1801 different features, including the process of creating transaction
1802 keys and using transaction signatures with <acronym>BIND</acronym>.
1805 <acronym>BIND</acronym> primarily supports TSIG for server
1806 to server communication.
1807 This includes zone transfer, notify, and recursive query messages.
1808 Resolvers based on newer versions of <acronym>BIND</acronym> 8 have limited support
1813 TSIG can also be useful for dynamic update. A primary
1814 server for a dynamic zone should control access to the dynamic
1815 update service, but IP-based access control is insufficient.
1816 The cryptographic access control provided by TSIG
1817 is far superior. The <command>nsupdate</command>
1818 program supports TSIG via the <option>-k</option> and
1819 <option>-y</option> command line options or inline by use
1820 of the <command>key</command>.
1824 <title>Generate Shared Keys for Each Pair of Hosts</title>
1826 A shared secret is generated to be shared between <emphasis>host1</emphasis> and <emphasis>host2</emphasis>.
1827 An arbitrary key name is chosen: "host1-host2.". The key name must
1828 be the same on both hosts.
1831 <title>Automatic Generation</title>
1833 The following command will generate a 128-bit (16 byte) HMAC-SHA256
1834 key as described above. Longer keys are better, but shorter keys
1835 are easier to read. Note that the maximum key length is the digest
1836 length, here 256 bits.
1839 <userinput>dnssec-keygen -a hmac-sha256 -b 128 -n HOST host1-host2.</userinput>
1842 The key is in the file <filename>Khost1-host2.+163+00000.private</filename>.
1843 Nothing directly uses this file, but the base-64 encoded string
1844 following "<literal>Key:</literal>"
1845 can be extracted from the file and used as a shared secret:
1847 <programlisting>Key: La/E5CjG9O+os1jq0a2jdA==</programlisting>
1849 The string "<literal>La/E5CjG9O+os1jq0a2jdA==</literal>" can
1850 be used as the shared secret.
1854 <title>Manual Generation</title>
1856 The shared secret is simply a random sequence of bits, encoded
1857 in base-64. Most ASCII strings are valid base-64 strings (assuming
1858 the length is a multiple of 4 and only valid characters are used),
1859 so the shared secret can be manually generated.
1862 Also, a known string can be run through <command>mmencode</command> or
1863 a similar program to generate base-64 encoded data.
1868 <title>Copying the Shared Secret to Both Machines</title>
1870 This is beyond the scope of DNS. A secure transport mechanism
1871 should be used. This could be secure FTP, ssh, telephone, etc.
1875 <title>Informing the Servers of the Key's Existence</title>
1877 Imagine <emphasis>host1</emphasis> and <emphasis>host 2</emphasis>
1879 both servers. The following is added to each server's <filename>named.conf</filename> file:
1884 algorithm hmac-sha256;
1885 secret "La/E5CjG9O+os1jq0a2jdA==";
1890 The secret is the one generated above. Since this is a secret, it
1891 is recommended that either <filename>named.conf</filename> be
1892 non-world readable, or the key directive be added to a non-world
1893 readable file that is included by <filename>named.conf</filename>.
1896 At this point, the key is recognized. This means that if the
1897 server receives a message signed by this key, it can verify the
1898 signature. If the signature is successfully verified, the
1899 response is signed by the same key.
1904 <title>Instructing the Server to Use the Key</title>
1906 Since keys are shared between two hosts only, the server must
1907 be told when keys are to be used. The following is added to the <filename>named.conf</filename> file
1908 for <emphasis>host1</emphasis>, if the IP address of <emphasis>host2</emphasis> is
1914 keys { host1-host2. ;};
1919 Multiple keys may be present, but only the first is used.
1920 This directive does not contain any secrets, so it may be in a
1925 If <emphasis>host1</emphasis> sends a message that is a request
1926 to that address, the message will be signed with the specified key. <emphasis>host1</emphasis> will
1927 expect any responses to signed messages to be signed with the same
1931 A similar statement must be present in <emphasis>host2</emphasis>'s
1932 configuration file (with <emphasis>host1</emphasis>'s address) for <emphasis>host2</emphasis> to
1933 sign request messages to <emphasis>host1</emphasis>.
1937 <title>TSIG Key Based Access Control</title>
1939 <acronym>BIND</acronym> allows IP addresses and ranges
1940 to be specified in ACL
1942 <command>allow-{ query | transfer | update }</command>
1944 This has been extended to allow TSIG keys also. The above key would
1945 be denoted <command>key host1-host2.</command>
1948 An example of an <command>allow-update</command> directive would be:
1952 allow-update { key host1-host2. ;};
1956 This allows dynamic updates to succeed only if the request
1957 was signed by a key named "<command>host1-host2.</command>".
1961 See <xref linkend="dynamic_update_policies"/> for a discussion of
1962 the more flexible <command>update-policy</command> statement.
1967 <title>Errors</title>
1970 The processing of TSIG signed messages can result in
1971 several errors. If a signed message is sent to a non-TSIG aware
1972 server, a FORMERR (format error) will be returned, since the server will not
1973 understand the record. This is a result of misconfiguration,
1974 since the server must be explicitly configured to send a TSIG
1975 signed message to a specific server.
1979 If a TSIG aware server receives a message signed by an
1980 unknown key, the response will be unsigned with the TSIG
1981 extended error code set to BADKEY. If a TSIG aware server
1982 receives a message with a signature that does not validate, the
1983 response will be unsigned with the TSIG extended error code set
1984 to BADSIG. If a TSIG aware server receives a message with a time
1985 outside of the allowed range, the response will be signed with
1986 the TSIG extended error code set to BADTIME, and the time values
1987 will be adjusted so that the response can be successfully
1988 verified. In any of these cases, the message's rcode (response code) is set to
1989 NOTAUTH (not authenticated).
1997 <para><command>TKEY</command>
1998 is a mechanism for automatically generating a shared secret
1999 between two hosts. There are several "modes" of
2000 <command>TKEY</command> that specify how the key is generated
2001 or assigned. <acronym>BIND</acronym> 9 implements only one of
2002 these modes, the Diffie-Hellman key exchange. Both hosts are
2003 required to have a Diffie-Hellman KEY record (although this
2004 record is not required to be present in a zone). The
2005 <command>TKEY</command> process must use signed messages,
2006 signed either by TSIG or SIG(0). The result of
2007 <command>TKEY</command> is a shared secret that can be used to
2008 sign messages with TSIG. <command>TKEY</command> can also be
2009 used to delete shared secrets that it had previously
2014 The <command>TKEY</command> process is initiated by a
2016 or server by sending a signed <command>TKEY</command>
2018 (including any appropriate KEYs) to a TKEY-aware server. The
2019 server response, if it indicates success, will contain a
2020 <command>TKEY</command> record and any appropriate keys.
2022 this exchange, both participants have enough information to
2023 determine the shared secret; the exact process depends on the
2024 <command>TKEY</command> mode. When using the
2026 <command>TKEY</command> mode, Diffie-Hellman keys are
2028 and the shared secret is derived by both participants.
2033 <title>SIG(0)</title>
2036 <acronym>BIND</acronym> 9 partially supports DNSSEC SIG(0)
2037 transaction signatures as specified in RFC 2535 and RFC 2931.
2039 uses public/private keys to authenticate messages. Access control
2040 is performed in the same manner as TSIG keys; privileges can be
2041 granted or denied based on the key name.
2045 When a SIG(0) signed message is received, it will only be
2046 verified if the key is known and trusted by the server; the server
2047 will not attempt to locate and/or validate the key.
2051 SIG(0) signing of multiple-message TCP streams is not
2056 The only tool shipped with <acronym>BIND</acronym> 9 that
2057 generates SIG(0) signed messages is <command>nsupdate</command>.
2062 <title>DNSSEC</title>
2065 Cryptographic authentication of DNS information is possible
2066 through the DNS Security (<emphasis>DNSSEC-bis</emphasis>) extensions,
2067 defined in RFC 4033, RFC 4034, and RFC 4035.
2068 This section describes the creation and use of DNSSEC signed zones.
2072 In order to set up a DNSSEC secure zone, there are a series
2073 of steps which must be followed. <acronym>BIND</acronym>
2076 that are used in this process, which are explained in more detail
2077 below. In all cases, the <option>-h</option> option prints a
2078 full list of parameters. Note that the DNSSEC tools require the
2079 keyset files to be in the working directory or the
2080 directory specified by the <option>-d</option> option, and
2081 that the tools shipped with BIND 9.2.x and earlier are not compatible
2082 with the current ones.
2086 There must also be communication with the administrators of
2087 the parent and/or child zone to transmit keys. A zone's security
2088 status must be indicated by the parent zone for a DNSSEC capable
2089 resolver to trust its data. This is done through the presence
2090 or absence of a <literal>DS</literal> record at the
2096 For other servers to trust data in this zone, they must
2097 either be statically configured with this zone's zone key or the
2098 zone key of another zone above this one in the DNS tree.
2102 <title>Generating Keys</title>
2105 The <command>dnssec-keygen</command> program is used to
2110 A secure zone must contain one or more zone keys. The
2111 zone keys will sign all other records in the zone, as well as
2112 the zone keys of any secure delegated zones. Zone keys must
2113 have the same name as the zone, a name type of
2114 <command>ZONE</command>, and must be usable for
2116 It is recommended that zone keys use a cryptographic algorithm
2117 designated as "mandatory to implement" by the IETF; currently
2118 the only one is RSASHA1.
2122 The following command will generate a 768-bit RSASHA1 key for
2123 the <filename>child.example</filename> zone:
2127 <userinput>dnssec-keygen -a RSASHA1 -b 768 -n ZONE child.example.</userinput>
2131 Two output files will be produced:
2132 <filename>Kchild.example.+005+12345.key</filename> and
2133 <filename>Kchild.example.+005+12345.private</filename>
2135 12345 is an example of a key tag). The key filenames contain
2136 the key name (<filename>child.example.</filename>),
2138 is DSA, 1 is RSAMD5, 5 is RSASHA1, etc.), and the key tag (12345 in
2140 The private key (in the <filename>.private</filename>
2142 used to generate signatures, and the public key (in the
2143 <filename>.key</filename> file) is used for signature
2148 To generate another key with the same properties (but with
2149 a different key tag), repeat the above command.
2153 The <command>dnssec-keyfromlabel</command> program is used
2154 to get a key pair from a crypto hardware and build the key
2155 files. Its usage is similar to <command>dnssec-keygen</command>.
2159 The public keys should be inserted into the zone file by
2160 including the <filename>.key</filename> files using
2161 <command>$INCLUDE</command> statements.
2166 <title>Signing the Zone</title>
2169 The <command>dnssec-signzone</command> program is used
2174 Any <filename>keyset</filename> files corresponding to
2175 secure subzones should be present. The zone signer will
2176 generate <literal>NSEC</literal>, <literal>NSEC3</literal>
2177 and <literal>RRSIG</literal> records for the zone, as
2178 well as <literal>DS</literal> for the child zones if
2179 <literal>'-g'</literal> is specified. If <literal>'-g'</literal>
2180 is not specified, then DS RRsets for the secure child
2181 zones need to be added manually.
2185 The following command signs the zone, assuming it is in a
2186 file called <filename>zone.child.example</filename>. By
2187 default, all zone keys which have an available private key are
2188 used to generate signatures.
2192 <userinput>dnssec-signzone -o child.example zone.child.example</userinput>
2196 One output file is produced:
2197 <filename>zone.child.example.signed</filename>. This
2199 should be referenced by <filename>named.conf</filename>
2201 input file for the zone.
2204 <para><command>dnssec-signzone</command>
2205 will also produce a keyset and dsset files and optionally a
2206 dlvset file. These are used to provide the parent zone
2207 administrators with the <literal>DNSKEYs</literal> (or their
2208 corresponding <literal>DS</literal> records) that are the
2209 secure entry point to the zone.
2215 <title>Configuring Servers</title>
2218 To enable <command>named</command> to respond appropriately
2219 to DNS requests from DNSSEC aware clients,
2220 <command>dnssec-enable</command> must be set to yes.
2221 (This is the default setting.)
2225 To enable <command>named</command> to validate answers from
2226 other servers, the <command>dnssec-enable</command> option
2227 must be set to <userinput>yes</userinput>, and the
2228 <command>dnssec-validation</command> options must be set to
2229 <userinput>yes</userinput> or <userinput>auto</userinput>.
2233 If <command>dnssec-validation</command> is set to
2234 <userinput>auto</userinput>, then a default
2235 trust anchor for the DNS root zone will be used.
2236 If it is set to <userinput>yes</userinput>, however,
2237 then at least one trust anchor must be configured
2238 with a <command>trusted-keys</command> or
2239 <command>managed-keys</command> statement in
2240 <filename>named.conf</filename>, or DNSSEC validation
2241 will not occur. The default setting is
2242 <userinput>yes</userinput>.
2246 <command>trusted-keys</command> are copies of DNSKEY RRs
2247 for zones that are used to form the first link in the
2248 cryptographic chain of trust. All keys listed in
2249 <command>trusted-keys</command> (and corresponding zones)
2250 are deemed to exist and only the listed keys will be used
2251 to validated the DNSKEY RRset that they are from.
2255 <command>managed-keys</command> are trusted keys which are
2256 automatically kept up to date via RFC 5011 trust anchor
2261 <command>trusted-keys</command> and
2262 <command>managed-keys</command> are described in more detail
2263 later in this document.
2267 Unlike <acronym>BIND</acronym> 8, <acronym>BIND</acronym>
2268 9 does not verify signatures on load, so zone keys for
2269 authoritative zones do not need to be specified in the
2274 After DNSSEC gets established, a typical DNSSEC configuration
2275 will look something like the following. It has one or
2276 more public keys for the root. This allows answers from
2277 outside the organization to be validated. It will also
2278 have several keys for parts of the namespace the organization
2279 controls. These are here to ensure that <command>named</command>
2280 is immune to compromises in the DNSSEC components of the security
2287 "." initial-key 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS
2288 JxrGkxJWoZu6I7PzJu/E9gx4UC1zGAHlXKdE4zYIpRh
2289 aBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3zy2Xy
2290 4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYg
2291 hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp
2292 5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M/lUUVRbke
2293 g1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq
2294 66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ
2295 97S+LKUTpQcq27R7AT3/V5hRQxScINqwcz4jYqZD2fQ
2296 dgxbcDTClU0CRBdiieyLMNzXG3";
2300 /* Key for our organization's forward zone */
2301 example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6
2302 5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z
2303 GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb
2304 4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL
2305 kBOUKUf/mC7HvfwYH/Be22GnClrinKJp1O
2306 g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S
2307 TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq
2308 FxmAVZP20igTixin/1LcrgX/KMEGd/biuv
2309 F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm
2310 /oyWR8BW/hWdzOvnSCThlHf3xiYleDbt/o
2313 /* Key for our reverse zone. */
2314 2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwc
2315 xOdNax071L18QqZnQQQAVVr+i
2316 LhGTnNGp3HoWQLUIzKrJVZ3zg
2317 gy3WwNT6kZo6c0tszYqbtvchm
2318 gQC8CzKojM/W16i6MG/eafGU3
2319 siaOdS0yOI6BgPsw+YZdzlYMa
2320 IJGf4M4dyoKIhzdZyQ2bYQrjy
2321 Q4LB0lC7aOnsMyYKHHYeRvPxj
2322 IQXmdqgOJGq+vsevG06zW+1xg
2323 YJh9rCIfnm1GX/KMgxLPG2vXT
2324 D/RnLX+D3T3UL7HJYHJhAZD5L
2325 59VvjSPsZJHeDCUyWYrvPZesZ
2326 DIRvhDD52SKvbheeTJUm6Ehkz
2327 ytNN2SN96QRk8j/iI8ib";
2333 dnssec-validation yes;
2338 None of the keys listed in this example are valid. In particular,
2339 the root key is not valid.
2343 When DNSSEC validation is enabled and properly configured,
2344 the resolver will reject any answers from signed, secure zones
2345 which fail to validate, and will return SERVFAIL to the client.
2349 Responses may fail to validate for any of several reasons,
2350 including missing, expired, or invalid signatures, a key which
2351 does not match the DS RRset in the parent zone, or an insecure
2352 response from a zone which, according to its parent, should have
2358 When the validator receives a response from an unsigned zone
2359 that has a signed parent, it must confirm with the parent
2360 that the zone was intentionally left unsigned. It does
2361 this by verifying, via signed and validated NSEC/NSEC3 records,
2362 that the parent zone contains no DS records for the child.
2365 If the validator <emphasis>can</emphasis> prove that the zone
2366 is insecure, then the response is accepted. However, if it
2367 cannot, then it must assume an insecure response to be a
2368 forgery; it rejects the response and logs an error.
2371 The logged error reads "insecurity proof failed" and
2372 "got insecure response; parent indicates it should be secure".
2373 (Prior to BIND 9.7, the logged error was "not insecure".
2374 This referred to the zone, not the response.)
2381 <xi:include href="dnssec.xml"/>
2383 <xi:include href="managed-keys.xml"/>
2385 <xi:include href="pkcs11.xml"/>
2388 <title>IPv6 Support in <acronym>BIND</acronym> 9</title>
2391 <acronym>BIND</acronym> 9 fully supports all currently
2392 defined forms of IPv6 name to address and address to name
2393 lookups. It will also use IPv6 addresses to make queries when
2394 running on an IPv6 capable system.
2398 For forward lookups, <acronym>BIND</acronym> 9 supports
2399 only AAAA records. RFC 3363 deprecated the use of A6 records,
2400 and client-side support for A6 records was accordingly removed
2401 from <acronym>BIND</acronym> 9.
2402 However, authoritative <acronym>BIND</acronym> 9 name servers still
2403 load zone files containing A6 records correctly, answer queries
2404 for A6 records, and accept zone transfer for a zone containing A6
2409 For IPv6 reverse lookups, <acronym>BIND</acronym> 9 supports
2410 the traditional "nibble" format used in the
2411 <emphasis>ip6.arpa</emphasis> domain, as well as the older, deprecated
2412 <emphasis>ip6.int</emphasis> domain.
2413 Older versions of <acronym>BIND</acronym> 9
2414 supported the "binary label" (also known as "bitstring") format,
2415 but support of binary labels has been completely removed per
2417 Many applications in <acronym>BIND</acronym> 9 do not understand
2418 the binary label format at all any more, and will return an
2420 In particular, an authoritative <acronym>BIND</acronym> 9
2421 name server will not load a zone file containing binary labels.
2425 For an overview of the format and structure of IPv6 addresses,
2426 see <xref linkend="ipv6addresses"/>.
2430 <title>Address Lookups Using AAAA Records</title>
2433 The IPv6 AAAA record is a parallel to the IPv4 A record,
2434 and, unlike the deprecated A6 record, specifies the entire
2435 IPv6 address in a single record. For example,
2439 $ORIGIN example.com.
2440 host 3600 IN AAAA 2001:db8::1
2444 Use of IPv4-in-IPv6 mapped addresses is not recommended.
2445 If a host has an IPv4 address, use an A record, not
2446 a AAAA, with <literal>::ffff:192.168.42.1</literal> as
2451 <title>Address to Name Lookups Using Nibble Format</title>
2454 When looking up an address in nibble format, the address
2455 components are simply reversed, just as in IPv4, and
2456 <literal>ip6.arpa.</literal> is appended to the
2458 For example, the following would provide reverse name lookup for
2460 <literal>2001:db8::1</literal>.
2464 $ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
2465 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR (
2473 <chapter id="Bv9ARM.ch05">
2474 <title>The <acronym>BIND</acronym> 9 Lightweight Resolver</title>
2476 <title>The Lightweight Resolver Library</title>
2478 Traditionally applications have been linked with a stub resolver
2479 library that sends recursive DNS queries to a local caching name
2483 IPv6 once introduced new complexity into the resolution process,
2484 such as following A6 chains and DNAME records, and simultaneous
2485 lookup of IPv4 and IPv6 addresses. Though most of the complexity was
2486 then removed, these are hard or impossible
2487 to implement in a traditional stub resolver.
2490 <acronym>BIND</acronym> 9 therefore can also provide resolution
2491 services to local clients
2492 using a combination of a lightweight resolver library and a resolver
2493 daemon process running on the local host. These communicate using
2494 a simple UDP-based protocol, the "lightweight resolver protocol"
2495 that is distinct from and simpler than the full DNS protocol.
2499 <title>Running a Resolver Daemon</title>
2502 To use the lightweight resolver interface, the system must
2503 run the resolver daemon <command>lwresd</command> or a
2505 name server configured with a <command>lwres</command>
2510 By default, applications using the lightweight resolver library will
2512 UDP requests to the IPv4 loopback address (127.0.0.1) on port 921.
2514 address can be overridden by <command>lwserver</command>
2516 <filename>/etc/resolv.conf</filename>.
2520 The daemon currently only looks in the DNS, but in the future
2521 it may use other sources such as <filename>/etc/hosts</filename>,
2526 The <command>lwresd</command> daemon is essentially a
2527 caching-only name server that responds to requests using the
2529 resolver protocol rather than the DNS protocol. Because it needs
2530 to run on each host, it is designed to require no or minimal
2532 Unless configured otherwise, it uses the name servers listed on
2533 <command>nameserver</command> lines in <filename>/etc/resolv.conf</filename>
2534 as forwarders, but is also capable of doing the resolution
2539 The <command>lwresd</command> daemon may also be
2541 <filename>named.conf</filename> style configuration file,
2543 <filename>/etc/lwresd.conf</filename> by default. A name
2545 be configured to act as a lightweight resolver daemon using the
2546 <command>lwres</command> statement in <filename>named.conf</filename>.
2552 <chapter id="Bv9ARM.ch06">
2553 <title><acronym>BIND</acronym> 9 Configuration Reference</title>
2556 <acronym>BIND</acronym> 9 configuration is broadly similar
2557 to <acronym>BIND</acronym> 8; however, there are a few new
2559 of configuration, such as views. <acronym>BIND</acronym>
2560 8 configuration files should work with few alterations in <acronym>BIND</acronym>
2561 9, although more complex configurations should be reviewed to check
2562 if they can be more efficiently implemented using the new features
2563 found in <acronym>BIND</acronym> 9.
2567 <acronym>BIND</acronym> 4 configuration files can be
2568 converted to the new format
2569 using the shell script
2570 <filename>contrib/named-bootconf/named-bootconf.sh</filename>.
2572 <sect1 id="configuration_file_elements">
2573 <title>Configuration File Elements</title>
2575 Following is a list of elements used throughout the <acronym>BIND</acronym> configuration
2578 <informaltable colsep="0" rowsep="0">
2579 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
2580 <colspec colname="1" colnum="1" colsep="0" colwidth="1.855in"/>
2581 <colspec colname="2" colnum="2" colsep="0" colwidth="3.770in"/>
2586 <varname>acl_name</varname>
2591 The name of an <varname>address_match_list</varname> as
2592 defined by the <command>acl</command> statement.
2599 <varname>address_match_list</varname>
2604 A list of one or more
2605 <varname>ip_addr</varname>,
2606 <varname>ip_prefix</varname>, <varname>key_id</varname>,
2607 or <varname>acl_name</varname> elements, see
2608 <xref linkend="address_match_lists"/>.
2615 <varname>masters_list</varname>
2620 A named list of one or more <varname>ip_addr</varname>
2621 with optional <varname>key_id</varname> and/or
2622 <varname>ip_port</varname>.
2623 A <varname>masters_list</varname> may include other
2624 <varname>masters_lists</varname>.
2631 <varname>domain_name</varname>
2636 A quoted string which will be used as
2637 a DNS name, for example "<literal>my.test.domain</literal>".
2644 <varname>namelist</varname>
2649 A list of one or more <varname>domain_name</varname>
2657 <varname>dotted_decimal</varname>
2662 One to four integers valued 0 through
2663 255 separated by dots (`.'), such as <command>123</command>,
2664 <command>45.67</command> or <command>89.123.45.67</command>.
2671 <varname>ip4_addr</varname>
2676 An IPv4 address with exactly four elements
2677 in <varname>dotted_decimal</varname> notation.
2684 <varname>ip6_addr</varname>
2689 An IPv6 address, such as <command>2001:db8::1234</command>.
2690 IPv6 scoped addresses that have ambiguity on their
2691 scope zones must be disambiguated by an appropriate
2692 zone ID with the percent character (`%') as
2693 delimiter. It is strongly recommended to use
2694 string zone names rather than numeric identifiers,
2695 in order to be robust against system configuration
2696 changes. However, since there is no standard
2697 mapping for such names and identifier values,
2698 currently only interface names as link identifiers
2699 are supported, assuming one-to-one mapping between
2700 interfaces and links. For example, a link-local
2701 address <command>fe80::1</command> on the link
2702 attached to the interface <command>ne0</command>
2703 can be specified as <command>fe80::1%ne0</command>.
2704 Note that on most systems link-local addresses
2705 always have the ambiguity, and need to be
2713 <varname>ip_addr</varname>
2718 An <varname>ip4_addr</varname> or <varname>ip6_addr</varname>.
2725 <varname>ip_port</varname>
2730 An IP port <varname>number</varname>.
2731 The <varname>number</varname> is limited to 0
2732 through 65535, with values
2733 below 1024 typically restricted to use by processes running
2735 In some cases, an asterisk (`*') character can be used as a
2737 select a random high-numbered port.
2744 <varname>ip_prefix</varname>
2749 An IP network specified as an <varname>ip_addr</varname>,
2750 followed by a slash (`/') and then the number of bits in the
2752 Trailing zeros in a <varname>ip_addr</varname>
2754 For example, <command>127/8</command> is the
2755 network <command>127.0.0.0</command> with
2756 netmask <command>255.0.0.0</command> and <command>1.2.3.0/28</command> is
2757 network <command>1.2.3.0</command> with netmask <command>255.255.255.240</command>.
2760 When specifying a prefix involving a IPv6 scoped address
2761 the scope may be omitted. In that case the prefix will
2762 match packets from any scope.
2769 <varname>key_id</varname>
2774 A <varname>domain_name</varname> representing
2775 the name of a shared key, to be used for transaction
2783 <varname>key_list</varname>
2788 A list of one or more
2789 <varname>key_id</varname>s,
2790 separated by semicolons and ending with a semicolon.
2797 <varname>number</varname>
2802 A non-negative 32-bit integer
2803 (i.e., a number between 0 and 4294967295, inclusive).
2804 Its acceptable value might further
2805 be limited by the context in which it is used.
2812 <varname>path_name</varname>
2817 A quoted string which will be used as
2818 a pathname, such as <filename>zones/master/my.test.domain</filename>.
2825 <varname>port_list</varname>
2830 A list of an <varname>ip_port</varname> or a port
2832 A port range is specified in the form of
2833 <userinput>range</userinput> followed by
2834 two <varname>ip_port</varname>s,
2835 <varname>port_low</varname> and
2836 <varname>port_high</varname>, which represents
2837 port numbers from <varname>port_low</varname> through
2838 <varname>port_high</varname>, inclusive.
2839 <varname>port_low</varname> must not be larger than
2840 <varname>port_high</varname>.
2842 <userinput>range 1024 65535</userinput> represents
2843 ports from 1024 through 65535.
2844 In either case an asterisk (`*') character is not
2845 allowed as a valid <varname>ip_port</varname>.
2852 <varname>size_spec</varname>
2857 A 64-bit unsigned integer, or the keywords
2858 <userinput>unlimited</userinput> or
2859 <userinput>default</userinput>.
2862 Integers may take values
2863 0 <= value <= 18446744073709551615, though
2864 certain parameters may use a more limited range
2865 within these extremes. In most cases, setting a
2866 value to 0 does not literally mean zero; it means
2867 "undefined" or "as big as psosible", depending on
2868 the context. See the expalantions of particular
2869 parameters that use <varname>size_spec</varname>
2870 for details on how they interpret its use.
2873 Numeric values can optionally be followed by a
2875 <userinput>K</userinput> or <userinput>k</userinput>
2877 <userinput>M</userinput> or <userinput>m</userinput>
2879 <userinput>G</userinput> or <userinput>g</userinput>
2880 for gigabytes, which scale by 1024, 1024*1024, and
2881 1024*1024*1024 respectively.
2884 <varname>unlimited</varname> generally means
2885 "as big as possible", though in certain contexts,
2886 (including <option>max-cache-size</option>), it may
2887 mean the largest possible 32-bit unsigned integer
2888 (0xffffffff); this distinction can be important when
2889 dealing with larger quantities.
2890 <varname>unlimited</varname> is usually the best way
2891 to safely set a very large number.
2894 <varname>default</varname>
2895 uses the limit that was in force when the server was started.
2902 <varname>yes_or_no</varname>
2907 Either <userinput>yes</userinput> or <userinput>no</userinput>.
2908 The words <userinput>true</userinput> and <userinput>false</userinput> are
2909 also accepted, as are the numbers <userinput>1</userinput>
2910 and <userinput>0</userinput>.
2917 <varname>dialup_option</varname>
2922 One of <userinput>yes</userinput>,
2923 <userinput>no</userinput>, <userinput>notify</userinput>,
2924 <userinput>notify-passive</userinput>, <userinput>refresh</userinput> or
2925 <userinput>passive</userinput>.
2926 When used in a zone, <userinput>notify-passive</userinput>,
2927 <userinput>refresh</userinput>, and <userinput>passive</userinput>
2928 are restricted to slave and stub zones.
2935 <sect2 id="address_match_lists">
2936 <title>Address Match Lists</title>
2938 <title>Syntax</title>
2940 <programlisting><varname>address_match_list</varname> = address_match_list_element ;
2941 <optional> address_match_list_element; ... </optional>
2942 <varname>address_match_list_element</varname> = <optional> ! </optional> (ip_address <optional>/length</optional> |
2943 key key_id | acl_name | { address_match_list } )
2948 <title>Definition and Usage</title>
2950 Address match lists are primarily used to determine access
2951 control for various server operations. They are also used in
2952 the <command>listen-on</command> and <command>sortlist</command>
2953 statements. The elements which constitute an address match
2954 list can be any of the following:
2958 <simpara>an IP address (IPv4 or IPv6)</simpara>
2961 <simpara>an IP prefix (in `/' notation)</simpara>
2965 a key ID, as defined by the <command>key</command>
2970 <simpara>the name of an address match list defined with
2971 the <command>acl</command> statement
2975 <simpara>a nested address match list enclosed in braces</simpara>
2980 Elements can be negated with a leading exclamation mark (`!'),
2981 and the match list names "any", "none", "localhost", and
2982 "localnets" are predefined. More information on those names
2983 can be found in the description of the acl statement.
2987 The addition of the key clause made the name of this syntactic
2988 element something of a misnomer, since security keys can be used
2989 to validate access without regard to a host or network address.
2990 Nonetheless, the term "address match list" is still used
2991 throughout the documentation.
2995 When a given IP address or prefix is compared to an address
2996 match list, the comparison takes place in approximately O(1)
2997 time. However, key comparisons require that the list of keys
2998 be traversed until a matching key is found, and therefore may
3003 The interpretation of a match depends on whether the list is being
3004 used for access control, defining <command>listen-on</command> ports, or in a
3005 <command>sortlist</command>, and whether the element was negated.
3009 When used as an access control list, a non-negated match
3010 allows access and a negated match denies access. If
3011 there is no match, access is denied. The clauses
3012 <command>allow-notify</command>,
3013 <command>allow-recursion</command>,
3014 <command>allow-recursion-on</command>,
3015 <command>allow-query</command>,
3016 <command>allow-query-on</command>,
3017 <command>allow-query-cache</command>,
3018 <command>allow-query-cache-on</command>,
3019 <command>allow-transfer</command>,
3020 <command>allow-update</command>,
3021 <command>allow-update-forwarding</command>, and
3022 <command>blackhole</command> all use address match
3023 lists. Similarly, the <command>listen-on</command> option will cause the
3024 server to refuse queries on any of the machine's
3025 addresses which do not match the list.
3029 Order of insertion is significant. If more than one element
3030 in an ACL is found to match a given IP address or prefix,
3031 preference will be given to the one that came
3032 <emphasis>first</emphasis> in the ACL definition.
3033 Because of this first-match behavior, an element that
3034 defines a subset of another element in the list should
3035 come before the broader element, regardless of whether
3036 either is negated. For example, in
3037 <command>1.2.3/24; ! 1.2.3.13;</command>
3038 the 1.2.3.13 element is completely useless because the
3039 algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
3040 element. Using <command>! 1.2.3.13; 1.2.3/24</command> fixes
3041 that problem by having 1.2.3.13 blocked by the negation, but
3042 all other 1.2.3.* hosts fall through.
3048 <title>Comment Syntax</title>
3051 The <acronym>BIND</acronym> 9 comment syntax allows for
3053 anywhere that whitespace may appear in a <acronym>BIND</acronym> configuration
3054 file. To appeal to programmers of all kinds, they can be written
3055 in the C, C++, or shell/perl style.
3059 <title>Syntax</title>
3062 <programlisting>/* This is a <acronym>BIND</acronym> comment as in C */</programlisting>
3063 <programlisting>// This is a <acronym>BIND</acronym> comment as in C++</programlisting>
3064 <programlisting># This is a <acronym>BIND</acronym> comment as in common UNIX shells
3065 # and perl</programlisting>
3069 <title>Definition and Usage</title>
3071 Comments may appear anywhere that whitespace may appear in
3072 a <acronym>BIND</acronym> configuration file.
3075 C-style comments start with the two characters /* (slash,
3076 star) and end with */ (star, slash). Because they are completely
3077 delimited with these characters, they can be used to comment only
3078 a portion of a line or to span multiple lines.
3081 C-style comments cannot be nested. For example, the following
3082 is not valid because the entire comment ends with the first */:
3086 <programlisting>/* This is the start of a comment.
3087 This is still part of the comment.
3088 /* This is an incorrect attempt at nesting a comment. */
3089 This is no longer in any comment. */
3095 C++-style comments start with the two characters // (slash,
3096 slash) and continue to the end of the physical line. They cannot
3097 be continued across multiple physical lines; to have one logical
3098 comment span multiple lines, each line must use the // pair.
3103 <programlisting>// This is the start of a comment. The next line
3104 // is a new comment, even though it is logically
3105 // part of the previous comment.
3110 Shell-style (or perl-style, if you prefer) comments start
3111 with the character <literal>#</literal> (number sign)
3112 and continue to the end of the
3113 physical line, as in C++ comments.
3119 <programlisting># This is the start of a comment. The next line
3120 # is a new comment, even though it is logically
3121 # part of the previous comment.
3128 You cannot use the semicolon (`;') character
3129 to start a comment such as you would in a zone file. The
3130 semicolon indicates the end of a configuration
3138 <sect1 id="Configuration_File_Grammar">
3139 <title>Configuration File Grammar</title>
3142 A <acronym>BIND</acronym> 9 configuration consists of
3143 statements and comments.
3144 Statements end with a semicolon. Statements and comments are the
3145 only elements that can appear without enclosing braces. Many
3146 statements contain a block of sub-statements, which are also
3147 terminated with a semicolon.
3151 The following statements are supported:
3154 <informaltable colsep="0" rowsep="0">
3155 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="2Level-table">
3156 <colspec colname="1" colnum="1" colsep="0" colwidth="1.336in"/>
3157 <colspec colname="2" colnum="2" colsep="0" colwidth="3.778in"/>
3161 <para><command>acl</command></para>
3165 defines a named IP address
3166 matching list, for access control and other uses.
3172 <para><command>controls</command></para>
3176 declares control channels to be used
3177 by the <command>rndc</command> utility.
3183 <para><command>include</command></para>
3193 <para><command>key</command></para>
3197 specifies key information for use in
3198 authentication and authorization using TSIG.
3204 <para><command>logging</command></para>
3208 specifies what the server logs, and where
3209 the log messages are sent.
3215 <para><command>lwres</command></para>
3219 configures <command>named</command> to
3220 also act as a light-weight resolver daemon (<command>lwresd</command>).
3226 <para><command>masters</command></para>
3230 defines a named masters list for
3231 inclusion in stub and slave zones'
3232 <command>masters</command> or
3233 <command>also-notify</command> lists.
3239 <para><command>options</command></para>
3243 controls global server configuration
3244 options and sets defaults for other statements.
3250 <para><command>server</command></para>
3254 sets certain configuration options on
3261 <para><command>statistics-channels</command></para>
3265 declares communication channels to get access to
3266 <command>named</command> statistics.
3272 <para><command>trusted-keys</command></para>
3276 defines trusted DNSSEC keys.
3282 <para><command>managed-keys</command></para>
3286 lists DNSSEC keys to be kept up to date
3287 using RFC 5011 trust anchor maintenance.
3293 <para><command>view</command></para>
3303 <para><command>zone</command></para>
3316 The <command>logging</command> and
3317 <command>options</command> statements may only occur once
3323 <title><command>acl</command> Statement Grammar</title>
3325 <programlisting><command>acl</command> acl-name {
3332 <title><command>acl</command> Statement Definition and
3336 The <command>acl</command> statement assigns a symbolic
3337 name to an address match list. It gets its name from a primary
3338 use of address match lists: Access Control Lists (ACLs).
3342 Note that an address match list's name must be defined
3343 with <command>acl</command> before it can be used
3344 elsewhere; no forward references are allowed.
3348 The following ACLs are built-in:
3351 <informaltable colsep="0" rowsep="0">
3352 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
3353 <colspec colname="1" colnum="1" colsep="0" colwidth="1.130in"/>
3354 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
3358 <para><command>any</command></para>
3368 <para><command>none</command></para>
3378 <para><command>localhost</command></para>
3382 Matches the IPv4 and IPv6 addresses of all network
3383 interfaces on the system.
3389 <para><command>localnets</command></para>
3393 Matches any host on an IPv4 or IPv6 network
3394 for which the system has an interface.
3395 Some systems do not provide a way to determine the prefix
3397 local IPv6 addresses.
3398 In such a case, <command>localnets</command>
3399 only matches the local
3400 IPv6 addresses, just like <command>localhost</command>.
3410 <title><command>controls</command> Statement Grammar</title>
3412 <programlisting><command>controls</command> {
3413 [ inet ( ip_addr | * ) [ port ip_port ]
3414 allow { <replaceable> address_match_list </replaceable> }
3415 keys { <replaceable>key_list</replaceable> }; ]
3417 [ unix <replaceable>path</replaceable> perm <replaceable>number</replaceable> owner <replaceable>number</replaceable> group <replaceable>number</replaceable>
3418 keys { <replaceable>key_list</replaceable> }; ]
3425 <sect2 id="controls_statement_definition_and_usage">
3426 <title><command>controls</command> Statement Definition and
3430 The <command>controls</command> statement declares control
3431 channels to be used by system administrators to control the
3432 operation of the name server. These control channels are
3433 used by the <command>rndc</command> utility to send
3434 commands to and retrieve non-DNS results from a name server.
3438 An <command>inet</command> control channel is a TCP socket
3439 listening at the specified <command>ip_port</command> on the
3440 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
3441 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
3442 interpreted as the IPv4 wildcard address; connections will be
3443 accepted on any of the system's IPv4 addresses.
3444 To listen on the IPv6 wildcard address,
3445 use an <command>ip_addr</command> of <literal>::</literal>.
3446 If you will only use <command>rndc</command> on the local host,
3447 using the loopback address (<literal>127.0.0.1</literal>
3448 or <literal>::1</literal>) is recommended for maximum security.
3452 If no port is specified, port 953 is used. The asterisk
3453 "<literal>*</literal>" cannot be used for <command>ip_port</command>.
3457 The ability to issue commands over the control channel is
3458 restricted by the <command>allow</command> and
3459 <command>keys</command> clauses.
3460 Connections to the control channel are permitted based on the
3461 <command>address_match_list</command>. This is for simple
3462 IP address based filtering only; any <command>key_id</command>
3463 elements of the <command>address_match_list</command>
3468 A <command>unix</command> control channel is a UNIX domain
3469 socket listening at the specified path in the file system.
3470 Access to the socket is specified by the <command>perm</command>,
3471 <command>owner</command> and <command>group</command> clauses.
3472 Note on some platforms (SunOS and Solaris) the permissions
3473 (<command>perm</command>) are applied to the parent directory
3474 as the permissions on the socket itself are ignored.
3478 The primary authorization mechanism of the command
3479 channel is the <command>key_list</command>, which
3480 contains a list of <command>key_id</command>s.
3481 Each <command>key_id</command> in the <command>key_list</command>
3482 is authorized to execute commands over the control channel.
3483 See <xref linkend="rndc"/> in <xref linkend="admin_tools"/>)
3484 for information about configuring keys in <command>rndc</command>.
3488 If no <command>controls</command> statement is present,
3489 <command>named</command> will set up a default
3490 control channel listening on the loopback address 127.0.0.1
3491 and its IPv6 counterpart ::1.
3492 In this case, and also when the <command>controls</command> statement
3493 is present but does not have a <command>keys</command> clause,
3494 <command>named</command> will attempt to load the command channel key
3495 from the file <filename>rndc.key</filename> in
3496 <filename>/etc</filename> (or whatever <varname>sysconfdir</varname>
3497 was specified as when <acronym>BIND</acronym> was built).
3498 To create a <filename>rndc.key</filename> file, run
3499 <userinput>rndc-confgen -a</userinput>.
3503 The <filename>rndc.key</filename> feature was created to
3504 ease the transition of systems from <acronym>BIND</acronym> 8,
3505 which did not have digital signatures on its command channel
3506 messages and thus did not have a <command>keys</command> clause.
3508 It makes it possible to use an existing <acronym>BIND</acronym> 8
3509 configuration file in <acronym>BIND</acronym> 9 unchanged,
3510 and still have <command>rndc</command> work the same way
3511 <command>ndc</command> worked in BIND 8, simply by executing the
3512 command <userinput>rndc-confgen -a</userinput> after BIND 9 is
3517 Since the <filename>rndc.key</filename> feature
3518 is only intended to allow the backward-compatible usage of
3519 <acronym>BIND</acronym> 8 configuration files, this
3521 have a high degree of configurability. You cannot easily change
3522 the key name or the size of the secret, so you should make a
3523 <filename>rndc.conf</filename> with your own key if you
3525 those things. The <filename>rndc.key</filename> file
3527 permissions set such that only the owner of the file (the user that
3528 <command>named</command> is running as) can access it.
3530 desire greater flexibility in allowing other users to access
3531 <command>rndc</command> commands, then you need to create
3533 <filename>rndc.conf</filename> file and make it group
3535 that contains the users who should have access.
3539 To disable the command channel, use an empty
3540 <command>controls</command> statement:
3541 <command>controls { };</command>.
3546 <title><command>include</command> Statement Grammar</title>
3547 <programlisting><command>include</command> <replaceable>filename</replaceable>;</programlisting>
3550 <title><command>include</command> Statement Definition and
3554 The <command>include</command> statement inserts the
3555 specified file at the point where the <command>include</command>
3556 statement is encountered. The <command>include</command>
3557 statement facilitates the administration of configuration
3559 by permitting the reading or writing of some things but not
3560 others. For example, the statement could include private keys
3561 that are readable only by the name server.
3566 <title><command>key</command> Statement Grammar</title>
3568 <programlisting><command>key</command> <replaceable>key_id</replaceable> {
3569 algorithm <replaceable>string</replaceable>;
3570 secret <replaceable>string</replaceable>;
3577 <title><command>key</command> Statement Definition and Usage</title>
3580 The <command>key</command> statement defines a shared
3581 secret key for use with TSIG (see <xref linkend="tsig"/>)
3582 or the command channel
3583 (see <xref linkend="controls_statement_definition_and_usage"/>).
3587 The <command>key</command> statement can occur at the
3589 of the configuration file or inside a <command>view</command>
3590 statement. Keys defined in top-level <command>key</command>
3591 statements can be used in all views. Keys intended for use in
3592 a <command>controls</command> statement
3593 (see <xref linkend="controls_statement_definition_and_usage"/>)
3594 must be defined at the top level.
3598 The <replaceable>key_id</replaceable>, also known as the
3599 key name, is a domain name uniquely identifying the key. It can
3600 be used in a <command>server</command>
3601 statement to cause requests sent to that
3602 server to be signed with this key, or in address match lists to
3603 verify that incoming requests have been signed with a key
3604 matching this name, algorithm, and secret.
3608 The <replaceable>algorithm_id</replaceable> is a string
3609 that specifies a security/authentication algorithm. Named
3610 supports <literal>hmac-md5</literal>,
3611 <literal>hmac-sha1</literal>, <literal>hmac-sha224</literal>,
3612 <literal>hmac-sha256</literal>, <literal>hmac-sha384</literal>
3613 and <literal>hmac-sha512</literal> TSIG authentication.
3614 Truncated hashes are supported by appending the minimum
3615 number of required bits preceded by a dash, e.g.
3616 <literal>hmac-sha1-80</literal>. The
3617 <replaceable>secret_string</replaceable> is the secret
3618 to be used by the algorithm, and is treated as a base-64
3624 <title><command>logging</command> Statement Grammar</title>
3626 <programlisting><command>logging</command> {
3627 [ <command>channel</command> <replaceable>channel_name</replaceable> {
3628 ( <command>file</command> <replaceable>path_name</replaceable>
3629 [ <command>versions</command> ( <replaceable>number</replaceable> | <command>unlimited</command> ) ]
3630 [ <command>size</command> <replaceable>size_spec</replaceable> ]
3631 | <command>syslog</command> <replaceable>syslog_facility</replaceable>
3632 | <command>stderr</command>
3633 | <command>null</command> );
3634 [ <command>severity</command> (<option>critical</option> | <option>error</option> | <option>warning</option> | <option>notice</option> |
3635 <option>info</option> | <option>debug</option> [ <replaceable>level</replaceable> ] | <option>dynamic</option> ); ]
3636 [ <command>print-category</command> <option>yes</option> or <option>no</option>; ]
3637 [ <command>print-severity</command> <option>yes</option> or <option>no</option>; ]
3638 [ <command>print-time</command> <option>yes</option> or <option>no</option>; ]
3640 [ <command>category</command> <replaceable>category_name</replaceable> {
3641 <replaceable>channel_name</replaceable> ; [ <replaceable>channel_name</replaceable> ; ... ]
3650 <title><command>logging</command> Statement Definition and
3654 The <command>logging</command> statement configures a
3656 variety of logging options for the name server. Its <command>channel</command> phrase
3657 associates output methods, format options and severity levels with
3658 a name that can then be used with the <command>category</command> phrase
3659 to select how various classes of messages are logged.
3662 Only one <command>logging</command> statement is used to
3664 as many channels and categories as are wanted. If there is no <command>logging</command> statement,
3665 the logging configuration will be:
3668 <programlisting>logging {
3669 category default { default_syslog; default_debug; };
3670 category unmatched { null; };
3675 In <acronym>BIND</acronym> 9, the logging configuration
3676 is only established when
3677 the entire configuration file has been parsed. In <acronym>BIND</acronym> 8, it was
3678 established as soon as the <command>logging</command>
3680 was parsed. When the server is starting up, all logging messages
3681 regarding syntax errors in the configuration file go to the default
3682 channels, or to standard error if the "<option>-g</option>" option
3687 <title>The <command>channel</command> Phrase</title>
3690 All log output goes to one or more <emphasis>channels</emphasis>;
3691 you can make as many of them as you want.
3695 Every channel definition must include a destination clause that
3696 says whether messages selected for the channel go to a file, to a
3697 particular syslog facility, to the standard error stream, or are
3698 discarded. It can optionally also limit the message severity level
3699 that will be accepted by the channel (the default is
3700 <command>info</command>), and whether to include a
3701 <command>named</command>-generated time stamp, the
3703 and/or severity level (the default is not to include any).
3707 The <command>null</command> destination clause
3708 causes all messages sent to the channel to be discarded;
3709 in that case, other options for the channel are meaningless.
3713 The <command>file</command> destination clause directs
3715 to a disk file. It can include limitations
3716 both on how large the file is allowed to become, and how many
3718 of the file will be saved each time the file is opened.
3722 If you use the <command>versions</command> log file
3724 <command>named</command> will retain that many backup
3725 versions of the file by
3726 renaming them when opening. For example, if you choose to keep
3728 of the file <filename>lamers.log</filename>, then just
3730 <filename>lamers.log.1</filename> is renamed to
3731 <filename>lamers.log.2</filename>, <filename>lamers.log.0</filename> is renamed
3732 to <filename>lamers.log.1</filename>, and <filename>lamers.log</filename> is
3733 renamed to <filename>lamers.log.0</filename>.
3734 You can say <command>versions unlimited</command> to
3736 the number of versions.
3737 If a <command>size</command> option is associated with
3739 then renaming is only done when the file being opened exceeds the
3740 indicated size. No backup versions are kept by default; any
3742 log file is simply appended.
3746 The <command>size</command> option for files is used
3748 growth. If the file ever exceeds the size, then <command>named</command> will
3749 stop writing to the file unless it has a <command>versions</command> option
3750 associated with it. If backup versions are kept, the files are
3752 described above and a new one begun. If there is no
3753 <command>versions</command> option, no more data will
3754 be written to the log
3755 until some out-of-band mechanism removes or truncates the log to
3757 maximum size. The default behavior is not to limit the size of
3763 Example usage of the <command>size</command> and
3764 <command>versions</command> options:
3767 <programlisting>channel an_example_channel {
3768 file "example.log" versions 3 size 20m;
3775 The <command>syslog</command> destination clause
3777 channel to the system log. Its argument is a
3778 syslog facility as described in the <command>syslog</command> man
3779 page. Known facilities are <command>kern</command>, <command>user</command>,
3780 <command>mail</command>, <command>daemon</command>, <command>auth</command>,
3781 <command>syslog</command>, <command>lpr</command>, <command>news</command>,
3782 <command>uucp</command>, <command>cron</command>, <command>authpriv</command>,
3783 <command>ftp</command>, <command>local0</command>, <command>local1</command>,
3784 <command>local2</command>, <command>local3</command>, <command>local4</command>,
3785 <command>local5</command>, <command>local6</command> and
3786 <command>local7</command>, however not all facilities
3788 all operating systems.
3789 How <command>syslog</command> will handle messages
3791 this facility is described in the <command>syslog.conf</command> man
3792 page. If you have a system which uses a very old version of <command>syslog</command> that
3793 only uses two arguments to the <command>openlog()</command> function,
3794 then this clause is silently ignored.
3797 On Windows machines syslog messages are directed to the EventViewer.
3800 The <command>severity</command> clause works like <command>syslog</command>'s
3801 "priorities", except that they can also be used if you are writing
3802 straight to a file rather than using <command>syslog</command>.
3803 Messages which are not at least of the severity level given will
3804 not be selected for the channel; messages of higher severity
3809 If you are using <command>syslog</command>, then the <command>syslog.conf</command> priorities
3810 will also determine what eventually passes through. For example,
3811 defining a channel facility and severity as <command>daemon</command> and <command>debug</command> but
3812 only logging <command>daemon.warning</command> via <command>syslog.conf</command> will
3813 cause messages of severity <command>info</command> and
3814 <command>notice</command> to
3815 be dropped. If the situation were reversed, with <command>named</command> writing
3816 messages of only <command>warning</command> or higher,
3817 then <command>syslogd</command> would
3818 print all messages it received from the channel.
3822 The <command>stderr</command> destination clause
3824 channel to the server's standard error stream. This is intended
3826 use when the server is running as a foreground process, for
3828 when debugging a configuration.
3832 The server can supply extensive debugging information when
3833 it is in debugging mode. If the server's global debug level is
3835 than zero, then debugging mode will be active. The global debug
3836 level is set either by starting the <command>named</command> server
3837 with the <option>-d</option> flag followed by a positive integer,
3838 or by running <command>rndc trace</command>.
3839 The global debug level
3840 can be set to zero, and debugging mode turned off, by running <command>rndc
3841 notrace</command>. All debugging messages in the server have a debug
3842 level, and higher debug levels give more detailed output. Channels
3843 that specify a specific debug severity, for example:
3846 <programlisting>channel specific_debug_level {
3853 will get debugging output of level 3 or less any time the
3854 server is in debugging mode, regardless of the global debugging
3855 level. Channels with <command>dynamic</command>
3857 server's global debug level to determine what messages to print.
3860 If <command>print-time</command> has been turned on,
3862 the date and time will be logged. <command>print-time</command> may
3863 be specified for a <command>syslog</command> channel,
3865 pointless since <command>syslog</command> also logs
3867 time. If <command>print-category</command> is
3869 category of the message will be logged as well. Finally, if <command>print-severity</command> is
3870 on, then the severity level of the message will be logged. The <command>print-</command> options may
3871 be used in any combination, and will always be printed in the
3873 order: time, category, severity. Here is an example where all
3874 three <command>print-</command> options
3879 <computeroutput>28-Feb-2000 15:05:32.863 general: notice: running</computeroutput>
3883 There are four predefined channels that are used for
3884 <command>named</command>'s default logging as follows.
3886 used is described in <xref linkend="the_category_phrase"/>.
3889 <programlisting>channel default_syslog {
3890 // send to syslog's daemon facility
3892 // only send priority info and higher
3895 channel default_debug {
3896 // write to named.run in the working directory
3897 // Note: stderr is used instead of "named.run" if
3898 // the server is started with the '-f' option.
3900 // log at the server's current debug level
3904 channel default_stderr {
3907 // only send priority info and higher
3912 // toss anything sent to this channel
3918 The <command>default_debug</command> channel has the
3920 property that it only produces output when the server's debug
3922 nonzero. It normally writes to a file called <filename>named.run</filename>
3923 in the server's working directory.
3927 For security reasons, when the "<option>-u</option>"
3928 command line option is used, the <filename>named.run</filename> file
3929 is created only after <command>named</command> has
3931 new UID, and any debug output generated while <command>named</command> is
3932 starting up and still running as root is discarded. If you need
3933 to capture this output, you must run the server with the "<option>-g</option>"
3934 option and redirect standard error to a file.
3938 Once a channel is defined, it cannot be redefined. Thus you
3939 cannot alter the built-in channels directly, but you can modify
3940 the default logging by pointing categories at channels you have
3945 <sect3 id="the_category_phrase">
3946 <title>The <command>category</command> Phrase</title>
3949 There are many categories, so you can send the logs you want
3950 to see wherever you want, without seeing logs you don't want. If
3951 you don't specify a list of channels for a category, then log
3953 in that category will be sent to the <command>default</command> category
3954 instead. If you don't specify a default category, the following
3955 "default default" is used:
3958 <programlisting>category default { default_syslog; default_debug; };
3962 As an example, let's say you want to log security events to
3963 a file, but you also want keep the default logging behavior. You'd
3964 specify the following:
3967 <programlisting>channel my_security_channel {
3968 file "my_security_file";
3972 my_security_channel;
3978 To discard all messages in a category, specify the <command>null</command> channel:
3981 <programlisting>category xfer-out { null; };
3982 category notify { null; };
3986 Following are the available categories and brief descriptions
3987 of the types of log information they contain. More
3988 categories may be added in future <acronym>BIND</acronym> releases.
3990 <informaltable colsep="0" rowsep="0">
3991 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
3992 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
3993 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
3997 <para><command>default</command></para>
4001 The default category defines the logging
4002 options for those categories where no specific
4003 configuration has been
4010 <para><command>general</command></para>
4014 The catch-all. Many things still aren't
4015 classified into categories, and they all end up here.
4021 <para><command>database</command></para>
4025 Messages relating to the databases used
4026 internally by the name server to store zone and cache
4033 <para><command>security</command></para>
4037 Approval and denial of requests.
4043 <para><command>config</command></para>
4047 Configuration file parsing and processing.
4053 <para><command>resolver</command></para>
4057 DNS resolution, such as the recursive
4058 lookups performed on behalf of clients by a caching name
4065 <para><command>xfer-in</command></para>
4069 Zone transfers the server is receiving.
4075 <para><command>xfer-out</command></para>
4079 Zone transfers the server is sending.
4085 <para><command>notify</command></para>
4089 The NOTIFY protocol.
4095 <para><command>client</command></para>
4099 Processing of client requests.
4105 <para><command>unmatched</command></para>
4109 Messages that <command>named</command> was unable to determine the
4110 class of or for which there was no matching <command>view</command>.
4111 A one line summary is also logged to the <command>client</command> category.
4112 This category is best sent to a file or stderr, by
4113 default it is sent to
4114 the <command>null</command> channel.
4120 <para><command>network</command></para>
4130 <para><command>update</command></para>
4140 <para><command>update-security</command></para>
4144 Approval and denial of update requests.
4150 <para><command>queries</command></para>
4154 Specify where queries should be logged to.
4157 At startup, specifying the category <command>queries</command> will also
4158 enable query logging unless <command>querylog</command> option has been
4163 The query log entry reports the client's IP
4164 address and port number, and the query name,
4165 class and type. Next it reports whether the
4166 Recursion Desired flag was set (+ if set, -
4167 if not set), if the query was signed (S),
4168 EDNS was in use (E), if TCP was used (T), if
4169 DO (DNSSEC Ok) was set (D), or if CD (Checking
4170 Disabled) was set (C). After this the
4171 destination address the query was sent to is
4176 <computeroutput>client 127.0.0.1#62536 (www.example.com): query: www.example.com IN AAAA +SE</computeroutput>
4179 <computeroutput>client ::1#62537 (www.example.net): query: www.example.net IN AAAA -SE</computeroutput>
4182 (The first part of this log message, showing the
4183 client address/port number and query name, is
4184 repeated in all subsequent log messages related
4191 <para><command>query-errors</command></para>
4195 Information about queries that resulted in some
4202 <para><command>dispatch</command></para>
4206 Dispatching of incoming packets to the
4207 server modules where they are to be processed.
4213 <para><command>dnssec</command></para>
4217 DNSSEC and TSIG protocol processing.
4223 <para><command>lame-servers</command></para>
4227 Lame servers. These are misconfigurations
4228 in remote servers, discovered by BIND 9 when trying to
4229 query those servers during resolution.
4235 <para><command>delegation-only</command></para>
4239 Delegation only. Logs queries that have been
4240 forced to NXDOMAIN as the result of a
4241 delegation-only zone or a
4242 <command>delegation-only</command> in a hint
4243 or stub zone declaration.
4249 <para><command>edns-disabled</command></para>
4253 Log queries that have been forced to use plain
4254 DNS due to timeouts. This is often due to
4255 the remote servers not being RFC 1034 compliant
4256 (not always returning FORMERR or similar to
4257 EDNS queries and other extensions to the DNS
4258 when they are not understood). In other words, this is
4259 targeted at servers that fail to respond to
4260 DNS queries that they don't understand.
4263 Note: the log message can also be due to
4264 packet loss. Before reporting servers for
4265 non-RFC 1034 compliance they should be re-tested
4266 to determine the nature of the non-compliance.
4267 This testing should prevent or reduce the
4268 number of false-positive reports.
4271 Note: eventually <command>named</command> will have to stop
4272 treating such timeouts as due to RFC 1034 non
4273 compliance and start treating it as plain
4274 packet loss. Falsely classifying packet
4275 loss as due to RFC 1034 non compliance impacts
4276 on DNSSEC validation which requires EDNS for
4277 the DNSSEC records to be returned.
4283 <para><command>RPZ</command></para>
4287 Information about errors in response policy zone files,
4288 rewritten responses, and at the highest
4289 <command>debug</command> levels, mere rewriting
4296 <para><command>rate-limit</command></para>
4300 (Only available when <acronym>BIND</acronym> 9 is
4301 configured with the <userinput>--enable-rrl</userinput>
4302 option at compile time.)
4305 The start, periodic, and final notices of the
4306 rate limiting of a stream of responses are logged at
4307 <command>info</command> severity in this category.
4308 These messages include a hash value of the domain name
4309 of the response and the name itself,
4310 except when there is insufficient memory to record
4311 the name for the final notice
4312 The final notice is normally delayed until about one
4313 minute after rate limit stops.
4314 A lack of memory can hurry the final notice,
4315 in which case it starts with an asterisk (*).
4316 Various internal events are logged at debug 1 level
4320 Rate limiting of individual requests
4321 is logged in the <command>query-errors</command> category.
4330 <title>The <command>query-errors</command> Category</title>
4332 The <command>query-errors</command> category is
4333 specifically intended for debugging purposes: To identify
4334 why and how specific queries result in responses which
4336 Messages of this category are therefore only logged
4337 with <command>debug</command> levels.
4341 At the debug levels of 1 or higher, each response with the
4342 rcode of SERVFAIL is logged as follows:
4345 <computeroutput>client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</computeroutput>
4348 This means an error resulting in SERVFAIL was
4349 detected at line 3880 of source file
4350 <filename>query.c</filename>.
4351 Log messages of this level will particularly
4352 help identify the cause of SERVFAIL for an
4353 authoritative server.
4356 At the debug levels of 2 or higher, detailed context
4357 information of recursive resolutions that resulted in
4359 The log message will look like as follows:
4362 <!-- NOTE: newlines and some spaces added so this would fit on page -->
4364 fetch completed at resolver.c:2970 for www.example.com/A
4365 in 30.000183: timed out/success [domain:example.com,
4366 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
4367 badresp:1,adberr:0,findfail:0,valfail:0]
4371 The first part before the colon shows that a recursive
4372 resolution for AAAA records of www.example.com completed
4373 in 30.000183 seconds and the final result that led to the
4374 SERVFAIL was determined at line 2970 of source file
4375 <filename>resolver.c</filename>.
4378 The following part shows the detected final result and the
4379 latest result of DNSSEC validation.
4380 The latter is always success when no validation attempt
4382 In this example, this query resulted in SERVFAIL probably
4383 because all name servers are down or unreachable, leading
4384 to a timeout in 30 seconds.
4385 DNSSEC validation was probably not attempted.
4388 The last part enclosed in square brackets shows statistics
4389 information collected for this particular resolution
4391 The <varname>domain</varname> field shows the deepest zone
4392 that the resolver reached;
4393 it is the zone where the error was finally detected.
4394 The meaning of the other fields is summarized in the
4398 <informaltable colsep="0" rowsep="0">
4399 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
4400 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
4401 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
4405 <para><varname>referral</varname></para>
4409 The number of referrals the resolver received
4410 throughout the resolution process.
4411 In the above example this is 2, which are most
4412 likely com and example.com.
4418 <para><varname>restart</varname></para>
4422 The number of cycles that the resolver tried
4423 remote servers at the <varname>domain</varname>
4425 In each cycle the resolver sends one query
4426 (possibly resending it, depending on the response)
4427 to each known name server of
4428 the <varname>domain</varname> zone.
4434 <para><varname>qrysent</varname></para>
4438 The number of queries the resolver sent at the
4439 <varname>domain</varname> zone.
4445 <para><varname>timeout</varname></para>
4449 The number of timeouts since the resolver
4450 received the last response.
4456 <para><varname>lame</varname></para>
4460 The number of lame servers the resolver detected
4461 at the <varname>domain</varname> zone.
4462 A server is detected to be lame either by an
4463 invalid response or as a result of lookup in
4464 BIND9's address database (ADB), where lame
4471 <para><varname>neterr</varname></para>
4475 The number of erroneous results that the
4476 resolver encountered in sending queries
4477 at the <varname>domain</varname> zone.
4478 One common case is the remote server is
4479 unreachable and the resolver receives an ICMP
4480 unreachable error message.
4486 <para><varname>badresp</varname></para>
4490 The number of unexpected responses (other than
4491 <varname>lame</varname>) to queries sent by the
4492 resolver at the <varname>domain</varname> zone.
4498 <para><varname>adberr</varname></para>
4502 Failures in finding remote server addresses
4503 of the <varname>domain</varname> zone in the ADB.
4504 One common case of this is that the remote
4505 server's name does not have any address records.
4511 <para><varname>findfail</varname></para>
4515 Failures of resolving remote server addresses.
4516 This is a total number of failures throughout
4517 the resolution process.
4523 <para><varname>valfail</varname></para>
4527 Failures of DNSSEC validation.
4528 Validation failures are counted throughout
4529 the resolution process (not limited to
4530 the <varname>domain</varname> zone), but should
4531 only happen in <varname>domain</varname>.
4539 At the debug levels of 3 or higher, the same messages
4540 as those at the debug 1 level are logged for other errors
4542 Note that negative responses such as NXDOMAIN are not
4543 regarded as errors here.
4546 At the debug levels of 4 or higher, the same messages
4547 as those at the debug 2 level are logged for other errors
4549 Unlike the above case of level 3, messages are logged for
4551 This is because any unexpected results can be difficult to
4552 debug in the recursion case.
4558 <title><command>lwres</command> Statement Grammar</title>
4561 This is the grammar of the <command>lwres</command>
4562 statement in the <filename>named.conf</filename> file:
4565 <programlisting><command>lwres</command> {
4566 <optional> listen-on { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
4567 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
4568 <optional> view <replaceable>view_name</replaceable>; </optional>
4569 <optional> search { <replaceable>domain_name</replaceable> ; <optional> <replaceable>domain_name</replaceable> ; ... </optional> }; </optional>
4570 <optional> ndots <replaceable>number</replaceable>; </optional>
4576 <title><command>lwres</command> Statement Definition and Usage</title>
4579 The <command>lwres</command> statement configures the
4581 server to also act as a lightweight resolver server. (See
4582 <xref linkend="lwresd"/>.) There may be multiple
4583 <command>lwres</command> statements configuring
4584 lightweight resolver servers with different properties.
4588 The <command>listen-on</command> statement specifies a
4590 addresses (and ports) that this instance of a lightweight resolver
4592 should accept requests on. If no port is specified, port 921 is
4594 If this statement is omitted, requests will be accepted on
4600 The <command>view</command> statement binds this
4602 lightweight resolver daemon to a view in the DNS namespace, so that
4604 response will be constructed in the same manner as a normal DNS
4606 matching this view. If this statement is omitted, the default view
4608 used, and if there is no default view, an error is triggered.
4612 The <command>search</command> statement is equivalent to
4614 <command>search</command> statement in
4615 <filename>/etc/resolv.conf</filename>. It provides a
4617 which are appended to relative names in queries.
4621 The <command>ndots</command> statement is equivalent to
4623 <command>ndots</command> statement in
4624 <filename>/etc/resolv.conf</filename>. It indicates the
4626 number of dots in a relative domain name that should result in an
4627 exact match lookup before search path elements are appended.
4631 <title><command>masters</command> Statement Grammar</title>
4634 <command>masters</command> <replaceable>name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> |
4635 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> };
4641 <title><command>masters</command> Statement Definition and
4643 <para><command>masters</command>
4644 lists allow for a common set of masters to be easily used by
4645 multiple stub and slave zones in their <command>masters</command>
4646 or <command>also-notify</command> lists.
4651 <title><command>options</command> Statement Grammar</title>
4654 This is the grammar of the <command>options</command>
4655 statement in the <filename>named.conf</filename> file:
4658 <programlisting><command>options</command> {
4659 <optional> attach-cache <replaceable>cache_name</replaceable>; </optional>
4660 <optional> version <replaceable>version_string</replaceable>; </optional>
4661 <optional> hostname <replaceable>hostname_string</replaceable>; </optional>
4662 <optional> server-id <replaceable>server_id_string</replaceable>; </optional>
4663 <optional> directory <replaceable>path_name</replaceable>; </optional>
4664 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
4665 <optional> managed-keys-directory <replaceable>path_name</replaceable>; </optional>
4666 <optional> named-xfer <replaceable>path_name</replaceable>; </optional>
4667 <optional> tkey-gssapi-keytab <replaceable>path_name</replaceable>; </optional>
4668 <optional> tkey-gssapi-credential <replaceable>principal</replaceable>; </optional>
4669 <optional> tkey-domain <replaceable>domainname</replaceable>; </optional>
4670 <optional> tkey-dhkey <replaceable>key_name</replaceable> <replaceable>key_tag</replaceable>; </optional>
4671 <optional> cache-file <replaceable>path_name</replaceable>; </optional>
4672 <optional> dump-file <replaceable>path_name</replaceable>; </optional>
4673 <optional> bindkeys-file <replaceable>path_name</replaceable>; </optional>
4674 <optional> secroots-file <replaceable>path_name</replaceable>; </optional>
4675 <optional> session-keyfile <replaceable>path_name</replaceable>; </optional>
4676 <optional> session-keyname <replaceable>key_name</replaceable>; </optional>
4677 <optional> session-keyalg <replaceable>algorithm_id</replaceable>; </optional>
4678 <optional> memstatistics <replaceable>yes_or_no</replaceable>; </optional>
4679 <optional> memstatistics-file <replaceable>path_name</replaceable>; </optional>
4680 <optional> pid-file <replaceable>path_name</replaceable>; </optional>
4681 <optional> recursing-file <replaceable>path_name</replaceable>; </optional>
4682 <optional> statistics-file <replaceable>path_name</replaceable>; </optional>
4683 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
4684 <optional> auth-nxdomain <replaceable>yes_or_no</replaceable>; </optional>
4685 <optional> deallocate-on-exit <replaceable>yes_or_no</replaceable>; </optional>
4686 <optional> dialup <replaceable>dialup_option</replaceable>; </optional>
4687 <optional> fake-iquery <replaceable>yes_or_no</replaceable>; </optional>
4688 <optional> fetch-glue <replaceable>yes_or_no</replaceable>; </optional>
4689 <optional> flush-zones-on-shutdown <replaceable>yes_or_no</replaceable>; </optional>
4690 <optional> has-old-clients <replaceable>yes_or_no</replaceable>; </optional>
4691 <optional> host-statistics <replaceable>yes_or_no</replaceable>; </optional>
4692 <optional> host-statistics-max <replaceable>number</replaceable>; </optional>
4693 <optional> minimal-responses <replaceable>yes_or_no</replaceable>; </optional>
4694 <optional> multiple-cnames <replaceable>yes_or_no</replaceable>; </optional>
4695 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable>; </optional>
4696 <optional> recursion <replaceable>yes_or_no</replaceable>; </optional>
4697 <optional> request-nsid <replaceable>yes_or_no</replaceable>; </optional>
4698 <optional> rfc2308-type1 <replaceable>yes_or_no</replaceable>; </optional>
4699 <optional> use-id-pool <replaceable>yes_or_no</replaceable>; </optional>
4700 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable>; </optional>
4701 <optional> ixfr-from-differences (<replaceable>yes_or_no</replaceable> | <constant>master</constant> | <constant>slave</constant>); </optional>
4702 <optional> dnssec-enable <replaceable>yes_or_no</replaceable>; </optional>
4703 <optional> dnssec-validation (<replaceable>yes_or_no</replaceable> | <constant>auto</constant>); </optional>
4704 <optional> dnssec-lookaside ( <replaceable>auto</replaceable> |
4705 <replaceable>no</replaceable> |
4706 <replaceable>domain</replaceable> trust-anchor <replaceable>domain</replaceable> ); </optional>
4707 <optional> dnssec-must-be-secure <replaceable>domain yes_or_no</replaceable>; </optional>
4708 <optional> dnssec-accept-expired <replaceable>yes_or_no</replaceable>; </optional>
4709 <optional> forward ( <replaceable>only</replaceable> | <replaceable>first</replaceable> ); </optional>
4710 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
4711 <optional> dual-stack-servers <optional>port <replaceable>ip_port</replaceable></optional> {
4712 ( <replaceable>domain_name</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> |
4713 <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ) ;
4715 <optional> check-names ( <replaceable>master</replaceable> | <replaceable>slave</replaceable> | <replaceable>response</replaceable> )
4716 ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4717 <optional> check-dup-records ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4718 <optional> check-mx ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4719 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
4720 <optional> check-integrity <replaceable>yes_or_no</replaceable>; </optional>
4721 <optional> check-mx-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4722 <optional> check-srv-cname ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4723 <optional> check-sibling <replaceable>yes_or_no</replaceable>; </optional>
4724 <optional> check-spf ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
4725 <optional> allow-new-zones { <replaceable>yes_or_no</replaceable> }; </optional>
4726 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
4727 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
4728 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
4729 <optional> allow-query-cache { <replaceable>address_match_list</replaceable> }; </optional>
4730 <optional> allow-query-cache-on { <replaceable>address_match_list</replaceable> }; </optional>
4731 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
4732 <optional> allow-recursion { <replaceable>address_match_list</replaceable> }; </optional>
4733 <optional> allow-recursion-on { <replaceable>address_match_list</replaceable> }; </optional>
4734 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
4735 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
4736 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
4737 <optional> dnssec-update-mode ( <replaceable>maintain</replaceable> | <replaceable>no-resign</replaceable> ); </optional>
4738 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
4739 <optional> dnssec-loadkeys-interval <replaceable>number</replaceable>; </optional>
4740 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ;</optional>
4741 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
4742 <optional> allow-v6-synthesis { <replaceable>address_match_list</replaceable> }; </optional>
4743 <optional> blackhole { <replaceable>address_match_list</replaceable> }; </optional>
4744 <optional> use-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4745 <optional> avoid-v4-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4746 <optional> use-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4747 <optional> avoid-v6-udp-ports { <replaceable>port_list</replaceable> }; </optional>
4748 <optional> listen-on <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
4749 <optional> listen-on-v6 <optional> port <replaceable>ip_port</replaceable> </optional> { <replaceable>address_match_list</replaceable> }; </optional>
4750 <optional> query-source ( ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> )
4751 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
4752 <optional> address ( <replaceable>ip4_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
4753 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
4754 <optional> query-source-v6 ( ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> )
4755 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> |
4756 <optional> address ( <replaceable>ip6_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
4757 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional> ) ; </optional>
4758 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
4759 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
4760 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
4761 <optional> max-transfer-time-in <replaceable>number</replaceable>; </optional>
4762 <optional> max-transfer-time-out <replaceable>number</replaceable>; </optional>
4763 <optional> max-transfer-idle-in <replaceable>number</replaceable>; </optional>
4764 <optional> max-transfer-idle-out <replaceable>number</replaceable>; </optional>
4765 <optional> tcp-clients <replaceable>number</replaceable>; </optional>
4766 <optional> reserved-sockets <replaceable>number</replaceable>; </optional>
4767 <optional> recursive-clients <replaceable>number</replaceable>; </optional>
4768 <optional> serial-query-rate <replaceable>number</replaceable>; </optional>
4769 <optional> serial-queries <replaceable>number</replaceable>; </optional>
4770 <optional> tcp-listen-queue <replaceable>number</replaceable>; </optional>
4771 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable>; </optional>
4772 <optional> transfers-in <replaceable>number</replaceable>; </optional>
4773 <optional> transfers-out <replaceable>number</replaceable>; </optional>
4774 <optional> transfers-per-ns <replaceable>number</replaceable>; </optional>
4775 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4776 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4777 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4778 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
4779 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4780 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
4781 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
4782 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4783 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
4784 <optional> notify-to-soa <replaceable>yes_or_no</replaceable> ; </optional>
4785 <optional> also-notify { <replaceable>ip_addr</replaceable>
4786 <optional>port <replaceable>ip_port</replaceable></optional> <optional>key <replaceable>keyname</replaceable></optional> ;
4787 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> <optional>key <replaceable>keyname</replaceable></optional> ; ... </optional> }; </optional>
4788 <optional> max-ixfr-log-size <replaceable>number</replaceable>; </optional>
4789 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
4790 <optional> coresize <replaceable>size_spec</replaceable> ; </optional>
4791 <optional> datasize <replaceable>size_spec</replaceable> ; </optional>
4792 <optional> files <replaceable>size_spec</replaceable> ; </optional>
4793 <optional> stacksize <replaceable>size_spec</replaceable> ; </optional>
4794 <optional> cleaning-interval <replaceable>number</replaceable>; </optional>
4795 <optional> heartbeat-interval <replaceable>number</replaceable>; </optional>
4796 <optional> interface-interval <replaceable>number</replaceable>; </optional>
4797 <optional> statistics-interval <replaceable>number</replaceable>; </optional>
4798 <optional> topology { <replaceable>address_match_list</replaceable> }</optional>;
4799 <optional> sortlist { <replaceable>address_match_list</replaceable> }</optional>;
4800 <optional> rrset-order { <replaceable>order_spec</replaceable> ; <optional> <replaceable>order_spec</replaceable> ; ... </optional> </optional> };
4801 <optional> lame-ttl <replaceable>number</replaceable>; </optional>
4802 <optional> max-ncache-ttl <replaceable>number</replaceable>; </optional>
4803 <optional> max-cache-ttl <replaceable>number</replaceable>; </optional>
4804 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
4805 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
4806 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
4807 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
4808 <optional> min-roots <replaceable>number</replaceable>; </optional>
4809 <optional> use-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
4810 <optional> provide-ixfr <replaceable>yes_or_no</replaceable>; </optional>
4811 <optional> request-ixfr <replaceable>yes_or_no</replaceable>; </optional>
4812 <optional> treat-cr-as-space <replaceable>yes_or_no</replaceable> ; </optional>
4813 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
4814 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
4815 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
4816 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
4817 <optional> port <replaceable>ip_port</replaceable>; </optional>
4818 <optional> additional-from-auth <replaceable>yes_or_no</replaceable> ; </optional>
4819 <optional> additional-from-cache <replaceable>yes_or_no</replaceable> ; </optional>
4820 <optional> random-device <replaceable>path_name</replaceable> ; </optional>
4821 <optional> max-cache-size <replaceable>size_spec</replaceable> ; </optional>
4822 <optional> match-mapped-addresses <replaceable>yes_or_no</replaceable>; </optional>
4823 <optional> filter-aaaa-on-v4 ( <replaceable>yes_or_no</replaceable> | <replaceable>break-dnssec</replaceable> ); </optional>
4824 <optional> filter-aaaa { <replaceable>address_match_list</replaceable> }; </optional>
4825 <optional> dns64 <replaceable>ipv6-prefix</replaceable> {
4826 <optional> clients { <replaceable>address_match_list</replaceable> }; </optional>
4827 <optional> mapped { <replaceable>address_match_list</replaceable> }; </optional>
4828 <optional> exclude { <replaceable>address_match_list</replaceable> }; </optional>
4829 <optional> suffix IPv6-address; </optional>
4830 <optional> recursive-only <replaceable>yes_or_no</replaceable>; </optional>
4831 <optional> break-dnssec <replaceable>yes_or_no</replaceable>; </optional>
4833 <optional> dns64-server <replaceable>name</replaceable> </optional>
4834 <optional> dns64-contact <replaceable>name</replaceable> </optional>
4835 <optional> preferred-glue ( <replaceable>A</replaceable> | <replaceable>AAAA</replaceable> | <replaceable>NONE</replaceable> ); </optional>
4836 <optional> edns-udp-size <replaceable>number</replaceable>; </optional>
4837 <optional> max-udp-size <replaceable>number</replaceable>; </optional>
4838 <optional> max-rsa-exponent-size <replaceable>number</replaceable>; </optional>
4839 <optional> root-delegation-only <optional> exclude { <replaceable>namelist</replaceable> } </optional> ; </optional>
4840 <optional> querylog <replaceable>yes_or_no</replaceable> ; </optional>
4841 <optional> disable-algorithms <replaceable>domain</replaceable> { <replaceable>algorithm</replaceable>;
4842 <optional> <replaceable>algorithm</replaceable>; </optional> }; </optional>
4843 <optional> acache-enable <replaceable>yes_or_no</replaceable> ; </optional>
4844 <optional> acache-cleaning-interval <replaceable>number</replaceable>; </optional>
4845 <optional> max-acache-size <replaceable>size_spec</replaceable> ; </optional>
4846 <optional> clients-per-query <replaceable>number</replaceable> ; </optional>
4847 <optional> max-clients-per-query <replaceable>number</replaceable> ; </optional>
4848 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
4849 <optional> empty-server <replaceable>name</replaceable> ; </optional>
4850 <optional> empty-contact <replaceable>name</replaceable> ; </optional>
4851 <optional> empty-zones-enable <replaceable>yes_or_no</replaceable> ; </optional>
4852 <optional> disable-empty-zone <replaceable>zone_name</replaceable> ; </optional>
4853 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
4854 <optional> zero-no-soa-ttl-cache <replaceable>yes_or_no</replaceable> ; </optional>
4855 <optional> resolver-query-timeout <replaceable>number</replaceable> ; </optional>
4856 <optional> deny-answer-addresses { <replaceable>address_match_list</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
4857 <optional> deny-answer-aliases { <replaceable>namelist</replaceable> } <optional> except-from { <replaceable>namelist</replaceable> } </optional>;</optional>
4858 <optional> rate-limit {
4859 <optional> responses-per-second <replaceable>number</replaceable> ; </optional>
4860 <optional> referrals-per-second <replaceable>number</replaceable> ; </optional>
4861 <optional> nodata-per-second <replaceable>number</replaceable> ; </optional>
4862 <optional> nxdomains-per-second <replaceable>number</replaceable> ; </optional>
4863 <optional> errors-per-second <replaceable>number</replaceable> ; </optional>
4864 <optional> all-per-second <replaceable>number</replaceable> ; </optional>
4865 <optional> window <replaceable>number</replaceable> ; </optional>
4866 <optional> log-only <replaceable>yes_or_no</replaceable> ; </optional>
4867 <optional> qps-scale <replaceable>number</replaceable> ; </optional>
4868 <optional> ipv4-prefix-length <replaceable>number</replaceable> ; </optional>
4869 <optional> ipv6-prefix-length <replaceable>number</replaceable> ; </optional>
4870 <optional> slip <replaceable>number</replaceable> ; </optional>
4871 <optional> exempt-clients { <replaceable>address_match_list</replaceable> } ; </optional>
4872 <optional> max-table-size <replaceable>number</replaceable> ; </optional>
4873 <optional> min-table-size <replaceable>number</replaceable> ; </optional>
4875 <optional> response-policy { <replaceable>zone_name</replaceable>
4876 <optional> policy given | disabled | passthru | nxdomain | nodata | cname <replaceable>domain</replaceable> </optional>
4877 <optional> recursive-only <replaceable>yes_or_no</replaceable> </optional> <optional> max-policy-ttl <replaceable>number</replaceable> </optional> ;
4878 } <optional> recursive-only <replaceable>yes_or_no</replaceable> </optional> <optional> max-policy-ttl <replaceable>number</replaceable> </optional>
4879 <optional> break-dnssec <replaceable>yes_or_no</replaceable> </optional> <optional> min-ns-dots <replaceable>number</replaceable> </optional> ; </optional>
4885 <sect2 id="options">
4886 <title><command>options</command> Statement Definition and
4890 The <command>options</command> statement sets up global
4892 to be used by <acronym>BIND</acronym>. This statement
4894 once in a configuration file. If there is no <command>options</command>
4895 statement, an options block with each option set to its default will
4902 <term><command>attach-cache</command></term>
4905 Allows multiple views to share a single cache
4907 Each view has its own cache database by default, but
4908 if multiple views have the same operational policy
4909 for name resolution and caching, those views can
4910 share a single cache to save memory and possibly
4911 improve resolution efficiency by using this option.
4915 The <command>attach-cache</command> option
4916 may also be specified in <command>view</command>
4917 statements, in which case it overrides the
4918 global <command>attach-cache</command> option.
4922 The <replaceable>cache_name</replaceable> specifies
4923 the cache to be shared.
4924 When the <command>named</command> server configures
4925 views which are supposed to share a cache, it
4926 creates a cache with the specified name for the
4927 first view of these sharing views.
4928 The rest of the views will simply refer to the
4929 already created cache.
4933 One common configuration to share a cache would be to
4934 allow all views to share a single cache.
4935 This can be done by specifying
4936 the <command>attach-cache</command> as a global
4937 option with an arbitrary name.
4941 Another possible operation is to allow a subset of
4942 all views to share a cache while the others to
4943 retain their own caches.
4944 For example, if there are three views A, B, and C,
4945 and only A and B should share a cache, specify the
4946 <command>attach-cache</command> option as a view A (or
4947 B)'s option, referring to the other view name:
4952 // this view has its own cache
4956 // this view refers to A's cache
4960 // this view has its own cache
4966 Views that share a cache must have the same policy
4967 on configurable parameters that may affect caching.
4968 The current implementation requires the following
4969 configurable options be consistent among these
4971 <command>check-names</command>,
4972 <command>cleaning-interval</command>,
4973 <command>dnssec-accept-expired</command>,
4974 <command>dnssec-validation</command>,
4975 <command>max-cache-ttl</command>,
4976 <command>max-ncache-ttl</command>,
4977 <command>max-cache-size</command>, and
4978 <command>zero-no-soa-ttl</command>.
4982 Note that there may be other parameters that may
4983 cause confusion if they are inconsistent for
4984 different views that share a single cache.
4985 For example, if these views define different sets of
4986 forwarders that can return different answers for the
4987 same question, sharing the answer does not make
4988 sense or could even be harmful.
4989 It is administrator's responsibility to ensure
4990 configuration differences in different views do
4991 not cause disruption with a shared cache.
4998 <term><command>directory</command></term>
5001 The working directory of the server.
5002 Any non-absolute pathnames in the configuration file will be
5004 as relative to this directory. The default location for most
5006 output files (e.g. <filename>named.run</filename>)
5008 If a directory is not specified, the working directory
5009 defaults to `<filename>.</filename>', the directory from
5011 was started. The directory specified should be an absolute
5018 <term><command>key-directory</command></term>
5021 When performing dynamic update of secure zones, the
5022 directory where the public and private DNSSEC key files
5023 should be found, if different than the current working
5024 directory. (Note that this option has no effect on the
5025 paths for files containing non-DNSSEC keys such as
5026 <filename>bind.keys</filename>,
5027 <filename>rndc.key</filename> or
5028 <filename>session.key</filename>.)
5034 <term><command>managed-keys-directory</command></term>
5037 Specifies the directory in which to store the files that
5038 track managed DNSSEC keys. By default, this is the working
5042 If <command>named</command> is not configured to use views,
5043 then managed keys for the server will be tracked in a single
5044 file called <filename>managed-keys.bind</filename>.
5045 Otherwise, managed keys will be tracked in separate files,
5046 one file per view; each file name will be the SHA256 hash
5047 of the view name, followed by the extension
5048 <filename>.mkeys</filename>.
5054 <term><command>named-xfer</command></term>
5057 <emphasis>This option is obsolete.</emphasis> It
5058 was used in <acronym>BIND</acronym> 8 to specify
5059 the pathname to the <command>named-xfer</command>
5060 program. In <acronym>BIND</acronym> 9, no separate
5061 <command>named-xfer</command> program is needed;
5062 its functionality is built into the name server.
5068 <term><command>tkey-gssapi-keytab</command></term>
5071 The KRB5 keytab file to use for GSS-TSIG updates. If
5072 this option is set and tkey-gssapi-credential is not
5073 set, then updates will be allowed with any key
5074 matching a principal in the specified keytab.
5080 <term><command>tkey-gssapi-credential</command></term>
5083 The security credential with which the server should
5084 authenticate keys requested by the GSS-TSIG protocol.
5085 Currently only Kerberos 5 authentication is available
5086 and the credential is a Kerberos principal which the
5087 server can acquire through the default system key
5088 file, normally <filename>/etc/krb5.keytab</filename>.
5089 The location keytab file can be overridden using the
5090 tkey-gssapi-keytab option. Normally this principal is
5091 of the form "<userinput>DNS/</userinput><varname>server.domain</varname>".
5092 To use GSS-TSIG, <command>tkey-domain</command> must
5093 also be set if a specific keytab is not set with
5100 <term><command>tkey-domain</command></term>
5103 The domain appended to the names of all shared keys
5104 generated with <command>TKEY</command>. When a
5105 client requests a <command>TKEY</command> exchange,
5106 it may or may not specify the desired name for the
5107 key. If present, the name of the shared key will
5108 be <varname>client specified part</varname> +
5109 <varname>tkey-domain</varname>. Otherwise, the
5110 name of the shared key will be <varname>random hex
5111 digits</varname> + <varname>tkey-domain</varname>.
5112 In most cases, the <command>domainname</command>
5113 should be the server's domain name, or an otherwise
5114 non-existent subdomain like
5115 "_tkey.<varname>domainname</varname>". If you are
5116 using GSS-TSIG, this variable must be defined, unless
5117 you specify a specific keytab using tkey-gssapi-keytab.
5123 <term><command>tkey-dhkey</command></term>
5126 The Diffie-Hellman key used by the server
5127 to generate shared keys with clients using the Diffie-Hellman
5129 of <command>TKEY</command>. The server must be
5131 public and private keys from files in the working directory.
5133 most cases, the keyname should be the server's host name.
5139 <term><command>cache-file</command></term>
5142 This is for testing only. Do not use.
5148 <term><command>dump-file</command></term>
5151 The pathname of the file the server dumps
5152 the database to when instructed to do so with
5153 <command>rndc dumpdb</command>.
5154 If not specified, the default is <filename>named_dump.db</filename>.
5160 <term><command>memstatistics-file</command></term>
5163 The pathname of the file the server writes memory
5164 usage statistics to on exit. If not specified,
5165 the default is <filename>named.memstats</filename>.
5171 <term><command>pid-file</command></term>
5174 The pathname of the file the server writes its process ID
5175 in. If not specified, the default is
5176 <filename>/var/run/named/named.pid</filename>.
5177 The PID file is used by programs that want to send signals to
5179 name server. Specifying <command>pid-file none</command> disables the
5180 use of a PID file — no file will be written and any
5181 existing one will be removed. Note that <command>none</command>
5182 is a keyword, not a filename, and therefore is not enclosed
5190 <term><command>recursing-file</command></term>
5193 The pathname of the file the server dumps
5194 the queries that are currently recursing when instructed
5195 to do so with <command>rndc recursing</command>.
5196 If not specified, the default is <filename>named.recursing</filename>.
5202 <term><command>statistics-file</command></term>
5205 The pathname of the file the server appends statistics
5206 to when instructed to do so using <command>rndc stats</command>.
5207 If not specified, the default is <filename>named.stats</filename> in the
5208 server's current directory. The format of the file is
5210 in <xref linkend="statsfile"/>.
5216 <term><command>bindkeys-file</command></term>
5219 The pathname of a file to override the built-in trusted
5220 keys provided by <command>named</command>.
5221 See the discussion of <command>dnssec-lookaside</command>
5222 and <command>dnssec-validation</command> for details.
5223 If not specified, the default is
5224 <filename>/etc/bind.keys</filename>.
5230 <term><command>secroots-file</command></term>
5233 The pathname of the file the server dumps
5234 security roots to when instructed to do so with
5235 <command>rndc secroots</command>.
5236 If not specified, the default is
5237 <filename>named.secroots</filename>.
5243 <term><command>session-keyfile</command></term>
5246 The pathname of the file into which to write a TSIG
5247 session key generated by <command>named</command> for use by
5248 <command>nsupdate -l</command>. If not specified, the
5249 default is <filename>/var/run/named/session.key</filename>.
5250 (See <xref linkend="dynamic_update_policies"/>, and in
5251 particular the discussion of the
5252 <command>update-policy</command> statement's
5253 <userinput>local</userinput> option for more
5254 information about this feature.)
5260 <term><command>session-keyname</command></term>
5263 The key name to use for the TSIG session key.
5264 If not specified, the default is "local-ddns".
5270 <term><command>session-keyalg</command></term>
5273 The algorithm to use for the TSIG session key.
5274 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
5275 hmac-sha384, hmac-sha512 and hmac-md5. If not
5276 specified, the default is hmac-sha256.
5282 <term><command>port</command></term>
5285 The UDP/TCP port number the server uses for
5286 receiving and sending DNS protocol traffic.
5287 The default is 53. This option is mainly intended for server
5289 a server using a port other than 53 will not be able to
5297 <term><command>random-device</command></term>
5300 The source of entropy to be used by the server. Entropy is
5302 for DNSSEC operations, such as TKEY transactions and dynamic
5304 zones. This options specifies the device (or file) from which
5306 entropy. If this is a file, operations requiring entropy will
5308 file has been exhausted. If not specified, the default value
5310 <filename>/dev/random</filename>
5311 (or equivalent) when present, and none otherwise. The
5312 <command>random-device</command> option takes
5314 the initial configuration load at server startup time and
5315 is ignored on subsequent reloads.
5321 <term><command>preferred-glue</command></term>
5324 If specified, the listed type (A or AAAA) will be emitted
5326 in the additional section of a query response.
5327 The default is not to prefer any type (NONE).
5332 <varlistentry id="root_delegation_only">
5333 <term><command>root-delegation-only</command></term>
5336 Turn on enforcement of delegation-only in TLDs
5337 (top level domains) and root zones with an optional
5341 DS queries are expected to be made to and be answered by
5342 delegation only zones. Such queries and responses are
5343 treated as an exception to delegation-only processing
5344 and are not converted to NXDOMAIN responses provided
5345 a CNAME is not discovered at the query name.
5348 If a delegation only zone server also serves a child
5349 zone it is not always possible to determine whether
5350 an answer comes from the delegation only zone or the
5351 child zone. SOA NS and DNSKEY records are apex
5352 only records and a matching response that contains
5353 these records or DS is treated as coming from a
5354 child zone. RRSIG records are also examined to see
5355 if they are signed by a child zone or not. The
5356 authority section is also examined to see if there
5357 is evidence that the answer is from the child zone.
5358 Answers that are determined to be from a child zone
5359 are not converted to NXDOMAIN responses. Despite
5360 all these checks there is still a possibility of
5361 false negatives when a child zone is being served.
5364 Similarly false positives can arise from empty nodes
5365 (no records at the name) in the delegation only zone
5366 when the query type is not ANY.
5369 Note some TLDs are not delegation only (e.g. "DE", "LV",
5370 "US" and "MUSEUM"). This list is not exhaustive.
5375 root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
5383 <term><command>disable-algorithms</command></term>
5386 Disable the specified DNSSEC algorithms at and below the
5388 Multiple <command>disable-algorithms</command>
5389 statements are allowed.
5390 Only the most specific will be applied.
5396 <term><command>dnssec-lookaside</command></term>
5399 When set, <command>dnssec-lookaside</command> provides the
5400 validator with an alternate method to validate DNSKEY
5401 records at the top of a zone. When a DNSKEY is at or
5402 below a domain specified by the deepest
5403 <command>dnssec-lookaside</command>, and the normal DNSSEC
5404 validation has left the key untrusted, the trust-anchor
5405 will be appended to the key name and a DLV record will be
5406 looked up to see if it can validate the key. If the DLV
5407 record validates a DNSKEY (similarly to the way a DS
5408 record does) the DNSKEY RRset is deemed to be trusted.
5411 If <command>dnssec-lookaside</command> is set to
5412 <userinput>auto</userinput>, then built-in default
5413 values for the DLV domain and trust anchor will be
5414 used, along with a built-in key for validation.
5417 If <command>dnssec-lookaside</command> is set to
5418 <userinput>no</userinput>, then dnssec-lookaside
5422 The default DLV key is stored in the file
5423 <filename>bind.keys</filename>;
5424 <command>named</command> will load that key at
5425 startup if <command>dnssec-lookaside</command> is set to
5426 <constant>auto</constant>. A copy of the file is
5427 installed along with <acronym>BIND</acronym> 9, and is
5428 current as of the release date. If the DLV key expires, a
5429 new copy of <filename>bind.keys</filename> can be downloaded
5430 from <ulink url="https://www.isc.org/solutions/dlv/"
5431 >https://www.isc.org/solutions/dlv/</ulink>.
5434 (To prevent problems if <filename>bind.keys</filename> is
5435 not found, the current key is also compiled in to
5436 <command>named</command>. Relying on this is not
5437 recommended, however, as it requires <command>named</command>
5438 to be recompiled with a new key when the DLV key expires.)
5441 NOTE: <command>named</command> only loads certain specific
5442 keys from <filename>bind.keys</filename>: those for the
5443 DLV zone and for the DNS root zone. The file cannot be
5444 used to store keys for other zones.
5450 <term><command>dnssec-must-be-secure</command></term>
5453 Specify hierarchies which must be or may not be secure
5454 (signed and validated). If <userinput>yes</userinput>,
5455 then <command>named</command> will only accept answers if
5456 they are secure. If <userinput>no</userinput>, then normal
5457 DNSSEC validation applies allowing for insecure answers to
5458 be accepted. The specified domain must be under a
5459 <command>trusted-keys</command> or
5460 <command>managed-keys</command> statement, or
5461 <command>dnssec-lookaside</command> must be active.
5467 <term><command>dns64</command></term>
5470 This directive instructs <command>named</command> to
5471 return mapped IPv4 addresses to AAAA queries when
5472 there are no AAAA records. It is intended to be
5473 used in conjunction with a NAT64. Each
5474 <command>dns64</command> defines one DNS64 prefix.
5475 Multiple DNS64 prefixes can be defined.
5478 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
5479 64 and 96 as per RFC 6052.
5482 Additionally a reverse IP6.ARPA zone will be created for
5483 the prefix to provide a mapping from the IP6.ARPA names
5484 to the corresponding IN-ADDR.ARPA names using synthesized
5485 CNAMEs. <command>dns64-server</command> and
5486 <command>dns64-contact</command> can be used to specify
5487 the name of the server and contact for the zones. These
5488 are settable at the view / options level. These are
5489 not settable on a per-prefix basis.
5492 Each <command>dns64</command> supports an optional
5493 <command>clients</command> ACL that determines which
5494 clients are affected by this directive. If not defined,
5495 it defaults to <userinput>any;</userinput>.
5498 Each <command>dns64</command> supports an optional
5499 <command>mapped</command> ACL that selects which
5500 IPv4 addresses are to be mapped in the corresponding
5501 A RRset. If not defined it defaults to
5502 <userinput>any;</userinput>.
5505 Normally, DNS64 won't apply to a domain name that
5506 owns one or more AAAA records; these records will
5507 simply be returned. The optional
5508 <command>exclude</command> ACL allows specification
5509 of a list of IPv6 addresses that will be ignored
5510 if they appear in a domain name's AAAA records, and
5511 DNS64 will be applied to any A records the domain
5512 name owns. If not defined, <command>exclude</command>
5516 A optional <command>suffix</command> can also
5517 be defined to set the bits trailing the mapped
5518 IPv4 address bits. By default these bits are
5519 set to <userinput>::</userinput>. The bits
5520 matching the prefix and mapped IPv4 address
5524 If <command>recursive-only</command> is set to
5525 <command>yes</command> the DNS64 synthesis will
5526 only happen for recursive queries. The default
5527 is <command>no</command>.
5530 If <command>break-dnssec</command> is set to
5531 <command>yes</command> the DNS64 synthesis will
5532 happen even if the result, if validated, would
5533 cause a DNSSEC validation failure. If this option
5534 is set to <command>no</command> (the default), the DO
5535 is set on the incoming query, and there are RRSIGs on
5536 the applicable records, then synthesis will not happen.
5539 acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
5541 dns64 64:FF9B::/96 {
5543 mapped { !rfc1918; any; };
5544 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
5552 <term><command>dnssec-update-mode</command></term>
5555 If this option is set to its default value of
5556 <literal>maintain</literal> in a zone of type
5557 <literal>master</literal> which is DNSSEC-signed
5558 and configured to allow dynamic updates (see
5559 <xref linkend="dynamic_update_policies"/>), and
5560 if <command>named</command> has access to the
5561 private signing key(s) for the zone, then
5562 <command>named</command> will automatically sign all new
5563 or changed records and maintain signatures for the zone
5564 by regenerating RRSIG records whenever they approach
5565 their expiration date.
5568 If the option is changed to <literal>no-resign</literal>,
5569 then <command>named</command> will sign all new or
5570 changed records, but scheduled maintenance of
5571 signatures is disabled.
5574 With either of these settings, <command>named</command>
5575 will reject updates to a DNSSEC-signed zone when the
5576 signing keys are inactive or unavailable to
5577 <command>named</command>. (A planned third option,
5578 <literal>external</literal>, will disable all automatic
5579 signing and allow DNSSEC data to be submitted into a zone
5580 via dynamic update; this is not yet implemented.)
5586 <term><command>zone-statistics</command></term>
5589 If <userinput>full</userinput>, the server will collect
5590 statistical data on all zones (unless specifically
5591 turned off on a per-zone basis by specifying
5592 <command>zone-statistics terse</command> or
5593 <command>zone-statistics none</command>
5594 in the <command>zone</command> statement).
5595 The default is <userinput>terse</userinput>, providing
5596 minimal statistics on zones (including name and
5597 current serial number, but not query type
5601 These statistics may be accessed via the
5602 <command>statistics-channel</command> or
5603 using <command>rndc stats</command>, which
5604 will dump them to the file listed
5605 in the <command>statistics-file</command>. See
5606 also <xref linkend="statsfile"/>.
5609 For backward compatibility with earlier versions
5610 of BIND 9, the <command>zone-statistics</command>
5611 option can also accept <userinput>yes</userinput>
5612 or <userinput>no</userinput>, which have the same
5613 effect as <userinput>full</userinput> and
5614 <userinput>terse</userinput>, respectively.
5620 <sect3 id="boolean_options">
5621 <title>Boolean Options</title>
5626 <term><command>allow-new-zones</command></term>
5629 If <userinput>yes</userinput>, then zones can be
5630 added at runtime via <command>rndc addzone</command>
5631 or deleted via <command>rndc delzone</command>.
5632 The default is <userinput>no</userinput>.
5638 <term><command>auth-nxdomain</command></term>
5641 If <userinput>yes</userinput>, then the <command>AA</command> bit
5642 is always set on NXDOMAIN responses, even if the server is
5644 authoritative. The default is <userinput>no</userinput>;
5646 a change from <acronym>BIND</acronym> 8. If you
5647 are using very old DNS software, you
5648 may need to set it to <userinput>yes</userinput>.
5654 <term><command>deallocate-on-exit</command></term>
5657 This option was used in <acronym>BIND</acronym>
5658 8 to enable checking
5659 for memory leaks on exit. <acronym>BIND</acronym> 9 ignores the option and always performs
5666 <term><command>memstatistics</command></term>
5669 Write memory statistics to the file specified by
5670 <command>memstatistics-file</command> at exit.
5671 The default is <userinput>no</userinput> unless
5672 '-m record' is specified on the command line in
5673 which case it is <userinput>yes</userinput>.
5679 <term><command>dialup</command></term>
5682 If <userinput>yes</userinput>, then the
5683 server treats all zones as if they are doing zone transfers
5685 a dial-on-demand dialup link, which can be brought up by
5687 originating from this server. This has different effects
5689 to zone type and concentrates the zone maintenance so that
5691 happens in a short interval, once every <command>heartbeat-interval</command> and
5692 hopefully during the one call. It also suppresses some of
5694 zone maintenance traffic. The default is <userinput>no</userinput>.
5697 The <command>dialup</command> option
5698 may also be specified in the <command>view</command> and
5699 <command>zone</command> statements,
5700 in which case it overrides the global <command>dialup</command>
5704 If the zone is a master zone, then the server will send out a
5706 request to all the slaves (default). This should trigger the
5708 number check in the slave (providing it supports NOTIFY)
5710 to verify the zone while the connection is active.
5711 The set of servers to which NOTIFY is sent can be controlled
5713 <command>notify</command> and <command>also-notify</command>.
5717 zone is a slave or stub zone, then the server will suppress
5719 "zone up to date" (refresh) queries and only perform them
5721 <command>heartbeat-interval</command> expires in
5726 Finer control can be achieved by using
5727 <userinput>notify</userinput> which only sends NOTIFY
5729 <userinput>notify-passive</userinput> which sends NOTIFY
5731 suppresses the normal refresh queries, <userinput>refresh</userinput>
5732 which suppresses normal refresh processing and sends refresh
5734 when the <command>heartbeat-interval</command>
5736 <userinput>passive</userinput> which just disables normal
5741 <informaltable colsep="0" rowsep="0">
5742 <tgroup cols="4" colsep="0" rowsep="0" tgroupstyle="4Level-table">
5743 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
5744 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
5745 <colspec colname="3" colnum="3" colsep="0" colwidth="1.150in"/>
5746 <colspec colname="4" colnum="4" colsep="0" colwidth="1.150in"/>
5772 <para><command>no</command> (default)</para>
5792 <para><command>yes</command></para>
5812 <para><command>notify</command></para>
5832 <para><command>refresh</command></para>
5852 <para><command>passive</command></para>
5872 <para><command>notify-passive</command></para>
5895 Note that normal NOTIFY processing is not affected by
5896 <command>dialup</command>.
5903 <term><command>fake-iquery</command></term>
5906 In <acronym>BIND</acronym> 8, this option
5907 enabled simulating the obsolete DNS query type
5908 IQUERY. <acronym>BIND</acronym> 9 never does
5915 <term><command>fetch-glue</command></term>
5918 This option is obsolete.
5919 In BIND 8, <userinput>fetch-glue yes</userinput>
5920 caused the server to attempt to fetch glue resource records
5922 didn't have when constructing the additional
5923 data section of a response. This is now considered a bad
5925 and BIND 9 never does it.
5931 <term><command>flush-zones-on-shutdown</command></term>
5934 When the nameserver exits due receiving SIGTERM,
5935 flush or do not flush any pending zone writes. The default
5937 <command>flush-zones-on-shutdown</command> <userinput>no</userinput>.
5943 <term><command>has-old-clients</command></term>
5946 This option was incorrectly implemented
5947 in <acronym>BIND</acronym> 8, and is ignored by <acronym>BIND</acronym> 9.
5948 To achieve the intended effect
5950 <command>has-old-clients</command> <userinput>yes</userinput>, specify
5951 the two separate options <command>auth-nxdomain</command> <userinput>yes</userinput>
5952 and <command>rfc2308-type1</command> <userinput>no</userinput> instead.
5958 <term><command>host-statistics</command></term>
5961 In BIND 8, this enables keeping of
5962 statistics for every host that the name server interacts
5964 Not implemented in BIND 9.
5970 <term><command>maintain-ixfr-base</command></term>
5973 <emphasis>This option is obsolete</emphasis>.
5974 It was used in <acronym>BIND</acronym> 8 to
5975 determine whether a transaction log was
5976 kept for Incremental Zone Transfer. <acronym>BIND</acronym> 9 maintains a transaction
5977 log whenever possible. If you need to disable outgoing
5979 transfers, use <command>provide-ixfr</command> <userinput>no</userinput>.
5985 <term><command>minimal-responses</command></term>
5988 If <userinput>yes</userinput>, then when generating
5989 responses the server will only add records to the authority
5990 and additional data sections when they are required (e.g.
5991 delegations, negative responses). This may improve the
5992 performance of the server.
5993 The default is <userinput>no</userinput>.
5999 <term><command>multiple-cnames</command></term>
6002 This option was used in <acronym>BIND</acronym> 8 to allow
6003 a domain name to have multiple CNAME records in violation of
6004 the DNS standards. <acronym>BIND</acronym> 9.2 onwards
6005 always strictly enforces the CNAME rules both in master
6006 files and dynamic updates.
6012 <term><command>notify</command></term>
6015 If <userinput>yes</userinput> (the default),
6016 DNS NOTIFY messages are sent when a zone the server is
6018 changes, see <xref linkend="notify"/>. The messages are
6020 servers listed in the zone's NS records (except the master
6022 in the SOA MNAME field), and to any servers listed in the
6023 <command>also-notify</command> option.
6026 If <userinput>master-only</userinput>, notifies are only
6029 If <userinput>explicit</userinput>, notifies are sent only
6031 servers explicitly listed using <command>also-notify</command>.
6032 If <userinput>no</userinput>, no notifies are sent.
6035 The <command>notify</command> option may also be
6036 specified in the <command>zone</command>
6038 in which case it overrides the <command>options notify</command> statement.
6039 It would only be necessary to turn off this option if it
6047 <term><command>notify-to-soa</command></term>
6050 If <userinput>yes</userinput> do not check the nameservers
6051 in the NS RRset against the SOA MNAME. Normally a NOTIFY
6052 message is not sent to the SOA MNAME (SOA ORIGIN) as it is
6053 supposed to contain the name of the ultimate master.
6054 Sometimes, however, a slave is listed as the SOA MNAME in
6055 hidden master configurations and in that case you would
6056 want the ultimate master to still send NOTIFY messages to
6057 all the nameservers listed in the NS RRset.
6063 <term><command>recursion</command></term>
6066 If <userinput>yes</userinput>, and a
6067 DNS query requests recursion, then the server will attempt
6069 all the work required to answer the query. If recursion is
6071 and the server does not already know the answer, it will
6073 referral response. The default is
6074 <userinput>yes</userinput>.
6075 Note that setting <command>recursion no</command> does not prevent
6076 clients from getting data from the server's cache; it only
6077 prevents new data from being cached as an effect of client
6079 Caching may still occur as an effect the server's internal
6080 operation, such as NOTIFY address lookups.
6081 See also <command>fetch-glue</command> above.
6087 <term><command>request-nsid</command></term>
6090 If <userinput>yes</userinput>, then an empty EDNS(0)
6091 NSID (Name Server Identifier) option is sent with all
6092 queries to authoritative name servers during iterative
6093 resolution. If the authoritative server returns an NSID
6094 option in its response, then its contents are logged in
6095 the <command>resolver</command> category at level
6096 <command>info</command>.
6097 The default is <userinput>no</userinput>.
6103 <term><command>rfc2308-type1</command></term>
6106 Setting this to <userinput>yes</userinput> will
6107 cause the server to send NS records along with the SOA
6109 answers. The default is <userinput>no</userinput>.
6113 Not yet implemented in <acronym>BIND</acronym>
6121 <term><command>use-id-pool</command></term>
6124 <emphasis>This option is obsolete</emphasis>.
6125 <acronym>BIND</acronym> 9 always allocates query
6132 <term><command>use-ixfr</command></term>
6135 <emphasis>This option is obsolete</emphasis>.
6136 If you need to disable IXFR to a particular server or
6138 the information on the <command>provide-ixfr</command> option
6139 in <xref linkend="server_statement_definition_and_usage"/>.
6141 <xref linkend="incremental_zone_transfers"/>.
6147 <term><command>provide-ixfr</command></term>
6150 See the description of
6151 <command>provide-ixfr</command> in
6152 <xref linkend="server_statement_definition_and_usage"/>.
6158 <term><command>request-ixfr</command></term>
6161 See the description of
6162 <command>request-ixfr</command> in
6163 <xref linkend="server_statement_definition_and_usage"/>.
6169 <term><command>treat-cr-as-space</command></term>
6172 This option was used in <acronym>BIND</acronym>
6174 the server treat carriage return ("<command>\r</command>") characters the same way
6175 as a space or tab character,
6176 to facilitate loading of zone files on a UNIX system that
6178 on an NT or DOS machine. In <acronym>BIND</acronym> 9, both UNIX "<command>\n</command>"
6179 and NT/DOS "<command>\r\n</command>" newlines
6180 are always accepted,
6181 and the option is ignored.
6187 <term><command>additional-from-auth</command></term>
6188 <term><command>additional-from-cache</command></term>
6192 These options control the behavior of an authoritative
6194 answering queries which have additional data, or when
6200 When both of these options are set to <userinput>yes</userinput>
6202 query is being answered from authoritative data (a zone
6203 configured into the server), the additional data section of
6205 reply will be filled in using data from other authoritative
6207 and from the cache. In some situations this is undesirable,
6209 as when there is concern over the correctness of the cache,
6211 in servers where slave zones may be added and modified by
6212 untrusted third parties. Also, avoiding
6213 the search for this additional data will speed up server
6215 at the possible expense of additional queries to resolve
6217 otherwise be provided in the additional section.
6221 For example, if a query asks for an MX record for host <literal>foo.example.com</literal>,
6222 and the record found is "<literal>MX 10 mail.example.net</literal>", normally the address
6223 records (A and AAAA) for <literal>mail.example.net</literal> will be provided as well,
6224 if known, even though they are not in the example.com zone.
6225 Setting these options to <command>no</command>
6226 disables this behavior and makes
6227 the server only search for additional data in the zone it
6232 These options are intended for use in authoritative-only
6233 servers, or in authoritative-only views. Attempts to set
6234 them to <command>no</command> without also
6236 <command>recursion no</command> will cause the
6238 ignore the options and log a warning message.
6242 Specifying <command>additional-from-cache no</command> actually
6243 disables the use of the cache not only for additional data
6245 but also when looking up the answer. This is usually the
6247 behavior in an authoritative-only server where the
6249 the cached data is an issue.
6253 When a name server is non-recursively queried for a name
6255 below the apex of any served zone, it normally answers with
6257 "upwards referral" to the root servers or the servers of
6259 known parent of the query name. Since the data in an
6261 comes from the cache, the server will not be able to provide
6263 referrals when <command>additional-from-cache no</command>
6264 has been specified. Instead, it will respond to such
6266 with REFUSED. This should not cause any problems since
6267 upwards referrals are not required for the resolution
6275 <term><command>match-mapped-addresses</command></term>
6278 If <userinput>yes</userinput>, then an
6279 IPv4-mapped IPv6 address will match any address match
6280 list entries that match the corresponding IPv4 address.
6283 This option was introduced to work around a kernel quirk
6284 in some operating systems that causes IPv4 TCP
6285 connections, such as zone transfers, to be accepted on an
6286 IPv6 socket using mapped addresses. This caused address
6287 match lists designed for IPv4 to fail to match. However,
6288 <command>named</command> now solves this problem
6289 internally. The use of this option is discouraged.
6295 <term><command>filter-aaaa-on-v4</command></term>
6298 This option is only available when
6299 <acronym>BIND</acronym> 9 is compiled with the
6300 <userinput>--enable-filter-aaaa</userinput> option on the
6301 "configure" command line. It is intended to help the
6302 transition from IPv4 to IPv6 by not giving IPv6 addresses
6303 to DNS clients unless they have connections to the IPv6
6304 Internet. This is not recommended unless absolutely
6305 necessary. The default is <userinput>no</userinput>.
6306 The <command>filter-aaaa-on-v4</command> option
6307 may also be specified in <command>view</command> statements
6308 to override the global <command>filter-aaaa-on-v4</command>
6312 If <userinput>yes</userinput>,
6313 the DNS client is at an IPv4 address, in <command>filter-aaaa</command>,
6314 and if the response does not include DNSSEC signatures,
6315 then all AAAA records are deleted from the response.
6316 This filtering applies to all responses and not only
6317 authoritative responses.
6320 If <userinput>break-dnssec</userinput>,
6321 then AAAA records are deleted even when dnssec is enabled.
6322 As suggested by the name, this makes the response not verify,
6323 because the DNSSEC protocol is designed detect deletions.
6326 This mechanism can erroneously cause other servers to
6327 not give AAAA records to their clients.
6328 A recursing server with both IPv6 and IPv4 network connections
6329 that queries an authoritative server using this mechanism
6330 via IPv4 will be denied AAAA records even if its client is
6334 This mechanism is applied to authoritative as well as
6335 non-authoritative records.
6336 A client using IPv4 that is not allowed recursion can
6337 erroneously be given AAAA records because the server is not
6338 allowed to check for A records.
6341 Some AAAA records are given to IPv4 clients in glue records.
6342 IPv4 clients that are servers can then erroneously
6343 answer requests for AAAA records received via IPv4.
6349 <term><command>ixfr-from-differences</command></term>
6352 When <userinput>yes</userinput> and the server loads a new
6353 version of a master zone from its zone file or receives a
6354 new version of a slave file via zone transfer, it will
6355 compare the new version to the previous one and calculate
6356 a set of differences. The differences are then logged in
6357 the zone's journal file such that the changes can be
6358 transmitted to downstream slaves as an incremental zone
6362 By allowing incremental zone transfers to be used for
6363 non-dynamic zones, this option saves bandwidth at the
6364 expense of increased CPU and memory consumption at the
6366 In particular, if the new version of a zone is completely
6367 different from the previous one, the set of differences
6368 will be of a size comparable to the combined size of the
6369 old and new zone version, and the server will need to
6370 temporarily allocate memory to hold this complete
6373 <para><command>ixfr-from-differences</command>
6374 also accepts <command>master</command> and
6375 <command>slave</command> at the view and options
6377 <command>ixfr-from-differences</command> to be enabled for
6378 all <command>master</command> or
6379 <command>slave</command> zones respectively.
6380 It is off by default.
6386 <term><command>multi-master</command></term>
6389 This should be set when you have multiple masters for a zone
6391 addresses refer to different machines. If <userinput>yes</userinput>, <command>named</command> will
6393 when the serial number on the master is less than what <command>named</command>
6395 has. The default is <userinput>no</userinput>.
6401 <term><command>dnssec-enable</command></term>
6404 Enable DNSSEC support in <command>named</command>. Unless set to <userinput>yes</userinput>,
6405 <command>named</command> behaves as if it does not support DNSSEC.
6406 The default is <userinput>yes</userinput>.
6412 <term><command>dnssec-validation</command></term>
6415 Enable DNSSEC validation in <command>named</command>.
6416 Note <command>dnssec-enable</command> also needs to be
6417 set to <userinput>yes</userinput> to be effective.
6418 If set to <userinput>no</userinput>, DNSSEC validation
6419 is disabled. If set to <userinput>auto</userinput>,
6420 DNSSEC validation is enabled, and a default
6421 trust-anchor for the DNS root zone is used. If set to
6422 <userinput>yes</userinput>, DNSSEC validation is enabled,
6423 but a trust anchor must be manually configured using
6424 a <command>trusted-keys</command> or
6425 <command>managed-keys</command> statement. The default
6426 is <userinput>yes</userinput>.
6432 <term><command>dnssec-accept-expired</command></term>
6435 Accept expired signatures when verifying DNSSEC signatures.
6436 The default is <userinput>no</userinput>.
6437 Setting this option to <userinput>yes</userinput>
6438 leaves <command>named</command> vulnerable to
6445 <term><command>querylog</command></term>
6448 Specify whether query logging should be started when <command>named</command>
6450 If <command>querylog</command> is not specified,
6451 then the query logging
6452 is determined by the presence of the logging category <command>queries</command>.
6458 <term><command>check-names</command></term>
6461 This option is used to restrict the character set and syntax
6463 certain domain names in master files and/or DNS responses
6465 from the network. The default varies according to usage
6467 <command>master</command> zones the default is <command>fail</command>.
6468 For <command>slave</command> zones the default
6469 is <command>warn</command>.
6470 For answers received from the network (<command>response</command>)
6471 the default is <command>ignore</command>.
6474 The rules for legal hostnames and mail domains are derived
6475 from RFC 952 and RFC 821 as modified by RFC 1123.
6477 <para><command>check-names</command>
6478 applies to the owner names of A, AAAA and MX records.
6479 It also applies to the domain names in the RDATA of NS, SOA,
6480 MX, and SRV records.
6481 It also applies to the RDATA of PTR records where the owner
6482 name indicated that it is a reverse lookup of a hostname
6483 (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
6489 <term><command>check-dup-records</command></term>
6492 Check master zones for records that are treated as different
6493 by DNSSEC but are semantically equal in plain DNS. The
6494 default is to <command>warn</command>. Other possible
6495 values are <command>fail</command> and
6496 <command>ignore</command>.
6502 <term><command>check-mx</command></term>
6505 Check whether the MX record appears to refer to a IP address.
6506 The default is to <command>warn</command>. Other possible
6507 values are <command>fail</command> and
6508 <command>ignore</command>.
6514 <term><command>check-wildcard</command></term>
6517 This option is used to check for non-terminal wildcards.
6518 The use of non-terminal wildcards is almost always as a
6520 to understand the wildcard matching algorithm (RFC 1034).
6522 affects master zones. The default (<command>yes</command>) is to check
6523 for non-terminal wildcards and issue a warning.
6529 <term><command>check-integrity</command></term>
6532 Perform post load zone integrity checks on master
6533 zones. This checks that MX and SRV records refer
6534 to address (A or AAAA) records and that glue
6535 address records exist for delegated zones. For
6536 MX and SRV records only in-zone hostnames are
6537 checked (for out-of-zone hostnames use
6538 <command>named-checkzone</command>).
6539 For NS records only names below top of zone are
6540 checked (for out-of-zone names and glue consistency
6541 checks use <command>named-checkzone</command>).
6542 The default is <command>yes</command>.
6545 Check that the two forms of Sender Policy Framework
6546 records (TXT records starting with "v=spf1" and SPF) either
6547 both exist or both don't exist. Warnings are
6548 emitted it they don't and be suppressed with
6549 <command>check-spf</command>.
6555 <term><command>check-mx-cname</command></term>
6558 If <command>check-integrity</command> is set then
6559 fail, warn or ignore MX records that refer
6560 to CNAMES. The default is to <command>warn</command>.
6566 <term><command>check-srv-cname</command></term>
6569 If <command>check-integrity</command> is set then
6570 fail, warn or ignore SRV records that refer
6571 to CNAMES. The default is to <command>warn</command>.
6577 <term><command>check-sibling</command></term>
6580 When performing integrity checks, also check that
6581 sibling glue exists. The default is <command>yes</command>.
6587 <term><command>check-spf</command></term>
6590 When performing integrity checks, check that the
6591 two forms of Sender Policy Framwork records (TXT
6592 records starting with "v=spf1" and SPF) both exist
6593 or both don't exist and issue a warning if not
6594 met. The default is <command>warn</command>.
6600 <term><command>zero-no-soa-ttl</command></term>
6603 When returning authoritative negative responses to
6604 SOA queries set the TTL of the SOA record returned in
6605 the authority section to zero.
6606 The default is <command>yes</command>.
6612 <term><command>zero-no-soa-ttl-cache</command></term>
6615 When caching a negative response to a SOA query
6616 set the TTL to zero.
6617 The default is <command>no</command>.
6623 <term><command>update-check-ksk</command></term>
6626 When set to the default value of <literal>yes</literal>,
6627 check the KSK bit in each key to determine how the key
6628 should be used when generating RRSIGs for a secure zone.
6631 Ordinarily, zone-signing keys (that is, keys without the
6632 KSK bit set) are used to sign the entire zone, while
6633 key-signing keys (keys with the KSK bit set) are only
6634 used to sign the DNSKEY RRset at the zone apex.
6635 However, if this option is set to <literal>no</literal>,
6636 then the KSK bit is ignored; KSKs are treated as if they
6637 were ZSKs and are used to sign the entire zone. This is
6638 similar to the <command>dnssec-signzone -z</command>
6639 command line option.
6642 When this option is set to <literal>yes</literal>, there
6643 must be at least two active keys for every algorithm
6644 represented in the DNSKEY RRset: at least one KSK and one
6645 ZSK per algorithm. If there is any algorithm for which
6646 this requirement is not met, this option will be ignored
6653 <term><command>dnssec-dnskey-kskonly</command></term>
6656 When this option and <command>update-check-ksk</command>
6657 are both set to <literal>yes</literal>, only key-signing
6658 keys (that is, keys with the KSK bit set) will be used
6659 to sign the DNSKEY RRset at the zone apex. Zone-signing
6660 keys (keys without the KSK bit set) will be used to sign
6661 the remainder of the zone, but not the DNSKEY RRset.
6662 This is similar to the
6663 <command>dnssec-signzone -x</command> command line option.
6666 The default is <command>no</command>. If
6667 <command>update-check-ksk</command> is set to
6668 <literal>no</literal>, this option is ignored.
6674 <term><command>dnssec-loadkeys-interval</command></term>
6677 When a zone is configured with <command>auto-dnssec
6678 maintain;</command> its key repository must be checked
6679 periodically to see if any new keys have been added
6680 or any existing keys' timing metadata has been updated
6681 (see <xref linkend="man.dnssec-keygen"/> and
6682 <xref linkend="man.dnssec-settime"/>). The
6683 <command>dnssec-loadkeys-interval</command> option
6684 sets the frequency of automatic repository checks, in
6685 minutes. The default is <literal>60</literal> (1 hour),
6686 the minimum is <literal>1</literal> (1 minute), and the
6687 maximum is <literal>1440</literal> (24 hours); any higher
6688 value is silently reduced.
6694 <term><command>try-tcp-refresh</command></term>
6697 Try to refresh the zone using TCP if UDP queries fail.
6698 For BIND 8 compatibility, the default is
6699 <command>yes</command>.
6705 <term><command>dnssec-secure-to-insecure</command></term>
6708 Allow a dynamic zone to transition from secure to
6709 insecure (i.e., signed to unsigned) by deleting all
6710 of the DNSKEY records. The default is <command>no</command>.
6711 If set to <command>yes</command>, and if the DNSKEY RRset
6712 at the zone apex is deleted, all RRSIG and NSEC records
6713 will be removed from the zone as well.
6716 If the zone uses NSEC3, then it is also necessary to
6717 delete the NSEC3PARAM RRset from the zone apex; this will
6718 cause the removal of all corresponding NSEC3 records.
6719 (It is expected that this requirement will be eliminated
6720 in a future release.)
6723 Note that if a zone has been configured with
6724 <command>auto-dnssec maintain</command> and the
6725 private keys remain accessible in the key repository,
6726 then the zone will be automatically signed again the
6727 next time <command>named</command> is started.
6737 <title>Forwarding</title>
6739 The forwarding facility can be used to create a large site-wide
6740 cache on a few servers, reducing traffic over links to external
6741 name servers. It can also be used to allow queries by servers that
6742 do not have direct access to the Internet, but wish to look up
6744 names anyway. Forwarding occurs only on those queries for which
6745 the server is not authoritative and does not have the answer in
6751 <term><command>forward</command></term>
6754 This option is only meaningful if the
6755 forwarders list is not empty. A value of <varname>first</varname>,
6756 the default, causes the server to query the forwarders
6758 if that doesn't answer the question, the server will then
6760 the answer itself. If <varname>only</varname> is
6762 server will only query the forwarders.
6768 <term><command>forwarders</command></term>
6771 Specifies the IP addresses to be used
6772 for forwarding. The default is the empty list (no
6781 Forwarding can also be configured on a per-domain basis, allowing
6782 for the global forwarding options to be overridden in a variety
6783 of ways. You can set particular domains to use different
6785 or have a different <command>forward only/first</command> behavior,
6786 or not forward at all, see <xref linkend="zone_statement_grammar"/>.
6791 <title>Dual-stack Servers</title>
6793 Dual-stack servers are used as servers of last resort to work
6795 problems in reachability due the lack of support for either IPv4
6797 on the host machine.
6802 <term><command>dual-stack-servers</command></term>
6805 Specifies host names or addresses of machines with access to
6806 both IPv4 and IPv6 transports. If a hostname is used, the
6808 to resolve the name using only the transport it has. If the
6810 stacked, then the <command>dual-stack-servers</command> have no effect unless
6811 access to a transport has been disabled on the command line
6812 (e.g. <command>named -4</command>).
6819 <sect3 id="access_control">
6820 <title>Access Control</title>
6823 Access to the server can be restricted based on the IP address
6824 of the requesting system. See <xref linkend="address_match_lists"/> for
6825 details on how to specify IP address lists.
6831 <term><command>allow-notify</command></term>
6834 Specifies which hosts are allowed to
6835 notify this server, a slave, of zone changes in addition
6836 to the zone masters.
6837 <command>allow-notify</command> may also be
6839 <command>zone</command> statement, in which case
6841 <command>options allow-notify</command>
6842 statement. It is only meaningful
6843 for a slave zone. If not specified, the default is to
6844 process notify messages
6845 only from a zone's master.
6851 <term><command>allow-query</command></term>
6854 Specifies which hosts are allowed to ask ordinary
6855 DNS questions. <command>allow-query</command> may
6856 also be specified in the <command>zone</command>
6857 statement, in which case it overrides the
6858 <command>options allow-query</command> statement.
6859 If not specified, the default is to allow queries
6864 <command>allow-query-cache</command> is now
6865 used to specify access to the cache.
6872 <term><command>allow-query-on</command></term>
6875 Specifies which local addresses can accept ordinary
6876 DNS questions. This makes it possible, for instance,
6877 to allow queries on internal-facing interfaces but
6878 disallow them on external-facing ones, without
6879 necessarily knowing the internal network's addresses.
6882 Note that <command>allow-query-on</command> is only
6883 checked for queries that are permitted by
6884 <command>allow-query</command>. A query must be
6885 allowed by both ACLs, or it will be refused.
6888 <command>allow-query-on</command> may
6889 also be specified in the <command>zone</command>
6890 statement, in which case it overrides the
6891 <command>options allow-query-on</command> statement.
6894 If not specified, the default is to allow queries
6899 <command>allow-query-cache</command> is
6900 used to specify access to the cache.
6907 <term><command>allow-query-cache</command></term>
6910 Specifies which hosts are allowed to get answers
6911 from the cache. If <command>allow-query-cache</command>
6912 is not set then <command>allow-recursion</command>
6913 is used if set, otherwise <command>allow-query</command>
6914 is used if set unless <command>recursion no;</command> is
6915 set in which case <command>none;</command> is used,
6916 otherwise the default (<command>localnets;</command>
6917 <command>localhost;</command>) is used.
6923 <term><command>allow-query-cache-on</command></term>
6926 Specifies which local addresses can give answers
6927 from the cache. If not specified, the default is
6928 to allow cache queries on any address,
6929 <command>localnets</command> and
6930 <command>localhost</command>.
6936 <term><command>allow-recursion</command></term>
6939 Specifies which hosts are allowed to make recursive
6940 queries through this server. If
6941 <command>allow-recursion</command> is not set
6942 then <command>allow-query-cache</command> is
6943 used if set, otherwise <command>allow-query</command>
6944 is used if set, otherwise the default
6945 (<command>localnets;</command>
6946 <command>localhost;</command>) is used.
6952 <term><command>allow-recursion-on</command></term>
6955 Specifies which local addresses can accept recursive
6956 queries. If not specified, the default is to allow
6957 recursive queries on all addresses.
6963 <term><command>allow-update</command></term>
6966 Specifies which hosts are allowed to
6967 submit Dynamic DNS updates for master zones. The default is
6969 updates from all hosts. Note that allowing updates based
6970 on the requestor's IP address is insecure; see
6971 <xref linkend="dynamic_update_security"/> for details.
6977 <term><command>allow-update-forwarding</command></term>
6980 Specifies which hosts are allowed to
6981 submit Dynamic DNS updates to slave zones to be forwarded to
6983 master. The default is <userinput>{ none; }</userinput>,
6985 means that no update forwarding will be performed. To
6987 update forwarding, specify
6988 <userinput>allow-update-forwarding { any; };</userinput>.
6989 Specifying values other than <userinput>{ none; }</userinput> or
6990 <userinput>{ any; }</userinput> is usually
6991 counterproductive, since
6992 the responsibility for update access control should rest
6994 master server, not the slaves.
6997 Note that enabling the update forwarding feature on a slave
6999 may expose master servers relying on insecure IP address
7001 access control to attacks; see <xref linkend="dynamic_update_security"/>
7008 <term><command>allow-v6-synthesis</command></term>
7011 This option was introduced for the smooth transition from
7013 to A6 and from "nibble labels" to binary labels.
7014 However, since both A6 and binary labels were then
7016 this option was also deprecated.
7017 It is now ignored with some warning messages.
7023 <term><command>allow-transfer</command></term>
7026 Specifies which hosts are allowed to
7027 receive zone transfers from the server. <command>allow-transfer</command> may
7028 also be specified in the <command>zone</command>
7030 case it overrides the <command>options allow-transfer</command> statement.
7031 If not specified, the default is to allow transfers to all
7038 <term><command>blackhole</command></term>
7041 Specifies a list of addresses that the
7042 server will not accept queries from or use to resolve a
7044 from these addresses will not be responded to. The default
7045 is <userinput>none</userinput>.
7051 <term><command>filter-aaaa</command></term>
7054 Specifies a list of addresses to which
7055 <command>filter-aaaa-on-v4</command>
7056 is applies. The default is <userinput>any</userinput>.
7062 <term><command>resolver-query-timeout</command></term>
7065 The amount of time the resolver will spend attempting
7066 to resolve a recursive query before failing. The default
7067 and minimum is <literal>10</literal> and the maximum is
7068 <literal>30</literal>. Setting it to <literal>0</literal>
7069 will result in the default being used.
7078 <title>Interfaces</title>
7080 The interfaces and ports that the server will answer queries
7081 from may be specified using the <command>listen-on</command> option. <command>listen-on</command> takes
7082 an optional port and an <varname>address_match_list</varname>.
7083 The server will listen on all interfaces allowed by the address
7084 match list. If a port is not specified, port 53 will be used.
7087 Multiple <command>listen-on</command> statements are
7092 <programlisting>listen-on { 5.6.7.8; };
7093 listen-on port 1234 { !1.2.3.4; 1.2/16; };
7097 will enable the name server on port 53 for the IP address
7098 5.6.7.8, and on port 1234 of an address on the machine in net
7099 1.2 that is not 1.2.3.4.
7103 If no <command>listen-on</command> is specified, the
7104 server will listen on port 53 on all IPv4 interfaces.
7108 The <command>listen-on-v6</command> option is used to
7109 specify the interfaces and the ports on which the server will
7111 for incoming queries sent using IPv6.
7115 When <programlisting>{ any; }</programlisting> is
7117 as the <varname>address_match_list</varname> for the
7118 <command>listen-on-v6</command> option,
7119 the server does not bind a separate socket to each IPv6 interface
7120 address as it does for IPv4 if the operating system has enough API
7121 support for IPv6 (specifically if it conforms to RFC 3493 and RFC
7123 Instead, it listens on the IPv6 wildcard address.
7124 If the system only has incomplete API support for IPv6, however,
7125 the behavior is the same as that for IPv4.
7129 A list of particular IPv6 addresses can also be specified, in
7131 the server listens on a separate socket for each specified
7133 regardless of whether the desired API is supported by the system.
7137 Multiple <command>listen-on-v6</command> options can
7142 <programlisting>listen-on-v6 { any; };
7143 listen-on-v6 port 1234 { !2001:db8::/32; any; };
7147 will enable the name server on port 53 for any IPv6 addresses
7148 (with a single wildcard socket),
7149 and on port 1234 of IPv6 addresses that is not in the prefix
7150 2001:db8::/32 (with separate sockets for each matched address.)
7154 To make the server not listen on any IPv6 address, use
7157 <programlisting>listen-on-v6 { none; };
7161 If no <command>listen-on-v6</command> option is
7162 specified, the server will not listen on any IPv6 address
7163 unless <command>-6</command> is specified when <command>named</command> is
7164 invoked. If <command>-6</command> is specified then
7165 <command>named</command> will listen on port 53 on all IPv6 interfaces by default.
7169 <sect3 id="query_address">
7170 <title>Query Address</title>
7172 If the server doesn't know the answer to a question, it will
7173 query other name servers. <command>query-source</command> specifies
7174 the address and port used for such queries. For queries sent over
7175 IPv6, there is a separate <command>query-source-v6</command> option.
7176 If <command>address</command> is <command>*</command> (asterisk) or is omitted,
7177 a wildcard IP address (<command>INADDR_ANY</command>)
7182 If <command>port</command> is <command>*</command> or is omitted,
7183 a random port number from a pre-configured
7184 range is picked up and will be used for each query.
7185 The port range(s) is that specified in
7186 the <command>use-v4-udp-ports</command> (for IPv4)
7187 and <command>use-v6-udp-ports</command> (for IPv6)
7188 options, excluding the ranges specified in
7189 the <command>avoid-v4-udp-ports</command>
7190 and <command>avoid-v6-udp-ports</command> options, respectively.
7194 The defaults of the <command>query-source</command> and
7195 <command>query-source-v6</command> options
7199 <programlisting>query-source address * port *;
7200 query-source-v6 address * port *;
7204 If <command>use-v4-udp-ports</command> or
7205 <command>use-v6-udp-ports</command> is unspecified,
7206 <command>named</command> will check if the operating
7207 system provides a programming interface to retrieve the
7208 system's default range for ephemeral ports.
7209 If such an interface is available,
7210 <command>named</command> will use the corresponding system
7211 default range; otherwise, it will use its own defaults:
7214 <programlisting>use-v4-udp-ports { range 1024 65535; };
7215 use-v6-udp-ports { range 1024 65535; };
7219 Note: make sure the ranges be sufficiently large for
7220 security. A desirable size depends on various parameters,
7221 but we generally recommend it contain at least 16384 ports
7222 (14 bits of entropy).
7223 Note also that the system's default range when used may be
7224 too small for this purpose, and that the range may even be
7225 changed while <command>named</command> is running; the new
7226 range will automatically be applied when <command>named</command>
7229 configure <command>use-v4-udp-ports</command> and
7230 <command>use-v6-udp-ports</command> explicitly so that the
7231 ranges are sufficiently large and are reasonably
7232 independent from the ranges used by other applications.
7236 Note: the operational configuration
7237 where <command>named</command> runs may prohibit the use
7238 of some ports. For example, UNIX systems will not allow
7239 <command>named</command> running without a root privilege
7240 to use ports less than 1024.
7241 If such ports are included in the specified (or detected)
7242 set of query ports, the corresponding query attempts will
7243 fail, resulting in resolution failures or delay.
7244 It is therefore important to configure the set of ports
7245 that can be safely used in the expected operational environment.
7249 The defaults of the <command>avoid-v4-udp-ports</command> and
7250 <command>avoid-v6-udp-ports</command> options
7254 <programlisting>avoid-v4-udp-ports {};
7255 avoid-v6-udp-ports {};
7259 Note: BIND 9.5.0 introduced
7260 the <command>use-queryport-pool</command>
7261 option to support a pool of such random ports, but this
7262 option is now obsolete because reusing the same ports in
7263 the pool may not be sufficiently secure.
7264 For the same reason, it is generally strongly discouraged to
7265 specify a particular port for the
7266 <command>query-source</command> or
7267 <command>query-source-v6</command> options;
7268 it implicitly disables the use of randomized port numbers.
7273 <term><command>use-queryport-pool</command></term>
7276 This option is obsolete.
7282 <term><command>queryport-pool-ports</command></term>
7285 This option is obsolete.
7291 <term><command>queryport-pool-updateinterval</command></term>
7294 This option is obsolete.
7302 The address specified in the <command>query-source</command> option
7303 is used for both UDP and TCP queries, but the port applies only
7304 to UDP queries. TCP queries always use a random
7310 Solaris 2.5.1 and earlier does not support setting the source
7311 address for TCP sockets.
7316 See also <command>transfer-source</command> and
7317 <command>notify-source</command>.
7322 <sect3 id="zone_transfers">
7323 <title>Zone Transfers</title>
7325 <acronym>BIND</acronym> has mechanisms in place to
7326 facilitate zone transfers
7327 and set limits on the amount of load that transfers place on the
7328 system. The following options apply to zone transfers.
7334 <term><command>also-notify</command></term>
7337 Defines a global list of IP addresses of name servers
7338 that are also sent NOTIFY messages whenever a fresh copy of
7340 zone is loaded, in addition to the servers listed in the
7342 This helps to ensure that copies of the zones will
7343 quickly converge on stealth servers.
7344 Optionally, a port may be specified with each
7345 <command>also-notify</command> address to send
7346 the notify messages to a port other than the
7348 An optional TSIG key can also be specified with each
7349 address to cause the notify messages to be signed; this
7350 can be useful when sending notifies to multiple views.
7351 In place of explicit addresses, one or more named
7352 <command>masters</command> lists can be used.
7355 If an <command>also-notify</command> list
7356 is given in a <command>zone</command> statement,
7358 the <command>options also-notify</command>
7359 statement. When a <command>zone notify</command>
7361 is set to <command>no</command>, the IP
7362 addresses in the global <command>also-notify</command> list will
7363 not be sent NOTIFY messages for that zone. The default is
7365 list (no global notification list).
7371 <term><command>max-transfer-time-in</command></term>
7374 Inbound zone transfers running longer than
7375 this many minutes will be terminated. The default is 120
7377 (2 hours). The maximum value is 28 days (40320 minutes).
7383 <term><command>max-transfer-idle-in</command></term>
7386 Inbound zone transfers making no progress
7387 in this many minutes will be terminated. The default is 60
7389 (1 hour). The maximum value is 28 days (40320 minutes).
7395 <term><command>max-transfer-time-out</command></term>
7398 Outbound zone transfers running longer than
7399 this many minutes will be terminated. The default is 120
7401 (2 hours). The maximum value is 28 days (40320 minutes).
7407 <term><command>max-transfer-idle-out</command></term>
7410 Outbound zone transfers making no progress
7411 in this many minutes will be terminated. The default is 60
7413 hour). The maximum value is 28 days (40320 minutes).
7419 <term><command>serial-query-rate</command></term>
7422 Slave servers will periodically query master
7423 servers to find out if zone serial numbers have
7424 changed. Each such query uses a minute amount of
7425 the slave server's network bandwidth. To limit
7426 the amount of bandwidth used, BIND 9 limits the
7427 rate at which queries are sent. The value of the
7428 <command>serial-query-rate</command> option, an
7429 integer, is the maximum number of queries sent
7430 per second. The default is 20.
7433 In addition to controlling the rate SOA refresh
7434 queries are issued at
7435 <command>serial-query-rate</command> also controls
7436 the rate at which NOTIFY messages are sent from
7437 both master and slave zones.
7443 <term><command>serial-queries</command></term>
7446 In BIND 8, the <command>serial-queries</command>
7448 set the maximum number of concurrent serial number queries
7449 allowed to be outstanding at any given time.
7450 BIND 9 does not limit the number of outstanding
7451 serial queries and ignores the <command>serial-queries</command> option.
7452 Instead, it limits the rate at which the queries are sent
7453 as defined using the <command>serial-query-rate</command> option.
7459 <term><command>transfer-format</command></term>
7463 Zone transfers can be sent using two different formats,
7464 <command>one-answer</command> and
7465 <command>many-answers</command>.
7466 The <command>transfer-format</command> option is used
7467 on the master server to determine which format it sends.
7468 <command>one-answer</command> uses one DNS message per
7469 resource record transferred.
7470 <command>many-answers</command> packs as many resource
7471 records as possible into a message.
7472 <command>many-answers</command> is more efficient, but is
7473 only supported by relatively new slave servers,
7474 such as <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
7475 8.x and <acronym>BIND</acronym> 4.9.5 onwards.
7476 The <command>many-answers</command> format is also supported by
7477 recent Microsoft Windows nameservers.
7478 The default is <command>many-answers</command>.
7479 <command>transfer-format</command> may be overridden on a
7480 per-server basis by using the <command>server</command>
7488 <term><command>transfers-in</command></term>
7491 The maximum number of inbound zone transfers
7492 that can be running concurrently. The default value is <literal>10</literal>.
7493 Increasing <command>transfers-in</command> may
7494 speed up the convergence
7495 of slave zones, but it also may increase the load on the
7502 <term><command>transfers-out</command></term>
7505 The maximum number of outbound zone transfers
7506 that can be running concurrently. Zone transfer requests in
7508 of the limit will be refused. The default value is <literal>10</literal>.
7514 <term><command>transfers-per-ns</command></term>
7517 The maximum number of inbound zone transfers
7518 that can be concurrently transferring from a given remote
7520 The default value is <literal>2</literal>.
7521 Increasing <command>transfers-per-ns</command>
7523 speed up the convergence of slave zones, but it also may
7525 the load on the remote name server. <command>transfers-per-ns</command> may
7526 be overridden on a per-server basis by using the <command>transfers</command> phrase
7527 of the <command>server</command> statement.
7533 <term><command>transfer-source</command></term>
7535 <para><command>transfer-source</command>
7536 determines which local address will be bound to IPv4
7537 TCP connections used to fetch zones transferred
7538 inbound by the server. It also determines the
7539 source IPv4 address, and optionally the UDP port,
7540 used for the refresh queries and forwarded dynamic
7541 updates. If not set, it defaults to a system
7542 controlled value which will usually be the address
7543 of the interface "closest to" the remote end. This
7544 address must appear in the remote end's
7545 <command>allow-transfer</command> option for the
7546 zone being transferred, if one is specified. This
7548 <command>transfer-source</command> for all zones,
7549 but can be overridden on a per-view or per-zone
7550 basis by including a
7551 <command>transfer-source</command> statement within
7552 the <command>view</command> or
7553 <command>zone</command> block in the configuration
7558 Solaris 2.5.1 and earlier does not support setting the
7559 source address for TCP sockets.
7566 <term><command>transfer-source-v6</command></term>
7569 The same as <command>transfer-source</command>,
7570 except zone transfers are performed using IPv6.
7576 <term><command>alt-transfer-source</command></term>
7579 An alternate transfer source if the one listed in
7580 <command>transfer-source</command> fails and
7581 <command>use-alt-transfer-source</command> is
7585 If you do not wish the alternate transfer source
7586 to be used, you should set
7587 <command>use-alt-transfer-source</command>
7588 appropriately and you should not depend upon
7589 getting an answer back to the first refresh
7596 <term><command>alt-transfer-source-v6</command></term>
7599 An alternate transfer source if the one listed in
7600 <command>transfer-source-v6</command> fails and
7601 <command>use-alt-transfer-source</command> is
7608 <term><command>use-alt-transfer-source</command></term>
7611 Use the alternate transfer sources or not. If views are
7612 specified this defaults to <command>no</command>
7613 otherwise it defaults to
7614 <command>yes</command> (for BIND 8
7621 <term><command>notify-source</command></term>
7623 <para><command>notify-source</command>
7624 determines which local source address, and
7625 optionally UDP port, will be used to send NOTIFY
7626 messages. This address must appear in the slave
7627 server's <command>masters</command> zone clause or
7628 in an <command>allow-notify</command> clause. This
7629 statement sets the <command>notify-source</command>
7630 for all zones, but can be overridden on a per-zone or
7631 per-view basis by including a
7632 <command>notify-source</command> statement within
7633 the <command>zone</command> or
7634 <command>view</command> block in the configuration
7639 Solaris 2.5.1 and earlier does not support setting the
7640 source address for TCP sockets.
7647 <term><command>notify-source-v6</command></term>
7650 Like <command>notify-source</command>,
7651 but applies to notify messages sent to IPv6 addresses.
7661 <title>UDP Port Lists</title>
7663 <command>use-v4-udp-ports</command>,
7664 <command>avoid-v4-udp-ports</command>,
7665 <command>use-v6-udp-ports</command>, and
7666 <command>avoid-v6-udp-ports</command>
7667 specify a list of IPv4 and IPv6 UDP ports that will be
7668 used or not used as source ports for UDP messages.
7669 See <xref linkend="query_address"/> about how the
7670 available ports are determined.
7671 For example, with the following configuration
7675 use-v6-udp-ports { range 32768 65535; };
7676 avoid-v6-udp-ports { 40000; range 50000 60000; };
7680 UDP ports of IPv6 messages sent
7681 from <command>named</command> will be in one
7682 of the following ranges: 32768 to 39999, 40001 to 49999,
7687 <command>avoid-v4-udp-ports</command> and
7688 <command>avoid-v6-udp-ports</command> can be used
7689 to prevent <command>named</command> from choosing as its random source port a
7690 port that is blocked by your firewall or a port that is
7691 used by other applications;
7692 if a query went out with a source port blocked by a
7694 answer would not get by the firewall and the name server would
7695 have to query again.
7696 Note: the desired range can also be represented only with
7697 <command>use-v4-udp-ports</command> and
7698 <command>use-v6-udp-ports</command>, and the
7699 <command>avoid-</command> options are redundant in that
7700 sense; they are provided for backward compatibility and
7701 to possibly simplify the port specification.
7706 <title>Operating System Resource Limits</title>
7709 The server's usage of many system resources can be limited.
7710 Scaled values are allowed when specifying resource limits. For
7711 example, <command>1G</command> can be used instead of
7712 <command>1073741824</command> to specify a limit of
7714 gigabyte. <command>unlimited</command> requests
7715 unlimited use, or the
7716 maximum available amount. <command>default</command>
7718 that was in force when the server was started. See the description
7719 of <command>size_spec</command> in <xref linkend="configuration_file_elements"/>.
7723 The following options set operating system resource limits for
7724 the name server process. Some operating systems don't support
7726 any of the limits. On such systems, a warning will be issued if
7728 unsupported limit is used.
7734 <term><command>coresize</command></term>
7737 The maximum size of a core dump. The default
7738 is <literal>default</literal>.
7744 <term><command>datasize</command></term>
7747 The maximum amount of data memory the server
7748 may use. The default is <literal>default</literal>.
7749 This is a hard limit on server memory usage.
7750 If the server attempts to allocate memory in excess of this
7751 limit, the allocation will fail, which may in turn leave
7752 the server unable to perform DNS service. Therefore,
7753 this option is rarely useful as a way of limiting the
7754 amount of memory used by the server, but it can be used
7755 to raise an operating system data size limit that is
7756 too small by default. If you wish to limit the amount
7757 of memory used by the server, use the
7758 <command>max-cache-size</command> and
7759 <command>recursive-clients</command>
7766 <term><command>files</command></term>
7769 The maximum number of files the server
7770 may have open concurrently. The default is <literal>unlimited</literal>.
7776 <term><command>stacksize</command></term>
7779 The maximum amount of stack memory the server
7780 may use. The default is <literal>default</literal>.
7789 <sect3 id="server_resource_limits">
7790 <title>Server Resource Limits</title>
7793 The following options set limits on the server's
7794 resource consumption that are enforced internally by the
7795 server rather than the operating system.
7801 <term><command>max-ixfr-log-size</command></term>
7804 This option is obsolete; it is accepted
7805 and ignored for BIND 8 compatibility. The option
7806 <command>max-journal-size</command> performs a
7807 similar function in BIND 9.
7813 <term><command>max-journal-size</command></term>
7816 Sets a maximum size for each journal file
7817 (see <xref linkend="journal"/>). When the journal file
7819 the specified size, some of the oldest transactions in the
7821 will be automatically removed. The largest permitted
7822 value is 2 gigabytes. The default is
7823 <literal>unlimited</literal>, which also
7825 This may also be set on a per-zone basis.
7831 <term><command>host-statistics-max</command></term>
7834 In BIND 8, specifies the maximum number of host statistics
7836 Not implemented in BIND 9.
7842 <term><command>recursive-clients</command></term>
7845 The maximum number of simultaneous recursive lookups
7846 the server will perform on behalf of clients. The default
7848 <literal>1000</literal>. Because each recursing
7850 bit of memory, on the order of 20 kilobytes, the value of
7852 <command>recursive-clients</command> option may
7853 have to be decreased
7854 on hosts with limited memory.
7860 <term><command>tcp-clients</command></term>
7863 The maximum number of simultaneous client TCP
7864 connections that the server will accept.
7865 The default is <literal>100</literal>.
7871 <term><command>reserved-sockets</command></term>
7874 The number of file descriptors reserved for TCP, stdio,
7875 etc. This needs to be big enough to cover the number of
7876 interfaces <command>named</command> listens on, <command>tcp-clients</command> as well as
7877 to provide room for outgoing TCP queries and incoming zone
7878 transfers. The default is <literal>512</literal>.
7879 The minimum value is <literal>128</literal> and the
7880 maximum value is <literal>128</literal> less than
7881 maxsockets (-S). This option may be removed in the future.
7884 This option has little effect on Windows.
7890 <term><command>max-cache-size</command></term>
7893 The maximum amount of memory to use for the
7894 server's cache, in bytes.
7895 When the amount of data in the cache
7896 reaches this limit, the server will cause records to expire
7897 prematurely based on an LRU based strategy so that
7898 the limit is not exceeded.
7899 A value of 0 is special, meaning that
7900 records are purged from the cache only when their
7902 Another special keyword <userinput>unlimited</userinput>
7903 means the maximum value of 32-bit unsigned integers
7904 (0xffffffff), which may not have the same effect as
7905 0 on machines that support more than 32 bits of
7907 Any positive values less than 2MB will be ignored reset
7909 In a server with multiple views, the limit applies
7910 separately to the cache of each view.
7917 <term><command>tcp-listen-queue</command></term>
7920 The listen queue depth. The default and minimum is 10.
7921 If the kernel supports the accept filter "dataready" this
7923 many TCP connections that will be queued in kernel space
7925 some data before being passed to accept. Nonzero values
7926 less than 10 will be silently raised. A value of 0 may also
7927 be used; on most platforms this sets the listen queue
7928 length to a system-defined default value.
7938 <title>Periodic Task Intervals</title>
7943 <term><command>cleaning-interval</command></term>
7946 This interval is effectively obsolete. Previously,
7947 the server would remove expired resource records
7948 from the cache every <command>cleaning-interval</command> minutes.
7949 <acronym>BIND</acronym> 9 now manages cache
7950 memory in a more sophisticated manner and does not
7951 rely on the periodic cleaning any more.
7952 Specifying this option therefore has no effect on
7953 the server's behavior.
7959 <term><command>heartbeat-interval</command></term>
7962 The server will perform zone maintenance tasks
7963 for all zones marked as <command>dialup</command> whenever this
7964 interval expires. The default is 60 minutes. Reasonable
7966 to 1 day (1440 minutes). The maximum value is 28 days
7968 If set to 0, no zone maintenance for these zones will occur.
7974 <term><command>interface-interval</command></term>
7977 The server will scan the network interface list
7978 every <command>interface-interval</command>
7979 minutes. The default
7980 is 60 minutes. The maximum value is 28 days (40320 minutes).
7981 If set to 0, interface scanning will only occur when
7982 the configuration file is loaded. After the scan, the
7984 begin listening for queries on any newly discovered
7985 interfaces (provided they are allowed by the
7986 <command>listen-on</command> configuration), and
7988 stop listening on interfaces that have gone away.
7994 <term><command>statistics-interval</command></term>
7997 Name server statistics will be logged
7998 every <command>statistics-interval</command>
7999 minutes. The default is
8000 60. The maximum value is 28 days (40320 minutes).
8001 If set to 0, no statistics will be logged.
8004 Not yet implemented in
8005 <acronym>BIND</acronym> 9.
8015 <sect3 id="topology">
8016 <title>Topology</title>
8019 All other things being equal, when the server chooses a name
8021 to query from a list of name servers, it prefers the one that is
8022 topologically closest to itself. The <command>topology</command> statement
8023 takes an <command>address_match_list</command> and
8025 in a special way. Each top-level list element is assigned a
8027 Non-negated elements get a distance based on their position in the
8028 list, where the closer the match is to the start of the list, the
8029 shorter the distance is between it and the server. A negated match
8030 will be assigned the maximum distance from the server. If there
8031 is no match, the address will get a distance which is further than
8032 any non-negated list element, and closer than any negated element.
8036 <programlisting>topology {
8043 will prefer servers on network 10 the most, followed by hosts
8044 on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
8045 exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
8046 is preferred least of all.
8049 The default topology is
8052 <programlisting> topology { localhost; localnets; };
8057 The <command>topology</command> option
8058 is not implemented in <acronym>BIND</acronym> 9.
8063 <sect3 id="the_sortlist_statement">
8065 <title>The <command>sortlist</command> Statement</title>
8068 The response to a DNS query may consist of multiple resource
8069 records (RRs) forming a resource records set (RRset).
8070 The name server will normally return the
8071 RRs within the RRset in an indeterminate order
8072 (but see the <command>rrset-order</command>
8073 statement in <xref linkend="rrset_ordering"/>).
8074 The client resolver code should rearrange the RRs as appropriate,
8075 that is, using any addresses on the local net in preference to
8077 However, not all resolvers can do this or are correctly
8079 When a client is using a local server, the sorting can be performed
8080 in the server, based on the client's address. This only requires
8081 configuring the name servers, not all the clients.
8085 The <command>sortlist</command> statement (see below)
8087 an <command>address_match_list</command> and
8089 more specifically than the <command>topology</command>
8091 does (<xref linkend="topology"/>).
8092 Each top level statement in the <command>sortlist</command> must
8093 itself be an explicit <command>address_match_list</command> with
8094 one or two elements. The first element (which may be an IP
8096 an IP prefix, an ACL name or a nested <command>address_match_list</command>)
8097 of each top level list is checked against the source address of
8098 the query until a match is found.
8101 Once the source address of the query has been matched, if
8102 the top level statement contains only one element, the actual
8104 element that matched the source address is used to select the
8106 in the response to move to the beginning of the response. If the
8107 statement is a list of two elements, then the second element is
8108 treated the same as the <command>address_match_list</command> in
8109 a <command>topology</command> statement. Each top
8111 is assigned a distance and the address in the response with the
8113 distance is moved to the beginning of the response.
8116 In the following example, any queries received from any of
8117 the addresses of the host itself will get responses preferring
8119 on any of the locally connected networks. Next most preferred are
8121 on the 192.168.1/24 network, and after that either the
8124 192.168.3/24 network with no preference shown between these two
8125 networks. Queries received from a host on the 192.168.1/24 network
8126 will prefer other addresses on that network to the 192.168.2/24
8128 192.168.3/24 networks. Queries received from a host on the
8130 or the 192.168.5/24 network will only prefer other addresses on
8131 their directly connected networks.
8134 <programlisting>sortlist {
8135 // IF the local host
8136 // THEN first fit on the following nets
8140 { 192.168.2/24; 192.168.3/24; }; }; };
8141 // IF on class C 192.168.1 THEN use .1, or .2 or .3
8144 { 192.168.2/24; 192.168.3/24; }; }; };
8145 // IF on class C 192.168.2 THEN use .2, or .1 or .3
8148 { 192.168.1/24; 192.168.3/24; }; }; };
8149 // IF on class C 192.168.3 THEN use .3, or .1 or .2
8152 { 192.168.1/24; 192.168.2/24; }; }; };
8153 // IF .4 or .5 THEN prefer that net
8154 { { 192.168.4/24; 192.168.5/24; };
8159 The following example will give reasonable behavior for the
8160 local host and hosts on directly connected networks. It is similar
8161 to the behavior of the address sort in <acronym>BIND</acronym> 4.9.x. Responses sent
8162 to queries from the local host will favor any of the directly
8164 networks. Responses sent to queries from any other hosts on a
8166 connected network will prefer addresses on that same network.
8168 to other queries will not be sorted.
8171 <programlisting>sortlist {
8172 { localhost; localnets; };
8178 <sect3 id="rrset_ordering">
8179 <title id="rrset_ordering_title">RRset Ordering</title>
8181 When multiple records are returned in an answer it may be
8182 useful to configure the order of the records placed into the
8184 The <command>rrset-order</command> statement permits
8186 of the ordering of the records in a multiple record response.
8187 See also the <command>sortlist</command> statement,
8188 <xref linkend="the_sortlist_statement"/>.
8192 An <command>order_spec</command> is defined as
8196 <optional>class <replaceable>class_name</replaceable></optional>
8197 <optional>type <replaceable>type_name</replaceable></optional>
8198 <optional>name <replaceable>"domain_name"</replaceable></optional>
8199 order <replaceable>ordering</replaceable>
8202 If no class is specified, the default is <command>ANY</command>.
8203 If no type is specified, the default is <command>ANY</command>.
8204 If no name is specified, the default is "<command>*</command>" (asterisk).
8207 The legal values for <command>ordering</command> are:
8209 <informaltable colsep="0" rowsep="0">
8210 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
8211 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
8212 <colspec colname="2" colnum="2" colsep="0" colwidth="3.750in"/>
8216 <para><command>fixed</command></para>
8220 Records are returned in the order they
8221 are defined in the zone file.
8227 <para><command>random</command></para>
8231 Records are returned in some random order.
8237 <para><command>cyclic</command></para>
8241 Records are returned in a cyclic round-robin order.
8244 If <acronym>BIND</acronym> is configured with the
8245 "--enable-fixed-rrset" option at compile time, then
8246 the initial ordering of the RRset will match the
8247 one specified in the zone file.
8258 <programlisting>rrset-order {
8259 class IN type A name "host.example.com" order random;
8265 will cause any responses for type A records in class IN that
8266 have "<literal>host.example.com</literal>" as a
8267 suffix, to always be returned
8268 in random order. All other records are returned in cyclic order.
8271 If multiple <command>rrset-order</command> statements
8272 appear, they are not combined — the last one applies.
8275 By default, all records are returned in random order.
8280 In this release of <acronym>BIND</acronym> 9, the
8281 <command>rrset-order</command> statement does not support
8282 "fixed" ordering by default. Fixed ordering can be enabled
8283 at compile time by specifying "--enable-fixed-rrset" on
8284 the "configure" command line.
8290 <title>Tuning</title>
8295 <term><command>lame-ttl</command></term>
8298 Sets the number of seconds to cache a
8299 lame server indication. 0 disables caching. (This is
8300 <emphasis role="bold">NOT</emphasis> recommended.)
8301 The default is <literal>600</literal> (10 minutes) and the
8303 <literal>1800</literal> (30 minutes).
8307 Lame-ttl also controls the amount of time DNSSEC
8308 validation failures are cached. There is a minimum
8309 of 30 seconds applied to bad cache entries if the
8310 lame-ttl is set to less than 30 seconds.
8317 <term><command>max-ncache-ttl</command></term>
8320 To reduce network traffic and increase performance,
8321 the server stores negative answers. <command>max-ncache-ttl</command> is
8322 used to set a maximum retention time for these answers in
8324 in seconds. The default
8325 <command>max-ncache-ttl</command> is <literal>10800</literal> seconds (3 hours).
8326 <command>max-ncache-ttl</command> cannot exceed
8328 be silently truncated to 7 days if set to a greater value.
8334 <term><command>max-cache-ttl</command></term>
8337 Sets the maximum time for which the server will
8338 cache ordinary (positive) answers. The default is
8340 A value of zero may cause all queries to return
8341 SERVFAIL, because of lost caches of intermediate
8342 RRsets (such as NS and glue AAAA/A records) in the
8349 <term><command>min-roots</command></term>
8352 The minimum number of root servers that
8353 is required for a request for the root servers to be
8354 accepted. The default
8355 is <userinput>2</userinput>.
8359 Not implemented in <acronym>BIND</acronym> 9.
8366 <term><command>sig-validity-interval</command></term>
8369 Specifies the number of days into the future when
8370 DNSSEC signatures automatically generated as a
8371 result of dynamic updates (<xref
8372 linkend="dynamic_update"/>) will expire. There
8373 is an optional second field which specifies how
8374 long before expiry that the signatures will be
8375 regenerated. If not specified, the signatures will
8376 be regenerated at 1/4 of base interval. The second
8377 field is specified in days if the base interval is
8378 greater than 7 days otherwise it is specified in hours.
8379 The default base interval is <literal>30</literal> days
8380 giving a re-signing interval of 7 1/2 days. The maximum
8381 values are 10 years (3660 days).
8384 The signature inception time is unconditionally
8385 set to one hour before the current time to allow
8386 for a limited amount of clock skew.
8389 The <command>sig-validity-interval</command>
8390 should be, at least, several multiples of the SOA
8391 expire interval to allow for reasonable interaction
8392 between the various timer and expiry dates.
8398 <term><command>sig-signing-nodes</command></term>
8401 Specify the maximum number of nodes to be
8402 examined in each quantum when signing a zone with
8403 a new DNSKEY. The default is
8404 <literal>100</literal>.
8410 <term><command>sig-signing-signatures</command></term>
8413 Specify a threshold number of signatures that
8414 will terminate processing a quantum when signing
8415 a zone with a new DNSKEY. The default is
8416 <literal>10</literal>.
8422 <term><command>sig-signing-type</command></term>
8425 Specify a private RDATA type to be used when generating
8426 key signing records. The default is
8427 <literal>65534</literal>.
8430 It is expected that this parameter may be removed
8431 in a future version once there is a standard type.
8434 These records can be removed from the zone once named
8435 has completed signing the zone with the matching key
8436 using <command>nsupdate</command> or
8437 <command>rndc signing -clear</command>.
8438 <command>rndc signing -clear</command> is the only supported
8439 way to remove these records from
8440 <command>inline-signing</command> zones.
8446 <term><command>min-refresh-time</command></term>
8447 <term><command>max-refresh-time</command></term>
8448 <term><command>min-retry-time</command></term>
8449 <term><command>max-retry-time</command></term>
8452 These options control the server's behavior on refreshing a
8454 (querying for SOA changes) or retrying failed transfers.
8455 Usually the SOA values for the zone are used, but these
8457 are set by the master, giving slave server administrators
8459 control over their contents.
8462 These options allow the administrator to set a minimum and
8464 refresh and retry time either per-zone, per-view, or
8466 These options are valid for slave and stub zones,
8467 and clamp the SOA refresh and retry times to the specified
8471 The following defaults apply.
8472 <command>min-refresh-time</command> 300 seconds,
8473 <command>max-refresh-time</command> 2419200 seconds
8474 (4 weeks), <command>min-retry-time</command> 500 seconds,
8475 and <command>max-retry-time</command> 1209600 seconds
8482 <term><command>edns-udp-size</command></term>
8485 Sets the advertised EDNS UDP buffer size in bytes
8486 to control the size of packets received.
8487 Valid values are 512 to 4096 (values outside this range
8488 will be silently adjusted). The default value
8489 is 4096. The usual reason for setting
8490 <command>edns-udp-size</command> to a non-default
8491 value is to get UDP answers to pass through broken
8492 firewalls that block fragmented packets and/or
8493 block UDP packets that are greater than 512 bytes.
8496 <command>named</command> will fallback to using 512 bytes
8497 if it get a series of timeout at the initial value. 512
8498 bytes is not being offered to encourage sites to fix their
8499 firewalls. Small EDNS UDP sizes will result in the
8500 excessive use of TCP.
8506 <term><command>max-udp-size</command></term>
8509 Sets the maximum EDNS UDP message size
8510 <command>named</command> will send in bytes.
8511 Valid values are 512 to 4096 (values outside this
8512 range will be silently adjusted). The default
8513 value is 4096. The usual reason for setting
8514 <command>max-udp-size</command> to a non-default
8515 value is to get UDP answers to pass through broken
8516 firewalls that block fragmented packets and/or
8517 block UDP packets that are greater than 512 bytes.
8518 This is independent of the advertised receive
8519 buffer (<command>edns-udp-size</command>).
8522 Setting this to a low value will encourage additional
8523 TCP traffic to the nameserver.
8529 <term><command>masterfile-format</command></term>
8532 the file format of zone files (see
8533 <xref linkend="zonefile_format"/>).
8534 The default value is <constant>text</constant>, which is the
8535 standard textual representation, except for slave zones,
8536 in which the default value is <constant>raw</constant>.
8537 Files in other formats than <constant>text</constant> are
8538 typically expected to be generated by the
8539 <command>named-compilezone</command> tool, or dumped by
8540 <command>named</command>.
8543 Note that when a zone file in a different format than
8544 <constant>text</constant> is loaded, <command>named</command>
8545 may omit some of the checks which would be performed for a
8546 file in the <constant>text</constant> format. In particular,
8547 <command>check-names</command> checks do not apply
8548 for the <constant>raw</constant> format. This means
8549 a zone file in the <constant>raw</constant> format
8550 must be generated with the same check level as that
8551 specified in the <command>named</command> configuration
8552 file. This statement sets the
8553 <command>masterfile-format</command> for all zones,
8554 but can be overridden on a per-zone or per-view basis
8555 by including a <command>masterfile-format</command>
8556 statement within the <command>zone</command> or
8557 <command>view</command> block in the configuration
8563 <varlistentry id="clients-per-query">
8564 <term><command>clients-per-query</command></term>
8565 <term><command>max-clients-per-query</command></term>
8568 initial value (minimum) and maximum number of recursive
8569 simultaneous clients for any given query
8570 (<qname,qtype,qclass>) that the server will accept
8571 before dropping additional clients. <command>named</command> will attempt to
8572 self tune this value and changes will be logged. The
8573 default values are 10 and 100.
8576 This value should reflect how many queries come in for
8577 a given name in the time it takes to resolve that name.
8578 If the number of queries exceed this value, <command>named</command> will
8579 assume that it is dealing with a non-responsive zone
8580 and will drop additional queries. If it gets a response
8581 after dropping queries, it will raise the estimate. The
8582 estimate will then be lowered in 20 minutes if it has
8586 If <command>clients-per-query</command> is set to zero,
8587 then there is no limit on the number of clients per query
8588 and no queries will be dropped.
8591 If <command>max-clients-per-query</command> is set to zero,
8592 then there is no upper bound other than imposed by
8593 <command>recursive-clients</command>.
8599 <term><command>notify-delay</command></term>
8602 The delay, in seconds, between sending sets of notify
8603 messages for a zone. The default is five (5) seconds.
8606 The overall rate that NOTIFY messages are sent for all
8607 zones is controlled by <command>serial-query-rate</command>.
8613 <term><command>max-rsa-exponent-size</command></term>
8616 The maximum RSA exponent size, in bits, that will
8617 be accepted when validating. Valid values are 35
8618 to 4096 bits. The default zero (0) is also accepted
8619 and is equivalent to 4096.
8627 <sect3 id="builtin">
8628 <title>Built-in server information zones</title>
8631 The server provides some helpful diagnostic information
8632 through a number of built-in zones under the
8633 pseudo-top-level-domain <literal>bind</literal> in the
8634 <command>CHAOS</command> class. These zones are part
8636 built-in view (see <xref linkend="view_statement_grammar"/>) of
8638 <command>CHAOS</command> which is separate from the
8639 default view of class <command>IN</command>. Most global
8640 configuration options (<command>allow-query</command>,
8641 etc) will apply to this view, but some are locally
8642 overridden: <command>notify</command>,
8643 <command>recursion</command> and
8644 <command>allow-new-zones</command> are
8645 always set to <userinput>no</userinput>.
8648 If you need to disable these zones, use the options
8649 below, or hide the built-in <command>CHAOS</command>
8651 defining an explicit view of class <command>CHAOS</command>
8652 that matches all clients.
8658 <term><command>version</command></term>
8661 The version the server should report
8662 via a query of the name <literal>version.bind</literal>
8663 with type <command>TXT</command>, class <command>CHAOS</command>.
8664 The default is the real version number of this server.
8665 Specifying <command>version none</command>
8666 disables processing of the queries.
8672 <term><command>hostname</command></term>
8675 The hostname the server should report via a query of
8676 the name <filename>hostname.bind</filename>
8677 with type <command>TXT</command>, class <command>CHAOS</command>.
8678 This defaults to the hostname of the machine hosting the
8680 found by the gethostname() function. The primary purpose of such queries
8682 identify which of a group of anycast servers is actually
8683 answering your queries. Specifying <command>hostname none;</command>
8684 disables processing of the queries.
8690 <term><command>server-id</command></term>
8693 The ID the server should report when receiving a Name
8694 Server Identifier (NSID) query, or a query of the name
8695 <filename>ID.SERVER</filename> with type
8696 <command>TXT</command>, class <command>CHAOS</command>.
8697 The primary purpose of such queries is to
8698 identify which of a group of anycast servers is actually
8699 answering your queries. Specifying <command>server-id none;</command>
8700 disables processing of the queries.
8701 Specifying <command>server-id hostname;</command> will cause <command>named</command> to
8702 use the hostname as found by the gethostname() function.
8703 The default <command>server-id</command> is <command>none</command>.
8713 <title>Built-in Empty Zones</title>
8715 Named has some built-in empty zones (SOA and NS records only).
8716 These are for zones that should normally be answered locally
8717 and which queries should not be sent to the Internet's root
8718 servers. The official servers which cover these namespaces
8719 return NXDOMAIN responses to these queries. In particular,
8720 these cover the reverse namespaces for addresses from
8721 RFC 1918, RFC 4193, RFC 5737 and RFC 6598. They also include the
8722 reverse namespace for IPv6 local address (locally assigned),
8723 IPv6 link local addresses, the IPv6 loopback address and the
8724 IPv6 unknown address.
8727 Named will attempt to determine if a built-in zone already exists
8728 or is active (covered by a forward-only forwarding declaration)
8729 and will not create an empty zone in that case.
8732 The current list of empty zones is:
8734 <listitem>10.IN-ADDR.ARPA</listitem>
8735 <listitem>16.172.IN-ADDR.ARPA</listitem>
8736 <listitem>17.172.IN-ADDR.ARPA</listitem>
8737 <listitem>18.172.IN-ADDR.ARPA</listitem>
8738 <listitem>19.172.IN-ADDR.ARPA</listitem>
8739 <listitem>20.172.IN-ADDR.ARPA</listitem>
8740 <listitem>21.172.IN-ADDR.ARPA</listitem>
8741 <listitem>22.172.IN-ADDR.ARPA</listitem>
8742 <listitem>23.172.IN-ADDR.ARPA</listitem>
8743 <listitem>24.172.IN-ADDR.ARPA</listitem>
8744 <listitem>25.172.IN-ADDR.ARPA</listitem>
8745 <listitem>26.172.IN-ADDR.ARPA</listitem>
8746 <listitem>27.172.IN-ADDR.ARPA</listitem>
8747 <listitem>28.172.IN-ADDR.ARPA</listitem>
8748 <listitem>29.172.IN-ADDR.ARPA</listitem>
8749 <listitem>30.172.IN-ADDR.ARPA</listitem>
8750 <listitem>31.172.IN-ADDR.ARPA</listitem>
8751 <listitem>168.192.IN-ADDR.ARPA</listitem>
8752 <listitem>64.100.IN-ADDR.ARPA</listitem>
8753 <listitem>65.100.IN-ADDR.ARPA</listitem>
8754 <listitem>66.100.IN-ADDR.ARPA</listitem>
8755 <listitem>67.100.IN-ADDR.ARPA</listitem>
8756 <listitem>68.100.IN-ADDR.ARPA</listitem>
8757 <listitem>69.100.IN-ADDR.ARPA</listitem>
8758 <listitem>70.100.IN-ADDR.ARPA</listitem>
8759 <listitem>71.100.IN-ADDR.ARPA</listitem>
8760 <listitem>72.100.IN-ADDR.ARPA</listitem>
8761 <listitem>73.100.IN-ADDR.ARPA</listitem>
8762 <listitem>74.100.IN-ADDR.ARPA</listitem>
8763 <listitem>75.100.IN-ADDR.ARPA</listitem>
8764 <listitem>76.100.IN-ADDR.ARPA</listitem>
8765 <listitem>77.100.IN-ADDR.ARPA</listitem>
8766 <listitem>78.100.IN-ADDR.ARPA</listitem>
8767 <listitem>79.100.IN-ADDR.ARPA</listitem>
8768 <listitem>80.100.IN-ADDR.ARPA</listitem>
8769 <listitem>81.100.IN-ADDR.ARPA</listitem>
8770 <listitem>82.100.IN-ADDR.ARPA</listitem>
8771 <listitem>83.100.IN-ADDR.ARPA</listitem>
8772 <listitem>84.100.IN-ADDR.ARPA</listitem>
8773 <listitem>85.100.IN-ADDR.ARPA</listitem>
8774 <listitem>86.100.IN-ADDR.ARPA</listitem>
8775 <listitem>87.100.IN-ADDR.ARPA</listitem>
8776 <listitem>88.100.IN-ADDR.ARPA</listitem>
8777 <listitem>89.100.IN-ADDR.ARPA</listitem>
8778 <listitem>90.100.IN-ADDR.ARPA</listitem>
8779 <listitem>91.100.IN-ADDR.ARPA</listitem>
8780 <listitem>92.100.IN-ADDR.ARPA</listitem>
8781 <listitem>93.100.IN-ADDR.ARPA</listitem>
8782 <listitem>94.100.IN-ADDR.ARPA</listitem>
8783 <listitem>95.100.IN-ADDR.ARPA</listitem>
8784 <listitem>96.100.IN-ADDR.ARPA</listitem>
8785 <listitem>97.100.IN-ADDR.ARPA</listitem>
8786 <listitem>98.100.IN-ADDR.ARPA</listitem>
8787 <listitem>99.100.IN-ADDR.ARPA</listitem>
8788 <listitem>100.100.IN-ADDR.ARPA</listitem>
8789 <listitem>101.100.IN-ADDR.ARPA</listitem>
8790 <listitem>102.100.IN-ADDR.ARPA</listitem>
8791 <listitem>103.100.IN-ADDR.ARPA</listitem>
8792 <listitem>104.100.IN-ADDR.ARPA</listitem>
8793 <listitem>105.100.IN-ADDR.ARPA</listitem>
8794 <listitem>106.100.IN-ADDR.ARPA</listitem>
8795 <listitem>107.100.IN-ADDR.ARPA</listitem>
8796 <listitem>108.100.IN-ADDR.ARPA</listitem>
8797 <listitem>109.100.IN-ADDR.ARPA</listitem>
8798 <listitem>110.100.IN-ADDR.ARPA</listitem>
8799 <listitem>111.100.IN-ADDR.ARPA</listitem>
8800 <listitem>112.100.IN-ADDR.ARPA</listitem>
8801 <listitem>113.100.IN-ADDR.ARPA</listitem>
8802 <listitem>114.100.IN-ADDR.ARPA</listitem>
8803 <listitem>115.100.IN-ADDR.ARPA</listitem>
8804 <listitem>116.100.IN-ADDR.ARPA</listitem>
8805 <listitem>117.100.IN-ADDR.ARPA</listitem>
8806 <listitem>118.100.IN-ADDR.ARPA</listitem>
8807 <listitem>119.100.IN-ADDR.ARPA</listitem>
8808 <listitem>120.100.IN-ADDR.ARPA</listitem>
8809 <listitem>121.100.IN-ADDR.ARPA</listitem>
8810 <listitem>122.100.IN-ADDR.ARPA</listitem>
8811 <listitem>123.100.IN-ADDR.ARPA</listitem>
8812 <listitem>124.100.IN-ADDR.ARPA</listitem>
8813 <listitem>125.100.IN-ADDR.ARPA</listitem>
8814 <listitem>126.100.IN-ADDR.ARPA</listitem>
8815 <listitem>127.100.IN-ADDR.ARPA</listitem>
8816 <listitem>0.IN-ADDR.ARPA</listitem>
8817 <listitem>127.IN-ADDR.ARPA</listitem>
8818 <listitem>254.169.IN-ADDR.ARPA</listitem>
8819 <listitem>2.0.192.IN-ADDR.ARPA</listitem>
8820 <listitem>100.51.198.IN-ADDR.ARPA</listitem>
8821 <listitem>113.0.203.IN-ADDR.ARPA</listitem>
8822 <listitem>255.255.255.255.IN-ADDR.ARPA</listitem>
8823 <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>
8824 <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>
8825 <listitem>8.B.D.0.1.0.0.2.IP6.ARPA</listitem>
8826 <listitem>D.F.IP6.ARPA</listitem>
8827 <listitem>8.E.F.IP6.ARPA</listitem>
8828 <listitem>9.E.F.IP6.ARPA</listitem>
8829 <listitem>A.E.F.IP6.ARPA</listitem>
8830 <listitem>B.E.F.IP6.ARPA</listitem>
8834 Empty zones are settable at the view level and only apply to
8835 views of class IN. Disabled empty zones are only inherited
8836 from options if there are no disabled empty zones specified
8837 at the view level. To override the options list of disabled
8838 zones, you can disable the root zone at the view level, for example:
8840 disable-empty-zone ".";
8844 If you are using the address ranges covered here, you should
8845 already have reverse zones covering the addresses you use.
8846 In practice this appears to not be the case with many queries
8847 being made to the infrastructure servers for names in these
8848 spaces. So many in fact that sacrificial servers were needed
8849 to be deployed to channel the query load away from the
8850 infrastructure servers.
8853 The real parent servers for these zones should disable all
8854 empty zone under the parent zone they serve. For the real
8855 root servers, this is all built-in empty zones. This will
8856 enable them to return referrals to deeper in the tree.
8860 <term><command>empty-server</command></term>
8863 Specify what server name will appear in the returned
8864 SOA record for empty zones. If none is specified, then
8865 the zone's name will be used.
8871 <term><command>empty-contact</command></term>
8874 Specify what contact name will appear in the returned
8875 SOA record for empty zones. If none is specified, then
8882 <term><command>empty-zones-enable</command></term>
8885 Enable or disable all empty zones. By default, they
8892 <term><command>disable-empty-zone</command></term>
8895 Disable individual empty zones. By default, none are
8896 disabled. This option can be specified multiple times.
8904 <title>Additional Section Caching</title>
8907 The additional section cache, also called <command>acache</command>,
8908 is an internal cache to improve the response performance of BIND 9.
8909 When additional section caching is enabled, BIND 9 will
8910 cache an internal short-cut to the additional section content for
8912 Note that <command>acache</command> is an internal caching
8913 mechanism of BIND 9, and is not related to the DNS caching
8918 Additional section caching does not change the
8919 response content (except the RRsets ordering of the additional
8920 section, see below), but can improve the response performance
8922 It is particularly effective when BIND 9 acts as an authoritative
8923 server for a zone that has many delegations with many glue RRs.
8927 In order to obtain the maximum performance improvement
8928 from additional section caching, setting
8929 <command>additional-from-cache</command>
8930 to <command>no</command> is recommended, since the current
8931 implementation of <command>acache</command>
8932 does not short-cut of additional section information from the
8937 One obvious disadvantage of <command>acache</command> is
8938 that it requires much more
8939 memory for the internal cached data.
8940 Thus, if the response performance does not matter and memory
8941 consumption is much more critical, the
8942 <command>acache</command> mechanism can be
8943 disabled by setting <command>acache-enable</command> to
8944 <command>no</command>.
8945 It is also possible to specify the upper limit of memory
8947 for acache by using <command>max-acache-size</command>.
8951 Additional section caching also has a minor effect on the
8952 RRset ordering in the additional section.
8953 Without <command>acache</command>,
8954 <command>cyclic</command> order is effective for the additional
8955 section as well as the answer and authority sections.
8956 However, additional section caching fixes the ordering when it
8957 first caches an RRset for the additional section, and the same
8958 ordering will be kept in succeeding responses, regardless of the
8959 setting of <command>rrset-order</command>.
8960 The effect of this should be minor, however, since an
8961 RRset in the additional section
8962 typically only contains a small number of RRs (and in many cases
8963 it only contains a single RR), in which case the
8964 ordering does not matter much.
8968 The following is a summary of options related to
8969 <command>acache</command>.
8975 <term><command>acache-enable</command></term>
8978 If <command>yes</command>, additional section caching is
8979 enabled. The default value is <command>no</command>.
8985 <term><command>acache-cleaning-interval</command></term>
8988 The server will remove stale cache entries, based on an LRU
8990 algorithm, every <command>acache-cleaning-interval</command> minutes.
8991 The default is 60 minutes.
8992 If set to 0, no periodic cleaning will occur.
8998 <term><command>max-acache-size</command></term>
9001 The maximum amount of memory in bytes to use for the server's acache.
9002 When the amount of data in the acache reaches this limit,
9004 will clean more aggressively so that the limit is not
9006 In a server with multiple views, the limit applies
9008 acache of each view.
9009 The default is <literal>16M</literal>.
9019 <title>Content Filtering</title>
9021 <acronym>BIND</acronym> 9 provides the ability to filter
9022 out DNS responses from external DNS servers containing
9023 certain types of data in the answer section.
9024 Specifically, it can reject address (A or AAAA) records if
9025 the corresponding IPv4 or IPv6 addresses match the given
9026 <varname>address_match_list</varname> of the
9027 <command>deny-answer-addresses</command> option.
9028 It can also reject CNAME or DNAME records if the "alias"
9029 name (i.e., the CNAME alias or the substituted query name
9030 due to DNAME) matches the
9031 given <varname>namelist</varname> of the
9032 <command>deny-answer-aliases</command> option, where
9033 "match" means the alias name is a subdomain of one of
9034 the <varname>name_list</varname> elements.
9035 If the optional <varname>namelist</varname> is specified
9036 with <command>except-from</command>, records whose query name
9037 matches the list will be accepted regardless of the filter
9039 Likewise, if the alias name is a subdomain of the
9040 corresponding zone, the <command>deny-answer-aliases</command>
9041 filter will not apply;
9042 for example, even if "example.com" is specified for
9043 <command>deny-answer-aliases</command>,
9045 <programlisting>www.example.com. CNAME xxx.example.com.</programlisting>
9048 returned by an "example.com" server will be accepted.
9052 In the <varname>address_match_list</varname> of the
9053 <command>deny-answer-addresses</command> option, only
9054 <varname>ip_addr</varname>
9055 and <varname>ip_prefix</varname>
9057 any <varname>key_id</varname> will be silently ignored.
9061 If a response message is rejected due to the filtering,
9062 the entire message is discarded without being cached, and
9063 a SERVFAIL error will be returned to the client.
9067 This filtering is intended to prevent "DNS rebinding attacks," in
9068 which an attacker, in response to a query for a domain name the
9069 attacker controls, returns an IP address within your own network or
9070 an alias name within your own domain.
9071 A naive web browser or script could then serve as an
9072 unintended proxy, allowing the attacker
9073 to get access to an internal node of your local network
9074 that couldn't be externally accessed otherwise.
9075 See the paper available at
9076 <ulink url="http://portal.acm.org/citation.cfm?id=1315245.1315298">
9077 http://portal.acm.org/citation.cfm?id=1315245.1315298
9079 for more details about the attacks.
9083 For example, if you own a domain named "example.net" and
9084 your internal network uses an IPv4 prefix 192.0.2.0/24,
9085 you might specify the following rules:
9088 <programlisting>deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
9089 deny-answer-aliases { "example.net"; };
9093 If an external attacker lets a web browser in your local
9094 network look up an IPv4 address of "attacker.example.com",
9095 the attacker's DNS server would return a response like this:
9098 <programlisting>attacker.example.com. A 192.0.2.1</programlisting>
9101 in the answer section.
9102 Since the rdata of this record (the IPv4 address) matches
9103 the specified prefix 192.0.2.0/24, this response will be
9108 On the other hand, if the browser looks up a legitimate
9109 internal web server "www.example.net" and the
9110 following response is returned to
9111 the <acronym>BIND</acronym> 9 server
9114 <programlisting>www.example.net. A 192.0.2.2</programlisting>
9117 it will be accepted since the owner name "www.example.net"
9118 matches the <command>except-from</command> element,
9123 Note that this is not really an attack on the DNS per se.
9124 In fact, there is nothing wrong for an "external" name to
9125 be mapped to your "internal" IP address or domain name
9126 from the DNS point of view.
9127 It might actually be provided for a legitimate purpose,
9128 such as for debugging.
9129 As long as the mapping is provided by the correct owner,
9130 it is not possible or does not make sense to detect
9131 whether the intent of the mapping is legitimate or not
9133 The "rebinding" attack must primarily be protected at the
9134 application that uses the DNS.
9135 For a large site, however, it may be difficult to protect
9136 all possible applications at once.
9137 This filtering feature is provided only to help such an
9138 operational environment;
9139 it is generally discouraged to turn it on unless you are
9140 very sure you have no other choice and the attack is a
9141 real threat for your applications.
9145 Care should be particularly taken if you want to use this
9146 option for addresses within 127.0.0.0/8.
9147 These addresses are obviously "internal", but many
9148 applications conventionally rely on a DNS mapping from
9149 some name to such an address.
9150 Filtering out DNS records containing this address
9151 spuriously can break such applications.
9156 <title>Response Policy Zone (RPZ) Rewriting</title>
9158 <acronym>BIND</acronym> 9 includes a limited
9159 mechanism to modify DNS responses for requests
9160 analogous to email anti-spam DNS blacklists.
9161 Responses can be changed to deny the existence of domains(NXDOMAIN),
9162 deny the existence of IP addresses for domains (NODATA),
9163 or contain other IP addresses or data.
9167 Response policy zones are named in the
9168 <command>response-policy</command> option for the view or among the
9169 global options if there is no response-policy option for the view.
9170 RPZs are ordinary DNS zones containing RRsets
9171 that can be queried normally if allowed.
9172 It is usually best to restrict those queries with something like
9173 <command>allow-query { localhost; };</command>.
9177 Four policy triggers are encoded in RPZ records, QNAME, IP, NSIP,
9179 QNAME RPZ records triggered by query names of requests and targets
9180 of CNAME records resolved to generate the response.
9181 The owner name of a QNAME RPZ record is the query name relativized
9186 The second kind of RPZ trigger is an IP address in an A and AAAA
9187 record in the ANSWER section of a response.
9188 IP address triggers are encoded in records that have owner names
9189 that are subdomains of <userinput>rpz-ip</userinput> relativized
9190 to the RPZ origin name and encode an IP address or address block.
9191 IPv4 trigger addresses are represented as
9192 <userinput>prefixlength.B4.B3.B2.B1.rpz-ip</userinput>.
9193 The prefix length must be between 1 and 32.
9194 All four bytes, B4, B3, B2, and B1, must be present.
9195 B4 is the decimal value of the least significant byte of the
9196 IPv4 address as in IN-ADDR.ARPA.
9197 IPv6 addresses are encoded in a format similar to the standard
9198 IPv6 text representation,
9199 <userinput>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</userinput>.
9200 Each of W8,...,W1 is a one to four digit hexadecimal number
9201 representing 16 bits of the IPv6 address as in the standard text
9202 representation of IPv6 addresses, but reversed as in IN-ADDR.ARPA.
9203 All 8 words must be present except when consecutive
9204 zero words are replaced with <userinput>.zz.</userinput>
9205 analogous to double colons (::) in standard IPv6 text encodings.
9206 The prefix length must be between 1 and 128.
9210 NSDNAME triggers match names of authoritative servers
9211 for the query name, a parent of the query name, a CNAME for
9212 query name, or a parent of a CNAME.
9213 They are encoded as subdomains of
9214 <userinput>rpz-nsdomain</userinput> relativized
9215 to the RPZ origin name.
9216 NSIP triggers match IP addresses in A and
9217 AAAA RRsets for domains that can be checked against NSDNAME
9219 NSIP triggers are encoded like IP triggers except as subdomains of
9220 <userinput>rpz-nsip</userinput>.
9221 NSDNAME and NSIP triggers are checked only for names with at
9222 least <command>min-ns-dots</command> dots.
9223 The default value of <command>min-ns-dots</command> is 1 to
9224 exclude top level domains.
9228 The query response is checked against all RPZs, so
9229 two or more policy records can be triggered by a response.
9230 Because DNS responses can be rewritten according to at most one
9231 policy record, a single record encoding an action (other than
9232 <command>DISABLED</command> actions) must be chosen.
9233 Triggers or the records that encode them are chosen in
9234 the following order:
9236 <listitem>Choose the triggered record in the zone that appears
9237 first in the response-policy option.
9239 <listitem>Prefer QNAME to IP to NSDNAME to NSIP triggers
9242 <listitem>Among NSDNAME triggers, prefer the
9243 trigger that matches the smallest name under the DNSSEC ordering.
9245 <listitem>Among IP or NSIP triggers, prefer the trigger
9246 with the longest prefix.
9248 <listitem>Among triggers with the same prefex length,
9249 prefer the IP or NSIP trigger that matches
9250 the smallest IP address.
9256 When the processing of a response is restarted to resolve
9257 DNAME or CNAME records and a policy record set has
9259 all RPZs are again consulted for the DNAME or CNAME names
9264 RPZ record sets are sets of any types of DNS record except
9265 DNAME or DNSSEC that encode actions or responses to queries.
9267 <listitem>The <command>NXDOMAIN</command> response is encoded
9268 by a CNAME whose target is the root domain (.)
9270 <listitem>A CNAME whose target is the wildcard top-level
9271 domain (*.) specifies the <command>NODATA</command> action,
9272 which rewrites the response to NODATA or ANCOUNT=1.
9274 <listitem>The <command>Local Data</command> action is
9275 represented by a set ordinary DNS records that are used
9276 to answer queries. Queries for record types not the
9277 set are answered with NODATA.
9279 A special form of local data is a CNAME whose target is a
9280 wildcard such as *.example.com.
9281 It is used as if were an ordinary CNAME after the astrisk (*)
9282 has been replaced with the query name.
9283 The purpose for this special form is query logging in the
9284 walled garden's authority DNS server.
9286 <listitem>The <command>PASSTHRU</command> policy is specified
9287 by a CNAME whose target is <command>rpz-passthru.</command>
9288 It causes the response to not be rewritten
9289 and is most often used to "poke holes" in policies for
9291 (A CNAME whose target is the variable part of its owner name
9292 is an obsolete specification of the PASSTHRU policy.)
9298 The actions specified in an RPZ can be overridden with a
9299 <command>policy</command> clause in the
9300 <command>response-policy</command> option.
9301 An organization using an RPZ provided by another organization might
9302 use this mechanism to redirect domains to its own walled garden.
9304 <listitem><command>GIVEN</command> says "do not override but
9305 perform the action specified in the zone."
9307 <listitem><command>DISABLED</command> causes policy records to do
9308 nothing but log what they might have done.
9309 The response to the DNS query will be written according to
9310 any triggered policy records that are not disabled.
9311 Disabled policy zones should appear first,
9312 because they will often not be logged
9313 if a higher precedence trigger is found first.
9315 <listitem><command>PASSTHRU</command> causes all policy records
9316 to act as if they were CNAME records with targets the variable
9317 part of their owner name. They protect the response from
9320 <listitem><command>NXDOMAIN</command> causes all RPZ records
9321 to specify NXDOMAIN policies.
9323 <listitem><command>NODATA</command> overrides with the
9326 <listitem><command>CNAME domain</command> causes all RPZ
9327 policy records to act as if they were "cname domain" records.
9333 By default, the actions encoded in an RPZ are applied
9334 only to queries that ask for recursion (RD=1).
9335 That default can be changed for a single RPZ or all RPZs in a view
9336 with a <command>recursive-only no</command> clause.
9337 This feature is useful for serving the same zone files
9338 both inside and outside an RFC 1918 cloud and using RPZ to
9339 delete answers that would otherwise contain RFC 1918 values
9340 on the externally visible name server or view.
9344 Also by default, RPZ actions are applied only to DNS requests that
9345 either do not request DNSSEC metadata (DO=0) or when no DNSSEC
9346 records are available for request name in the original zone (not
9347 the response policy zone).
9348 This default can be changed for all RPZs in a view with a
9349 <command>break-dnssec yes</command> clause.
9350 In that case, RPZ actions are applied regardless of DNSSEC.
9351 The name of the clause option reflects the fact that results
9352 rewritten by RPZ actions cannot verify.
9356 The TTL of a record modified by RPZ policies is set from the
9357 TTL of the relevant record in policy zone. It is then limited
9359 The <command>max-policy-ttl</command> clause changes that
9360 maximum from its default of 5.
9364 For example, you might use this option statement
9366 <programlisting> response-policy { zone "badlist"; };</programlisting>
9368 and this zone statement
9370 <programlisting> zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</programlisting>
9374 <programlisting>$TTL 1H
9375 @ SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
9378 ; QNAME policy records. There are no periods (.) after the owner names.
9379 nxdomain.domain.com CNAME . ; NXDOMAIN policy
9380 nodata.domain.com CNAME *. ; NODATA policy
9381 bad.domain.com A 10.0.0.1 ; redirect to a walled garden
9384 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
9385 ok.domain.com CNAME rpz-passthru.
9387 bzone.domain.com CNAME garden.example.com.
9389 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
9390 *.bzone.domain.com CNAME *.garden.example.com.
9393 ; IP policy records that rewrite all answers for 127/8 except 127.0.0.1
9394 8.0.0.0.127.rpz-ip CNAME .
9395 32.1.0.0.127.rpz-ip CNAME rpz-passthru.
9397 ; NSDNAME and NSIP policy records
9398 ns.domain.com.rpz-nsdname CNAME .
9399 48.zz.2.2001.rpz-nsip CNAME .
9402 RPZ can affect server performance.
9403 Each configured response policy zone requires the server to
9404 perform one to four additional database lookups before a
9405 query can be answered.
9406 For example, a DNS server with four policy zones, each with all
9407 four kinds of response triggers, QNAME, IP, NSIP, and
9408 NSDNAME, requires a total of 17 times as many database
9409 lookups as a similar DNS server with no response policy zones.
9410 A <acronym>BIND9</acronym> server with adequate memory and one
9411 response policy zone with QNAME and IP triggers might achieve a
9412 maximum queries-per-second rate about 20% lower.
9413 A server with four response policy zones with QNAME and IP
9414 triggers might have a maximum QPS rate about 50% lower.
9418 Responses rewritten by RPZ are counted in the
9419 <command>RPZRewrites</command> statistics.
9424 <title>Response Rate Limiting</title>
9426 This feature is only available when <acronym>BIND</acronym> 9
9427 is compiled with the <userinput>--enable-rrl</userinput>
9428 option on the "configure" command line.
9431 Excessive almost identical UDP <emphasis>responses</emphasis>
9432 can be controlled by configuring a
9433 <command>rate-limit</command> clause in an
9434 <command>options</command> or <command>view</command> statement.
9435 This mechanism keeps authoritative BIND 9 from being used
9436 in amplifying reflection denial of service (DoS) attacks.
9437 Short truncated (TC=1) responses can be sent to provide
9438 rate-limited responses to legitimate clients within
9439 a range of forged, attacked IP addresses.
9440 Legitimate clients react to dropped or truncated response
9441 by retrying with UDP or with TCP respectively.
9445 This mechanism is intended for authoritative DNS servers.
9446 It can be used on recursive servers but can slow
9447 applications such as SMTP servers (mail receivers) and
9448 HTTP clients (web browsers) that repeatedly request the
9450 When possible, closing "open" recursive servers is better.
9454 Response rate limiting uses a "credit" or "token bucket" scheme.
9455 Each combination of identical response and client
9456 has a conceptual account that earns a specified number
9457 of credits every second.
9458 A prospective response debits its account by one.
9459 Responses are dropped or truncated
9460 while the account is negative.
9461 Responses are tracked within a rolling window of time
9462 which defaults to 15 seconds, but can be configured with
9463 the <command>window</command> option to any value from
9464 1 to 3600 seconds (1 hour).
9465 The account cannot become more positive than
9466 the per-second limit
9467 or more negative than <command>window</command>
9468 times the per-second limit.
9469 When the specified number of credits for a class of
9470 responses is set to 0, those responses are not rate limited.
9474 The notions of "identical response" and "DNS client"
9475 for rate limiting are not simplistic.
9476 All responses to an address block are counted as if to a
9478 The prefix lengths of addresses blocks are
9479 specified with <command>ipv4-prefix-length</command> (default 24)
9480 and <command>ipv6-prefix-length</command> (default 56).
9484 All non-empty responses for a valid domain name (qname)
9485 and record type (qtype) are identical and have a limit specified
9486 with <command>responses-per-second</command>
9487 (default 0 or no limit).
9488 All empty (NODATA) responses for a valid domain,
9489 regardless of query type, are identical.
9490 Responses in the NODATA class are limited by
9491 <command>nodata-per-second</command>
9492 (default <command>responses-per-second</command>).
9493 Requests for any and all undefined subdomains of a given
9494 valid domain result in NXDOMAIN errors, and are identical
9495 regardless of query type.
9496 They are limited by <command>nxdomain-per-second</command>
9497 (default <command>responses-per-second</command>).
9498 This controls some attacks using random names, but
9499 can be relaxed or turned off (set to 0)
9500 on servers that expect many legitimate
9501 NXDOMAIN responses, such as from anti-spam blacklists.
9502 Referrals or delegations to the server of a given
9503 domain are identical and are limited by
9504 <command>referrals-per-second</command>
9505 (default <command>responses-per-second</command>).
9509 Responses generated from local wildcards are counted and limited
9510 as if they were for the parent domain name.
9511 This controls flooding using random.wild.example.com.
9515 All requests that result in DNS errors other
9516 than NXDOMAIN, such as SERVFAIL and FORMERR, are identical
9517 regardless of requested name (qname) or record type (qtype).
9518 This controls attacks using invalid requests or distant,
9519 broken authoritative servers.
9520 By default the limit on errors is the same as the
9521 <command>responses-per-second</command> value,
9522 but it can be set separately with
9523 <command>errors-per-second</command>.
9527 Many attacks using DNS involve UDP requests with forged source
9529 Rate limiting prevents the use of BIND 9 to flood a network
9530 with responses to requests with forged source addresses,
9531 but could let a third party block responses to legitimate requests.
9532 There is a mechanism that can answer some legitimate
9533 requests from a client whose address is being forged in a flood.
9534 Setting <command>slip</command> to 2 (its default) causes every
9535 other UDP request to be answered with a small truncated (TC=1)
9537 The small size and reduced frequency, and so lack of
9538 amplification, of "slipped" responses make them unattractive
9539 for reflection DoS attacks.
9540 <command>slip</command> must be between 0 and 10.
9541 A value of 0 does not "slip":
9542 no truncated responses are sent due to rate limiting,
9543 all responses are dropped.
9544 A value of 1 causes every response to slip;
9545 values between 2 and 10 cause every n'th response to slip.
9546 Some error responses including REFUSED and SERVFAIL
9547 cannot be replaced with truncated responses and are instead
9548 leaked at the <command>slip</command> rate.
9552 (NOTE: Dropped responses from an authoritative server may
9553 reduce the difficulty of a third party successfully forging
9554 a response to a recursive resolver. The best security
9555 against forged responses is for authoritative operators
9556 to sign their zones using DNSSEC and for resolver operators
9557 to validate the responses. When this is not an option,
9558 operators who are more concerned with response integrity
9559 than with flood mitigation may consider setting
9560 <command>slip</command> to 1, causing all rate-limited
9561 responses to be truncated rather than dropped. This reduces
9562 the effectiveness of rate-limiting against reflection attacks.)
9566 When the approximate query per second rate exceeds
9567 the <command>qps-scale</command> value,
9568 then the <command>responses-per-second</command>,
9569 <command>errors-per-second</command>,
9570 <command>nxdomains-per-second</command> and
9571 <command>all-per-second</command> values are reduced by the
9572 ratio of the current rate to the <command>qps-scale</command> value.
9573 This feature can tighten defenses during attacks.
9575 <command>qps-scale 250; responses-per-second 20;</command> and
9576 a total query rate of 1000 queries/second for all queries from
9577 all DNS clients including via TCP,
9578 then the effective responses/second limit changes to
9580 Responses sent via TCP are not limited
9581 but are counted to compute the query per second rate.
9585 Communities of DNS clients can be given their own parameters or no
9586 rate limiting by putting
9587 <command>rate-limit</command> statements in <command>view</command>
9588 statements instead of the global <command>option</command>
9590 A <command>rate-limit</command> statement in a view replaces,
9591 rather than supplementing, a <command>rate-limit</command>
9592 statement among the main options.
9593 DNS clients within a view can be exempted from rate limits
9594 with the <command>exempt-clients</command> clause.
9598 UDP responses of all kinds can be limited with the
9599 <command>all-per-second</command> phrase.
9600 This rate limiting is unlike the rate limiting provided by
9601 <command>responses-per-second</command>,
9602 <command>errors-per-second</command>, and
9603 <command>nxdomains-per-second</command> on a DNS server
9604 which are often invisible to the victim of a DNS reflection attack.
9605 Unless the forged requests of the attack are the same as the
9606 legitimate requests of the victim, the victim's requests are
9608 Responses affected by an <command>all-per-second</command> limit
9609 are always dropped; the <command>slip</command> value has no
9611 An <command>all-per-second</command> limit should be
9612 at least 4 times as large as the other limits,
9613 because single DNS clients often send bursts of legitimate
9615 For example, the receipt of a single mail message can prompt
9616 requests from an SMTP server for NS, PTR, A, and AAAA records
9617 as the incoming SMTP/TCP/IP connection is considered.
9618 The SMTP server can need additional NS, A, AAAA, MX, TXT, and SPF
9619 records as it considers the STMP <command>Mail From</command>
9621 Web browsers often repeatedly resolve the same names that
9622 are repeated in HTML <IMG> tags in a page.
9623 <command>All-per-second</command> is similar to the
9624 rate limiting offered by firewalls but often inferior.
9625 Attacks that justify ignoring the
9626 contents of DNS responses are likely to be attacks on the
9628 They usually should be discarded before the DNS server
9629 spends resources making TCP connections or parsing DNS requests,
9630 but that rate limiting must be done before the
9631 DNS server sees the requests.
9635 The maximum size of the table used to track requests and
9636 rate limit responses is set with <command>max-table-size</command>.
9637 Each entry in the table is between 40 and 80 bytes.
9638 The table needs approximately as many entries as the number
9639 of requests received per second.
9640 The default is 20,000.
9641 To reduce the cold start of growing the table,
9642 <command>min-table-size</command> (default 500)
9643 can set the minimum table size.
9644 Enable <command>rate-limit</command> category logging to monitor
9645 expansions of the table and inform
9646 choices for the initial and maximum table size.
9650 Use <command>log-only yes</command> to test rate limiting parameters
9651 without actually dropping any requests.
9655 Responses dropped by rate limits are included in the
9656 <command>RateDropped</command> and <command>QryDropped</command>
9658 Responses that truncated by rate limits are included in
9659 <command>RateSlipped</command> and <command>RespTruncated</command>.
9664 <sect2 id="server_statement_grammar">
9665 <title><command>server</command> Statement Grammar</title>
9667 <programlisting><command>server</command> <replaceable>ip_addr[/prefixlen]</replaceable> {
9668 <optional> bogus <replaceable>yes_or_no</replaceable> ; </optional>
9669 <optional> provide-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9670 <optional> request-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
9671 <optional> edns <replaceable>yes_or_no</replaceable> ; </optional>
9672 <optional> edns-udp-size <replaceable>number</replaceable> ; </optional>
9673 <optional> max-udp-size <replaceable>number</replaceable> ; </optional>
9674 <optional> transfers <replaceable>number</replaceable> ; </optional>
9675 <optional> transfer-format <replaceable>( one-answer | many-answers )</replaceable> ; ]</optional>
9676 <optional> keys <replaceable>{ string ; <optional> string ; <optional>...</optional></optional> }</replaceable> ; </optional>
9677 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9678 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9679 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9680 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
9681 <optional> query-source <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9682 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9683 <optional> query-source-v6 <optional> address ( <replaceable>ip_addr</replaceable> | <replaceable>*</replaceable> ) </optional>
9684 <optional> port ( <replaceable>ip_port</replaceable> | <replaceable>*</replaceable> ) </optional>; </optional>
9685 <optional> use-queryport-pool <replaceable>yes_or_no</replaceable>; </optional>
9686 <optional> queryport-pool-ports <replaceable>number</replaceable>; </optional>
9687 <optional> queryport-pool-updateinterval <replaceable>number</replaceable>; </optional>
9693 <sect2 id="server_statement_definition_and_usage">
9694 <title><command>server</command> Statement Definition and
9698 The <command>server</command> statement defines
9700 to be associated with a remote name server. If a prefix length is
9701 specified, then a range of servers is covered. Only the most
9703 server clause applies regardless of the order in
9704 <filename>named.conf</filename>.
9708 The <command>server</command> statement can occur at
9709 the top level of the
9710 configuration file or inside a <command>view</command>
9712 If a <command>view</command> statement contains
9713 one or more <command>server</command> statements, only
9715 apply to the view and any top-level ones are ignored.
9716 If a view contains no <command>server</command>
9718 any top-level <command>server</command> statements are
9724 If you discover that a remote server is giving out bad data,
9725 marking it as bogus will prevent further queries to it. The
9727 value of <command>bogus</command> is <command>no</command>.
9730 The <command>provide-ixfr</command> clause determines
9732 the local server, acting as master, will respond with an
9734 zone transfer when the given remote server, a slave, requests it.
9735 If set to <command>yes</command>, incremental transfer
9737 whenever possible. If set to <command>no</command>,
9739 to the remote server will be non-incremental. If not set, the
9741 of the <command>provide-ixfr</command> option in the
9743 global options block is used as a default.
9747 The <command>request-ixfr</command> clause determines
9749 the local server, acting as a slave, will request incremental zone
9750 transfers from the given remote server, a master. If not set, the
9751 value of the <command>request-ixfr</command> option in
9752 the view or global options block is used as a default. It may
9753 also be set in the zone block and, if set there, it will
9754 override the global or view setting for that zone.
9758 IXFR requests to servers that do not support IXFR will
9760 fall back to AXFR. Therefore, there is no need to manually list
9761 which servers support IXFR and which ones do not; the global
9763 of <command>yes</command> should always work.
9764 The purpose of the <command>provide-ixfr</command> and
9765 <command>request-ixfr</command> clauses is
9766 to make it possible to disable the use of IXFR even when both
9768 and slave claim to support it, for example if one of the servers
9769 is buggy and crashes or corrupts data when IXFR is used.
9773 The <command>edns</command> clause determines whether
9774 the local server will attempt to use EDNS when communicating
9775 with the remote server. The default is <command>yes</command>.
9779 The <command>edns-udp-size</command> option sets the EDNS UDP size
9780 that is advertised by <command>named</command> when querying the remote server.
9781 Valid values are 512 to 4096 bytes (values outside this range will be
9782 silently adjusted). This option is useful when you wish to
9783 advertises a different value to this server than the value you
9784 advertise globally, for example, when there is a firewall at the
9785 remote site that is blocking large replies.
9789 The <command>max-udp-size</command> option sets the
9790 maximum EDNS UDP message size <command>named</command> will send. Valid
9791 values are 512 to 4096 bytes (values outside this range will
9792 be silently adjusted). This option is useful when you
9793 know that there is a firewall that is blocking large
9794 replies from <command>named</command>.
9798 The server supports two zone transfer methods. The first, <command>one-answer</command>,
9799 uses one DNS message per resource record transferred. <command>many-answers</command> packs
9800 as many resource records as possible into a message. <command>many-answers</command> is
9801 more efficient, but is only known to be understood by <acronym>BIND</acronym> 9, <acronym>BIND</acronym>
9802 8.x, and patched versions of <acronym>BIND</acronym>
9803 4.9.5. You can specify which method
9804 to use for a server with the <command>transfer-format</command> option.
9805 If <command>transfer-format</command> is not
9806 specified, the <command>transfer-format</command>
9808 by the <command>options</command> statement will be
9812 <para><command>transfers</command>
9813 is used to limit the number of concurrent inbound zone
9814 transfers from the specified server. If no
9815 <command>transfers</command> clause is specified, the
9816 limit is set according to the
9817 <command>transfers-per-ns</command> option.
9821 The <command>keys</command> clause identifies a
9822 <command>key_id</command> defined by the <command>key</command> statement,
9823 to be used for transaction security (TSIG, <xref linkend="tsig"/>)
9824 when talking to the remote server.
9825 When a request is sent to the remote server, a request signature
9826 will be generated using the key specified here and appended to the
9827 message. A request originating from the remote server is not
9829 to be signed by this key.
9833 Although the grammar of the <command>keys</command>
9835 allows for multiple keys, only a single key per server is
9841 The <command>transfer-source</command> and
9842 <command>transfer-source-v6</command> clauses specify
9843 the IPv4 and IPv6 source
9844 address to be used for zone transfer with the remote server,
9846 For an IPv4 remote server, only <command>transfer-source</command> can
9848 Similarly, for an IPv6 remote server, only
9849 <command>transfer-source-v6</command> can be
9851 For more details, see the description of
9852 <command>transfer-source</command> and
9853 <command>transfer-source-v6</command> in
9854 <xref linkend="zone_transfers"/>.
9858 The <command>notify-source</command> and
9859 <command>notify-source-v6</command> clauses specify the
9860 IPv4 and IPv6 source address to be used for notify
9861 messages sent to remote servers, respectively. For an
9862 IPv4 remote server, only <command>notify-source</command>
9863 can be specified. Similarly, for an IPv6 remote server,
9864 only <command>notify-source-v6</command> can be specified.
9868 The <command>query-source</command> and
9869 <command>query-source-v6</command> clauses specify the
9870 IPv4 and IPv6 source address to be used for queries
9871 sent to remote servers, respectively. For an IPv4
9872 remote server, only <command>query-source</command> can
9873 be specified. Similarly, for an IPv6 remote server,
9874 only <command>query-source-v6</command> can be specified.
9879 <sect2 id="statschannels">
9880 <title><command>statistics-channels</command> Statement Grammar</title>
9882 <programlisting><command>statistics-channels</command> {
9883 [ inet ( ip_addr | * ) [ port ip_port ]
9884 [ allow { <replaceable> address_match_list </replaceable> } ]; ]
9891 <title><command>statistics-channels</command> Statement Definition and
9895 The <command>statistics-channels</command> statement
9896 declares communication channels to be used by system
9897 administrators to get access to statistics information of
9902 This statement intends to be flexible to support multiple
9903 communication protocols in the future, but currently only
9904 HTTP access is supported.
9905 It requires that BIND 9 be compiled with libxml2;
9906 the <command>statistics-channels</command> statement is
9907 still accepted even if it is built without the library,
9908 but any HTTP access will fail with an error.
9912 An <command>inet</command> control channel is a TCP socket
9913 listening at the specified <command>ip_port</command> on the
9914 specified <command>ip_addr</command>, which can be an IPv4 or IPv6
9915 address. An <command>ip_addr</command> of <literal>*</literal> (asterisk) is
9916 interpreted as the IPv4 wildcard address; connections will be
9917 accepted on any of the system's IPv4 addresses.
9918 To listen on the IPv6 wildcard address,
9919 use an <command>ip_addr</command> of <literal>::</literal>.
9923 If no port is specified, port 80 is used for HTTP channels.
9924 The asterisk "<literal>*</literal>" cannot be used for
9925 <command>ip_port</command>.
9929 The attempt of opening a statistics channel is
9930 restricted by the optional <command>allow</command> clause.
9931 Connections to the statistics channel are permitted based on the
9932 <command>address_match_list</command>.
9933 If no <command>allow</command> clause is present,
9934 <command>named</command> accepts connection
9935 attempts from any address; since the statistics may
9936 contain sensitive internal information, it is highly
9937 recommended to restrict the source of connection requests
9942 If no <command>statistics-channels</command> statement is present,
9943 <command>named</command> will not open any communication channels.
9947 If the statistics channel is configured to listen on 127.0.0.1
9948 port 8888, then the statistics are accessible in XML format at
9949 <ulink url="http://127.0.0.1:8888/"
9950 >http://127.0.0.1:8888/</ulink> or
9951 <ulink url="http://127.0.0.1:8888/xml"
9952 >http://127.0.0.1:8888/xml</ulink>. A CSS file is
9953 included which can format the XML statistics into tables
9954 when viewed with a stylesheet-capable browser. When
9955 <acronym>BIND</acronym> 9 is configured with --enable-newstats,
9956 a new XML schema is used (version 3) which adds additional
9957 zone statistics and uses a flatter tree for more efficient
9958 parsing. The stylesheet included uses the Google Charts API
9959 to render data into into charts and graphs when using a
9960 javascript-capable browser.
9964 Applications that depend on a particular XML schema
9966 <ulink url="http://127.0.0.1:8888/xml/v2"
9967 >http://127.0.0.1:8888/xml/v2</ulink> for version 2
9968 of the statistics XML schema or
9969 <ulink url="http://127.0.0.1:8888/xml/v3"
9970 >http://127.0.0.1:8888/xml/v3</ulink> for version 3.
9971 If the requested schema is supported by the server, then
9972 it will respond; if not, it will return a "page not found"
9977 <sect2 id="trusted-keys">
9978 <title><command>trusted-keys</command> Statement Grammar</title>
9980 <programlisting><command>trusted-keys</command> {
9981 <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ;
9982 <optional> <replaceable>string</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; <optional>...</optional></optional>
9988 <title><command>trusted-keys</command> Statement Definition
9991 The <command>trusted-keys</command> statement defines
9992 DNSSEC security roots. DNSSEC is described in <xref
9993 linkend="DNSSEC"/>. A security root is defined when the
9994 public key for a non-authoritative zone is known, but
9995 cannot be securely obtained through DNS, either because
9996 it is the DNS root zone or because its parent zone is
9997 unsigned. Once a key has been configured as a trusted
9998 key, it is treated as if it had been validated and
9999 proven secure. The resolver attempts DNSSEC validation
10000 on all DNS data in subdomains of a security root.
10003 All keys (and corresponding zones) listed in
10004 <command>trusted-keys</command> are deemed to exist regardless
10005 of what parent zones say. Similarly for all keys listed in
10006 <command>trusted-keys</command> only those keys are
10007 used to validate the DNSKEY RRset. The parent's DS RRset
10011 The <command>trusted-keys</command> statement can contain
10012 multiple key entries, each consisting of the key's
10013 domain name, flags, protocol, algorithm, and the Base-64
10014 representation of the key data.
10015 Spaces, tabs, newlines and carriage returns are ignored
10016 in the key data, so the configuration may be split up into
10020 <command>trusted-keys</command> may be set at the top level
10021 of <filename>named.conf</filename> or within a view. If it is
10022 set in both places, they are additive: keys defined at the top
10023 level are inherited by all views, but keys defined in a view
10024 are only used within that view.
10029 <title><command>managed-keys</command> Statement Grammar</title>
10031 <programlisting><command>managed-keys</command> {
10032 <replaceable>name</replaceable> <literal>initial-key</literal> <replaceable>flags</replaceable> <replaceable>protocol</replaceable> <replaceable>algorithm</replaceable> <replaceable>key-data</replaceable> ;
10033 <optional> <replaceable>name</replaceable> <literal>initial-key</literal> <replaceable>flags</replaceable> <replaceable>protocol</replaceable> <replaceable>algorithm</replaceable> <replaceable>key-data</replaceable> ; <optional>...</optional></optional>
10038 <sect2 id="managed-keys">
10039 <title><command>managed-keys</command> Statement Definition
10042 The <command>managed-keys</command> statement, like
10043 <command>trusted-keys</command>, defines DNSSEC
10044 security roots. The difference is that
10045 <command>managed-keys</command> can be kept up to date
10046 automatically, without intervention from the resolver
10050 Suppose, for example, that a zone's key-signing
10051 key was compromised, and the zone owner had to revoke and
10052 replace the key. A resolver which had the old key in a
10053 <command>trusted-keys</command> statement would be
10054 unable to validate this zone any longer; it would
10055 reply with a SERVFAIL response code. This would
10056 continue until the resolver operator had updated the
10057 <command>trusted-keys</command> statement with the new key.
10060 If, however, the zone were listed in a
10061 <command>managed-keys</command> statement instead, then the
10062 zone owner could add a "stand-by" key to the zone in advance.
10063 <command>named</command> would store the stand-by key, and
10064 when the original key was revoked, <command>named</command>
10065 would be able to transition smoothly to the new key. It would
10066 also recognize that the old key had been revoked, and cease
10067 using that key to validate answers, minimizing the damage that
10068 the compromised key could do.
10071 A <command>managed-keys</command> statement contains a list of
10072 the keys to be managed, along with information about how the
10073 keys are to be initialized for the first time. The only
10074 initialization method currently supported (as of
10075 <acronym>BIND</acronym> 9.7.0) is <literal>initial-key</literal>.
10076 This means the <command>managed-keys</command> statement must
10077 contain a copy of the initializing key. (Future releases may
10078 allow keys to be initialized by other methods, eliminating this
10082 Consequently, a <command>managed-keys</command> statement
10083 appears similar to a <command>trusted-keys</command>, differing
10084 in the presence of the second field, containing the keyword
10085 <literal>initial-key</literal>. The difference is, whereas the
10086 keys listed in a <command>trusted-keys</command> continue to be
10087 trusted until they are removed from
10088 <filename>named.conf</filename>, an initializing key listed
10089 in a <command>managed-keys</command> statement is only trusted
10090 <emphasis>once</emphasis>: for as long as it takes to load the
10091 managed key database and start the RFC 5011 key maintenance
10095 The first time <command>named</command> runs with a managed key
10096 configured in <filename>named.conf</filename>, it fetches the
10097 DNSKEY RRset directly from the zone apex, and validates it
10098 using the key specified in the <command>managed-keys</command>
10099 statement. If the DNSKEY RRset is validly signed, then it is
10100 used as the basis for a new managed keys database.
10103 From that point on, whenever <command>named</command> runs, it
10104 sees the <command>managed-keys</command> statement, checks to
10105 make sure RFC 5011 key maintenance has already been initialized
10106 for the specified domain, and if so, it simply moves on. The
10107 key specified in the <command>managed-keys</command> is not
10108 used to validate answers; it has been superseded by the key or
10109 keys stored in the managed keys database.
10112 The next time <command>named</command> runs after a name
10113 has been <emphasis>removed</emphasis> from the
10114 <command>managed-keys</command> statement, the corresponding
10115 zone will be removed from the managed keys database,
10116 and RFC 5011 key maintenance will no longer be used for that
10120 <command>named</command> only maintains a single managed keys
10121 database; consequently, unlike <command>trusted-keys</command>,
10122 <command>managed-keys</command> may only be set at the top
10123 level of <filename>named.conf</filename>, not within a view.
10126 In the current implementation, the managed keys database is
10127 stored as a master-format zone file called
10128 <filename>managed-keys.bind</filename>. When the key database
10129 is changed, the zone is updated. As with any other dynamic
10130 zone, changes will be written into a journal file,
10131 <filename>managed-keys.bind.jnl</filename>. They are committed
10132 to the master file as soon as possible afterward; in the case
10133 of the managed key database, this will usually occur within 30
10134 seconds. So, whenever <command>named</command> is using
10135 automatic key maintenance, those two files can be expected to
10136 exist in the working directory. (For this reason among others,
10137 the working directory should be always be writable by
10138 <command>named</command>.)
10141 If the <command>dnssec-validation</command> option is
10142 set to <userinput>auto</userinput>, <command>named</command>
10143 will automatically initialize a managed key for the
10144 root zone. Similarly, if the <command>dnssec-lookaside</command>
10145 option is set to <userinput>auto</userinput>,
10146 <command>named</command> will automatically initialize
10147 a managed key for the zone <literal>dlv.isc.org</literal>.
10148 In both cases, the key that is used to initialize the key
10149 maintenance process is built into <command>named</command>,
10150 and can be overridden from <command>bindkeys-file</command>.
10154 <sect2 id="view_statement_grammar">
10155 <title><command>view</command> Statement Grammar</title>
10157 <programlisting><command>view</command> <replaceable>view_name</replaceable>
10158 <optional><replaceable>class</replaceable></optional> {
10159 match-clients { <replaceable>address_match_list</replaceable> };
10160 match-destinations { <replaceable>address_match_list</replaceable> };
10161 match-recursive-only <replaceable>yes_or_no</replaceable> ;
10162 <optional> <replaceable>view_option</replaceable>; ...</optional>
10163 <optional> <replaceable>zone_statement</replaceable>; ...</optional>
10169 <title><command>view</command> Statement Definition and Usage</title>
10172 The <command>view</command> statement is a powerful
10174 of <acronym>BIND</acronym> 9 that lets a name server
10175 answer a DNS query differently
10176 depending on who is asking. It is particularly useful for
10178 split DNS setups without having to run multiple servers.
10182 Each <command>view</command> statement defines a view
10184 DNS namespace that will be seen by a subset of clients. A client
10186 a view if its source IP address matches the
10187 <varname>address_match_list</varname> of the view's
10188 <command>match-clients</command> clause and its
10189 destination IP address matches
10190 the <varname>address_match_list</varname> of the
10192 <command>match-destinations</command> clause. If not
10194 <command>match-clients</command> and <command>match-destinations</command>
10195 default to matching all addresses. In addition to checking IP
10197 <command>match-clients</command> and <command>match-destinations</command>
10198 can also take <command>keys</command> which provide an
10200 client to select the view. A view can also be specified
10201 as <command>match-recursive-only</command>, which
10202 means that only recursive
10203 requests from matching clients will match that view.
10204 The order of the <command>view</command> statements is
10205 significant —
10206 a client request will be resolved in the context of the first
10207 <command>view</command> that it matches.
10211 Zones defined within a <command>view</command>
10213 only be accessible to clients that match the <command>view</command>.
10214 By defining a zone of the same name in multiple views, different
10215 zone data can be given to different clients, for example,
10217 and "external" clients in a split DNS setup.
10221 Many of the options given in the <command>options</command> statement
10222 can also be used within a <command>view</command>
10223 statement, and then
10224 apply only when resolving queries with that view. When no
10226 value is given, the value in the <command>options</command> statement
10227 is used as a default. Also, zone options can have default values
10229 in the <command>view</command> statement; these
10230 view-specific defaults
10231 take precedence over those in the <command>options</command> statement.
10235 Views are class specific. If no class is given, class IN
10236 is assumed. Note that all non-IN views must contain a hint zone,
10237 since only the IN class has compiled-in default hints.
10241 If there are no <command>view</command> statements in
10243 file, a default view that matches any client is automatically
10245 in class IN. Any <command>zone</command> statements
10247 the top level of the configuration file are considered to be part
10249 this default view, and the <command>options</command>
10251 apply to the default view. If any explicit <command>view</command>
10252 statements are present, all <command>zone</command>
10254 occur inside <command>view</command> statements.
10258 Here is an example of a typical split DNS setup implemented
10259 using <command>view</command> statements:
10262 <programlisting>view "internal" {
10263 // This should match our internal networks.
10264 match-clients { 10.0.0.0/8; };
10266 // Provide recursive service to internal
10270 // Provide a complete view of the example.com
10271 // zone including addresses of internal hosts.
10272 zone "example.com" {
10274 file "example-internal.db";
10279 // Match all clients not matched by the
10281 match-clients { any; };
10283 // Refuse recursive service to external clients.
10286 // Provide a restricted view of the example.com
10287 // zone containing only publicly accessible hosts.
10288 zone "example.com" {
10290 file "example-external.db";
10296 <sect2 id="zone_statement_grammar">
10297 <title><command>zone</command>
10298 Statement Grammar</title>
10300 <programlisting><command>zone</command> <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10302 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10303 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10304 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
10305 <optional> allow-update { <replaceable>address_match_list</replaceable> }; </optional>
10306 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
10307 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
10308 <optional> dnssec-loadkeys-interval <replaceable>number</replaceable>; </optional>
10309 <optional> update-policy <replaceable>local</replaceable> | { <replaceable>update_policy_rule</replaceable> <optional>...</optional> }; </optional>
10310 <optional> also-notify { <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ;
10311 <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10312 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10313 <optional> check-mx (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10314 <optional> check-wildcard <replaceable>yes_or_no</replaceable>; </optional>
10315 <optional> check-spf ( <replaceable>warn</replaceable> | <replaceable>fail</replaceable> | <replaceable>ignore</replaceable> ); </optional>
10316 <optional> check-integrity <replaceable>yes_or_no</replaceable> ; </optional>
10317 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10318 <optional> file <replaceable>string</replaceable> ; </optional>
10319 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10320 <optional> journal <replaceable>string</replaceable> ; </optional>
10321 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
10322 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10323 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10324 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
10325 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
10326 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
10327 <optional> request-ixfr <replaceable>yes_or_no</replaceable> ; </optional>
10328 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
10329 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
10330 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
10331 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
10332 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
10333 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
10334 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
10335 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10336 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10337 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10338 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
10339 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
10340 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
10341 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
10342 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
10343 <optional> database <replaceable>string</replaceable> ; </optional>
10344 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10345 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10346 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10347 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10348 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
10349 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>off</constant>; </optional>
10350 <optional> inline-signing <replaceable>yes_or_no</replaceable>; </optional>
10351 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
10352 <optional> serial-update-method <constant>increment</constant>|<constant>unixtime</constant>; </optional>
10355 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10357 <optional> allow-notify { <replaceable>address_match_list</replaceable> }; </optional>
10358 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10359 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10360 <optional> allow-transfer { <replaceable>address_match_list</replaceable> }; </optional>
10361 <optional> allow-update-forwarding { <replaceable>address_match_list</replaceable> }; </optional>
10362 <optional> dnssec-update-mode ( <replaceable>maintain</replaceable> | <replaceable>no-resign</replaceable> ); </optional>
10363 <optional> update-check-ksk <replaceable>yes_or_no</replaceable>; </optional>
10364 <optional> dnssec-dnskey-kskonly <replaceable>yes_or_no</replaceable>; </optional>
10365 <optional> dnssec-loadkeys-interval <replaceable>number</replaceable>; </optional>
10366 <optional> dnssec-secure-to-insecure <replaceable>yes_or_no</replaceable> ; </optional>
10367 <optional> try-tcp-refresh <replaceable>yes_or_no</replaceable>; </optional>
10368 <optional> also-notify <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10369 <optional>port <replaceable>ip_port</replaceable></optional>
10370 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10371 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10372 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10373 <optional> file <replaceable>string</replaceable> ; </optional>
10374 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10375 <optional> journal <replaceable>string</replaceable> ; </optional>
10376 <optional> max-journal-size <replaceable>size_spec</replaceable>; </optional>
10377 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10378 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10379 <optional> ixfr-base <replaceable>string</replaceable> ; </optional>
10380 <optional> ixfr-from-differences <replaceable>yes_or_no</replaceable>; </optional>
10381 <optional> ixfr-tmp-file <replaceable>string</replaceable> ; </optional>
10382 <optional> maintain-ixfr-base <replaceable>yes_or_no</replaceable> ; </optional>
10383 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10384 <optional>port <replaceable>ip_port</replaceable></optional>
10385 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10386 <optional> max-ixfr-log-size <replaceable>number</replaceable> ; </optional>
10387 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10388 <optional> max-transfer-idle-out <replaceable>number</replaceable> ; </optional>
10389 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10390 <optional> max-transfer-time-out <replaceable>number</replaceable> ; </optional>
10391 <optional> notify <replaceable>yes_or_no</replaceable> | <replaceable>explicit</replaceable> | <replaceable>master-only</replaceable> ; </optional>
10392 <optional> notify-delay <replaceable>seconds</replaceable> ; </optional>
10393 <optional> notify-to-soa <replaceable>yes_or_no</replaceable>; </optional>
10394 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10395 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10396 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10397 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10398 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10399 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10400 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10401 <optional> notify-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10402 <optional> notify-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10403 <optional> zone-statistics <replaceable>full</replaceable> | <replaceable>terse</replaceable> | <replaceable>none</replaceable>; </optional>
10404 <optional> sig-validity-interval <replaceable>number</replaceable> <optional><replaceable>number</replaceable></optional> ; </optional>
10405 <optional> sig-signing-nodes <replaceable>number</replaceable> ; </optional>
10406 <optional> sig-signing-signatures <replaceable>number</replaceable> ; </optional>
10407 <optional> sig-signing-type <replaceable>number</replaceable> ; </optional>
10408 <optional> database <replaceable>string</replaceable> ; </optional>
10409 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10410 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10411 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10412 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10413 <optional> key-directory <replaceable>path_name</replaceable>; </optional>
10414 <optional> auto-dnssec <constant>allow</constant>|<constant>maintain</constant>|<constant>off</constant>; </optional>
10415 <optional> inline-signing <replaceable>yes_or_no</replaceable>; </optional>
10416 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10417 <optional> zero-no-soa-ttl <replaceable>yes_or_no</replaceable> ; </optional>
10420 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10422 file <replaceable>string</replaceable> ;
10423 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10424 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional> // Not Implemented.
10427 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10429 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10430 <optional> allow-query-on { <replaceable>address_match_list</replaceable> }; </optional>
10431 <optional> check-names (<constant>warn</constant>|<constant>fail</constant>|<constant>ignore</constant>) ; </optional>
10432 <optional> dialup <replaceable>dialup_option</replaceable> ; </optional>
10433 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10434 <optional> file <replaceable>string</replaceable> ; </optional>
10435 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10436 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10437 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10438 <optional> masters <optional>port <replaceable>ip_port</replaceable></optional> { ( <replaceable>masters_list</replaceable> | <replaceable>ip_addr</replaceable>
10439 <optional>port <replaceable>ip_port</replaceable></optional>
10440 <optional>key <replaceable>key</replaceable></optional> ) ; <optional>...</optional> }; </optional>
10441 <optional> max-transfer-idle-in <replaceable>number</replaceable> ; </optional>
10442 <optional> max-transfer-time-in <replaceable>number</replaceable> ; </optional>
10443 <optional> pubkey <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>number</replaceable> <replaceable>string</replaceable> ; </optional>
10444 <optional> transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10445 <optional> transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10446 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10447 <optional> alt-transfer-source (<replaceable>ip4_addr</replaceable> | <constant>*</constant>) <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10448 <optional> alt-transfer-source-v6 (<replaceable>ip6_addr</replaceable> | <constant>*</constant>)
10449 <optional>port <replaceable>ip_port</replaceable></optional> ; </optional>
10450 <optional> use-alt-transfer-source <replaceable>yes_or_no</replaceable>; </optional>
10451 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10452 <optional> database <replaceable>string</replaceable> ; </optional>
10453 <optional> min-refresh-time <replaceable>number</replaceable> ; </optional>
10454 <optional> max-refresh-time <replaceable>number</replaceable> ; </optional>
10455 <optional> min-retry-time <replaceable>number</replaceable> ; </optional>
10456 <optional> max-retry-time <replaceable>number</replaceable> ; </optional>
10457 <optional> multi-master <replaceable>yes_or_no</replaceable> ; </optional>
10460 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10462 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10463 <optional> server-addresses { <optional> <replaceable>ip_addr</replaceable> ; ... </optional> }; </optional>
10464 <optional> server-names { <optional> <replaceable>namelist</replaceable> </optional> }; </optional>
10465 <optional> zone-statistics <replaceable>yes_or_no</replaceable> ; </optional>
10468 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10470 <optional> forward (<constant>only</constant>|<constant>first</constant>) ; </optional>
10471 <optional> forwarders { <optional> <replaceable>ip_addr</replaceable> <optional>port <replaceable>ip_port</replaceable></optional> ; ... </optional> }; </optional>
10472 <optional> delegation-only <replaceable>yes_or_no</replaceable> ; </optional>
10475 zone <replaceable>"."</replaceable> <optional><replaceable>class</replaceable></optional> {
10477 file <replaceable>string</replaceable> ;
10478 <optional> masterfile-format (<constant>text</constant>|<constant>raw</constant>) ; </optional>
10479 <optional> allow-query { <replaceable>address_match_list</replaceable> }; </optional>
10482 zone <replaceable>zone_name</replaceable> <optional><replaceable>class</replaceable></optional> {
10483 type delegation-only;
10490 <title><command>zone</command> Statement Definition and Usage</title>
10492 <title>Zone Types</title>
10493 <informaltable colsep="0" rowsep="0">
10494 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
10495 <!--colspec colname="1" colnum="1" colsep="0" colwidth="1.108in"/-->
10496 <!--colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/-->
10497 <colspec colname="1" colnum="1" colsep="0"/>
10498 <colspec colname="2" colnum="2" colsep="0" colwidth="4.017in"/>
10501 <entry colname="1">
10503 <varname>master</varname>
10506 <entry colname="2">
10508 The server has a master copy of the data
10509 for the zone and will be able to provide authoritative
10516 <entry colname="1">
10518 <varname>slave</varname>
10521 <entry colname="2">
10523 A slave zone is a replica of a master
10524 zone. The <command>masters</command> list
10525 specifies one or more IP addresses
10526 of master servers that the slave contacts to update
10527 its copy of the zone.
10528 Masters list elements can also be names of other
10530 By default, transfers are made from port 53 on the
10532 be changed for all servers by specifying a port number
10534 list of IP addresses, or on a per-server basis after
10536 Authentication to the master can also be done with
10537 per-server TSIG keys.
10538 If a file is specified, then the
10539 replica will be written to this file whenever the zone
10541 and reloaded from this file on a server restart. Use
10543 recommended, since it often speeds server startup and
10545 a needless waste of bandwidth. Note that for large
10547 tens or hundreds of thousands) of zones per server, it
10549 use a two-level naming scheme for zone filenames. For
10551 a slave server for the zone <literal>example.com</literal> might place
10552 the zone contents into a file called
10553 <filename>ex/example.com</filename> where <filename>ex/</filename> is
10554 just the first two letters of the zone name. (Most
10556 behave very slowly if you put 100000 files into
10557 a single directory.)
10562 <entry colname="1">
10564 <varname>stub</varname>
10567 <entry colname="2">
10569 A stub zone is similar to a slave zone,
10570 except that it replicates only the NS records of a
10571 master zone instead
10572 of the entire zone. Stub zones are not a standard part
10574 they are a feature specific to the <acronym>BIND</acronym> implementation.
10578 Stub zones can be used to eliminate the need for glue
10580 in a parent zone at the expense of maintaining a stub
10582 a set of name server addresses in <filename>named.conf</filename>.
10583 This usage is not recommended for new configurations,
10585 supports it only in a limited way.
10586 In <acronym>BIND</acronym> 4/8, zone
10587 transfers of a parent zone
10588 included the NS records from stub children of that
10590 that, in some cases, users could get away with
10591 configuring child stubs
10592 only in the master server for the parent zone. <acronym>BIND</acronym>
10593 9 never mixes together zone data from different zones
10595 way. Therefore, if a <acronym>BIND</acronym> 9 master serving a parent
10596 zone has child stub zones configured, all the slave
10598 parent zone also need to have the same child stub
10604 Stub zones can also be used as a way of forcing the
10606 of a given domain to use a particular set of
10607 authoritative servers.
10608 For example, the caching name servers on a private
10610 RFC1918 addressing may be configured with stub zones
10612 <literal>10.in-addr.arpa</literal>
10613 to use a set of internal name servers as the
10615 servers for that domain.
10620 <entry colname="1">
10622 <varname>static-stub</varname>
10625 <entry colname="2">
10627 A static-stub zone is similar to a stub zone
10628 with the following exceptions:
10629 the zone data is statically configured, rather
10630 than transferred from a master server;
10631 when recursion is necessary for a query that
10632 matches a static-stub zone, the locally
10633 configured data (nameserver names and glue addresses)
10634 is always used even if different authoritative
10635 information is cached.
10638 Zone data is configured via the
10639 <command>server-addresses</command> and
10640 <command>server-names</command> zone options.
10643 The zone data is maintained in the form of NS
10644 and (if necessary) glue A or AAAA RRs
10645 internally, which can be seen by dumping zone
10646 databases by <command>rndc dumpdb -all</command>.
10647 The configured RRs are considered local configuration
10648 parameters rather than public data.
10649 Non recursive queries (i.e., those with the RD
10650 bit off) to a static-stub zone are therefore
10651 prohibited and will be responded with REFUSED.
10654 Since the data is statically configured, no
10655 zone maintenance action takes place for a static-stub
10657 For example, there is no periodic refresh
10658 attempt, and an incoming notify message
10659 will be rejected with an rcode of NOTAUTH.
10662 Each static-stub zone is configured with
10663 internally generated NS and (if necessary)
10669 <entry colname="1">
10671 <varname>forward</varname>
10674 <entry colname="2">
10676 A "forward zone" is a way to configure
10677 forwarding on a per-domain basis. A <command>zone</command> statement
10678 of type <command>forward</command> can
10679 contain a <command>forward</command>
10680 and/or <command>forwarders</command>
10682 which will apply to queries within the domain given by
10684 name. If no <command>forwarders</command>
10685 statement is present or
10686 an empty list for <command>forwarders</command> is given, then no
10687 forwarding will be done for the domain, canceling the
10689 any forwarders in the <command>options</command> statement. Thus
10690 if you want to use this type of zone to change the
10692 global <command>forward</command> option
10693 (that is, "forward first"
10694 to, then "forward only", or vice versa, but want to
10696 servers as set globally) you need to re-specify the
10702 <entry colname="1">
10704 <varname>hint</varname>
10707 <entry colname="2">
10709 The initial set of root name servers is
10710 specified using a "hint zone". When the server starts
10712 the root hints to find a root name server and get the
10714 list of root name servers. If no hint zone is
10715 specified for class
10716 IN, the server uses a compiled-in default set of root
10718 Classes other than IN have no built-in defaults hints.
10723 <entry colname="1">
10725 <varname>redirect</varname>
10728 <entry colname="2">
10730 Redirect zones are used to provide answers to
10731 queries when normal resolution would result in
10732 NXDOMAIN being returned.
10733 Only one redirect zone is supported
10734 per view. <command>allow-query</command> can be
10735 used to restrict which clients see these answers.
10738 If the client has requested DNSSEC records (DO=1) and
10739 the NXDOMAIN response is signed then no substitution
10743 To redirect all NXDOMAIN responses to
10745 2001:ffff:ffff::100.100.100.2, one would
10746 configure a type redirect zone named ".",
10747 with the zone file containing wildcard records
10748 that point to the desired addresses:
10749 <literal>"*. IN A 100.100.100.2"</literal>
10751 <literal>"*. IN AAAA 2001:ffff:ffff::100.100.100.2"</literal>.
10754 To redirect all Spanish names (under .ES) one
10755 would use similar entries but with the names
10756 "*.ES." instead of "*.". To redirect all
10757 commercial Spanish names (under COM.ES) one
10758 would use wildcard entries called "*.COM.ES.".
10761 Note that the redirect zone supports all
10762 possible types; it is not limited to A and
10766 Because redirect zones are not referenced
10767 directly by name, they are not kept in the
10768 zone lookup table with normal master and slave
10769 zones. Consequently, it is not currently possible
10771 <command>rndc reload
10772 <replaceable>zonename</replaceable></command>
10773 to reload a redirect zone. However, when using
10774 <command>rndc reload</command> without specifying
10775 a zone name, redirect zones will be reloaded along
10781 <entry colname="1">
10783 <varname>delegation-only</varname>
10786 <entry colname="2">
10788 This is used to enforce the delegation-only
10789 status of infrastructure zones (e.g. COM,
10790 NET, ORG). Any answer that is received
10791 without an explicit or implicit delegation
10792 in the authority section will be treated
10793 as NXDOMAIN. This does not apply to the
10794 zone apex. This should not be applied to
10798 <varname>delegation-only</varname> has no
10799 effect on answers received from forwarders.
10802 See caveats in <xref linkend="root_delegation_only"/>.
10812 <title>Class</title>
10814 The zone's name may optionally be followed by a class. If
10815 a class is not specified, class <literal>IN</literal> (for <varname>Internet</varname>),
10816 is assumed. This is correct for the vast majority of cases.
10819 The <literal>hesiod</literal> class is
10820 named for an information service from MIT's Project Athena. It
10822 used to share information about various systems databases, such
10823 as users, groups, printers and so on. The keyword
10824 <literal>HS</literal> is
10825 a synonym for hesiod.
10828 Another MIT development is Chaosnet, a LAN protocol created
10829 in the mid-1970s. Zone data for it can be specified with the <literal>CHAOS</literal> class.
10834 <title>Zone Options</title>
10839 <term><command>allow-notify</command></term>
10842 See the description of
10843 <command>allow-notify</command> in <xref linkend="access_control"/>.
10849 <term><command>allow-query</command></term>
10852 See the description of
10853 <command>allow-query</command> in <xref linkend="access_control"/>.
10859 <term><command>allow-query-on</command></term>
10862 See the description of
10863 <command>allow-query-on</command> in <xref linkend="access_control"/>.
10869 <term><command>allow-transfer</command></term>
10872 See the description of <command>allow-transfer</command>
10873 in <xref linkend="access_control"/>.
10879 <term><command>allow-update</command></term>
10882 See the description of <command>allow-update</command>
10883 in <xref linkend="access_control"/>.
10889 <term><command>update-policy</command></term>
10892 Specifies a "Simple Secure Update" policy. See
10893 <xref linkend="dynamic_update_policies"/>.
10899 <term><command>allow-update-forwarding</command></term>
10902 See the description of <command>allow-update-forwarding</command>
10903 in <xref linkend="access_control"/>.
10909 <term><command>also-notify</command></term>
10912 Only meaningful if <command>notify</command>
10914 active for this zone. The set of machines that will
10916 <literal>DNS NOTIFY</literal> message
10917 for this zone is made up of all the listed name servers
10919 the primary master) for the zone plus any IP addresses
10921 with <command>also-notify</command>. A port
10923 with each <command>also-notify</command>
10924 address to send the notify
10925 messages to a port other than the default of 53.
10926 A TSIG key may also be specified to cause the
10927 <literal>NOTIFY</literal> to be signed by the
10929 <command>also-notify</command> is not
10930 meaningful for stub zones.
10931 The default is the empty list.
10937 <term><command>check-names</command></term>
10940 This option is used to restrict the character set and
10942 certain domain names in master files and/or DNS responses
10944 network. The default varies according to zone type. For <command>master</command> zones the default is <command>fail</command>. For <command>slave</command>
10945 zones the default is <command>warn</command>.
10946 It is not implemented for <command>hint</command> zones.
10952 <term><command>check-mx</command></term>
10955 See the description of
10956 <command>check-mx</command> in <xref linkend="boolean_options"/>.
10962 <term><command>check-spf</command></term>
10965 See the description of
10966 <command>check-spf</command> in <xref linkend="boolean_options"/>.
10972 <term><command>check-wildcard</command></term>
10975 See the description of
10976 <command>check-wildcard</command> in <xref linkend="boolean_options"/>.
10982 <term><command>check-integrity</command></term>
10985 See the description of
10986 <command>check-integrity</command> in <xref linkend="boolean_options"/>.
10992 <term><command>check-sibling</command></term>
10995 See the description of
10996 <command>check-sibling</command> in <xref linkend="boolean_options"/>.
11002 <term><command>zero-no-soa-ttl</command></term>
11005 See the description of
11006 <command>zero-no-soa-ttl</command> in <xref linkend="boolean_options"/>.
11012 <term><command>update-check-ksk</command></term>
11015 See the description of
11016 <command>update-check-ksk</command> in <xref linkend="boolean_options"/>.
11022 <term><command>dnssec-update-mode</command></term>
11025 See the description of
11026 <command>dnssec-update-mode</command> in <xref linkend="options"/>.
11032 <term><command>dnssec-dnskey-kskonly</command></term>
11035 See the description of
11036 <command>dnssec-dnskey-kskonly</command> in <xref linkend="boolean_options"/>.
11042 <term><command>try-tcp-refresh</command></term>
11045 See the description of
11046 <command>try-tcp-refresh</command> in <xref linkend="boolean_options"/>.
11052 <term><command>database</command></term>
11055 Specify the type of database to be used for storing the
11056 zone data. The string following the <command>database</command> keyword
11057 is interpreted as a list of whitespace-delimited words.
11059 identifies the database type, and any subsequent words are
11061 as arguments to the database to be interpreted in a way
11063 to the database type.
11066 The default is <userinput>"rbt"</userinput>, BIND 9's
11068 red-black-tree database. This database does not take
11072 Other values are possible if additional database drivers
11073 have been linked into the server. Some sample drivers are
11075 with the distribution but none are linked in by default.
11081 <term><command>dialup</command></term>
11084 See the description of
11085 <command>dialup</command> in <xref linkend="boolean_options"/>.
11091 <term><command>delegation-only</command></term>
11094 The flag only applies to hint and stub zones. If set
11095 to <userinput>yes</userinput>, then the zone will also be
11096 treated as if it is also a delegation-only type zone.
11099 See caveats in <xref linkend="root_delegation_only"/>.
11105 <term><command>forward</command></term>
11108 Only meaningful if the zone has a forwarders
11109 list. The <command>only</command> value causes
11111 after trying the forwarders and getting no answer, while <command>first</command> would
11112 allow a normal lookup to be tried.
11118 <term><command>forwarders</command></term>
11121 Used to override the list of global forwarders.
11122 If it is not specified in a zone of type <command>forward</command>,
11123 no forwarding is done for the zone and the global options are
11130 <term><command>ixfr-base</command></term>
11133 Was used in <acronym>BIND</acronym> 8 to
11135 of the transaction log (journal) file for dynamic update
11137 <acronym>BIND</acronym> 9 ignores the option
11138 and constructs the name of the journal
11139 file by appending "<filename>.jnl</filename>"
11147 <term><command>ixfr-tmp-file</command></term>
11150 Was an undocumented option in <acronym>BIND</acronym> 8.
11151 Ignored in <acronym>BIND</acronym> 9.
11157 <term><command>journal</command></term>
11160 Allow the default journal's filename to be overridden.
11161 The default is the zone's filename with "<filename>.jnl</filename>" appended.
11162 This is applicable to <command>master</command> and <command>slave</command> zones.
11168 <term><command>max-journal-size</command></term>
11171 See the description of
11172 <command>max-journal-size</command> in <xref linkend="server_resource_limits"/>.
11178 <term><command>max-transfer-time-in</command></term>
11181 See the description of
11182 <command>max-transfer-time-in</command> in <xref linkend="zone_transfers"/>.
11188 <term><command>max-transfer-idle-in</command></term>
11191 See the description of
11192 <command>max-transfer-idle-in</command> in <xref linkend="zone_transfers"/>.
11198 <term><command>max-transfer-time-out</command></term>
11201 See the description of
11202 <command>max-transfer-time-out</command> in <xref linkend="zone_transfers"/>.
11208 <term><command>max-transfer-idle-out</command></term>
11211 See the description of
11212 <command>max-transfer-idle-out</command> in <xref linkend="zone_transfers"/>.
11218 <term><command>notify</command></term>
11221 See the description of
11222 <command>notify</command> in <xref linkend="boolean_options"/>.
11228 <term><command>notify-delay</command></term>
11231 See the description of
11232 <command>notify-delay</command> in <xref linkend="tuning"/>.
11238 <term><command>notify-to-soa</command></term>
11241 See the description of
11242 <command>notify-to-soa</command> in
11243 <xref linkend="boolean_options"/>.
11249 <term><command>pubkey</command></term>
11252 In <acronym>BIND</acronym> 8, this option was
11253 intended for specifying
11254 a public zone key for verification of signatures in DNSSEC
11256 zones when they are loaded from disk. <acronym>BIND</acronym> 9 does not verify signatures
11257 on load and ignores the option.
11263 <term><command>zone-statistics</command></term>
11266 If <userinput>yes</userinput>, the server will keep
11268 information for this zone, which can be dumped to the
11269 <command>statistics-file</command> defined in
11270 the server options.
11276 <term><command>server-addresses</command></term>
11279 Only meaningful for static-stub zones.
11280 This is a list of IP addresses to which queries
11281 should be sent in recursive resolution for the
11283 A non empty list for this option will internally
11284 configure the apex NS RR with associated glue A or
11288 For example, if "example.com" is configured as a
11289 static-stub zone with 192.0.2.1 and 2001:db8::1234
11290 in a <command>server-addresses</command> option,
11291 the following RRs will be internally configured.
11293 <programlisting>example.com. NS example.com.
11294 example.com. A 192.0.2.1
11295 example.com. AAAA 2001:db8::1234</programlisting>
11297 These records are internally used to resolve
11298 names under the static-stub zone.
11299 For instance, if the server receives a query for
11300 "www.example.com" with the RD bit on, the server
11301 will initiate recursive resolution and send
11302 queries to 192.0.2.1 and/or 2001:db8::1234.
11308 <term><command>server-names</command></term>
11311 Only meaningful for static-stub zones.
11312 This is a list of domain names of nameservers that
11313 act as authoritative servers of the static-stub
11315 These names will be resolved to IP addresses when
11316 <command>named</command> needs to send queries to
11318 To make this supplemental resolution successful,
11319 these names must not be a subdomain of the origin
11320 name of static-stub zone.
11321 That is, when "example.net" is the origin of a
11322 static-stub zone, "ns.example" and
11323 "master.example.com" can be specified in the
11324 <command>server-names</command> option, but
11325 "ns.example.net" cannot, and will be rejected by
11326 the configuration parser.
11329 A non empty list for this option will internally
11330 configure the apex NS RR with the specified names.
11331 For example, if "example.com" is configured as a
11332 static-stub zone with "ns1.example.net" and
11334 in a <command>server-names</command> option,
11335 the following RRs will be internally configured.
11337 <programlisting>example.com. NS ns1.example.net.
11338 example.com. NS ns2.example.net.
11341 These records are internally used to resolve
11342 names under the static-stub zone.
11343 For instance, if the server receives a query for
11344 "www.example.com" with the RD bit on, the server
11345 initiate recursive resolution,
11346 resolve "ns1.example.net" and/or
11347 "ns2.example.net" to IP addresses, and then send
11348 queries to (one or more of) these addresses.
11354 <term><command>sig-validity-interval</command></term>
11357 See the description of
11358 <command>sig-validity-interval</command> in <xref linkend="tuning"/>.
11364 <term><command>sig-signing-nodes</command></term>
11367 See the description of
11368 <command>sig-signing-nodes</command> in <xref linkend="tuning"/>.
11374 <term><command>sig-signing-signatures</command></term>
11377 See the description of
11378 <command>sig-signing-signatures</command> in <xref linkend="tuning"/>.
11384 <term><command>sig-signing-type</command></term>
11387 See the description of
11388 <command>sig-signing-type</command> in <xref linkend="tuning"/>.
11394 <term><command>transfer-source</command></term>
11397 See the description of
11398 <command>transfer-source</command> in <xref linkend="zone_transfers"/>.
11404 <term><command>transfer-source-v6</command></term>
11407 See the description of
11408 <command>transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
11414 <term><command>alt-transfer-source</command></term>
11417 See the description of
11418 <command>alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
11424 <term><command>alt-transfer-source-v6</command></term>
11427 See the description of
11428 <command>alt-transfer-source-v6</command> in <xref linkend="zone_transfers"/>.
11434 <term><command>use-alt-transfer-source</command></term>
11437 See the description of
11438 <command>use-alt-transfer-source</command> in <xref linkend="zone_transfers"/>.
11445 <term><command>notify-source</command></term>
11448 See the description of
11449 <command>notify-source</command> in <xref linkend="zone_transfers"/>.
11455 <term><command>notify-source-v6</command></term>
11458 See the description of
11459 <command>notify-source-v6</command> in <xref linkend="zone_transfers"/>.
11465 <term><command>min-refresh-time</command></term>
11466 <term><command>max-refresh-time</command></term>
11467 <term><command>min-retry-time</command></term>
11468 <term><command>max-retry-time</command></term>
11471 See the description in <xref linkend="tuning"/>.
11477 <term><command>ixfr-from-differences</command></term>
11480 See the description of
11481 <command>ixfr-from-differences</command> in <xref linkend="boolean_options"/>.
11482 (Note that the <command>ixfr-from-differences</command>
11483 <userinput>master</userinput> and
11484 <userinput>slave</userinput> choices are not
11485 available at the zone level.)
11491 <term><command>key-directory</command></term>
11494 See the description of
11495 <command>key-directory</command> in <xref linkend="options"/>.
11501 <term><command>auto-dnssec</command></term>
11504 Zones configured for dynamic DNS may also use this
11505 option to allow varying levels of automatic DNSSEC key
11506 management. There are three possible settings:
11509 <command>auto-dnssec allow;</command> permits
11510 keys to be updated and the zone fully re-signed
11511 whenever the user issues the command <command>rndc sign
11512 <replaceable>zonename</replaceable></command>.
11515 <command>auto-dnssec maintain;</command> includes the
11516 above, but also automatically adjusts the zone's DNSSEC
11517 keys on schedule, according to the keys' timing metadata
11518 (see <xref linkend="man.dnssec-keygen"/> and
11519 <xref linkend="man.dnssec-settime"/>). The command
11521 <replaceable>zonename</replaceable></command> causes
11522 <command>named</command> to load keys from the key
11523 repository and sign the zone with all keys that are
11525 <command>rndc loadkeys
11526 <replaceable>zonename</replaceable></command> causes
11527 <command>named</command> to load keys from the key
11528 repository and schedule key maintenance events to occur
11529 in the future, but it does not sign the full zone
11530 immediately. Note: once keys have been loaded for a
11531 zone the first time, the repository will be searched
11532 for changes periodically, regardless of whether
11533 <command>rndc loadkeys</command> is used. The recheck
11534 interval is defined by
11535 <command>dnssec-loadkeys-interval</command>.)
11538 The default setting is <command>auto-dnssec off</command>.
11544 <term><command>serial-update-method</command></term>
11547 Zones configured for dynamic DNS may use this
11548 option to set the update method that will be used for
11549 the zone serial number in the SOA record.
11552 With the default setting of
11553 <command>serial-update-method increment;</command>, the
11554 SOA serial number will be incremented by one each time
11555 the zone is updated.
11559 <command>serial-update-method unixtime;</command>, the
11560 SOA serial number will be set to the number of seconds
11561 since the UNIX epoch, unless the serial number is
11562 already greater than or equal to that value, in which
11563 case it is simply incremented by one.
11569 <term><command>inline-signing</command></term>
11572 If <literal>yes</literal>, this enables
11573 "bump in the wire" signing of a zone, where a
11574 unsigned zone is transferred in or loaded from
11575 disk and a signed version of the zone is served,
11576 with possibly, a different serial number. This
11577 behaviour is disabled by default.
11583 <term><command>multi-master</command></term>
11586 See the description of <command>multi-master</command> in
11587 <xref linkend="boolean_options"/>.
11593 <term><command>masterfile-format</command></term>
11596 See the description of <command>masterfile-format</command>
11597 in <xref linkend="tuning"/>.
11603 <term><command>dnssec-secure-to-insecure</command></term>
11606 See the description of
11607 <command>dnssec-secure-to-insecure</command> in <xref linkend="boolean_options"/>.
11615 <sect3 id="dynamic_update_policies">
11616 <title>Dynamic Update Policies</title>
11617 <para><acronym>BIND</acronym> 9 supports two alternative
11618 methods of granting clients the right to perform
11619 dynamic updates to a zone, configured by the
11620 <command>allow-update</command> and
11621 <command>update-policy</command> option, respectively.
11624 The <command>allow-update</command> clause works the
11625 same way as in previous versions of <acronym>BIND</acronym>.
11626 It grants given clients the permission to update any
11627 record of any name in the zone.
11630 The <command>update-policy</command> clause
11631 allows more fine-grained control over what updates are
11632 allowed. A set of rules is specified, where each rule
11633 either grants or denies permissions for one or more
11634 names to be updated by one or more identities. If
11635 the dynamic update request message is signed (that is,
11636 it includes either a TSIG or SIG(0) record), the
11637 identity of the signer can be determined.
11640 Rules are specified in the <command>update-policy</command>
11641 zone option, and are only meaningful for master zones.
11642 When the <command>update-policy</command> statement
11643 is present, it is a configuration error for the
11644 <command>allow-update</command> statement to be
11645 present. The <command>update-policy</command> statement
11646 only examines the signer of a message; the source
11647 address is not relevant.
11650 There is a pre-defined <command>update-policy</command>
11651 rule which can be switched on with the command
11652 <command>update-policy local;</command>.
11653 Switching on this rule in a zone causes
11654 <command>named</command> to generate a TSIG session
11655 key and place it in a file, and to allow that key
11656 to update the zone. (By default, the file is
11657 <filename>/var/run/named/session.key</filename>, the key
11658 name is "local-ddns" and the key algorithm is HMAC-SHA256,
11659 but these values are configurable with the
11660 <command>session-keyfile</command>,
11661 <command>session-keyname</command> and
11662 <command>session-keyalg</command> options, respectively).
11665 A client running on the local system, and with appropriate
11666 permissions, may read that file and use the key to sign update
11667 requests. The zone's update policy will be set to allow that
11668 key to change any record within the zone. Assuming the
11669 key name is "local-ddns", this policy is equivalent to:
11672 <programlisting>update-policy { grant local-ddns zonesub any; };
11676 The command <command>nsupdate -l</command> sends update
11677 requests to localhost, and signs them using the session key.
11681 Other rule definitions look like this:
11685 ( <command>grant</command> | <command>deny</command> ) <replaceable>identity</replaceable> <replaceable>nametype</replaceable> <optional> <replaceable>name</replaceable> </optional> <optional> <replaceable>types</replaceable> </optional>
11689 Each rule grants or denies privileges. Once a message has
11690 successfully matched a rule, the operation is immediately
11691 granted or denied and no further rules are examined. A rule
11692 is matched when the signer matches the identity field, the
11693 name matches the name field in accordance with the nametype
11694 field, and the type matches the types specified in the type
11698 No signer is required for <replaceable>tcp-self</replaceable>
11699 or <replaceable>6to4-self</replaceable> however the standard
11700 reverse mapping / prefix conversion must match the identity
11704 The identity field specifies a name or a wildcard
11705 name. Normally, this is the name of the TSIG or
11706 SIG(0) key used to sign the update request. When a
11707 TKEY exchange has been used to create a shared secret,
11708 the identity of the shared secret is the same as the
11709 identity of the key used to authenticate the TKEY
11710 exchange. TKEY is also the negotiation method used
11711 by GSS-TSIG, which establishes an identity that is
11712 the Kerberos principal of the client, such as
11713 <userinput>"user@host.domain"</userinput>. When the
11714 <replaceable>identity</replaceable> field specifies
11715 a wildcard name, it is subject to DNS wildcard
11716 expansion, so the rule will apply to multiple identities.
11717 The <replaceable>identity</replaceable> field must
11718 contain a fully-qualified domain name.
11721 For nametypes <varname>krb5-self</varname>,
11722 <varname>ms-self</varname>, <varname>krb5-subdomain</varname>,
11723 and <varname>ms-subdomain</varname> the
11724 <replaceable>identity</replaceable> field specifies
11725 the Windows or Kerberos realm of the machine belongs to.
11728 The <replaceable>nametype</replaceable> field has 13
11730 <varname>name</varname>, <varname>subdomain</varname>,
11731 <varname>wildcard</varname>, <varname>self</varname>,
11732 <varname>selfsub</varname>, <varname>selfwild</varname>,
11733 <varname>krb5-self</varname>, <varname>ms-self</varname>,
11734 <varname>krb5-subdomain</varname>,
11735 <varname>ms-subdomain</varname>,
11736 <varname>tcp-self</varname>, <varname>6to4-self</varname>,
11737 <varname>zonesub</varname>, and <varname>external</varname>.
11740 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
11741 <colspec colname="1" colnum="1" colsep="0" colwidth="0.819in"/>
11742 <colspec colname="2" colnum="2" colsep="0" colwidth="3.681in"/>
11745 <entry colname="1">
11747 <varname>name</varname>
11749 </entry> <entry colname="2">
11751 Exact-match semantics. This rule matches
11752 when the name being updated is identical
11753 to the contents of the
11754 <replaceable>name</replaceable> field.
11759 <entry colname="1">
11761 <varname>subdomain</varname>
11763 </entry> <entry colname="2">
11765 This rule matches when the name being updated
11766 is a subdomain of, or identical to, the
11767 contents of the <replaceable>name</replaceable>
11773 <entry colname="1">
11775 <varname>zonesub</varname>
11777 </entry> <entry colname="2">
11779 This rule is similar to subdomain, except that
11780 it matches when the name being updated is a
11781 subdomain of the zone in which the
11782 <command>update-policy</command> statement
11783 appears. This obviates the need to type the zone
11784 name twice, and enables the use of a standard
11785 <command>update-policy</command> statement in
11786 multiple zones without modification.
11789 When this rule is used, the
11790 <replaceable>name</replaceable> field is omitted.
11795 <entry colname="1">
11797 <varname>wildcard</varname>
11799 </entry> <entry colname="2">
11801 The <replaceable>name</replaceable> field
11802 is subject to DNS wildcard expansion, and
11803 this rule matches when the name being updated
11804 name is a valid expansion of the wildcard.
11809 <entry colname="1">
11811 <varname>self</varname>
11814 <entry colname="2">
11816 This rule matches when the name being updated
11817 matches the contents of the
11818 <replaceable>identity</replaceable> field.
11819 The <replaceable>name</replaceable> field
11820 is ignored, but should be the same as the
11821 <replaceable>identity</replaceable> field.
11822 The <varname>self</varname> nametype is
11823 most useful when allowing using one key per
11824 name to update, where the key has the same
11825 name as the name to be updated. The
11826 <replaceable>identity</replaceable> would
11827 be specified as <constant>*</constant> (an asterisk) in
11833 <entry colname="1">
11835 <varname>selfsub</varname>
11837 </entry> <entry colname="2">
11839 This rule is similar to <varname>self</varname>
11840 except that subdomains of <varname>self</varname>
11841 can also be updated.
11846 <entry colname="1">
11848 <varname>selfwild</varname>
11850 </entry> <entry colname="2">
11852 This rule is similar to <varname>self</varname>
11853 except that only subdomains of
11854 <varname>self</varname> can be updated.
11859 <entry colname="1">
11861 <varname>ms-self</varname>
11863 </entry> <entry colname="2">
11865 This rule takes a Windows machine principal
11866 (machine$@REALM) for machine in REALM and
11867 and converts it machine.realm allowing the machine
11868 to update machine.realm. The REALM to be matched
11869 is specified in the <replaceable>identity</replaceable>
11875 <entry colname="1">
11877 <varname>ms-subdomain</varname>
11879 </entry> <entry colname="2">
11881 This rule takes a Windows machine principal
11882 (machine$@REALM) for machine in REALM and
11883 converts it to machine.realm allowing the machine
11884 to update subdomains of machine.realm. The REALM
11885 to be matched is specified in the
11886 <replaceable>identity</replaceable> field.
11891 <entry colname="1">
11893 <varname>krb5-self</varname>
11895 </entry> <entry colname="2">
11897 This rule takes a Kerberos machine principal
11898 (host/machine@REALM) for machine in REALM and
11899 and converts it machine.realm allowing the machine
11900 to update machine.realm. The REALM to be matched
11901 is specified in the <replaceable>identity</replaceable>
11907 <entry colname="1">
11909 <varname>krb5-subdomain</varname>
11911 </entry> <entry colname="2">
11913 This rule takes a Kerberos machine principal
11914 (host/machine@REALM) for machine in REALM and
11915 converts it to machine.realm allowing the machine
11916 to update subdomains of machine.realm. The REALM
11917 to be matched is specified in the
11918 <replaceable>identity</replaceable> field.
11923 <entry colname="1">
11925 <varname>tcp-self</varname>
11927 </entry> <entry colname="2">
11929 Allow updates that have been sent via TCP and
11930 for which the standard mapping from the initiating
11931 IP address into the IN-ADDR.ARPA and IP6.ARPA
11932 namespaces match the name to be updated.
11935 It is theoretically possible to spoof these TCP
11941 <entry colname="1">
11943 <varname>6to4-self</varname>
11945 </entry> <entry colname="2">
11947 Allow the 6to4 prefix to be update by any TCP
11948 connection from the 6to4 network or from the
11949 corresponding IPv4 address. This is intended
11950 to allow NS or DNAME RRsets to be added to the
11954 It is theoretically possible to spoof these TCP
11960 <entry colname="1">
11962 <varname>external</varname>
11964 </entry> <entry colname="2">
11966 This rule allows <command>named</command>
11967 to defer the decision of whether to allow a
11968 given update to an external daemon.
11971 The method of communicating with the daemon is
11972 specified in the <replaceable>identity</replaceable>
11973 field, the format of which is
11974 "<constant>local:</constant><replaceable>path</replaceable>",
11975 where <replaceable>path</replaceable> is the location
11976 of a UNIX-domain socket. (Currently, "local" is the
11977 only supported mechanism.)
11980 Requests to the external daemon are sent over the
11981 UNIX-domain socket as datagrams with the following
11985 Protocol version number (4 bytes, network byte order, currently 1)
11986 Request length (4 bytes, network byte order)
11987 Signer (null-terminated string)
11988 Name (null-terminated string)
11989 TCP source address (null-terminated string)
11990 Rdata type (null-terminated string)
11991 Key (null-terminated string)
11992 TKEY token length (4 bytes, network byte order)
11993 TKEY token (remainder of packet)</programlisting>
11995 The daemon replies with a four-byte value in
11996 network byte order, containing either 0 or 1; 0
11997 indicates that the specified update is not
11998 permitted, and 1 indicates that it is.
12007 In all cases, the <replaceable>name</replaceable>
12008 field must specify a fully-qualified domain name.
12012 If no types are explicitly specified, this rule matches
12013 all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
12014 may be specified by name, including "ANY" (ANY matches
12015 all types except NSEC and NSEC3, which can never be
12016 updated). Note that when an attempt is made to delete
12017 all records associated with a name, the rules are
12018 checked for each existing record type.
12024 <title>Zone File</title>
12025 <sect2 id="types_of_resource_records_and_when_to_use_them">
12026 <title>Types of Resource Records and When to Use Them</title>
12028 This section, largely borrowed from RFC 1034, describes the
12029 concept of a Resource Record (RR) and explains when each is used.
12030 Since the publication of RFC 1034, several new RRs have been
12032 and implemented in the DNS. These are also included.
12035 <title>Resource Records</title>
12038 A domain name identifies a node. Each node has a set of
12039 resource information, which may be empty. The set of resource
12040 information associated with a particular name is composed of
12041 separate RRs. The order of RRs in a set is not significant and
12042 need not be preserved by name servers, resolvers, or other
12043 parts of the DNS. However, sorting of multiple RRs is
12044 permitted for optimization purposes, for example, to specify
12045 that a particular nearby server be tried first. See <xref linkend="the_sortlist_statement"/> and <xref linkend="rrset_ordering"/>.
12049 The components of a Resource Record are:
12051 <informaltable colsep="0" rowsep="0">
12052 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12053 <colspec colname="1" colnum="1" colsep="0" colwidth="1.000in"/>
12054 <colspec colname="2" colnum="2" colsep="0" colwidth="3.500in"/>
12057 <entry colname="1">
12062 <entry colname="2">
12064 The domain name where the RR is found.
12069 <entry colname="1">
12074 <entry colname="2">
12076 An encoded 16-bit value that specifies
12077 the type of the resource record.
12082 <entry colname="1">
12087 <entry colname="2">
12089 The time-to-live of the RR. This field
12090 is a 32-bit integer in units of seconds, and is
12092 resolvers when they cache RRs. The TTL describes how
12094 be cached before it should be discarded.
12099 <entry colname="1">
12104 <entry colname="2">
12106 An encoded 16-bit value that identifies
12107 a protocol family or instance of a protocol.
12112 <entry colname="1">
12117 <entry colname="2">
12119 The resource data. The format of the
12120 data is type (and sometimes class) specific.
12128 The following are <emphasis>types</emphasis> of valid RRs:
12130 <informaltable colsep="0" rowsep="0">
12131 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12132 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
12133 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
12136 <entry colname="1">
12141 <entry colname="2">
12143 A host address. In the IN class, this is a
12144 32-bit IP address. Described in RFC 1035.
12149 <entry colname="1">
12154 <entry colname="2">
12156 IPv6 address. Described in RFC 1886.
12161 <entry colname="1">
12166 <entry colname="2">
12168 IPv6 address. This can be a partial
12169 address (a suffix) and an indirection to the name
12170 where the rest of the
12171 address (the prefix) can be found. Experimental.
12172 Described in RFC 2874.
12177 <entry colname="1">
12182 <entry colname="2">
12184 Location of AFS database servers.
12185 Experimental. Described in RFC 1183.
12190 <entry colname="1">
12195 <entry colname="2">
12197 Address prefix list. Experimental.
12198 Described in RFC 3123.
12203 <entry colname="1">
12208 <entry colname="2">
12210 Holds a digital certificate.
12211 Described in RFC 2538.
12216 <entry colname="1">
12221 <entry colname="2">
12223 Identifies the canonical name of an alias.
12224 Described in RFC 1035.
12229 <entry colname="1">
12234 <entry colname="2">
12236 Is used for identifying which DHCP client is
12237 associated with this name. Described in RFC 4701.
12242 <entry colname="1">
12247 <entry colname="2">
12249 Replaces the domain name specified with
12250 another name to be looked up, effectively aliasing an
12252 subtree of the domain name space rather than a single
12254 as in the case of the CNAME RR.
12255 Described in RFC 2672.
12260 <entry colname="1">
12265 <entry colname="2">
12267 Stores a public key associated with a signed
12268 DNS zone. Described in RFC 4034.
12273 <entry colname="1">
12278 <entry colname="2">
12280 Stores the hash of a public key associated with a
12281 signed DNS zone. Described in RFC 4034.
12286 <entry colname="1">
12291 <entry colname="2">
12293 Specifies the global position. Superseded by LOC.
12298 <entry colname="1">
12303 <entry colname="2">
12305 Identifies the CPU and OS used by a host.
12306 Described in RFC 1035.
12311 <entry colname="1">
12316 <entry colname="2">
12318 Provides a method for storing IPsec keying material in
12319 DNS. Described in RFC 4025.
12324 <entry colname="1">
12329 <entry colname="2">
12331 Representation of ISDN addresses.
12332 Experimental. Described in RFC 1183.
12337 <entry colname="1">
12342 <entry colname="2">
12344 Stores a public key associated with a
12345 DNS name. Used in original DNSSEC; replaced
12346 by DNSKEY in DNSSECbis, but still used with
12347 SIG(0). Described in RFCs 2535 and 2931.
12352 <entry colname="1">
12357 <entry colname="2">
12359 Identifies a key exchanger for this
12360 DNS name. Described in RFC 2230.
12365 <entry colname="1">
12370 <entry colname="2">
12372 For storing GPS info. Described in RFC 1876.
12378 <entry colname="1">
12383 <entry colname="2">
12385 Identifies a mail exchange for the domain with
12386 a 16-bit preference value (lower is better)
12387 followed by the host name of the mail exchange.
12388 Described in RFC 974, RFC 1035.
12393 <entry colname="1">
12398 <entry colname="2">
12400 Name authority pointer. Described in RFC 2915.
12405 <entry colname="1">
12410 <entry colname="2">
12412 A network service access point.
12413 Described in RFC 1706.
12418 <entry colname="1">
12423 <entry colname="2">
12425 The authoritative name server for the
12426 domain. Described in RFC 1035.
12431 <entry colname="1">
12436 <entry colname="2">
12438 Used in DNSSECbis to securely indicate that
12439 RRs with an owner name in a certain name interval do
12441 a zone and indicate what RR types are present for an
12443 Described in RFC 4034.
12448 <entry colname="1">
12453 <entry colname="2">
12455 Used in DNSSECbis to securely indicate that
12456 RRs with an owner name in a certain name
12457 interval do not exist in a zone and indicate
12458 what RR types are present for an existing
12459 name. NSEC3 differs from NSEC in that it
12460 prevents zone enumeration but is more
12461 computationally expensive on both the server
12462 and the client than NSEC. Described in RFC
12468 <entry colname="1">
12473 <entry colname="2">
12475 Used in DNSSECbis to tell the authoritative
12476 server which NSEC3 chains are available to use.
12477 Described in RFC 5155.
12482 <entry colname="1">
12487 <entry colname="2">
12489 Used in DNSSEC to securely indicate that
12490 RRs with an owner name in a certain name interval do
12492 a zone and indicate what RR types are present for an
12494 Used in original DNSSEC; replaced by NSEC in
12496 Described in RFC 2535.
12501 <entry colname="1">
12506 <entry colname="2">
12508 A pointer to another part of the domain
12509 name space. Described in RFC 1035.
12514 <entry colname="1">
12519 <entry colname="2">
12521 Provides mappings between RFC 822 and X.400
12522 addresses. Described in RFC 2163.
12527 <entry colname="1">
12532 <entry colname="2">
12534 Information on persons responsible
12535 for the domain. Experimental. Described in RFC 1183.
12540 <entry colname="1">
12545 <entry colname="2">
12547 Contains DNSSECbis signature data. Described
12553 <entry colname="1">
12558 <entry colname="2">
12560 Route-through binding for hosts that
12561 do not have their own direct wide area network
12563 Experimental. Described in RFC 1183.
12568 <entry colname="1">
12573 <entry colname="2">
12575 Contains DNSSEC signature data. Used in
12576 original DNSSEC; replaced by RRSIG in
12577 DNSSECbis, but still used for SIG(0).
12578 Described in RFCs 2535 and 2931.
12583 <entry colname="1">
12588 <entry colname="2">
12590 Identifies the start of a zone of authority.
12591 Described in RFC 1035.
12596 <entry colname="1">
12601 <entry colname="2">
12603 Contains the Sender Policy Framework information
12604 for a given email domain. Described in RFC 4408.
12609 <entry colname="1">
12614 <entry colname="2">
12616 Information about well known network
12617 services (replaces WKS). Described in RFC 2782.
12622 <entry colname="1">
12627 <entry colname="2">
12629 Provides a way to securely publish a secure shell key's
12630 fingerprint. Described in RFC 4255.
12635 <entry colname="1">
12640 <entry colname="2">
12642 Text records. Described in RFC 1035.
12647 <entry colname="1">
12652 <entry colname="2">
12654 Information about which well known
12655 network services, such as SMTP, that a domain
12656 supports. Historical.
12661 <entry colname="1">
12666 <entry colname="2">
12668 Representation of X.25 network addresses.
12669 Experimental. Described in RFC 1183.
12677 The following <emphasis>classes</emphasis> of resource records
12678 are currently valid in the DNS:
12680 <informaltable colsep="0" rowsep="0"><tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12681 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
12682 <colspec colname="2" colnum="2" colsep="0" colwidth="3.625in"/>
12686 <entry colname="1">
12691 <entry colname="2">
12699 <entry colname="1">
12704 <entry colname="2">
12706 Chaosnet, a LAN protocol created at MIT in the
12708 Rarely used for its historical purpose, but reused for
12710 built-in server information zones, e.g.,
12711 <literal>version.bind</literal>.
12717 <entry colname="1">
12722 <entry colname="2">
12724 Hesiod, an information service
12725 developed by MIT's Project Athena. It is used to share
12727 about various systems databases, such as users,
12739 The owner name is often implicit, rather than forming an
12741 part of the RR. For example, many name servers internally form
12743 or hash structures for the name space, and chain RRs off nodes.
12744 The remaining RR parts are the fixed header (type, class, TTL)
12745 which is consistent for all RRs, and a variable part (RDATA)
12747 fits the needs of the resource being described.
12750 The meaning of the TTL field is a time limit on how long an
12751 RR can be kept in a cache. This limit does not apply to
12753 data in zones; it is also timed out, but by the refreshing
12755 for the zone. The TTL is assigned by the administrator for the
12756 zone where the data originates. While short TTLs can be used to
12757 minimize caching, and a zero TTL prohibits caching, the
12759 of Internet performance suggest that these times should be on
12761 order of days for the typical host. If a change can be
12763 the TTL can be reduced prior to the change to minimize
12765 during the change, and then increased back to its former value
12770 The data in the RDATA section of RRs is carried as a combination
12771 of binary strings and domain names. The domain names are
12773 used as "pointers" to other data in the DNS.
12777 <title>Textual expression of RRs</title>
12779 RRs are represented in binary form in the packets of the DNS
12780 protocol, and are usually represented in highly encoded form
12782 stored in a name server or resolver. In the examples provided
12784 RFC 1034, a style similar to that used in master files was
12786 in order to show the contents of RRs. In this format, most RRs
12787 are shown on a single line, although continuation lines are
12792 The start of the line gives the owner of the RR. If a line
12793 begins with a blank, then the owner is assumed to be the same as
12794 that of the previous RR. Blank lines are often included for
12798 Following the owner, we list the TTL, type, and class of the
12799 RR. Class and type use the mnemonics defined above, and TTL is
12800 an integer before the type field. In order to avoid ambiguity
12802 parsing, type and class mnemonics are disjoint, TTLs are
12804 and the type mnemonic is always last. The IN class and TTL
12806 are often omitted from examples in the interests of clarity.
12809 The resource data or RDATA section of the RR are given using
12810 knowledge of the typical representation for the data.
12813 For example, we might show the RRs carried in a message as:
12815 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12816 <colspec colname="1" colnum="1" colsep="0" colwidth="1.381in"/>
12817 <colspec colname="2" colnum="2" colsep="0" colwidth="1.020in"/>
12818 <colspec colname="3" colnum="3" colsep="0" colwidth="2.099in"/>
12821 <entry colname="1">
12823 <literal>ISI.EDU.</literal>
12826 <entry colname="2">
12828 <literal>MX</literal>
12831 <entry colname="3">
12833 <literal>10 VENERA.ISI.EDU.</literal>
12838 <entry colname="1">
12841 <entry colname="2">
12843 <literal>MX</literal>
12846 <entry colname="3">
12848 <literal>10 VAXA.ISI.EDU</literal>
12853 <entry colname="1">
12855 <literal>VENERA.ISI.EDU</literal>
12858 <entry colname="2">
12860 <literal>A</literal>
12863 <entry colname="3">
12865 <literal>128.9.0.32</literal>
12870 <entry colname="1">
12873 <entry colname="2">
12875 <literal>A</literal>
12878 <entry colname="3">
12880 <literal>10.1.0.52</literal>
12885 <entry colname="1">
12887 <literal>VAXA.ISI.EDU</literal>
12890 <entry colname="2">
12892 <literal>A</literal>
12895 <entry colname="3">
12897 <literal>10.2.0.27</literal>
12902 <entry colname="1">
12905 <entry colname="2">
12907 <literal>A</literal>
12910 <entry colname="3">
12912 <literal>128.9.0.33</literal>
12920 The MX RRs have an RDATA section which consists of a 16-bit
12921 number followed by a domain name. The address RRs use a
12923 IP address format to contain a 32-bit internet address.
12926 The above example shows six RRs, with two RRs at each of three
12930 Similarly we might see:
12932 <informaltable colsep="0" rowsep="0"><tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
12933 <colspec colname="1" colnum="1" colsep="0" colwidth="1.491in"/>
12934 <colspec colname="2" colnum="2" colsep="0" colwidth="1.067in"/>
12935 <colspec colname="3" colnum="3" colsep="0" colwidth="2.067in"/>
12938 <entry colname="1">
12940 <literal>XX.LCS.MIT.EDU.</literal>
12943 <entry colname="2">
12945 <literal>IN A</literal>
12948 <entry colname="3">
12950 <literal>10.0.0.44</literal>
12955 <entry colname="1"/>
12956 <entry colname="2">
12958 <literal>CH A</literal>
12961 <entry colname="3">
12963 <literal>MIT.EDU. 2420</literal>
12971 This example shows two addresses for
12972 <literal>XX.LCS.MIT.EDU</literal>, each of a different class.
12978 <title>Discussion of MX Records</title>
12981 As described above, domain servers store information as a
12982 series of resource records, each of which contains a particular
12983 piece of information about a given domain name (which is usually,
12984 but not always, a host). The simplest way to think of a RR is as
12985 a typed pair of data, a domain name matched with a relevant datum,
12986 and stored with some additional type information to help systems
12987 determine when the RR is relevant.
12991 MX records are used to control delivery of email. The data
12992 specified in the record is a priority and a domain name. The
12994 controls the order in which email delivery is attempted, with the
12995 lowest number first. If two priorities are the same, a server is
12996 chosen randomly. If no servers at a given priority are responding,
12997 the mail transport agent will fall back to the next largest
12999 Priority numbers do not have any absolute meaning — they are
13001 only respective to other MX records for that domain name. The
13003 name given is the machine to which the mail will be delivered.
13004 It <emphasis>must</emphasis> have an associated address record
13005 (A or AAAA) — CNAME is not sufficient.
13008 For a given domain, if there is both a CNAME record and an
13009 MX record, the MX record is in error, and will be ignored.
13011 the mail will be delivered to the server specified in the MX
13013 pointed to by the CNAME.
13016 <informaltable colsep="0" rowsep="0">
13017 <tgroup cols="5" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13018 <colspec colname="1" colnum="1" colsep="0" colwidth="1.708in"/>
13019 <colspec colname="2" colnum="2" colsep="0" colwidth="0.444in"/>
13020 <colspec colname="3" colnum="3" colsep="0" colwidth="0.444in"/>
13021 <colspec colname="4" colnum="4" colsep="0" colwidth="0.976in"/>
13022 <colspec colname="5" colnum="5" colsep="0" colwidth="1.553in"/>
13025 <entry colname="1">
13027 <literal>example.com.</literal>
13030 <entry colname="2">
13032 <literal>IN</literal>
13035 <entry colname="3">
13037 <literal>MX</literal>
13040 <entry colname="4">
13042 <literal>10</literal>
13045 <entry colname="5">
13047 <literal>mail.example.com.</literal>
13052 <entry colname="1">
13055 <entry colname="2">
13057 <literal>IN</literal>
13060 <entry colname="3">
13062 <literal>MX</literal>
13065 <entry colname="4">
13067 <literal>10</literal>
13070 <entry colname="5">
13072 <literal>mail2.example.com.</literal>
13077 <entry colname="1">
13080 <entry colname="2">
13082 <literal>IN</literal>
13085 <entry colname="3">
13087 <literal>MX</literal>
13090 <entry colname="4">
13092 <literal>20</literal>
13095 <entry colname="5">
13097 <literal>mail.backup.org.</literal>
13102 <entry colname="1">
13104 <literal>mail.example.com.</literal>
13107 <entry colname="2">
13109 <literal>IN</literal>
13112 <entry colname="3">
13114 <literal>A</literal>
13117 <entry colname="4">
13119 <literal>10.0.0.1</literal>
13122 <entry colname="5">
13127 <entry colname="1">
13129 <literal>mail2.example.com.</literal>
13132 <entry colname="2">
13134 <literal>IN</literal>
13137 <entry colname="3">
13139 <literal>A</literal>
13142 <entry colname="4">
13144 <literal>10.0.0.2</literal>
13147 <entry colname="5">
13153 </informaltable><para>
13154 Mail delivery will be attempted to <literal>mail.example.com</literal> and
13155 <literal>mail2.example.com</literal> (in
13156 any order), and if neither of those succeed, delivery to <literal>mail.backup.org</literal> will
13160 <sect2 id="Setting_TTLs">
13161 <title>Setting TTLs</title>
13163 The time-to-live of the RR field is a 32-bit integer represented
13164 in units of seconds, and is primarily used by resolvers when they
13165 cache RRs. The TTL describes how long a RR can be cached before it
13166 should be discarded. The following three types of TTL are
13168 used in a zone file.
13170 <informaltable colsep="0" rowsep="0">
13171 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13172 <colspec colname="1" colnum="1" colsep="0" colwidth="0.750in"/>
13173 <colspec colname="2" colnum="2" colsep="0" colwidth="4.375in"/>
13176 <entry colname="1">
13181 <entry colname="2">
13183 The last field in the SOA is the negative
13184 caching TTL. This controls how long other servers will
13185 cache no-such-domain
13186 (NXDOMAIN) responses from you.
13189 The maximum time for
13190 negative caching is 3 hours (3h).
13195 <entry colname="1">
13200 <entry colname="2">
13202 The $TTL directive at the top of the
13203 zone file (before the SOA) gives a default TTL for every
13205 a specific TTL set.
13210 <entry colname="1">
13215 <entry colname="2">
13217 Each RR can have a TTL as the second
13218 field in the RR, which will control how long other
13228 All of these TTLs default to units of seconds, though units
13229 can be explicitly specified, for example, <literal>1h30m</literal>.
13233 <title>Inverse Mapping in IPv4</title>
13235 Reverse name resolution (that is, translation from IP address
13236 to name) is achieved by means of the <emphasis>in-addr.arpa</emphasis> domain
13237 and PTR records. Entries in the in-addr.arpa domain are made in
13238 least-to-most significant order, read left to right. This is the
13239 opposite order to the way IP addresses are usually written. Thus,
13240 a machine with an IP address of 10.1.2.3 would have a
13242 in-addr.arpa name of
13243 3.2.1.10.in-addr.arpa. This name should have a PTR resource record
13244 whose data field is the name of the machine or, optionally,
13246 PTR records if the machine has more than one name. For example,
13247 in the <optional>example.com</optional> domain:
13249 <informaltable colsep="0" rowsep="0">
13250 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13251 <colspec colname="1" colnum="1" colsep="0" colwidth="1.125in"/>
13252 <colspec colname="2" colnum="2" colsep="0" colwidth="4.000in"/>
13255 <entry colname="1">
13257 <literal>$ORIGIN</literal>
13260 <entry colname="2">
13262 <literal>2.1.10.in-addr.arpa</literal>
13267 <entry colname="1">
13269 <literal>3</literal>
13272 <entry colname="2">
13274 <literal>IN PTR foo.example.com.</literal>
13283 The <command>$ORIGIN</command> lines in the examples
13284 are for providing context to the examples only — they do not
13286 appear in the actual usage. They are only used here to indicate
13287 that the example is relative to the listed origin.
13292 <title>Other Zone File Directives</title>
13294 The Master File Format was initially defined in RFC 1035 and
13295 has subsequently been extended. While the Master File Format
13297 is class independent all records in a Master File must be of the
13302 Master File Directives include <command>$ORIGIN</command>, <command>$INCLUDE</command>,
13303 and <command>$TTL.</command>
13306 <title>The <command>@</command> (at-sign)</title>
13308 When used in the label (or name) field, the asperand or
13309 at-sign (@) symbol represents the current origin.
13310 At the start of the zone file, it is the
13311 <<varname>zone_name</varname>> (followed by
13316 <title>The <command>$ORIGIN</command> Directive</title>
13318 Syntax: <command>$ORIGIN</command>
13319 <replaceable>domain-name</replaceable>
13320 <optional><replaceable>comment</replaceable></optional>
13322 <para><command>$ORIGIN</command>
13323 sets the domain name that will be appended to any
13324 unqualified records. When a zone is first read in there
13325 is an implicit <command>$ORIGIN</command>
13326 <<varname>zone_name</varname>><command>.</command>
13327 (followed by trailing dot).
13328 The current <command>$ORIGIN</command> is appended to
13329 the domain specified in the <command>$ORIGIN</command>
13330 argument if it is not absolute.
13334 $ORIGIN example.com.
13335 WWW CNAME MAIN-SERVER
13343 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
13348 <title>The <command>$INCLUDE</command> Directive</title>
13350 Syntax: <command>$INCLUDE</command>
13351 <replaceable>filename</replaceable>
13353 <replaceable>origin</replaceable> </optional>
13354 <optional> <replaceable>comment</replaceable> </optional>
13357 Read and process the file <filename>filename</filename> as
13358 if it were included into the file at this point. If <command>origin</command> is
13359 specified the file is processed with <command>$ORIGIN</command> set
13360 to that value, otherwise the current <command>$ORIGIN</command> is
13364 The origin and the current domain name
13365 revert to the values they had prior to the <command>$INCLUDE</command> once
13366 the file has been read.
13370 RFC 1035 specifies that the current origin should be restored
13372 an <command>$INCLUDE</command>, but it is silent
13373 on whether the current
13374 domain name should also be restored. BIND 9 restores both of
13376 This could be construed as a deviation from RFC 1035, a
13382 <title>The <command>$TTL</command> Directive</title>
13384 Syntax: <command>$TTL</command>
13385 <replaceable>default-ttl</replaceable>
13387 <replaceable>comment</replaceable> </optional>
13390 Set the default Time To Live (TTL) for subsequent records
13391 with undefined TTLs. Valid TTLs are of the range 0-2147483647
13394 <para><command>$TTL</command>
13395 is defined in RFC 2308.
13400 <title><acronym>BIND</acronym> Master File Extension: the <command>$GENERATE</command> Directive</title>
13402 Syntax: <command>$GENERATE</command>
13403 <replaceable>range</replaceable>
13404 <replaceable>lhs</replaceable>
13405 <optional><replaceable>ttl</replaceable></optional>
13406 <optional><replaceable>class</replaceable></optional>
13407 <replaceable>type</replaceable>
13408 <replaceable>rhs</replaceable>
13409 <optional><replaceable>comment</replaceable></optional>
13411 <para><command>$GENERATE</command>
13412 is used to create a series of resource records that only
13413 differ from each other by an
13414 iterator. <command>$GENERATE</command> can be used to
13415 easily generate the sets of records required to support
13416 sub /24 reverse delegations described in RFC 2317:
13417 Classless IN-ADDR.ARPA delegation.
13420 <programlisting>$ORIGIN 0.0.192.IN-ADDR.ARPA.
13421 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
13422 $GENERATE 1-127 $ CNAME $.0</programlisting>
13428 <programlisting>0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
13429 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
13430 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
13431 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
13433 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
13437 Generate a set of A and MX records. Note the MX's right hand
13438 side is a quoted string. The quotes will be stripped when the
13439 right hand side is processed.
13444 $GENERATE 1-127 HOST-$ A 1.2.3.$
13445 $GENERATE 1-127 HOST-$ MX "0 ."</programlisting>
13451 <programlisting>HOST-1.EXAMPLE. A 1.2.3.1
13452 HOST-1.EXAMPLE. MX 0 .
13453 HOST-2.EXAMPLE. A 1.2.3.2
13454 HOST-2.EXAMPLE. MX 0 .
13455 HOST-3.EXAMPLE. A 1.2.3.3
13456 HOST-3.EXAMPLE. MX 0 .
13458 HOST-127.EXAMPLE. A 1.2.3.127
13459 HOST-127.EXAMPLE. MX 0 .
13462 <informaltable colsep="0" rowsep="0">
13463 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="3Level-table">
13464 <colspec colname="1" colnum="1" colsep="0" colwidth="0.875in"/>
13465 <colspec colname="2" colnum="2" colsep="0" colwidth="4.250in"/>
13468 <entry colname="1">
13469 <para><command>range</command></para>
13471 <entry colname="2">
13473 This can be one of two forms: start-stop
13474 or start-stop/step. If the first form is used, then step
13476 1. All of start, stop and step must be positive.
13481 <entry colname="1">
13482 <para><command>lhs</command></para>
13484 <entry colname="2">
13486 describes the owner name of the resource records
13487 to be created. Any single <command>$</command>
13489 symbols within the <command>lhs</command> string
13490 are replaced by the iterator value.
13492 To get a $ in the output, you need to escape the
13493 <command>$</command> using a backslash
13494 <command>\</command>,
13495 e.g. <command>\$</command>. The
13496 <command>$</command> may optionally be followed
13497 by modifiers which change the offset from the
13498 iterator, field width and base.
13500 Modifiers are introduced by a
13501 <command>{</command> (left brace) immediately following the
13502 <command>$</command> as
13503 <command>${offset[,width[,base]]}</command>.
13504 For example, <command>${-20,3,d}</command>
13505 subtracts 20 from the current value, prints the
13506 result as a decimal in a zero-padded field of
13509 Available output forms are decimal
13510 (<command>d</command>), octal
13511 (<command>o</command>), hexadecimal
13512 (<command>x</command> or <command>X</command>
13513 for uppercase) and nibble
13514 (<command>n</command> or <command>N</command>\
13515 for uppercase). The default modifier is
13516 <command>${0,0,d}</command>. If the
13517 <command>lhs</command> is not absolute, the
13518 current <command>$ORIGIN</command> is appended
13522 In nibble mode the value will be treated as
13523 if it was a reversed hexadecimal string
13524 with each hexadecimal digit as a separate
13525 label. The width field includes the label
13529 For compatibility with earlier versions,
13530 <command>$$</command> is still recognized as
13531 indicating a literal $ in the output.
13536 <entry colname="1">
13537 <para><command>ttl</command></para>
13539 <entry colname="2">
13541 Specifies the time-to-live of the generated records. If
13542 not specified this will be inherited using the
13543 normal TTL inheritance rules.
13545 <para><command>class</command>
13546 and <command>ttl</command> can be
13547 entered in either order.
13552 <entry colname="1">
13553 <para><command>class</command></para>
13555 <entry colname="2">
13557 Specifies the class of the generated records.
13558 This must match the zone class if it is
13561 <para><command>class</command>
13562 and <command>ttl</command> can be
13563 entered in either order.
13568 <entry colname="1">
13569 <para><command>type</command></para>
13571 <entry colname="2">
13578 <entry colname="1">
13579 <para><command>rhs</command></para>
13581 <entry colname="2">
13583 <command>rhs</command>, optionally, quoted string.
13591 The <command>$GENERATE</command> directive is a <acronym>BIND</acronym> extension
13592 and not part of the standard zone file format.
13595 BIND 8 does not support the optional TTL and CLASS fields.
13599 <sect2 id="zonefile_format">
13600 <title>Additional File Formats</title>
13602 In addition to the standard textual format, BIND 9
13603 supports the ability to read or dump to zone files in
13604 other formats. The <constant>raw</constant> format is
13605 currently available as an additional format. It is a
13606 binary format representing BIND 9's internal data
13607 structure directly, thereby remarkably improving the
13611 For a primary server, a zone file in the
13612 <constant>raw</constant> format is expected to be
13613 generated from a textual zone file by the
13614 <command>named-compilezone</command> command. For a
13615 secondary server or for a dynamic zone, it is automatically
13616 generated (if this format is specified by the
13617 <command>masterfile-format</command> option) when
13618 <command>named</command> dumps the zone contents after
13619 zone transfer or when applying prior updates.
13622 If a zone file in a binary format needs manual modification,
13623 it first must be converted to a textual form by the
13624 <command>named-compilezone</command> command. All
13625 necessary modification should go to the text file, which
13626 should then be converted to the binary form by the
13627 <command>named-compilezone</command> command again.
13630 Although the <constant>raw</constant> format uses the
13631 network byte order and avoids architecture-dependent
13632 data alignment so that it is as much portable as
13633 possible, it is primarily expected to be used inside
13634 the same single system. In order to export a zone
13635 file in the <constant>raw</constant> format or make a
13636 portable backup of the file, it is recommended to
13637 convert the file to the standard textual representation.
13642 <sect1 id="statistics">
13643 <title>BIND9 Statistics</title>
13645 <acronym>BIND</acronym> 9 maintains lots of statistics
13646 information and provides several interfaces for users to
13647 get access to the statistics.
13648 The available statistics include all statistics counters
13649 that were available in <acronym>BIND</acronym> 8 and
13650 are meaningful in <acronym>BIND</acronym> 9,
13651 and other information that is considered useful.
13655 The statistics information is categorized into the following
13659 <informaltable frame="all">
13661 <colspec colname="1" colnum="1" colsep="0" colwidth="3.300in"/>
13662 <colspec colname="2" colnum="2" colsep="0" colwidth="2.625in"/>
13666 <entry colname="1">
13667 <para>Incoming Requests</para>
13669 <entry colname="2">
13671 The number of incoming DNS requests for each OPCODE.
13677 <entry colname="1">
13678 <para>Incoming Queries</para>
13680 <entry colname="2">
13682 The number of incoming queries for each RR type.
13688 <entry colname="1">
13689 <para>Outgoing Queries</para>
13691 <entry colname="2">
13693 The number of outgoing queries for each RR
13694 type sent from the internal resolver.
13695 Maintained per view.
13701 <entry colname="1">
13702 <para>Name Server Statistics</para>
13704 <entry colname="2">
13706 Statistics counters about incoming request processing.
13712 <entry colname="1">
13713 <para>Zone Maintenance Statistics</para>
13715 <entry colname="2">
13717 Statistics counters regarding zone maintenance
13718 operations such as zone transfers.
13724 <entry colname="1">
13725 <para>Resolver Statistics</para>
13727 <entry colname="2">
13729 Statistics counters about name resolution
13730 performed in the internal resolver.
13731 Maintained per view.
13737 <entry colname="1">
13738 <para>Cache DB RRsets</para>
13740 <entry colname="2">
13742 The number of RRsets per RR type and nonexistent
13743 names stored in the cache database.
13744 If the exclamation mark (!) is printed for a RR
13745 type, it means that particular type of RRset is
13746 known to be nonexistent (this is also known as
13748 Maintained per view.
13754 <entry colname="1">
13755 <para>Socket I/O Statistics</para>
13757 <entry colname="2">
13759 Statistics counters about network related events.
13769 A subset of Name Server Statistics is collected and shown
13770 per zone for which the server has the authority when
13771 <command>zone-statistics</command> is set to
13772 <userinput>yes</userinput>.
13773 These statistics counters are shown with their zone and view
13775 In some cases the view names are omitted for the default view.
13779 There are currently two user interfaces to get access to the
13781 One is in the plain text format dumped to the file specified
13782 by the <command>statistics-file</command> configuration option.
13783 The other is remotely accessible via a statistics channel
13784 when the <command>statistics-channels</command> statement
13785 is specified in the configuration file
13786 (see <xref linkend="statschannels"/>.)
13789 <sect3 id="statsfile">
13790 <title>The Statistics File</title>
13792 The text format statistics dump begins with a line, like:
13795 <command>+++ Statistics Dump +++ (973798949)</command>
13798 The number in parentheses is a standard
13799 Unix-style timestamp, measured as seconds since January 1, 1970.
13802 that line is a set of statistics information, which is categorized
13803 as described above.
13804 Each section begins with a line, like:
13808 <command>++ Name Server Statistics ++</command>
13812 Each section consists of lines, each containing the statistics
13813 counter value followed by its textual description.
13814 See below for available counters.
13815 For brevity, counters that have a value of 0 are not shown
13816 in the statistics file.
13820 The statistics dump ends with the line where the
13821 number is identical to the number in the beginning line; for example:
13824 <command>--- Statistics Dump --- (973798949)</command>
13828 <sect2 id="statistics_counters">
13829 <title>Statistics Counters</title>
13831 The following tables summarize statistics counters that
13832 <acronym>BIND</acronym> 9 provides.
13833 For each row of the tables, the leftmost column is the
13834 abbreviated symbol name of that counter.
13835 These symbols are shown in the statistics information
13836 accessed via an HTTP statistics channel.
13837 The rightmost column gives the description of the counter,
13838 which is also shown in the statistics file
13839 (but, in this document, possibly with slight modification
13840 for better readability).
13841 Additional notes may also be provided in this column.
13842 When a middle column exists between these two columns,
13843 it gives the corresponding counter name of the
13844 <acronym>BIND</acronym> 8 statistics, if applicable.
13848 <title>Name Server Statistics Counters</title>
13850 <informaltable colsep="0" rowsep="0">
13851 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
13852 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
13853 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
13854 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
13857 <entry colname="1">
13859 <emphasis>Symbol</emphasis>
13862 <entry colname="2">
13864 <emphasis>BIND8 Symbol</emphasis>
13867 <entry colname="3">
13869 <emphasis>Description</emphasis>
13875 <entry colname="1">
13876 <para><command>Requestv4</command></para>
13878 <entry colname="2">
13879 <para><command>RQ</command></para>
13881 <entry colname="3">
13883 IPv4 requests received.
13884 Note: this also counts non query requests.
13889 <entry colname="1">
13890 <para><command>Requestv6</command></para>
13892 <entry colname="2">
13893 <para><command>RQ</command></para>
13895 <entry colname="3">
13897 IPv6 requests received.
13898 Note: this also counts non query requests.
13903 <entry colname="1">
13904 <para><command>ReqEdns0</command></para>
13906 <entry colname="2">
13907 <para><command></command></para>
13909 <entry colname="3">
13911 Requests with EDNS(0) received.
13916 <entry colname="1">
13917 <para><command>ReqBadEDNSVer</command></para>
13919 <entry colname="2">
13920 <para><command></command></para>
13922 <entry colname="3">
13924 Requests with unsupported EDNS version received.
13929 <entry colname="1">
13930 <para><command>ReqTSIG</command></para>
13932 <entry colname="2">
13933 <para><command></command></para>
13935 <entry colname="3">
13937 Requests with TSIG received.
13942 <entry colname="1">
13943 <para><command>ReqSIG0</command></para>
13945 <entry colname="2">
13946 <para><command></command></para>
13948 <entry colname="3">
13950 Requests with SIG(0) received.
13955 <entry colname="1">
13956 <para><command>ReqBadSIG</command></para>
13958 <entry colname="2">
13959 <para><command></command></para>
13961 <entry colname="3">
13963 Requests with invalid (TSIG or SIG(0)) signature.
13968 <entry colname="1">
13969 <para><command>ReqTCP</command></para>
13971 <entry colname="2">
13972 <para><command>RTCP</command></para>
13974 <entry colname="3">
13976 TCP requests received.
13981 <entry colname="1">
13982 <para><command>AuthQryRej</command></para>
13984 <entry colname="2">
13985 <para><command>RUQ</command></para>
13987 <entry colname="3">
13989 Authoritative (non recursive) queries rejected.
13994 <entry colname="1">
13995 <para><command>RecQryRej</command></para>
13997 <entry colname="2">
13998 <para><command>RURQ</command></para>
14000 <entry colname="3">
14002 Recursive queries rejected.
14007 <entry colname="1">
14008 <para><command>XfrRej</command></para>
14010 <entry colname="2">
14011 <para><command>RUXFR</command></para>
14013 <entry colname="3">
14015 Zone transfer requests rejected.
14020 <entry colname="1">
14021 <para><command>UpdateRej</command></para>
14023 <entry colname="2">
14024 <para><command>RUUpd</command></para>
14026 <entry colname="3">
14028 Dynamic update requests rejected.
14033 <entry colname="1">
14034 <para><command>Response</command></para>
14036 <entry colname="2">
14037 <para><command>SAns</command></para>
14039 <entry colname="3">
14046 <entry colname="1">
14047 <para><command>RespTruncated</command></para>
14049 <entry colname="2">
14050 <para><command></command></para>
14052 <entry colname="3">
14054 Truncated responses sent.
14059 <entry colname="1">
14060 <para><command>RespEDNS0</command></para>
14062 <entry colname="2">
14063 <para><command></command></para>
14065 <entry colname="3">
14067 Responses with EDNS(0) sent.
14072 <entry colname="1">
14073 <para><command>RespTSIG</command></para>
14075 <entry colname="2">
14076 <para><command></command></para>
14078 <entry colname="3">
14080 Responses with TSIG sent.
14085 <entry colname="1">
14086 <para><command>RespSIG0</command></para>
14088 <entry colname="2">
14089 <para><command></command></para>
14091 <entry colname="3">
14093 Responses with SIG(0) sent.
14098 <entry colname="1">
14099 <para><command>QrySuccess</command></para>
14101 <entry colname="2">
14102 <para><command></command></para>
14104 <entry colname="3">
14106 Queries resulted in a successful answer.
14107 This means the query which returns a NOERROR response
14108 with at least one answer RR.
14109 This corresponds to the
14110 <command>success</command> counter
14111 of previous versions of
14112 <acronym>BIND</acronym> 9.
14117 <entry colname="1">
14118 <para><command>QryAuthAns</command></para>
14120 <entry colname="2">
14121 <para><command></command></para>
14123 <entry colname="3">
14125 Queries resulted in authoritative answer.
14130 <entry colname="1">
14131 <para><command>QryNoauthAns</command></para>
14133 <entry colname="2">
14134 <para><command>SNaAns</command></para>
14136 <entry colname="3">
14138 Queries resulted in non authoritative answer.
14143 <entry colname="1">
14144 <para><command>QryReferral</command></para>
14146 <entry colname="2">
14147 <para><command></command></para>
14149 <entry colname="3">
14151 Queries resulted in referral answer.
14152 This corresponds to the
14153 <command>referral</command> counter
14154 of previous versions of
14155 <acronym>BIND</acronym> 9.
14160 <entry colname="1">
14161 <para><command>QryNxrrset</command></para>
14163 <entry colname="2">
14164 <para><command></command></para>
14166 <entry colname="3">
14168 Queries resulted in NOERROR responses with no data.
14169 This corresponds to the
14170 <command>nxrrset</command> counter
14171 of previous versions of
14172 <acronym>BIND</acronym> 9.
14177 <entry colname="1">
14178 <para><command>QrySERVFAIL</command></para>
14180 <entry colname="2">
14181 <para><command>SFail</command></para>
14183 <entry colname="3">
14185 Queries resulted in SERVFAIL.
14190 <entry colname="1">
14191 <para><command>QryFORMERR</command></para>
14193 <entry colname="2">
14194 <para><command>SFErr</command></para>
14196 <entry colname="3">
14198 Queries resulted in FORMERR.
14203 <entry colname="1">
14204 <para><command>QryNXDOMAIN</command></para>
14206 <entry colname="2">
14207 <para><command>SNXD</command></para>
14209 <entry colname="3">
14211 Queries resulted in NXDOMAIN.
14212 This corresponds to the
14213 <command>nxdomain</command> counter
14214 of previous versions of
14215 <acronym>BIND</acronym> 9.
14220 <entry colname="1">
14221 <para><command>QryRecursion</command></para>
14223 <entry colname="2">
14224 <para><command>RFwdQ</command></para>
14226 <entry colname="3">
14228 Queries which caused the server
14229 to perform recursion in order to find the final answer.
14230 This corresponds to the
14231 <command>recursion</command> counter
14232 of previous versions of
14233 <acronym>BIND</acronym> 9.
14238 <entry colname="1">
14239 <para><command>QryDuplicate</command></para>
14241 <entry colname="2">
14242 <para><command>RDupQ</command></para>
14244 <entry colname="3">
14246 Queries which the server attempted to
14247 recurse but discovered an existing query with the same
14248 IP address, port, query ID, name, type and class
14249 already being processed.
14250 This corresponds to the
14251 <command>duplicate</command> counter
14252 of previous versions of
14253 <acronym>BIND</acronym> 9.
14258 <entry colname="1">
14259 <para><command>QryDropped</command></para>
14261 <entry colname="2">
14262 <para><command></command></para>
14264 <entry colname="3">
14266 Recursive queries for which the server
14267 discovered an excessive number of existing
14268 recursive queries for the same name, type and
14269 class and were subsequently dropped.
14270 This is the number of dropped queries due to
14271 the reason explained with the
14272 <command>clients-per-query</command>
14274 <command>max-clients-per-query</command>
14276 (see the description about
14277 <xref linkend="clients-per-query"/>.)
14278 This corresponds to the
14279 <command>dropped</command> counter
14280 of previous versions of
14281 <acronym>BIND</acronym> 9.
14286 <entry colname="1">
14287 <para><command>QryFailure</command></para>
14289 <entry colname="2">
14290 <para><command></command></para>
14292 <entry colname="3">
14294 Other query failures.
14295 This corresponds to the
14296 <command>failure</command> counter
14297 of previous versions of
14298 <acronym>BIND</acronym> 9.
14299 Note: this counter is provided mainly for
14300 backward compatibility with the previous versions.
14301 Normally a more fine-grained counters such as
14302 <command>AuthQryRej</command> and
14303 <command>RecQryRej</command>
14304 that would also fall into this counter are provided,
14305 and so this counter would not be of much
14306 interest in practice.
14311 <entry colname="1">
14312 <para><command>XfrReqDone</command></para>
14314 <entry colname="2">
14315 <para><command></command></para>
14317 <entry colname="3">
14319 Requested zone transfers completed.
14324 <entry colname="1">
14325 <para><command>UpdateReqFwd</command></para>
14327 <entry colname="2">
14328 <para><command></command></para>
14330 <entry colname="3">
14332 Update requests forwarded.
14337 <entry colname="1">
14338 <para><command>UpdateRespFwd</command></para>
14340 <entry colname="2">
14341 <para><command></command></para>
14343 <entry colname="3">
14345 Update responses forwarded.
14350 <entry colname="1">
14351 <para><command>UpdateFwdFail</command></para>
14353 <entry colname="2">
14354 <para><command></command></para>
14356 <entry colname="3">
14358 Dynamic update forward failed.
14363 <entry colname="1">
14364 <para><command>UpdateDone</command></para>
14366 <entry colname="2">
14367 <para><command></command></para>
14369 <entry colname="3">
14371 Dynamic updates completed.
14376 <entry colname="1">
14377 <para><command>UpdateFail</command></para>
14379 <entry colname="2">
14380 <para><command></command></para>
14382 <entry colname="3">
14384 Dynamic updates failed.
14389 <entry colname="1">
14390 <para><command>UpdateBadPrereq</command></para>
14392 <entry colname="2">
14393 <para><command></command></para>
14395 <entry colname="3">
14397 Dynamic updates rejected due to prerequisite failure.
14402 <entry colname="1">
14403 <para><command>RPZRewrites</command></para>
14405 <entry colname="2">
14406 <para><command></command></para>
14408 <entry colname="3">
14410 Response policy zone rewrites.
14415 <entry colname="1">
14416 <para><command>RateDropped</command></para>
14418 <entry colname="2">
14419 <para><command></command></para>
14421 <entry colname="3">
14423 Responses dropped by rate limits.
14428 <entry colname="1">
14429 <para><command>RateSlipped</command></para>
14431 <entry colname="2">
14432 <para><command></command></para>
14434 <entry colname="3">
14436 Responses truncated by rate limits.
14446 <title>Zone Maintenance Statistics Counters</title>
14448 <informaltable colsep="0" rowsep="0">
14449 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14450 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14451 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
14454 <entry colname="1">
14456 <emphasis>Symbol</emphasis>
14459 <entry colname="2">
14461 <emphasis>Description</emphasis>
14467 <entry colname="1">
14468 <para><command>NotifyOutv4</command></para>
14470 <entry colname="2">
14472 IPv4 notifies sent.
14477 <entry colname="1">
14478 <para><command>NotifyOutv6</command></para>
14480 <entry colname="2">
14482 IPv6 notifies sent.
14487 <entry colname="1">
14488 <para><command>NotifyInv4</command></para>
14490 <entry colname="2">
14492 IPv4 notifies received.
14497 <entry colname="1">
14498 <para><command>NotifyInv6</command></para>
14500 <entry colname="2">
14502 IPv6 notifies received.
14507 <entry colname="1">
14508 <para><command>NotifyRej</command></para>
14510 <entry colname="2">
14512 Incoming notifies rejected.
14517 <entry colname="1">
14518 <para><command>SOAOutv4</command></para>
14520 <entry colname="2">
14522 IPv4 SOA queries sent.
14527 <entry colname="1">
14528 <para><command>SOAOutv6</command></para>
14530 <entry colname="2">
14532 IPv6 SOA queries sent.
14537 <entry colname="1">
14538 <para><command>AXFRReqv4</command></para>
14540 <entry colname="2">
14542 IPv4 AXFR requested.
14547 <entry colname="1">
14548 <para><command>AXFRReqv6</command></para>
14550 <entry colname="2">
14552 IPv6 AXFR requested.
14557 <entry colname="1">
14558 <para><command>IXFRReqv4</command></para>
14560 <entry colname="2">
14562 IPv4 IXFR requested.
14567 <entry colname="1">
14568 <para><command>IXFRReqv6</command></para>
14570 <entry colname="2">
14572 IPv6 IXFR requested.
14577 <entry colname="1">
14578 <para><command>XfrSuccess</command></para>
14580 <entry colname="2">
14582 Zone transfer requests succeeded.
14587 <entry colname="1">
14588 <para><command>XfrFail</command></para>
14590 <entry colname="2">
14592 Zone transfer requests failed.
14602 <title>Resolver Statistics Counters</title>
14604 <informaltable colsep="0" rowsep="0">
14605 <tgroup cols="3" colsep="0" rowsep="0" tgroupstyle="4Level-table">
14606 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
14607 <colspec colname="2" colnum="2" colsep="0" colwidth="1.150in"/>
14608 <colspec colname="3" colnum="3" colsep="0" colwidth="3.350in"/>
14611 <entry colname="1">
14613 <emphasis>Symbol</emphasis>
14616 <entry colname="2">
14618 <emphasis>BIND8 Symbol</emphasis>
14621 <entry colname="3">
14623 <emphasis>Description</emphasis>
14629 <entry colname="1">
14630 <para><command>Queryv4</command></para>
14632 <entry colname="2">
14633 <para><command>SFwdQ</command></para>
14635 <entry colname="3">
14642 <entry colname="1">
14643 <para><command>Queryv6</command></para>
14645 <entry colname="2">
14646 <para><command>SFwdQ</command></para>
14648 <entry colname="3">
14655 <entry colname="1">
14656 <para><command>Responsev4</command></para>
14658 <entry colname="2">
14659 <para><command>RR</command></para>
14661 <entry colname="3">
14663 IPv4 responses received.
14668 <entry colname="1">
14669 <para><command>Responsev6</command></para>
14671 <entry colname="2">
14672 <para><command>RR</command></para>
14674 <entry colname="3">
14676 IPv6 responses received.
14681 <entry colname="1">
14682 <para><command>NXDOMAIN</command></para>
14684 <entry colname="2">
14685 <para><command>RNXD</command></para>
14687 <entry colname="3">
14694 <entry colname="1">
14695 <para><command>SERVFAIL</command></para>
14697 <entry colname="2">
14698 <para><command>RFail</command></para>
14700 <entry colname="3">
14707 <entry colname="1">
14708 <para><command>FORMERR</command></para>
14710 <entry colname="2">
14711 <para><command>RFErr</command></para>
14713 <entry colname="3">
14720 <entry colname="1">
14721 <para><command>OtherError</command></para>
14723 <entry colname="2">
14724 <para><command>RErr</command></para>
14726 <entry colname="3">
14728 Other errors received.
14733 <entry colname="1">
14734 <para><command>EDNS0Fail</command></para>
14736 <entry colname="2">
14737 <para><command></command></para>
14739 <entry colname="3">
14741 EDNS(0) query failures.
14746 <entry colname="1">
14747 <para><command>Mismatch</command></para>
14749 <entry colname="2">
14750 <para><command>RDupR</command></para>
14752 <entry colname="3">
14754 Mismatch responses received.
14755 The DNS ID, response's source address,
14756 and/or the response's source port does not
14757 match what was expected.
14758 (The port must be 53 or as defined by
14759 the <command>port</command> option.)
14760 This may be an indication of a cache
14766 <entry colname="1">
14767 <para><command>Truncated</command></para>
14769 <entry colname="2">
14770 <para><command></command></para>
14772 <entry colname="3">
14774 Truncated responses received.
14779 <entry colname="1">
14780 <para><command>Lame</command></para>
14782 <entry colname="2">
14783 <para><command>RLame</command></para>
14785 <entry colname="3">
14787 Lame delegations received.
14792 <entry colname="1">
14793 <para><command>Retry</command></para>
14795 <entry colname="2">
14796 <para><command>SDupQ</command></para>
14798 <entry colname="3">
14800 Query retries performed.
14805 <entry colname="1">
14806 <para><command>QueryAbort</command></para>
14808 <entry colname="2">
14809 <para><command></command></para>
14811 <entry colname="3">
14813 Queries aborted due to quota control.
14818 <entry colname="1">
14819 <para><command>QuerySockFail</command></para>
14821 <entry colname="2">
14822 <para><command></command></para>
14824 <entry colname="3">
14826 Failures in opening query sockets.
14827 One common reason for such failures is a
14828 failure of opening a new socket due to a
14829 limitation on file descriptors.
14834 <entry colname="1">
14835 <para><command>QueryTimeout</command></para>
14837 <entry colname="2">
14838 <para><command></command></para>
14840 <entry colname="3">
14847 <entry colname="1">
14848 <para><command>GlueFetchv4</command></para>
14850 <entry colname="2">
14851 <para><command>SSysQ</command></para>
14853 <entry colname="3">
14855 IPv4 NS address fetches invoked.
14860 <entry colname="1">
14861 <para><command>GlueFetchv6</command></para>
14863 <entry colname="2">
14864 <para><command>SSysQ</command></para>
14866 <entry colname="3">
14868 IPv6 NS address fetches invoked.
14873 <entry colname="1">
14874 <para><command>GlueFetchv4Fail</command></para>
14876 <entry colname="2">
14877 <para><command></command></para>
14879 <entry colname="3">
14881 IPv4 NS address fetch failed.
14886 <entry colname="1">
14887 <para><command>GlueFetchv6Fail</command></para>
14889 <entry colname="2">
14890 <para><command></command></para>
14892 <entry colname="3">
14894 IPv6 NS address fetch failed.
14899 <entry colname="1">
14900 <para><command>ValAttempt</command></para>
14902 <entry colname="2">
14903 <para><command></command></para>
14905 <entry colname="3">
14907 DNSSEC validation attempted.
14912 <entry colname="1">
14913 <para><command>ValOk</command></para>
14915 <entry colname="2">
14916 <para><command></command></para>
14918 <entry colname="3">
14920 DNSSEC validation succeeded.
14925 <entry colname="1">
14926 <para><command>ValNegOk</command></para>
14928 <entry colname="2">
14929 <para><command></command></para>
14931 <entry colname="3">
14933 DNSSEC validation on negative information succeeded.
14938 <entry colname="1">
14939 <para><command>ValFail</command></para>
14941 <entry colname="2">
14942 <para><command></command></para>
14944 <entry colname="3">
14946 DNSSEC validation failed.
14951 <entry colname="1">
14952 <para><command>QryRTTnn</command></para>
14954 <entry colname="2">
14955 <para><command></command></para>
14957 <entry colname="3">
14959 Frequency table on round trip times (RTTs) of
14961 Each <command>nn</command> specifies the corresponding
14964 <command>nn_1</command>,
14965 <command>nn_2</command>,
14967 <command>nn_m</command>,
14968 the value of <command>nn_i</command> is the
14969 number of queries whose RTTs are between
14970 <command>nn_(i-1)</command> (inclusive) and
14971 <command>nn_i</command> (exclusive) milliseconds.
14972 For the sake of convenience we define
14973 <command>nn_0</command> to be 0.
14974 The last entry should be represented as
14975 <command>nn_m+</command>, which means the
14976 number of queries whose RTTs are equal to or over
14977 <command>nn_m</command> milliseconds.
14988 <title>Socket I/O Statistics Counters</title>
14991 Socket I/O statistics counters are defined per socket
14993 <command>UDP4</command> (UDP/IPv4),
14994 <command>UDP6</command> (UDP/IPv6),
14995 <command>TCP4</command> (TCP/IPv4),
14996 <command>TCP6</command> (TCP/IPv6),
14997 <command>Unix</command> (Unix Domain), and
14998 <command>FDwatch</command> (sockets opened outside the
15000 In the following table <command><TYPE></command>
15001 represents a socket type.
15002 Not all counters are available for all socket types;
15003 exceptions are noted in the description field.
15006 <informaltable colsep="0" rowsep="0">
15007 <tgroup cols="2" colsep="0" rowsep="0" tgroupstyle="4Level-table">
15008 <colspec colname="1" colnum="1" colsep="0" colwidth="1.150in"/>
15009 <colspec colname="2" colnum="2" colsep="0" colwidth="3.350in"/>
15012 <entry colname="1">
15014 <emphasis>Symbol</emphasis>
15017 <entry colname="2">
15019 <emphasis>Description</emphasis>
15025 <entry colname="1">
15026 <para><command><TYPE>Open</command></para>
15028 <entry colname="2">
15030 Sockets opened successfully.
15031 This counter is not applicable to the
15032 <command>FDwatch</command> type.
15037 <entry colname="1">
15038 <para><command><TYPE>OpenFail</command></para>
15040 <entry colname="2">
15042 Failures of opening sockets.
15043 This counter is not applicable to the
15044 <command>FDwatch</command> type.
15049 <entry colname="1">
15050 <para><command><TYPE>Close</command></para>
15052 <entry colname="2">
15059 <entry colname="1">
15060 <para><command><TYPE>BindFail</command></para>
15062 <entry colname="2">
15064 Failures of binding sockets.
15069 <entry colname="1">
15070 <para><command><TYPE>ConnFail</command></para>
15072 <entry colname="2">
15074 Failures of connecting sockets.
15079 <entry colname="1">
15080 <para><command><TYPE>Conn</command></para>
15082 <entry colname="2">
15084 Connections established successfully.
15089 <entry colname="1">
15090 <para><command><TYPE>AcceptFail</command></para>
15092 <entry colname="2">
15094 Failures of accepting incoming connection requests.
15095 This counter is not applicable to the
15096 <command>UDP</command> and
15097 <command>FDwatch</command> types.
15102 <entry colname="1">
15103 <para><command><TYPE>Accept</command></para>
15105 <entry colname="2">
15107 Incoming connections successfully accepted.
15108 This counter is not applicable to the
15109 <command>UDP</command> and
15110 <command>FDwatch</command> types.
15115 <entry colname="1">
15116 <para><command><TYPE>SendErr</command></para>
15118 <entry colname="2">
15120 Errors in socket send operations.
15121 This counter corresponds
15122 to <command>SErr</command> counter of
15123 <command>BIND</command> 8.
15128 <entry colname="1">
15129 <para><command><TYPE>RecvErr</command></para>
15131 <entry colname="2">
15133 Errors in socket receive operations.
15134 This includes errors of send operations on a
15135 connected UDP socket notified by an ICMP error
15145 <title>Compatibility with <emphasis>BIND</emphasis> 8 Counters</title>
15147 Most statistics counters that were available
15148 in <command>BIND</command> 8 are also supported in
15149 <command>BIND</command> 9 as shown in the above tables.
15150 Here are notes about other counters that do not appear
15156 <term><command>RFwdR,SFwdR</command></term>
15159 These counters are not supported
15160 because <command>BIND</command> 9 does not adopt
15161 the notion of <emphasis>forwarding</emphasis>
15162 as <command>BIND</command> 8 did.
15168 <term><command>RAXFR</command></term>
15171 This counter is accessible in the Incoming Queries section.
15177 <term><command>RIQ</command></term>
15180 This counter is accessible in the Incoming Requests section.
15186 <term><command>ROpts</command></term>
15189 This counter is not supported
15190 because <command>BIND</command> 9 does not care
15191 about IP options in the first place.
15201 <chapter id="Bv9ARM.ch07">
15202 <title><acronym>BIND</acronym> 9 Security Considerations</title>
15203 <sect1 id="Access_Control_Lists">
15204 <title>Access Control Lists</title>
15206 Access Control Lists (ACLs) are address match lists that
15207 you can set up and nickname for future use in <command>allow-notify</command>,
15208 <command>allow-query</command>, <command>allow-query-on</command>,
15209 <command>allow-recursion</command>, <command>allow-recursion-on</command>,
15210 <command>blackhole</command>, <command>allow-transfer</command>,
15214 Using ACLs allows you to have finer control over who can access
15215 your name server, without cluttering up your config files with huge
15216 lists of IP addresses.
15219 It is a <emphasis>good idea</emphasis> to use ACLs, and to
15220 control access to your server. Limiting access to your server by
15221 outside parties can help prevent spoofing and denial of service (DoS) attacks against
15225 Here is an example of how to properly apply ACLs:
15229 // Set up an ACL named "bogusnets" that will block
15230 // RFC1918 space and some reserved space, which is
15231 // commonly used in spoofing attacks.
15233 0.0.0.0/8; 192.0.2.0/24; 224.0.0.0/3;
15234 10.0.0.0/8; 172.16.0.0/12; 192.168.0.0/16;
15237 // Set up an ACL called our-nets. Replace this with the
15238 // real IP numbers.
15239 acl our-nets { x.x.x.x/24; x.x.x.x/21; };
15243 allow-query { our-nets; };
15244 allow-recursion { our-nets; };
15246 blackhole { bogusnets; };
15250 zone "example.com" {
15252 file "m/example.com";
15253 allow-query { any; };
15258 This allows recursive queries of the server from the outside
15259 unless recursion has been previously disabled.
15263 <title><command>Chroot</command> and <command>Setuid</command></title>
15265 On UNIX servers, it is possible to run <acronym>BIND</acronym>
15266 in a <emphasis>chrooted</emphasis> environment (using
15267 the <command>chroot()</command> function) by specifying
15268 the "<option>-t</option>" option for <command>named</command>.
15269 This can help improve system security by placing
15270 <acronym>BIND</acronym> in a "sandbox", which will limit
15271 the damage done if a server is compromised.
15274 Another useful feature in the UNIX version of <acronym>BIND</acronym> is the
15275 ability to run the daemon as an unprivileged user ( <option>-u</option> <replaceable>user</replaceable> ).
15276 We suggest running as an unprivileged user when using the <command>chroot</command> feature.
15279 Here is an example command line to load <acronym>BIND</acronym> in a <command>chroot</command> sandbox,
15280 <command>/var/named</command>, and to run <command>named</command> <command>setuid</command> to
15284 <userinput>/usr/local/sbin/named -u 202 -t /var/named</userinput>
15288 <title>The <command>chroot</command> Environment</title>
15291 In order for a <command>chroot</command> environment
15293 work properly in a particular directory
15294 (for example, <filename>/var/named</filename>),
15295 you will need to set up an environment that includes everything
15296 <acronym>BIND</acronym> needs to run.
15297 From <acronym>BIND</acronym>'s point of view, <filename>/var/named</filename> is
15298 the root of the filesystem. You will need to adjust the values of
15300 like <command>directory</command> and <command>pid-file</command> to account
15304 Unlike with earlier versions of BIND, you typically will
15305 <emphasis>not</emphasis> need to compile <command>named</command>
15306 statically nor install shared libraries under the new root.
15307 However, depending on your operating system, you may need
15308 to set up things like
15309 <filename>/dev/zero</filename>,
15310 <filename>/dev/random</filename>,
15311 <filename>/dev/log</filename>, and
15312 <filename>/etc/localtime</filename>.
15317 <title>Using the <command>setuid</command> Function</title>
15320 Prior to running the <command>named</command> daemon,
15322 the <command>touch</command> utility (to change file
15324 modification times) or the <command>chown</command>
15326 set the user id and/or group id) on files
15327 to which you want <acronym>BIND</acronym>
15331 Note that if the <command>named</command> daemon is running as an
15332 unprivileged user, it will not be able to bind to new restricted
15333 ports if the server is reloaded.
15338 <sect1 id="dynamic_update_security">
15339 <title>Dynamic Update Security</title>
15342 Access to the dynamic
15343 update facility should be strictly limited. In earlier versions of
15344 <acronym>BIND</acronym>, the only way to do this was
15346 address of the host requesting the update, by listing an IP address
15348 network prefix in the <command>allow-update</command>
15350 This method is insecure since the source address of the update UDP
15352 is easily forged. Also note that if the IP addresses allowed by the
15353 <command>allow-update</command> option include the
15355 server which performs forwarding of dynamic updates, the master can
15357 trivially attacked by sending the update to the slave, which will
15358 forward it to the master with its own source IP address causing the
15359 master to approve it without question.
15363 For these reasons, we strongly recommend that updates be
15364 cryptographically authenticated by means of transaction signatures
15365 (TSIG). That is, the <command>allow-update</command>
15367 list only TSIG key names, not IP addresses or network
15368 prefixes. Alternatively, the new <command>update-policy</command>
15369 option can be used.
15373 Some sites choose to keep all dynamically-updated DNS data
15374 in a subdomain and delegate that subdomain to a separate zone. This
15375 way, the top-level zone containing critical data such as the IP
15377 of public web and mail servers need not allow dynamic update at
15384 <chapter id="Bv9ARM.ch08">
15385 <title>Troubleshooting</title>
15387 <title>Common Problems</title>
15389 <title>It's not working; how can I figure out what's wrong?</title>
15392 The best solution to solving installation and
15393 configuration issues is to take preventative measures by setting
15394 up logging files beforehand. The log files provide a
15395 source of hints and information that can be used to figure out
15396 what went wrong and how to fix the problem.
15402 <title>Incrementing and Changing the Serial Number</title>
15405 Zone serial numbers are just numbers — they aren't
15406 date related. A lot of people set them to a number that
15407 represents a date, usually of the form YYYYMMDDRR.
15408 Occasionally they will make a mistake and set them to a
15409 "date in the future" then try to correct them by setting
15410 them to the "current date". This causes problems because
15411 serial numbers are used to indicate that a zone has been
15412 updated. If the serial number on the slave server is
15413 lower than the serial number on the master, the slave
15414 server will attempt to update its copy of the zone.
15418 Setting the serial number to a lower number on the master
15419 server than the slave server means that the slave will not perform
15420 updates to its copy of the zone.
15424 The solution to this is to add 2147483647 (2^31-1) to the
15425 number, reload the zone and make sure all slaves have updated to
15426 the new zone serial number, then reset the number to what you want
15427 it to be, and reload the zone again.
15432 <title>Where Can I Get Help?</title>
15435 The Internet Systems Consortium
15436 (<acronym>ISC</acronym>) offers a wide range
15437 of support and service agreements for <acronym>BIND</acronym> and <acronym>DHCP</acronym> servers. Four
15438 levels of premium support are available and each level includes
15439 support for all <acronym>ISC</acronym> programs,
15440 significant discounts on products
15441 and training, and a recognized priority on bug fixes and
15442 non-funded feature requests. In addition, <acronym>ISC</acronym> offers a standard
15443 support agreement package which includes services ranging from bug
15444 fix announcements to remote support. It also includes training in
15445 <acronym>BIND</acronym> and <acronym>DHCP</acronym>.
15449 To discuss arrangements for support, contact
15450 <ulink url="mailto:info@isc.org">info@isc.org</ulink> or visit the
15451 <acronym>ISC</acronym> web page at
15452 <ulink url="http://www.isc.org/services/support/"
15453 >http://www.isc.org/services/support/</ulink>
15458 <appendix id="Bv9ARM.ch09">
15459 <title>Appendices</title>
15461 <title>Acknowledgments</title>
15462 <sect2 id="historical_dns_information">
15463 <title>A Brief History of the <acronym>DNS</acronym> and <acronym>BIND</acronym></title>
15466 Although the "official" beginning of the Domain Name
15467 System occurred in 1984 with the publication of RFC 920, the
15468 core of the new system was described in 1983 in RFCs 882 and
15469 883. From 1984 to 1987, the ARPAnet (the precursor to today's
15470 Internet) became a testbed of experimentation for developing the
15471 new naming/addressing scheme in a rapidly expanding,
15472 operational network environment. New RFCs were written and
15473 published in 1987 that modified the original documents to
15474 incorporate improvements based on the working model. RFC 1034,
15475 "Domain Names-Concepts and Facilities", and RFC 1035, "Domain
15476 Names-Implementation and Specification" were published and
15477 became the standards upon which all <acronym>DNS</acronym> implementations are
15482 The first working domain name server, called "Jeeves", was
15483 written in 1983-84 by Paul Mockapetris for operation on DEC
15485 machines located at the University of Southern California's
15487 Sciences Institute (USC-ISI) and SRI International's Network
15489 Center (SRI-NIC). A <acronym>DNS</acronym> server for
15490 Unix machines, the Berkeley Internet
15491 Name Domain (<acronym>BIND</acronym>) package, was
15492 written soon after by a group of
15493 graduate students at the University of California at Berkeley
15495 a grant from the US Defense Advanced Research Projects
15500 Versions of <acronym>BIND</acronym> through
15501 4.8.3 were maintained by the Computer
15502 Systems Research Group (CSRG) at UC Berkeley. Douglas Terry, Mark
15503 Painter, David Riggle and Songnian Zhou made up the initial <acronym>BIND</acronym>
15504 project team. After that, additional work on the software package
15505 was done by Ralph Campbell. Kevin Dunlap, a Digital Equipment
15507 employee on loan to the CSRG, worked on <acronym>BIND</acronym> for 2 years, from 1985
15508 to 1987. Many other people also contributed to <acronym>BIND</acronym> development
15509 during that time: Doug Kingston, Craig Partridge, Smoot
15511 Mike Muuss, Jim Bloom and Mike Schwartz. <acronym>BIND</acronym> maintenance was subsequently
15512 handled by Mike Karels and Øivind Kure.
15515 <acronym>BIND</acronym> versions 4.9 and 4.9.1 were
15516 released by Digital Equipment
15517 Corporation (now Compaq Computer Corporation). Paul Vixie, then
15518 a DEC employee, became <acronym>BIND</acronym>'s
15519 primary caretaker. He was assisted
15520 by Phil Almquist, Robert Elz, Alan Barrett, Paul Albitz, Bryan
15522 Partan, Andy Cherenson, Tom Limoncelli, Berthold Paffrath, Fuat
15523 Baran, Anant Kumar, Art Harkin, Win Treese, Don Lewis, Christophe
15524 Wolfhugel, and others.
15527 In 1994, <acronym>BIND</acronym> version 4.9.2 was sponsored by
15528 Vixie Enterprises. Paul
15529 Vixie became <acronym>BIND</acronym>'s principal
15530 architect/programmer.
15533 <acronym>BIND</acronym> versions from 4.9.3 onward
15534 have been developed and maintained
15535 by the Internet Systems Consortium and its predecessor,
15536 the Internet Software Consortium, with support being provided
15540 As co-architects/programmers, Bob Halley and
15541 Paul Vixie released the first production-ready version of
15542 <acronym>BIND</acronym> version 8 in May 1997.
15545 BIND version 9 was released in September 2000 and is a
15546 major rewrite of nearly all aspects of the underlying
15550 BIND versions 4 and 8 are officially deprecated.
15551 No additional development is done
15552 on BIND version 4 or BIND version 8.
15555 <acronym>BIND</acronym> development work is made
15556 possible today by the sponsorship
15557 of several corporations, and by the tireless work efforts of
15558 numerous individuals.
15563 <title>General <acronym>DNS</acronym> Reference Information</title>
15564 <sect2 id="ipv6addresses">
15565 <title>IPv6 addresses (AAAA)</title>
15567 IPv6 addresses are 128-bit identifiers for interfaces and
15568 sets of interfaces which were introduced in the <acronym>DNS</acronym> to facilitate
15569 scalable Internet routing. There are three types of addresses: <emphasis>Unicast</emphasis>,
15570 an identifier for a single interface;
15571 <emphasis>Anycast</emphasis>,
15572 an identifier for a set of interfaces; and <emphasis>Multicast</emphasis>,
15573 an identifier for a set of interfaces. Here we describe the global
15574 Unicast address scheme. For more information, see RFC 3587,
15575 "Global Unicast Address Format."
15578 IPv6 unicast addresses consist of a
15579 <emphasis>global routing prefix</emphasis>, a
15580 <emphasis>subnet identifier</emphasis>, and an
15581 <emphasis>interface identifier</emphasis>.
15584 The global routing prefix is provided by the
15585 upstream provider or ISP, and (roughly) corresponds to the
15586 IPv4 <emphasis>network</emphasis> section
15587 of the address range.
15589 The subnet identifier is for local subnetting, much the
15590 same as subnetting an
15591 IPv4 /16 network into /24 subnets.
15593 The interface identifier is the address of an individual
15594 interface on a given network; in IPv6, addresses belong to
15595 interfaces rather than to machines.
15598 The subnetting capability of IPv6 is much more flexible than
15599 that of IPv4: subnetting can be carried out on bit boundaries,
15600 in much the same way as Classless InterDomain Routing
15601 (CIDR), and the DNS PTR representation ("nibble" format)
15602 makes setting up reverse zones easier.
15605 The Interface Identifier must be unique on the local link,
15606 and is usually generated automatically by the IPv6
15607 implementation, although it is usually possible to
15608 override the default setting if necessary. A typical IPv6
15609 address might look like:
15610 <command>2001:db8:201:9:a00:20ff:fe81:2b32</command>
15613 IPv6 address specifications often contain long strings
15614 of zeros, so the architects have included a shorthand for
15616 them. The double colon (`::') indicates the longest possible
15618 of zeros that can fit, and can be used only once in an address.
15622 <sect1 id="bibliography">
15623 <title>Bibliography (and Suggested Reading)</title>
15625 <title>Request for Comments (RFCs)</title>
15627 Specification documents for the Internet protocol suite, including
15628 the <acronym>DNS</acronym>, are published as part of
15629 the Request for Comments (RFCs)
15630 series of technical notes. The standards themselves are defined
15631 by the Internet Engineering Task Force (IETF) and the Internet
15632 Engineering Steering Group (IESG). RFCs can be obtained online via FTP at:
15635 <ulink url="ftp://www.isi.edu/in-notes/">
15636 ftp://www.isi.edu/in-notes/RFC<replaceable>xxxx</replaceable>.txt
15640 (where <replaceable>xxxx</replaceable> is
15641 the number of the RFC). RFCs are also available via the Web at:
15644 <ulink url="http://www.ietf.org/rfc/"
15645 >http://www.ietf.org/rfc/</ulink>.
15649 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
15650 <title>Standards</title>
15652 <abbrev>RFC974</abbrev>
15654 <surname>Partridge</surname>
15655 <firstname>C.</firstname>
15657 <title>Mail Routing and the Domain System</title>
15658 <pubdate>January 1986</pubdate>
15661 <abbrev>RFC1034</abbrev>
15663 <surname>Mockapetris</surname>
15664 <firstname>P.V.</firstname>
15666 <title>Domain Names — Concepts and Facilities</title>
15667 <pubdate>November 1987</pubdate>
15670 <abbrev>RFC1035</abbrev>
15672 <surname>Mockapetris</surname>
15673 <firstname>P. V.</firstname>
15674 </author> <title>Domain Names — Implementation and
15675 Specification</title>
15676 <pubdate>November 1987</pubdate>
15679 <bibliodiv id="proposed_standards" xreflabel="Proposed Standards">
15681 <title>Proposed Standards</title>
15682 <!-- one of (BIBLIOENTRY BIBLIOMIXED) -->
15684 <abbrev>RFC2181</abbrev>
15686 <surname>Elz</surname>
15687 <firstname>R., R. Bush</firstname>
15689 <title>Clarifications to the <acronym>DNS</acronym>
15690 Specification</title>
15691 <pubdate>July 1997</pubdate>
15694 <abbrev>RFC2308</abbrev>
15696 <surname>Andrews</surname>
15697 <firstname>M.</firstname>
15699 <title>Negative Caching of <acronym>DNS</acronym>
15701 <pubdate>March 1998</pubdate>
15704 <abbrev>RFC1995</abbrev>
15706 <surname>Ohta</surname>
15707 <firstname>M.</firstname>
15709 <title>Incremental Zone Transfer in <acronym>DNS</acronym></title>
15710 <pubdate>August 1996</pubdate>
15713 <abbrev>RFC1996</abbrev>
15715 <surname>Vixie</surname>
15716 <firstname>P.</firstname>
15718 <title>A Mechanism for Prompt Notification of Zone Changes</title>
15719 <pubdate>August 1996</pubdate>
15722 <abbrev>RFC2136</abbrev>
15725 <surname>Vixie</surname>
15726 <firstname>P.</firstname>
15729 <firstname>S.</firstname>
15730 <surname>Thomson</surname>
15733 <firstname>Y.</firstname>
15734 <surname>Rekhter</surname>
15737 <firstname>J.</firstname>
15738 <surname>Bound</surname>
15741 <title>Dynamic Updates in the Domain Name System</title>
15742 <pubdate>April 1997</pubdate>
15745 <abbrev>RFC2671</abbrev>
15748 <firstname>P.</firstname>
15749 <surname>Vixie</surname>
15752 <title>Extension Mechanisms for DNS (EDNS0)</title>
15753 <pubdate>August 1997</pubdate>
15756 <abbrev>RFC2672</abbrev>
15759 <firstname>M.</firstname>
15760 <surname>Crawford</surname>
15763 <title>Non-Terminal DNS Name Redirection</title>
15764 <pubdate>August 1999</pubdate>
15767 <abbrev>RFC2845</abbrev>
15770 <surname>Vixie</surname>
15771 <firstname>P.</firstname>
15774 <firstname>O.</firstname>
15775 <surname>Gudmundsson</surname>
15778 <firstname>D.</firstname>
15779 <surname>Eastlake</surname>
15780 <lineage>3rd</lineage>
15783 <firstname>B.</firstname>
15784 <surname>Wellington</surname>
15787 <title>Secret Key Transaction Authentication for <acronym>DNS</acronym> (TSIG)</title>
15788 <pubdate>May 2000</pubdate>
15791 <abbrev>RFC2930</abbrev>
15794 <firstname>D.</firstname>
15795 <surname>Eastlake</surname>
15796 <lineage>3rd</lineage>
15799 <title>Secret Key Establishment for DNS (TKEY RR)</title>
15800 <pubdate>September 2000</pubdate>
15803 <abbrev>RFC2931</abbrev>
15806 <firstname>D.</firstname>
15807 <surname>Eastlake</surname>
15808 <lineage>3rd</lineage>
15811 <title>DNS Request and Transaction Signatures (SIG(0)s)</title>
15812 <pubdate>September 2000</pubdate>
15815 <abbrev>RFC3007</abbrev>
15818 <firstname>B.</firstname>
15819 <surname>Wellington</surname>
15822 <title>Secure Domain Name System (DNS) Dynamic Update</title>
15823 <pubdate>November 2000</pubdate>
15826 <abbrev>RFC3645</abbrev>
15829 <firstname>S.</firstname>
15830 <surname>Kwan</surname>
15833 <firstname>P.</firstname>
15834 <surname>Garg</surname>
15837 <firstname>J.</firstname>
15838 <surname>Gilroy</surname>
15841 <firstname>L.</firstname>
15842 <surname>Esibov</surname>
15845 <firstname>J.</firstname>
15846 <surname>Westhead</surname>
15849 <firstname>R.</firstname>
15850 <surname>Hall</surname>
15853 <title>Generic Security Service Algorithm for Secret
15854 Key Transaction Authentication for DNS
15856 <pubdate>October 2003</pubdate>
15860 <title><acronym>DNS</acronym> Security Proposed Standards</title>
15862 <abbrev>RFC3225</abbrev>
15865 <firstname>D.</firstname>
15866 <surname>Conrad</surname>
15869 <title>Indicating Resolver Support of DNSSEC</title>
15870 <pubdate>December 2001</pubdate>
15873 <abbrev>RFC3833</abbrev>
15876 <firstname>D.</firstname>
15877 <surname>Atkins</surname>
15880 <firstname>R.</firstname>
15881 <surname>Austein</surname>
15884 <title>Threat Analysis of the Domain Name System (DNS)</title>
15885 <pubdate>August 2004</pubdate>
15888 <abbrev>RFC4033</abbrev>
15891 <firstname>R.</firstname>
15892 <surname>Arends</surname>
15895 <firstname>R.</firstname>
15896 <surname>Austein</surname>
15899 <firstname>M.</firstname>
15900 <surname>Larson</surname>
15903 <firstname>D.</firstname>
15904 <surname>Massey</surname>
15907 <firstname>S.</firstname>
15908 <surname>Rose</surname>
15911 <title>DNS Security Introduction and Requirements</title>
15912 <pubdate>March 2005</pubdate>
15915 <abbrev>RFC4034</abbrev>
15918 <firstname>R.</firstname>
15919 <surname>Arends</surname>
15922 <firstname>R.</firstname>
15923 <surname>Austein</surname>
15926 <firstname>M.</firstname>
15927 <surname>Larson</surname>
15930 <firstname>D.</firstname>
15931 <surname>Massey</surname>
15934 <firstname>S.</firstname>
15935 <surname>Rose</surname>
15938 <title>Resource Records for the DNS Security Extensions</title>
15939 <pubdate>March 2005</pubdate>
15942 <abbrev>RFC4035</abbrev>
15945 <firstname>R.</firstname>
15946 <surname>Arends</surname>
15949 <firstname>R.</firstname>
15950 <surname>Austein</surname>
15953 <firstname>M.</firstname>
15954 <surname>Larson</surname>
15957 <firstname>D.</firstname>
15958 <surname>Massey</surname>
15961 <firstname>S.</firstname>
15962 <surname>Rose</surname>
15965 <title>Protocol Modifications for the DNS
15966 Security Extensions</title>
15967 <pubdate>March 2005</pubdate>
15971 <title>Other Important RFCs About <acronym>DNS</acronym>
15972 Implementation</title>
15974 <abbrev>RFC1535</abbrev>
15976 <surname>Gavron</surname>
15977 <firstname>E.</firstname>
15979 <title>A Security Problem and Proposed Correction With Widely
15980 Deployed <acronym>DNS</acronym> Software.</title>
15981 <pubdate>October 1993</pubdate>
15984 <abbrev>RFC1536</abbrev>
15987 <surname>Kumar</surname>
15988 <firstname>A.</firstname>
15991 <firstname>J.</firstname>
15992 <surname>Postel</surname>
15995 <firstname>C.</firstname>
15996 <surname>Neuman</surname>
15999 <firstname>P.</firstname>
16000 <surname>Danzig</surname>
16003 <firstname>S.</firstname>
16004 <surname>Miller</surname>
16007 <title>Common <acronym>DNS</acronym> Implementation
16008 Errors and Suggested Fixes</title>
16009 <pubdate>October 1993</pubdate>
16012 <abbrev>RFC1982</abbrev>
16015 <surname>Elz</surname>
16016 <firstname>R.</firstname>
16019 <firstname>R.</firstname>
16020 <surname>Bush</surname>
16023 <title>Serial Number Arithmetic</title>
16024 <pubdate>August 1996</pubdate>
16027 <abbrev>RFC4074</abbrev>
16030 <surname>Morishita</surname>
16031 <firstname>Y.</firstname>
16034 <firstname>T.</firstname>
16035 <surname>Jinmei</surname>
16038 <title>Common Misbehaviour Against <acronym>DNS</acronym>
16039 Queries for IPv6 Addresses</title>
16040 <pubdate>May 2005</pubdate>
16044 <title>Resource Record Types</title>
16046 <abbrev>RFC1183</abbrev>
16049 <surname>Everhart</surname>
16050 <firstname>C.F.</firstname>
16053 <firstname>L. A.</firstname>
16054 <surname>Mamakos</surname>
16057 <firstname>R.</firstname>
16058 <surname>Ullmann</surname>
16061 <firstname>P.</firstname>
16062 <surname>Mockapetris</surname>
16065 <title>New <acronym>DNS</acronym> RR Definitions</title>
16066 <pubdate>October 1990</pubdate>
16069 <abbrev>RFC1706</abbrev>
16072 <surname>Manning</surname>
16073 <firstname>B.</firstname>
16076 <firstname>R.</firstname>
16077 <surname>Colella</surname>
16080 <title><acronym>DNS</acronym> NSAP Resource Records</title>
16081 <pubdate>October 1994</pubdate>
16084 <abbrev>RFC2168</abbrev>
16087 <surname>Daniel</surname>
16088 <firstname>R.</firstname>
16091 <firstname>M.</firstname>
16092 <surname>Mealling</surname>
16095 <title>Resolution of Uniform Resource Identifiers using
16096 the Domain Name System</title>
16097 <pubdate>June 1997</pubdate>
16100 <abbrev>RFC1876</abbrev>
16103 <surname>Davis</surname>
16104 <firstname>C.</firstname>
16107 <firstname>P.</firstname>
16108 <surname>Vixie</surname>
16111 <firstname>T.</firstname>
16112 <firstname>Goodwin</firstname>
16115 <firstname>I.</firstname>
16116 <surname>Dickinson</surname>
16119 <title>A Means for Expressing Location Information in the
16121 Name System</title>
16122 <pubdate>January 1996</pubdate>
16125 <abbrev>RFC2052</abbrev>
16128 <surname>Gulbrandsen</surname>
16129 <firstname>A.</firstname>
16132 <firstname>P.</firstname>
16133 <surname>Vixie</surname>
16136 <title>A <acronym>DNS</acronym> RR for Specifying the
16139 <pubdate>October 1996</pubdate>
16142 <abbrev>RFC2163</abbrev>
16144 <surname>Allocchio</surname>
16145 <firstname>A.</firstname>
16147 <title>Using the Internet <acronym>DNS</acronym> to
16149 Conformant Global Address Mapping</title>
16150 <pubdate>January 1998</pubdate>
16153 <abbrev>RFC2230</abbrev>
16155 <surname>Atkinson</surname>
16156 <firstname>R.</firstname>
16158 <title>Key Exchange Delegation Record for the <acronym>DNS</acronym></title>
16159 <pubdate>October 1997</pubdate>
16162 <abbrev>RFC2536</abbrev>
16164 <surname>Eastlake</surname>
16165 <firstname>D.</firstname>
16166 <lineage>3rd</lineage>
16168 <title>DSA KEYs and SIGs in the Domain Name System (DNS)</title>
16169 <pubdate>March 1999</pubdate>
16172 <abbrev>RFC2537</abbrev>
16174 <surname>Eastlake</surname>
16175 <firstname>D.</firstname>
16176 <lineage>3rd</lineage>
16178 <title>RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)</title>
16179 <pubdate>March 1999</pubdate>
16182 <abbrev>RFC2538</abbrev>
16185 <surname>Eastlake</surname>
16186 <firstname>D.</firstname>
16187 <lineage>3rd</lineage>
16190 <surname>Gudmundsson</surname>
16191 <firstname>O.</firstname>
16194 <title>Storing Certificates in the Domain Name System (DNS)</title>
16195 <pubdate>March 1999</pubdate>
16198 <abbrev>RFC2539</abbrev>
16201 <surname>Eastlake</surname>
16202 <firstname>D.</firstname>
16203 <lineage>3rd</lineage>
16206 <title>Storage of Diffie-Hellman Keys in the Domain Name System (DNS)</title>
16207 <pubdate>March 1999</pubdate>
16210 <abbrev>RFC2540</abbrev>
16213 <surname>Eastlake</surname>
16214 <firstname>D.</firstname>
16215 <lineage>3rd</lineage>
16218 <title>Detached Domain Name System (DNS) Information</title>
16219 <pubdate>March 1999</pubdate>
16222 <abbrev>RFC2782</abbrev>
16224 <surname>Gulbrandsen</surname>
16225 <firstname>A.</firstname>
16228 <surname>Vixie</surname>
16229 <firstname>P.</firstname>
16232 <surname>Esibov</surname>
16233 <firstname>L.</firstname>
16235 <title>A DNS RR for specifying the location of services (DNS SRV)</title>
16236 <pubdate>February 2000</pubdate>
16239 <abbrev>RFC2915</abbrev>
16241 <surname>Mealling</surname>
16242 <firstname>M.</firstname>
16245 <surname>Daniel</surname>
16246 <firstname>R.</firstname>
16248 <title>The Naming Authority Pointer (NAPTR) DNS Resource Record</title>
16249 <pubdate>September 2000</pubdate>
16252 <abbrev>RFC3110</abbrev>
16254 <surname>Eastlake</surname>
16255 <firstname>D.</firstname>
16256 <lineage>3rd</lineage>
16258 <title>RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)</title>
16259 <pubdate>May 2001</pubdate>
16262 <abbrev>RFC3123</abbrev>
16264 <surname>Koch</surname>
16265 <firstname>P.</firstname>
16267 <title>A DNS RR Type for Lists of Address Prefixes (APL RR)</title>
16268 <pubdate>June 2001</pubdate>
16271 <abbrev>RFC3596</abbrev>
16274 <surname>Thomson</surname>
16275 <firstname>S.</firstname>
16278 <firstname>C.</firstname>
16279 <surname>Huitema</surname>
16282 <firstname>V.</firstname>
16283 <surname>Ksinant</surname>
16286 <firstname>M.</firstname>
16287 <surname>Souissi</surname>
16290 <title><acronym>DNS</acronym> Extensions to support IP
16292 <pubdate>October 2003</pubdate>
16295 <abbrev>RFC3597</abbrev>
16297 <surname>Gustafsson</surname>
16298 <firstname>A.</firstname>
16300 <title>Handling of Unknown DNS Resource Record (RR) Types</title>
16301 <pubdate>September 2003</pubdate>
16305 <title><acronym>DNS</acronym> and the Internet</title>
16307 <abbrev>RFC1101</abbrev>
16309 <surname>Mockapetris</surname>
16310 <firstname>P. V.</firstname>
16312 <title><acronym>DNS</acronym> Encoding of Network Names
16313 and Other Types</title>
16314 <pubdate>April 1989</pubdate>
16317 <abbrev>RFC1123</abbrev>
16319 <surname>Braden</surname>
16320 <surname>R.</surname>
16322 <title>Requirements for Internet Hosts - Application and
16324 <pubdate>October 1989</pubdate>
16327 <abbrev>RFC1591</abbrev>
16329 <surname>Postel</surname>
16330 <firstname>J.</firstname>
16332 <title>Domain Name System Structure and Delegation</title>
16333 <pubdate>March 1994</pubdate>
16336 <abbrev>RFC2317</abbrev>
16339 <surname>Eidnes</surname>
16340 <firstname>H.</firstname>
16343 <firstname>G.</firstname>
16344 <surname>de Groot</surname>
16347 <firstname>P.</firstname>
16348 <surname>Vixie</surname>
16351 <title>Classless IN-ADDR.ARPA Delegation</title>
16352 <pubdate>March 1998</pubdate>
16355 <abbrev>RFC2826</abbrev>
16358 <surname>Internet Architecture Board</surname>
16361 <title>IAB Technical Comment on the Unique DNS Root</title>
16362 <pubdate>May 2000</pubdate>
16365 <abbrev>RFC2929</abbrev>
16368 <surname>Eastlake</surname>
16369 <firstname>D.</firstname>
16370 <lineage>3rd</lineage>
16373 <surname>Brunner-Williams</surname>
16374 <firstname>E.</firstname>
16377 <surname>Manning</surname>
16378 <firstname>B.</firstname>
16381 <title>Domain Name System (DNS) IANA Considerations</title>
16382 <pubdate>September 2000</pubdate>
16386 <title><acronym>DNS</acronym> Operations</title>
16388 <abbrev>RFC1033</abbrev>
16390 <surname>Lottor</surname>
16391 <firstname>M.</firstname>
16393 <title>Domain administrators operations guide.</title>
16394 <pubdate>November 1987</pubdate>
16397 <abbrev>RFC1537</abbrev>
16399 <surname>Beertema</surname>
16400 <firstname>P.</firstname>
16402 <title>Common <acronym>DNS</acronym> Data File
16403 Configuration Errors</title>
16404 <pubdate>October 1993</pubdate>
16407 <abbrev>RFC1912</abbrev>
16409 <surname>Barr</surname>
16410 <firstname>D.</firstname>
16412 <title>Common <acronym>DNS</acronym> Operational and
16413 Configuration Errors</title>
16414 <pubdate>February 1996</pubdate>
16417 <abbrev>RFC2010</abbrev>
16420 <surname>Manning</surname>
16421 <firstname>B.</firstname>
16424 <firstname>P.</firstname>
16425 <surname>Vixie</surname>
16428 <title>Operational Criteria for Root Name Servers.</title>
16429 <pubdate>October 1996</pubdate>
16432 <abbrev>RFC2219</abbrev>
16435 <surname>Hamilton</surname>
16436 <firstname>M.</firstname>
16439 <firstname>R.</firstname>
16440 <surname>Wright</surname>
16443 <title>Use of <acronym>DNS</acronym> Aliases for
16444 Network Services.</title>
16445 <pubdate>October 1997</pubdate>
16449 <title>Internationalized Domain Names</title>
16451 <abbrev>RFC2825</abbrev>
16454 <surname>IAB</surname>
16457 <surname>Daigle</surname>
16458 <firstname>R.</firstname>
16461 <title>A Tangled Web: Issues of I18N, Domain Names,
16462 and the Other Internet protocols</title>
16463 <pubdate>May 2000</pubdate>
16466 <abbrev>RFC3490</abbrev>
16469 <surname>Faltstrom</surname>
16470 <firstname>P.</firstname>
16473 <surname>Hoffman</surname>
16474 <firstname>P.</firstname>
16477 <surname>Costello</surname>
16478 <firstname>A.</firstname>
16481 <title>Internationalizing Domain Names in Applications (IDNA)</title>
16482 <pubdate>March 2003</pubdate>
16485 <abbrev>RFC3491</abbrev>
16488 <surname>Hoffman</surname>
16489 <firstname>P.</firstname>
16492 <surname>Blanchet</surname>
16493 <firstname>M.</firstname>
16496 <title>Nameprep: A Stringprep Profile for Internationalized Domain Names</title>
16497 <pubdate>March 2003</pubdate>
16500 <abbrev>RFC3492</abbrev>
16503 <surname>Costello</surname>
16504 <firstname>A.</firstname>
16507 <title>Punycode: A Bootstring encoding of Unicode
16508 for Internationalized Domain Names in
16509 Applications (IDNA)</title>
16510 <pubdate>March 2003</pubdate>
16514 <title>Other <acronym>DNS</acronym>-related RFCs</title>
16517 Note: the following list of RFCs, although
16518 <acronym>DNS</acronym>-related, are not
16519 concerned with implementing software.
16523 <abbrev>RFC1464</abbrev>
16525 <surname>Rosenbaum</surname>
16526 <firstname>R.</firstname>
16528 <title>Using the Domain Name System To Store Arbitrary String
16530 <pubdate>May 1993</pubdate>
16533 <abbrev>RFC1713</abbrev>
16535 <surname>Romao</surname>
16536 <firstname>A.</firstname>
16538 <title>Tools for <acronym>DNS</acronym> Debugging</title>
16539 <pubdate>November 1994</pubdate>
16542 <abbrev>RFC1794</abbrev>
16544 <surname>Brisco</surname>
16545 <firstname>T.</firstname>
16547 <title><acronym>DNS</acronym> Support for Load
16549 <pubdate>April 1995</pubdate>
16552 <abbrev>RFC2240</abbrev>
16554 <surname>Vaughan</surname>
16555 <firstname>O.</firstname>
16557 <title>A Legal Basis for Domain Name Allocation</title>
16558 <pubdate>November 1997</pubdate>
16561 <abbrev>RFC2345</abbrev>
16564 <surname>Klensin</surname>
16565 <firstname>J.</firstname>
16568 <firstname>T.</firstname>
16569 <surname>Wolf</surname>
16572 <firstname>G.</firstname>
16573 <surname>Oglesby</surname>
16576 <title>Domain Names and Company Name Retrieval</title>
16577 <pubdate>May 1998</pubdate>
16580 <abbrev>RFC2352</abbrev>
16582 <surname>Vaughan</surname>
16583 <firstname>O.</firstname>
16585 <title>A Convention For Using Legal Names as Domain Names</title>
16586 <pubdate>May 1998</pubdate>
16589 <abbrev>RFC3071</abbrev>
16592 <surname>Klensin</surname>
16593 <firstname>J.</firstname>
16596 <title>Reflections on the DNS, RFC 1591, and Categories of Domains</title>
16597 <pubdate>February 2001</pubdate>
16600 <abbrev>RFC3258</abbrev>
16603 <surname>Hardie</surname>
16604 <firstname>T.</firstname>
16607 <title>Distributing Authoritative Name Servers via
16608 Shared Unicast Addresses</title>
16609 <pubdate>April 2002</pubdate>
16612 <abbrev>RFC3901</abbrev>
16615 <surname>Durand</surname>
16616 <firstname>A.</firstname>
16619 <firstname>J.</firstname>
16620 <surname>Ihren</surname>
16623 <title>DNS IPv6 Transport Operational Guidelines</title>
16624 <pubdate>September 2004</pubdate>
16628 <title>Obsolete and Unimplemented Experimental RFC</title>
16630 <abbrev>RFC1712</abbrev>
16633 <surname>Farrell</surname>
16634 <firstname>C.</firstname>
16637 <firstname>M.</firstname>
16638 <surname>Schulze</surname>
16641 <firstname>S.</firstname>
16642 <surname>Pleitner</surname>
16645 <firstname>D.</firstname>
16646 <surname>Baldoni</surname>
16649 <title><acronym>DNS</acronym> Encoding of Geographical
16651 <pubdate>November 1994</pubdate>
16654 <abbrev>RFC2673</abbrev>
16657 <surname>Crawford</surname>
16658 <firstname>M.</firstname>
16661 <title>Binary Labels in the Domain Name System</title>
16662 <pubdate>August 1999</pubdate>
16665 <abbrev>RFC2874</abbrev>
16668 <surname>Crawford</surname>
16669 <firstname>M.</firstname>
16672 <surname>Huitema</surname>
16673 <firstname>C.</firstname>
16676 <title>DNS Extensions to Support IPv6 Address Aggregation
16677 and Renumbering</title>
16678 <pubdate>July 2000</pubdate>
16682 <title>Obsoleted DNS Security RFCs</title>
16685 Most of these have been consolidated into RFC4033,
16686 RFC4034 and RFC4035 which collectively describe DNSSECbis.
16690 <abbrev>RFC2065</abbrev>
16693 <surname>Eastlake</surname>
16694 <lineage>3rd</lineage>
16695 <firstname>D.</firstname>
16698 <firstname>C.</firstname>
16699 <surname>Kaufman</surname>
16702 <title>Domain Name System Security Extensions</title>
16703 <pubdate>January 1997</pubdate>
16706 <abbrev>RFC2137</abbrev>
16708 <surname>Eastlake</surname>
16709 <lineage>3rd</lineage>
16710 <firstname>D.</firstname>
16712 <title>Secure Domain Name System Dynamic Update</title>
16713 <pubdate>April 1997</pubdate>
16716 <abbrev>RFC2535</abbrev>
16719 <surname>Eastlake</surname>
16720 <lineage>3rd</lineage>
16721 <firstname>D.</firstname>
16724 <title>Domain Name System Security Extensions</title>
16725 <pubdate>March 1999</pubdate>
16728 <abbrev>RFC3008</abbrev>
16731 <surname>Wellington</surname>
16732 <firstname>B.</firstname>
16735 <title>Domain Name System Security (DNSSEC)
16736 Signing Authority</title>
16737 <pubdate>November 2000</pubdate>
16740 <abbrev>RFC3090</abbrev>
16743 <surname>Lewis</surname>
16744 <firstname>E.</firstname>
16747 <title>DNS Security Extension Clarification on Zone Status</title>
16748 <pubdate>March 2001</pubdate>
16751 <abbrev>RFC3445</abbrev>
16754 <surname>Massey</surname>
16755 <firstname>D.</firstname>
16758 <surname>Rose</surname>
16759 <firstname>S.</firstname>
16762 <title>Limiting the Scope of the KEY Resource Record (RR)</title>
16763 <pubdate>December 2002</pubdate>
16766 <abbrev>RFC3655</abbrev>
16769 <surname>Wellington</surname>
16770 <firstname>B.</firstname>
16773 <surname>Gudmundsson</surname>
16774 <firstname>O.</firstname>
16777 <title>Redefinition of DNS Authenticated Data (AD) bit</title>
16778 <pubdate>November 2003</pubdate>
16781 <abbrev>RFC3658</abbrev>
16784 <surname>Gudmundsson</surname>
16785 <firstname>O.</firstname>
16788 <title>Delegation Signer (DS) Resource Record (RR)</title>
16789 <pubdate>December 2003</pubdate>
16792 <abbrev>RFC3755</abbrev>
16795 <surname>Weiler</surname>
16796 <firstname>S.</firstname>
16799 <title>Legacy Resolver Compatibility for Delegation Signer (DS)</title>
16800 <pubdate>May 2004</pubdate>
16803 <abbrev>RFC3757</abbrev>
16806 <surname>Kolkman</surname>
16807 <firstname>O.</firstname>
16810 <surname>Schlyter</surname>
16811 <firstname>J.</firstname>
16814 <surname>Lewis</surname>
16815 <firstname>E.</firstname>
16818 <title>Domain Name System KEY (DNSKEY) Resource Record
16819 (RR) Secure Entry Point (SEP) Flag</title>
16820 <pubdate>April 2004</pubdate>
16823 <abbrev>RFC3845</abbrev>
16826 <surname>Schlyter</surname>
16827 <firstname>J.</firstname>
16830 <title>DNS Security (DNSSEC) NextSECure (NSEC) RDATA Format</title>
16831 <pubdate>August 2004</pubdate>
16836 <sect2 id="internet_drafts">
16837 <title>Internet Drafts</title>
16839 Internet Drafts (IDs) are rough-draft working documents of
16840 the Internet Engineering Task Force. They are, in essence, RFCs
16841 in the preliminary stages of development. Implementors are
16843 to regard IDs as archival, and they should not be quoted or cited
16844 in any formal documents unless accompanied by the disclaimer that
16845 they are "works in progress." IDs have a lifespan of six months
16846 after which they are deleted unless updated by their authors.
16850 <title>Other Documents About <acronym>BIND</acronym></title>
16856 <surname>Albitz</surname>
16857 <firstname>Paul</firstname>
16860 <firstname>Cricket</firstname>
16861 <surname>Liu</surname>
16864 <title><acronym>DNS</acronym> and <acronym>BIND</acronym></title>
16867 <holder>Sebastopol, CA: O'Reilly and Associates</holder>
16874 <xi:include href="libdns.xml"/>
16879 <reference id="Bv9ARM.ch10">
16880 <title>Manual pages</title>
16881 <xi:include href="../../bin/dig/dig.docbook"/>
16882 <xi:include href="../../bin/dig/host.docbook"/>
16883 <xi:include href="../../bin/python/dnssec-checkds.docbook"/>
16884 <xi:include href="../../bin/python/dnssec-coverage.docbook"/>
16885 <xi:include href="../../bin/dnssec/dnssec-dsfromkey.docbook"/>
16886 <xi:include href="../../bin/dnssec/dnssec-keyfromlabel.docbook"/>
16887 <xi:include href="../../bin/dnssec/dnssec-keygen.docbook"/>
16888 <xi:include href="../../bin/dnssec/dnssec-revoke.docbook"/>
16889 <xi:include href="../../bin/dnssec/dnssec-settime.docbook"/>
16890 <xi:include href="../../bin/dnssec/dnssec-signzone.docbook"/>
16891 <xi:include href="../../bin/dnssec/dnssec-verify.docbook"/>
16892 <xi:include href="../../bin/check/named-checkconf.docbook"/>
16893 <xi:include href="../../bin/check/named-checkzone.docbook"/>
16894 <xi:include href="../../bin/named/named.docbook"/>
16895 <xi:include href="../../bin/tools/named-journalprint.docbook"/>
16896 <!-- named.conf.docbook and others? -->
16897 <xi:include href="../../bin/nsupdate/nsupdate.docbook"/>
16898 <xi:include href="../../bin/rndc/rndc.docbook"/>
16899 <xi:include href="../../bin/rndc/rndc.conf.docbook"/>
16900 <xi:include href="../../bin/confgen/rndc-confgen.docbook"/>
16901 <xi:include href="../../bin/confgen/ddns-confgen.docbook"/>
16902 <xi:include href="../../bin/tools/arpaname.docbook"/>
16903 <xi:include href="../../bin/tools/genrandom.docbook"/>
16904 <xi:include href="../../bin/tools/isc-hmac-fixup.docbook"/>
16905 <xi:include href="../../bin/tools/nsec3hash.docbook"/>