bind  9.11.35
About: BIND 9.11 implements the Domain Name System (DNS) protocols for the Internet (see the Release Notes). ESV = Extended Supported Version. Source code distribution.
  Fossies Dox: bind-9.11.35.tar.gz  ("unofficial" and yet experimental doxygen-generated source code documentation)  

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  1. Introduction
  2. Reporting bugs and getting help
  3. Contributing to BIND
  4. BIND 9.11 features
  5. Building BIND
  6. macOS
  7. Dependencies
  8. Compile-time options
  9. Automated testing
  10. Documentation
  11. Change log
  12. Acknowledgments


BIND (Berkeley Internet Name Domain) is a complete, highly portable implementation of the DNS (Domain Name System) protocol.

The BIND name server, named, is able to serve as an authoritative name server, recursive resolver, DNS forwarder, or all three simultaneously. It implements views for split-horizon DNS, automatic DNSSEC zone signing and key management, catalog zones to facilitate provisioning of zone data throughout a name server constellation, response policy zones (RPZ) to protect clients from malicious data, response rate limiting (RRL) and recursive query limits to reduce distributed denial of service attacks, and many other advanced DNS features. BIND also includes a suite of administrative tools, including the dig and delv DNS lookup tools, nsupdate for dynamic DNS zone updates, rndc for remote name server administration, and more.

BIND 9 is a complete re-write of the BIND architecture that was used in versions 4 and 8. Internet Systems Consortium (, a 501(c)(3) public benefit corporation dedicated to providing software and services in support of the Internet infrastructure, developed BIND 9 and is responsible for its ongoing maintenance and improvement. BIND is open source software licensed under the terms of ISC License for all versions up to and including BIND 9.10, and the Mozilla Public License version 2.0 for all subsequent versions.

For a summary of features introduced in past major releases of BIND, see the file HISTORY.

For a detailed list of changes made throughout the history of BIND 9, see the file CHANGES. See below for details on the CHANGES file format.

For up-to-date versions and release notes, see

Reporting bugs and getting help

To report non-security-sensitive bugs or request new features, you may open an Issue in the BIND 9 project on the ISC GitLab server at

Please note that, unless you explicitly mark the newly created Issue as "confidential", it will be publicly readable. Please do not include any information in bug reports that you consider to be confidential unless the issue has been marked as such. In particular, if submitting the contents of your configuration file in a non-confidential Issue, it is advisable to obscure key secrets: this can be done automatically by using named-checkconf -px.

If the bug you are reporting is a potential security issue, such as an assertion failure or other crash in named, please do NOT use GitLab to report it. Instead, send mail to using our OpenPGP key to secure your message. (Information about OpenPGP and links to our key can be found at Please do not discuss the bug on any public mailing list.

For a general overview of ISC security policies, read the Knowledge Base article at

Professional support and training for BIND are available from ISC at

To join the BIND Users mailing list, or view the archives, visit

If you're planning on making changes to the BIND 9 source code, you may also want to join the BIND Workers mailing list, at

Contributing to BIND

ISC maintains a public git repository for BIND; details can be found at

Information for BIND contributors can be found in the following files:

Patches for BIND may be submitted as merge requests in the ISC GitLab server at at

By default, external contributors don't have ability to fork BIND in the GitLab server, but if you wish to contribute code to BIND, you may request permission to do so. Thereafter, you can create git branches and directly submit requests that they be reviewed and merged.

If you prefer, you may also submit code by opening a GitLab Issue and including your patch as an attachment, preferably generated by git format-patch.

BIND 9.11 features

BIND 9.11.0 includes a number of changes from BIND 9.10 and earlier releases. New features include:

  • Added support for Catalog Zones, a new method for provisioning servers: a list of zones to be served is stored in a DNS zone, along with their configuration parameters. Changes to the catalog zone are propagated to slaves via normal AXFR/IXFR, whereupon the zones that are listed in it are automatically added, deleted or reconfigured.
  • Added support for "dnstap", a fast and flexible method of capturing and logging DNS traffic.
  • Added support for "dyndb", a new API for loading zone data from an external database, developed by Red Hat for the FreeIPA project.
  • "fetchlimit" quotas are now compiled in by default. These are for the use of recursive resolvers that are are under high query load for domains whose authoritative servers are nonresponsive or are experiencing a denial of service attack:
    • fetches-per-server limits the number of simultaneous queries that can be sent to any single authoritative server. The configured value is a starting point; it is automatically adjusted downward if the server is partially or completely non-responsive. The algorithm used to adjust the quota can be configured via the "fetch-quota-params" option.
    • fetches-per-zone limits the number of simultaneous queries that can be sent for names within a single domain. (Note: Unlike fetches-per-server, this value is not self-tuning.)
    • New stats counters have been added to count queries spilled due to these quotas.
  • Added a new dnssec-keymgr key maintenance utility, which can generate or update keys as needed to ensure that a zone's keys match a defined DNSSEC policy.
  • The experimental "SIT" feature in BIND 9.10 has been renamed "COOKIE" and is no longer optional. EDNS COOKIE is a mechanism enabling clients to detect off-path spoofed responses, and servers to detect spoofed-source queries. Clients that identify themselves using COOKIE options are not subject to response rate limiting (RRL) and can receive larger UDP responses.
  • SERVFAIL responses can now be cached for a limited time (defaulting to 1 second, with an upper limit of 30). This can reduce the frequency of retries when a query is persistently failing.
  • Added an nsip-wait-recurse switch to RPZ. This causes NSIP rules to be skipped if a name server IP address isn't in the cache yet; the address will be looked up and the rule will be applied on future queries.
  • Added a Python RNDC module. This allows multiple commands to sent over a persistent RNDC channel, which saves time.
  • The controls block in named.conf can now grant read-only rndc access to specified clients or keys. Read-only clients could, for example, check rndc status but could not reconfigure or shut down the server.
  • rndc commands can now return arbitrarily large amounts of text to the caller.
  • The zone serial number of a dynamically updatable zone can now be set via rndc signing -serial <number> <zonename>. This allows inline-signing zones to be set to a specific serial number.
  • The new rndc nta command can be used to set a Negative Trust Anchor (NTA), disabling DNSSEC validation for a specific domain; this can be used when responses from a domain are known to be failing validation due to administrative error rather than because of a spoofing attack. Negative trust anchors are strictly temporary; by default they expire after one hour, but can be configured to last up to one week.
  • rndc delzone can now be used on zones that were not originally created by "rndc addzone".
  • rndc modzone reconfigures a single zone, without requiring the entire server to be reconfigured.
  • rndc showzone displays the current configuration of a zone.
  • rndc managed-keys can be used to check the status of RFC 5001 managed trust anchors, or to force trust anchors to be refreshed.
  • max-cache-size can now be set to a percentage of available memory. The default is 90%.
  • Update forwarding performance has been improved by allowing a single TCP connection to be shared by multiple updates.
  • The EDNS Client Subnet (ECS) option is now supported for authoritative servers; if a query contains an ECS option then ACLs containing geoip or ecs elements can match against the the address encoded in the option. This can be used to select a view for a query, so that different answers can be provided depending on the client network.
  • The EDNS EXPIRE option has been implemented on the client side, allowing a slave server to set the expiration timer correctly when transferring zone data from another slave server.
  • The key generation and manipulation tools (dnssec-keygen, dnssec-settime, dnssec-importkey, dnssec-keyfromlabel) now take -Psync and -Dsync options to set the publication and deletion times of CDS and CDNSKEY parent-synchronization records. Both named and dnssec-signzone can now publish and remove these records at the scheduled times.
  • A new minimal-any option reduces the size of UDP responses for query type ANY by returning a single arbitrarily selected RRset instead of all RRsets.
  • A new masterfile-style zone option controls the formatting of text zone files: When set to full, a zone file is dumped in single-line-per-record format.
  • serial-update-method can now be set to date. On update, the serial number will be set to the current date in YYYYMMDDNN format.
  • dnssec-signzone -N date sets the serial number to YYYYMMDDNN.
  • named -L <filename> causes named to send log messages to the specified file by default instead of to the system log.
  • dig +ttlunits prints TTL values with time-unit suffixes: w, d, h, m, s for weeks, days, hours, minutes, and seconds.
  • dig +unknownformat prints dig output in RFC 3597 "unknown record" presentation format.
  • dig +ednsopt allows dig to set arbitrary EDNS options on requests.
  • dig +ednsflags allows dig to set yet-to-be-defined EDNS flags on requests.
  • mdig is an alternate version of dig which sends multiple pipelined TCP queries to a server. Instead of waiting for a response after sending a query, it sends all queries immediately and displays responses in the order received.
  • serial-query-rate no longer controls NOTIFY messages. These are separately controlled by notify-rate and startup-notify-rate.
  • nsupdate now performs check-names processing by default on records to be added. This can be disabled with check-names no.
  • The statistics channel now supports DEFLATE compression, reducing the size of the data sent over the network when querying statistics.
  • New counters have been added to the statistics channel to track the sizes of incoming queries and outgoing responses in histogram buckets, as specified in RSSAC002.
  • A new NXDOMAIN redirect method (option nxdomain-redirect) has been added, allowing redirection to a specified DNS namespace instead of a single redirect zone.
  • When starting up, named now ensures that no other named process is already running.
  • Files created by named to store information, including mkeys and nzf files, are now named after their corresponding views unless the view name contains characters incompatible with use as a filename. Old style filenames (based on the hash of the view name) will still work.

BIND 9.11.1

BIND 9.11.1 is a maintenance release, and addresses the security flaws disclosed in CVE-2016-6170, CVE-2016-8864, CVE-2016-9131, CVE-2016-9147, CVE-2016-9444, CVE-2016-9778, CVE-2017-3135, CVE-2017-3136, CVE-2017-3137 and CVE-2017-3138.

BIND 9.11.2

BIND 9.11.2 is a maintenance release, and addresses the security flaws disclosed in CVE-2017-3140, CVE-2017-3141, CVE-2017-3142 and CVE-2017-3143. It also addresses several bugs related to the use of an LMDB database to store data related to zones added via rndc addzone or catalog zones.

BIND 9.11.3

BIND 9.11.3 is a maintenance release, and addresses the security flaw disclosed in CVE-2017-3145.

BIND 9.11.4

BIND 9.11.4 is a maintenance release, and addresses the security flaw disclosed in CVE-2018-5738. It also introduces "root key sentinel" support, enabling validating resolvers to indicate via a special query which trust anchors are configured for the root zone.

BIND 9.11.5

BIND 9.11.5 is a maintenance release, and also addresses CVE-2018-5741 by correcting faulty documentation and introducing the following new feature:

  • New krb5-selfsub and ms-selfsub rule types for update-policy statements allow updating of subdomains based on a Kerberos or Active Directory machine principal.

BIND 9.11.6

BIND 9.11.6 is a maintenance release, and also addresses the security flaws disclosed in CVE-2018-5743, CVE-2018-5745, CVE-2018-5744, and CVE-2019-6465.

BIND 9.11.7

BIND 9.11.7 is a maintenance release, and also addresses the security flaw disclosed in CVE-2018-5743.

BIND 9.11.8

BIND 9.11.8 is a maintenance release, and also addresses the security flaw disclosed in CVE-2019-6471.

BIND 9.11.9

BIND 9.11.9 is a maintenance release, and also adds support for the new MaxMind GeoIP2 geolocation API when built with configure --with-geoip2.

BIND 9.11.10

BIND 9.11.10 is a maintenance release.

BIND 9.11.11

BIND 9.11.11 is a maintenance release.

BIND 9.11.12

BIND 9.11.12 is a maintenance release.

BIND 9.11.13

BIND 9.11.13 is a maintenance release, and also addresses the security vulnerability disclosed in CVE-2019-6477.

BIND 9.11.14

BIND 9.11.14 is a maintenance release.

BIND 9.11.15

BIND 9.11.15 is a maintenance release.

BIND 9.11.16

BIND 9.11.16 is a maintenance release.

BIND 9.11.17

BIND 9.11.17 is a maintenance release.

BIND 9.11.18

BIND 9.11.18 is a maintenance release.

BIND 9.11.19

BIND 9.11.19 is a maintenance release, and also addresses the security vulnerabilities disclosed in CVE-2020-8616 and CVE-2020-8617.

BIND 9.11.20

BIND 9.11.20 is a maintenance release, and also addresses the security vulnerability disclosed in CVE-2020-8619.

BIND 9.11.21

BIND 9.11.21 is a maintenance release.

BIND 9.11.22

BIND 9.11.22 is a maintenance release, and also addresses the security vulnerabilities disclosed in CVE-2020-8622, CVE-2020-8623, and CVE-2020-8624.

BIND 9.11.23

BIND 9.11.23 is a maintenance release.

BIND 9.11.24

BIND 9.11.24 is a maintenance release.

BIND 9.11.25

BIND 9.11.25 is a maintenance release.

BIND 9.11.26

BIND 9.11.26 is a maintenance release.

BIND 9.11.27

BIND 9.11.27 is a maintenance release.

BIND 9.11.28

BIND 9.11.28 is a maintenance release, and also addresses the security vulnerability disclosed in CVE-2020-8625.

BIND 9.11.29

BIND 9.11.29 is a maintenance release.

BIND 9.11.30

This release was withdrawn.

BIND 9.11.31

BIND 9.11.31 is a maintenance release, and also addresses the security vulnerabilities disclosed in CVE-2021-25214, CVE-2021-25215, and CVE-2021-25216.

BIND 9.11.32

BIND 9.11.32 is a maintenance release.

BIND 9.11.33

BIND 9.11.33 is a maintenance release.

BIND 9.11.34

BIND 9.11.34 is a maintenance release.

BIND 9.11.35

BIND 9.11.35 is a maintenance release.

Building BIND

Minimally, BIND requires a UNIX or Linux system with an ANSI C compiler, basic POSIX support, and a 64-bit integer type. Successful builds have been observed on many versions of Linux and UNIX, including RHEL/CentOS, Fedora, Debian, Ubuntu, SLES, openSUSE, Slackware, Alpine, FreeBSD, NetBSD, OpenBSD, macOS, Solaris, OpenIndiana, OmniOS CE, HP-UX, and OpenWRT.

BIND is also available for Windows Server 2008 and higher. See win32utils/build.txt for details on building for Windows systems.

To build on a UNIX or Linux system, use:

    $ ./configure
    $ make

If you're planning on making changes to the BIND 9 source, you should run make depend. If you're using Emacs, you might find make tags helpful.

Several environment variables that can be set before running configure will affect compilation. Significant ones are:

Variable Description
CC The C compiler to use. configure tries to figure out the right one for supported systems.
CFLAGS C compiler flags. Defaults to include -g and/or -O2 as supported by the compiler. Please include '-g' if you need to set CFLAGS.
STD_CINCLUDES System header file directories. Can be used to specify where add-on thread or IPv6 support is, for example. Defaults to empty string.
STD_CDEFINES Any additional preprocessor symbols you want defined. Defaults to empty string. For a list of possible settings, see the file OPTIONS.
LDFLAGS Linker flags. Defaults to empty string.
BUILD_CC Needed when cross-compiling: the native C compiler to use when building for the target system.
BUILD_CFLAGS CFLAGS for the target system during cross-compiling.
BUILD_CPPFLAGS CPPFLAGS for the target system during cross-compiling.
BUILD_LDFLAGS LDFLAGS for the target system during cross-compiling.
BUILD_LIBS LIBS for the target system during cross-compiling.

Additional environment variables affecting the build are listed at the end of the configure help text, which can be obtained by running the command:

$ ./configure --help

On platforms where neither the C11 Atomic operations library nor custom ISC atomic operations are available, updating the statistics counters is not locked due to performance reasons and therefore the counters might be inaccurate. Anybody building BIND 9 is strongly advised to use a modern C11 compiler with C11 Atomic operations library support.


Building on macOS assumes that the "Command Tools for Xcode" is installed. This can be downloaded from or, if you have Xcode already installed, you can run xcode-select --install. (Note that an Apple ID may be required to access the download page.)


Portions of BIND that are written in Python, including dnssec-keymgr, dnssec-coverage, dnssec-checkds, and some of the system tests, require the argparse, ply and distutils.core modules to be available. argparse is a standard module as of Python 2.7 and Python 3.2. ply is available from distutils.core is required for installation.

Compile-time options

To see a full list of configuration options, run configure --help.

On most platforms, BIND 9 is built with multithreading support, allowing it to take advantage of multiple CPUs. You can configure this by specifying --enable-threads or --disable-threads on the configure command line. The default is to enable threads, except on some older operating systems on which threads are known to have had problems in the past. (Note: Prior to BIND 9.10, the default was to disable threads on Linux systems; this has now been reversed. On Linux systems, the threaded build is known to change BIND's behavior with respect to file permissions; it may be necessary to specify a user with the -u option when running named.)

To build shared libraries, specify --with-libtool on the configure command line.

For the server to support DNSSEC, you need to build it with crypto support. To use OpenSSL, you should have OpenSSL 1.0.2e or newer installed. If the OpenSSL library is installed in a nonstandard location, specify the prefix using --with-openssl=<PREFIX> on the configure command line. To use a PKCS#11 hardware service module for cryptographic operations, specify the path to the PKCS#11 provider library using --with-pkcs11=<PREFIX>, and configure BIND with "--enable-native-pkcs11".

To support the HTTP statistics channel, the server must be linked with at least one of the following libraries: libxml2 or json-c If these are installed at a nonstandard location, then:

  • for libxml2, specify the prefix using --with-libxml2=/prefix,
  • for json-c, adjust PKG_CONFIG_PATH.

To support compression on the HTTP statistics channel, the server must be linked against libzlib. If this is installed in a nonstandard location, specify the prefix using --with-zlib=/prefix.

To support storing configuration data for runtime-added zones in an LMDB database, the server must be linked with liblmdb. If this is installed in a nonstandard location, specify the prefix using with-lmdb=/prefix.

To support GeoIP location-based ACLs, the server must be linked with libGeoIP. This is not turned on by default; BIND must be configured with "--with-geoip". If the library is installed in a nonstandard location, use specify the prefix using "--with-geoip=/prefix".

For DNSTAP packet logging, you must have installed libfstrm and libprotobuf-c, and BIND must be configured with --enable-dnstap.

Certain compiled-in constants and default settings can be increased to values better suited to large servers with abundant memory resources (e.g, 64-bit servers with 12G or more of memory) by specifying --with-tuning=large on the configure command line. This can improve performance on big servers, but will consume more memory and may degrade performance on smaller systems.

On some platforms it is necessary to explicitly request large file support to handle files bigger than 2GB. This can be done by using --enable-largefile on the configure command line.

Support for the "fixed" rrset-order option can be enabled or disabled by specifying --enable-fixed-rrset or --disable-fixed-rrset on the configure command line. By default, fixed rrset-order is disabled to reduce memory footprint.

If your operating system has integrated support for IPv6, it will be used automatically. If you have installed KAME IPv6 separately, use --with-kame[=PATH] to specify its location.

The --enable-querytrace option causes named to log every step of processing every query. This should only be enabled when debugging, because it has a significant negative impact on query performance.

make install will install named and the various BIND 9 libraries. By default, installation is into /usr/local, but this can be changed with the --prefix option when running configure.

You may specify the option --sysconfdir to set the directory where configuration files like named.conf go by default, and --localstatedir to set the default parent directory of run/ For backwards compatibility with BIND 8, --sysconfdir defaults to /etc and --localstatedir defaults to /var if no --prefix option is given. If there is a --prefix option, sysconfdir defaults to $prefix/etc and localstatedir defaults to $prefix/var.

Automated testing

A system test suite can be run with make test. The system tests require you to configure a set of virtual IP addresses on your system (this allows multiple servers to run locally and communicate with one another). These IP addresses can be configured by running the command bin/tests/system/ up as root.

Some tests require Perl and the Net::DNS and/or IO::Socket::INET6 modules, and will be skipped if these are not available. Some tests require Python and the dnspython module and will be skipped if these are not available. See bin/tests/system/README for further details.

Unit tests are implemented using the CMocka unit testing framework. To build them, use configure --with-cmocka. Execution of tests is done by the Kyua test execution engine; if the `kyua` command is available, then unit tests can be run via make test or make unit.


The BIND 9 Administrator Reference Manual is included with the source distribution, in DocBook XML, HTML, and PDF format, in the doc/arm directory.

Some of the programs in the BIND 9 distribution have man pages in their directories. In particular, the command line options of named are documented in bin/named/named.8.

Frequently (and not-so-frequently) asked questions and their answers can be found in the ISC Knowledge Base at

Additional information on various subjects can be found in other README files throughout the source tree.

Change log

A detailed list of all changes that have been made throughout the development BIND 9 is included in the file CHANGES, with the most recent changes listed first. Change notes include tags indicating the category of the change that was made; these categories are:

Category Description
[func] New feature
[bug] General bug fix
[security] Fix for a significant security flaw
[experimental] Used for new features when the syntax or other aspects of the design are still in flux and may change
[port] Portability enhancement
[maint] Updates to built-in data such as root server addresses and keys
[tuning] Changes to built-in configuration defaults and constants to improve performance
[performance] Other changes to improve server performance
[protocol] Updates to the DNS protocol such as new RR types
[test] Changes to the automatic tests, not affecting server functionality
[cleanup] Minor corrections and refactoring
[doc] Documentation
[contrib] Changes to the contributed tools and libraries in the 'contrib' subdirectory
[placeholder] Used in the master development branch to reserve change numbers for use in other branches, e.g. when fixing a bug that only exists in older releases

In general, [func] and [experimental] tags will only appear in new-feature releases (i.e., those with version numbers ending in zero). Some new functionality may be backported to older releases on a case-by-case basis. All other change types may be applied to all currently-supported releases.

Bug report identifiers

Most notes in the CHANGES file include a reference to a bug report or issue number. Prior to 2018, these were usually of the form [RT #NNN] and referred to entries in the "bind9-bugs" RT database, which was not open to the public. More recent entries use the form [GL #NNN] or, less often, [GL !NNN], which, respectively, refer to issues or merge requests in the GitLab database. Most of these are publicly readable, unless they include information which is confidential or security sensitive.

To look up a GitLab issue by its number, use the URL To look up a merge request, use

In rare cases, an issue or merge request number may be followed with the letter "P". This indicates that the information is in the private ISC GitLab instance, which is not visible to the public.