General DNS Reference Information

Requests for Comment (RFCs)

Specification documents for the Internet protocol suite, including the DNS, are published as part of the Request for Comments (RFCs) series of technical notes. The standards themselves are defined by the Internet Engineering Task Force (IETF) and the Internet Engineering Steering Group (IESG). RFCs can be viewed online at:

While reading RFCs, please keep in mind that not all RFCs are standards, and also that the validity of documents does change over time. Every RFC needs to be interpreted in the context of other documents.

BIND 9 strives for strict compliance with IETF standards. To the best of our knowledge, BIND 9 complies with the following RFCs, with the caveats and exceptions listed in the numbered notes below. Many of these RFCs were written by current or former ISC staff members. The list is non-exhaustive.

Some of these RFCs, though DNS-related, are not concerned with implementing software.

Protocol Specifications

RFC 1034 - P. Mockapetris. Domain Names — Concepts and Facilities. November 1987.

RFC 1035 - P. Mockapetris. Domain Names — Implementation and Specification. November 1987. 1 2

RFC 1183 - C. F. Everhart, L. A. Mamakos, R. Ullmann, P. Mockapetris. New DNS RR Definitions. October 1990.

RFC 1706 - B. Manning and R. Colella. DNS NSAP Resource Records. October 1994.

RFC 1712 - C. Farrell, M. Schulze, S. Pleitner, and D. Baldoni. DNS Encoding of Geographical Location. November 1994.

RFC 1876 - C. Davis, P. Vixie, T. Goodwin, and I. Dickinson. A Means for Expressing Location Information in the Domain Name System. January 1996.

RFC 1982 - R. Elz and R. Bush. Serial Number Arithmetic. August 1996.

RFC 1995 - M. Ohta. Incremental Zone Transfer in DNS. August 1996.

RFC 1996 - P. Vixie. A Mechanism for Prompt Notification of Zone Changes (DNS NOTIFY). August 1996.

RFC 2136 - P. Vixie, S. Thomson, Y. Rekhter, and J. Bound. Dynamic Updates in the Domain Name System (DNS UPDATE). April 1997.

RFC 2163 - A. Allocchio. Using the Internet DNS to Distribute MIXER Conformant Global Address Mapping (MCGAM). January 1998.

RFC 2181 - R. Elz and R. Bush. Clarifications to the DNS Specification. July 1997.

RFC 2230 - R. Atkinson. Key Exchange Delegation Record for the DNS. November 1997.

RFC 2308 - M. Andrews. Negative Caching of DNS Queries (DNS NCACHE). March 1998.

RFC 2539 - D. Eastlake, 3rd. Storage of Diffie-Hellman Keys in the Domain Name System (DNS). March 1999.

RFC 2782 - A. Gulbrandsen, P. Vixie, and L. Esibov. A DNS RR for Specifying the Location of Services (DNS SRV). February 2000.

RFC 2930 - D. Eastlake, 3rd. Secret Key Establishment for DNS (TKEY RR). September 2000.

RFC 2931 - D. Eastlake, 3rd. DNS Request and Transaction Signatures (SIG(0)s). September 2000. 3

RFC 3007 - B. Wellington. Secure Domain Name System (DNS) Dynamic Update. November 2000.

RFC 3110 - D. Eastlake, 3rd. RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS). May 2001.

RFC 3123 - P. Koch. A DNS RR Type for Lists of Address Prefixes (APL RR). June 2001.

RFC 3225 - D. Conrad. Indicating Resolver Support of DNSSEC. December 2001.

RFC 3226 - O. Gudmundsson. DNSSEC and IPv6 A6 Aware Server/Resolver Message Size Requirements. December 2001.

RFC 3363 - R. Bush, A. Durand, B. Fink, O. Gudmundsson, and T. Hain. Representing Internet Protocol Version 6 (IPv6) Addresses in the Domain Name System (DNS). August 2002. 15

RFC 3403 - M. Mealling. Dynamic Delegation Discovery System (DDDS). Part Three: The Domain Name System (DNS) Database. October 2002.

RFC 3492 - A. Costello. Punycode: A Bootstring Encoding of Unicode for Internationalized Domain Names in Applications (IDNA). March 2003.

RFC 3493 - R. Gilligan, S. Thomson, J. Bound, J. McCann, and W. Stevens. Basic Socket Interface Extensions for IPv6. March 2003.

RFC 3496 - A. G. Malis and T. Hsiao. Protocol Extension for Support of Asynchronous Transfer Mode (ATM) Service Class-aware Multiprotocol Label Switching (MPLS) Traffic Engineering. March 2003.

RFC 3596 - S. Thomson, C. Huitema, V. Ksinant, and M. Souissi. DNS Extensions to Support IP Version 6. October 2003.

RFC 3597 - A. Gustafsson. Handling of Unknown DNS Resource Record (RR) Types. September 2003.

RFC 3645 - S. Kwan, P. Garg, J. Gilroy, L. Esibov, J. Westhead, and R. Hall. Generic Security Service Algorithm for Secret Key Transaction Authentication for DNS (GSS-TSIG). October 2003.

RFC 4025 - M. Richardson. A Method for Storing IPsec Keying Material in DNS. March 2005.

RFC 4033 - R. Arends, R. Austein, M. Larson, D. Massey, and S. Rose. DNS Security Introduction and Requirements. March 2005.

RFC 4034 - R. Arends, R. Austein, M. Larson, D. Massey, and S. Rose. Resource Records for the DNS Security Extensions. March 2005.

RFC 4035 - R. Arends, R. Austein, M. Larson, D. Massey, and S. Rose. Protocol Modifications for the DNS Security Extensions. March 2005.

RFC 4255 - J. Schlyter and W. Griffin. Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints. January 2006.

RFC 4343 - D. Eastlake, 3rd. Domain Name System (DNS) Case Insensitivity Clarification. January 2006.

RFC 4398 - S. Josefsson. Storing Certificates in the Domain Name System (DNS). March 2006.

RFC 4470 - S. Weiler and J. Ihren. Minimally covering NSEC Records and DNSSEC On-line Signing. April 2006. 6

RFC 4509 - W. Hardaker. Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs). May 2006.

RFC 4592 - E. Lewis. The Role of Wildcards in the Domain Name System. July 2006.

RFC 4635 - D. Eastlake, 3rd. HMAC SHA (Hashed Message Authentication Code, Secure Hash Algorithm) TSIG Algorithm Identifiers. August 2006.

RFC 4701 - M. Stapp, T. Lemon, and A. Gustafsson. A DNS Resource Record (RR) for Encoding Dynamic Host Configuration Protocol (DHCP) Information (DHCID RR). October 2006.

RFC 4955 - D. Blacka. DNS Security (DNSSEC) Experiments. July 2007. 7

RFC 5001 - R. Austein. DNS Name Server Identifier (NSID) Option. August 2007.

RFC 5011 - M. StJohns. Automated Updates of DNS Security (DNSSEC) Trust Anchors.

RFC 5155 - B. Laurie, G. Sisson, R. Arends, and D. Blacka. DNS Security (DNSSEC) Hashed Authenticated Denial of Existence. March 2008.

RFC 5205 - P. Nikander and J. Laganier. Host Identity Protocol (HIP) Domain Name System (DNS) Extension. April 2008.

RFC 5452 - A. Hubert and R. van Mook. Measures for Making DNS More Resilient Against Forged Answers. January 2009. 8

RFC 5702 - J. Jansen. Use of SHA-2 Algorithms with RSA in DNSKEY and RRSIG Resource Records for DNSSEC. October 2009.

RFC 5891 - J. Klensin. Internationalized Domain Names in Applications (IDNA): Protocol. August 2010

RFC 5936 - E. Lewis and A. Hoenes, Ed. DNS Zone Transfer Protocol (AXFR). June 2010.

RFC 5952 - S. Kawamura and M. Kawashima. A Recommendation for IPv6 Address Text Representation. August 2010.

RFC 6052 - C. Bao, C. Huitema, M. Bagnulo, M. Boucadair, and X. Li. IPv6 Addressing of IPv4/IPv6 Translators. October 2010.

RFC 6147 - M. Bagnulo, A. Sullivan, P. Matthews, and I. van Beijnum. DNS64: DNS Extensions for Network Address Translation from IPv6 Clients to IPv4 Servers. April 2011. 9

RFC 6604 - D. Eastlake, 3rd. xNAME RCODE and Status Bits Clarification. April 2012.

RFC 6605 - P. Hoffman and W. C. A. Wijngaards. Elliptic Curve Digital Signature Algorithm (DSA) for DNSSEC. April 2012. 10

RFC 6672 - S. Rose and W. Wijngaards. DNAME Redirection in the DNS. June 2012.

RFC 6698 - P. Hoffman and J. Schlyter. The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA. August 2012.

RFC 6725 - S. Rose. DNS Security (DNSSEC) DNSKEY Algorithm IANA Registry Updates. August 2012. 11

RFC 6742 - RJ Atkinson, SN Bhatti, U. St. Andrews, and S. Rose. DNS Resource Records for the Identifier-Locator Network Protocol (ILNP). November 2012.

RFC 6840 - S. Weiler, Ed., and D. Blacka, Ed. Clarifications and Implementation Notes for DNS Security (DNSSEC). February 2013. 12

RFC 6891 - J. Damas, M. Graff, and P. Vixie. Extension Mechanisms for DNS (EDNS(0)). April 2013.

RFC 7043 - J. Abley. Resource Records for EUI-48 and EUI-64 Addresses in the DNS. October 2013.

RFC 7050 - T. Savolainen, J. Korhonen, and D. Wing. Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis. November 2013. 20

RFC 7208 - S. Kitterman. Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1. April 2014.

RFC 7314 - M. Andrews. Extension Mechanisms for DNS (EDNS) EXPIRE Option. July 2014.

RFC 7344 - W. Kumari, O. Gudmundsson, and G. Barwood. Automating DNSSEC Delegation Trust Maintenance. September 2014. 13

RFC 7477 - W. Hardaker. Child-to-Parent Synchronization in DNS. March 2015.

RFC 7553 - P. Faltstrom and O. Kolkman. The Uniform Resource Identifier (URI) DNS Resource Record. June 2015.

RFC 7583 - S. Morris, J. Ihren, J. Dickinson, and W. Mekking. DNSSEC Key Rollover Timing Considerations. October 2015.

RFC 7766 - J. Dickinson, S. Dickinson, R. Bellis, A. Mankin, and D. Wessels. DNS Transport over TCP - Implementation Requirements. March 2016.

RFC 7828 - P. Wouters, J. Abley, S. Dickinson, and R. Bellis. The edns-tcp-keepalive EDNS0 Option. April 2016.

RFC 7830 - A. Mayrhofer. The EDNS(0) Padding Option. May 2016. 14

RFC 7858 - Z. Hu, L. Zhu, J. Heidemann, A. Mankin, D. Wessels, and P. Hoffman. Specification for DNS over Transport Layer Security (TLS). May 2016. 21

RFC 7929 - P. Wouters. DNS-Based Authentication of Named Entities (DANE) Bindings for OpenPGP. August 2016.

RFC 8078 - O. Gudmundsson and P. Wouters. Managing DS Records from the Parent via CDS/CDNSKEY. March 2017. 22

RFC 8080 - O. Sury and R. Edmonds. Edwards-Curve Digital Security Algorithm (EdDSA) for DNSSEC. February 2017.

RFC 8484 - P. Hoffman and P. McManus. DNS Queries over HTTPS (DoH). October 2018. 21

RFC 8624 - P. Wouters and O. Sury. Algorithm Implementation Requirements and Usage Guidance for DNSSEC. June 2019.

RFC 8659 - P. Hallam-Baker, R. Stradling, and J. Hoffman-Andrews. DNS Certification Authority Authorization (CAA) Resource Record. November 2019.

RFC 8880 - S. Cheshire and D. Schinazi. Special Use Domain Name ‘’. August 2020.

RFC 8945 - F. Dupont, S. Morris, P. Vixie, D. Eastlake 3rd, O. Gudmundsson, and B. Wellington. Secret Key Transaction Authentication for DNS (TSIG). November 2020.

RFC 9103 - W. Toorop, S. Dickinson, S. Sahib, P. Aras, and A. Mankin. DNS Zone Transfer over TLS. August 2021. 23

Best Current Practice RFCs

RFC 2219 - M. Hamilton and R. Wright. Use of DNS Aliases for Network Services. October 1997.

RFC 2317 - H. Eidnes, G. de Groot, and P. Vixie. Classless IN-ADDR.ARPA Delegation. March 1998.

RFC 2606 - D. Eastlake, 3rd and A. Panitz. Reserved Top Level DNS Names. June 1999. 16

RFC 3901 - A. Durand and J. Ihren. DNS IPv6 Transport Operational Guidelines. September 2004.

RFC 5625 - R. Bellis. DNS Proxy Implementation Guidelines. August 2009.

RFC 6303 - M. Andrews. Locally Served DNS Zones. July 2011.

RFC 7793 - M. Andrews. Adding Prefixes to the IPv4 Locally-Served DNS Zones Registry. May 2016.

RFC 8906 - M. Andrews and R. Bellis. A Common Operational Problem in DNS Servers: Failure to Communicate. September 2020.

For Your Information

RFC 1101 - P. Mockapetris. DNS Encoding of Network Names and Other Types. April 1989.

RFC 1123 - R. Braden. Requirements for Internet Hosts - Application and Support. October 1989.

RFC 1535 - E. Gavron. A Security Problem and Proposed Correction With Widely Deployed DNS Software. October 1993.

RFC 1536 - A. Kumar, J. Postel, C. Neuman, P. Danzig, and S. Miller. Common DNS Implementation Errors and Suggested Fixes. October 1993.

RFC 1912 - D. Barr. Common DNS Operational and Configuration Errors. February 1996.

RFC 2874 - M. Crawford and C. Huitema. DNS Extensions to Support IPv6 Address Aggregation and Renumbering. July 2000. 4

RFC 3833 - D. Atkins and R. Austein. Threat Analysis of the Domain Name System (DNS). August 2004.

RFC 4074 - Y. Morishita and T. Jinmei. Common Misbehavior Against DNS Queries for IPv6 Addresses. June 2005.

RFC 4431 - M. Andrews and S. Weiler. The DNSSEC Lookaside Validation (DLV) DNS Resource Record. February 2006. 5

RFC 4892 - S. Woolf and D. Conrad. Requirements for a Mechanism Identifying a Name Server Instance. June 2007.

RFC 6781 - O. Kolkman, W. Mekking, and R. Gieben. DNSSEC Operational Practices, Version 2. December 2012.

RFC 7129 - R. Gieben and W. Mekking. Authenticated Denial of Existence in the DNS. February 2014.

RFC 8749 - W. Mekking and D. Mahoney. Moving DNSSEC Lookaside Validation (DLV) to Historic Status. March 2020.



Queries to zones that have failed to load return SERVFAIL rather than a non-authoritative response. This is considered a feature.


CLASS ANY queries are not supported. This is considered a feature.


When receiving a query signed with a SIG(0), the server is only able to verify the signature if it has the key in its local authoritative data; it cannot do recursion or validation to retrieve unknown keys.


Compliance is with loading and serving of A6 records only. A6 records were moved to the experimental category by RFC 3363.


Compliance is with loading and serving of DLV records only. DLV records were moved to the historic category by RFC 8749.


Minimally Covering NSEC records are accepted but not generated.


BIND 9 interoperates with correctly designed experiments.


named only uses ports to extend the ID space; addresses are not used.


Section 5.5 does not match reality. named uses the presence of DO=1 to detect if validation may be occurring. CD has no bearing on whether validation occurs.


Compliance is conditional on the OpenSSL library being linked against a supporting ECDSA.


RSAMD5 support has been removed. See RFC 8624.


Section 5.9 - Always set CD=1 on queries. This is not done, as it prevents DNSSEC from working correctly through another recursive server.

When talking to a recursive server, the best algorithm is to send CD=0 and then send CD=1 iff SERVFAIL is returned, in case the recursive server has a bad clock and/or bad trust anchor. Alternatively, one can send CD=1 then CD=0 on validation failure, in case the recursive server is under attack or there is stale/bogus authoritative data.


Updating of parent zones is not yet implemented.


named does not currently encrypt DNS requests, so the PAD option is accepted but not returned in responses.


Section 4 is ignored.


This does not apply to DNS server implementations.


Only the Base 64 encoding specification is supported.


BIND 9 requires --with-libidn2 to enable entry of IDN labels within dig, host, and nslookup at compile time. ACE labels are supported everywhere with or without --with-libidn2.


Section 5.1 - DNAME records are fully supported.


RFC 7050 is updated by RFC 8880.


Forwarding DNS queries over encrypted transports is not supported yet.


Updating of parent zones is not yet implemented.


Strict TLS and Mutual TLS authentication mechanisms are not supported yet.

Internet Drafts

Internet Drafts (IDs) are rough-draft working documents of the Internet Engineering Task Force (IETF). They are, in essence, RFCs in the preliminary stages of development. Implementors are cautioned not to regard IDs as archival, and they should not be quoted or cited in any formal documents unless accompanied by the disclaimer that they are “works in progress.” IDs have a lifespan of six months, after which they are deleted unless updated by their authors.