List of DNS record types

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The Domain name system (DNS) implements a distributed, hierarchical, and redundant database for information associated with Internet domain names and addresses. This List of DNS record types provides an overview of the types of database records (resource records) stored in the zone files of this system.

Code	Number	Defining RFC	Description	Function
A	1	RFC 1035	address record	returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host.
AAAA	28	RFC 3596	IPv6 address record	returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.
AFSDB	18	RFC 1183	AFS database record	location of the database servers of an AFS cell. This record is commonly used by AFS clients to contact AFS cells outside their local domain. A subtype of this record is used by the obsolete DCE/DFS file system.
AXFR	252	RFC 1035	Full Zone Transfer	Transfer the entire zone file from the master name server to secondary name servers.
CERT	37	RFC 4398	Certificate record	can store PKIX, SPKI, PGP, etc.
CNAME	5	RFC 1035	canonical name record	an alias of one name to another: the DNS lookup will continue by retrying the lookup with the new name. This helps when running multiple services (like an FTP and a webserver; each running on different ports) from a single IP address. Each service can then have its own entry in DNS (like ftp.example.com. and www.example.com.). Network administrators also use CNAMEs when running multiple HTTP servers on the same port, with different names, on the same physical host. This however requires host headers support for the two sites to both listen on the default port (port 80).
DHCID	49	RFC 4701	DHCP identifier	Used in conjunction with the FQDN option to DHCP
DLV	32769	RFC 4431	DNSSEC Lookaside Validation record	for publishing DNSSEC trust anchors outside of the DNS delegation chain.
DNAME	39	RFC 2672	delegation name	Unlike the CNAME record which creates a single alias, a DNAME will delegate an entire portion of the DNS tree under a new name. Like the CNAME record, the DNS lookup will continue by retrying the lookup with the new name.
DNSKEY	48	RFC 3755	DNS Key record	The key record used in DNSSEC
DS	43	RFC 3658	Delegation signer	The record used to identify the DNSSEC signing key of a delegated zone
HIP	55	RFC 5205	Host Identity Protocol	a method of separating the end-point identifier and locator roles of IP addresses.
IPSECKEY	45	RFC 4025	IPSEC Key	Key record that can be used with IPSEC
IXFR	251	RFC 1995	Incremental Zone Transfer	Transfer the changed parts of the zone file from the master name server to secondary name servers.
KEY	25	RFC 4034	Key record	Used only for TKEY (RFC 2930). Before RFC 3755 was published, this was also used for DNSSEC, but DNSSEC now uses DNSKEY.
LOC	29	RFC 1876	Location record	Specifies a geographical location associated with a domain name.
MX	15	RFC 1035	mail exchange record	maps a domain name to a list of mail exchange servers for that domain.
NAPTR	35	RFC 3403	Naming Authority Pointer	a newer type of DNS record that support regular expression based rewriting.
NS	2	RFC 1035	name server record	delegates a DNS zone to use the given authoritative name servers
NSEC	47	RFC 3755	Next-Secure record	Part of DNSSEC. Used to prove that a name does not exist.
NSEC3	50	RFC 5155	NSEC record version 3	An extension to DNSSEC that allows proof of nonexistence for a name without permitting zonewalking.
NSEC3PARAM	51	RFC 5155	NSEC3 parameters	Parameter record for use with NSEC3
OPT	41	RFC 2671	Option	This is a "pseudo DNS record type" needed to support EDNS
PTR	12	RFC 1035	pointer record	a pointer to a canonical name. Unlike a CNAME, DNS processing does NOT proceed, just the name is returned. The most common use is for implementing reverse DNS lookups by putting a PTR record for a hostname in the in-addr.arpa. domain that corresponds to an IP address. For example (at the time of writing), www.icann.net has the IP address 192.0.34.164, but a PTR record maps 164.34.0.192.in-addr.arpa to its canonical name, referrals.icann.org.
RRSIG	46	RFC 3755	DNSSEC signature	Signature for a DNSSEC-secured record set
SIG	24	RFC 2535	Signature	Signature record used in SIG(0) (RFC 2931). Until RFC 3755 was published, the SIG record was part of DNSSEC; now RRSIG is used for that.
SOA	6	RFC 1035	start of authority record	specifies the authoritative information about a DNS zone, including the primary name server, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.
SPF	99	RFC 4408	SPF record	Specified as part of the SPF protocol, as an alternative to storing SPF data in TXT records.
SRV	33	RFC 2782	Service locator	a generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX.
SSHFP	44	RFC 4255	SSH Public Key Fingerprint	a resource record for publishing SSH public host key fingerprints in the DNS System, in order to aid in verifying the authenticity of the host.
TA	32768	None	DNSSEC Trust Authorities	Part of a deployment proposal for DNSSEC without a signed DNS root. See the IANA database and Weiler Spec] for details
TKEY	249	RFC 2930	Transaction Key	a record that supports one set of security mechanisms for the DNS. Used between DNS resolvers and Name servers, in contrast to DNSSEC which secures DNS records.
TSIG	250	RFC 2845	Transaction Signature	a record that supports one set of security mechanisms for DNS. Used between DNS resolvers and Name servers, in contrast to DNSSEC which secures DNS records.
TXT	16	RFC 1035	Text record	originally intended to carry arbitrary human-readable text in a DNS record. Since the early 1990s, however, this record is more often used to carry machine-readable data such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework and DomainKeys.

Contents 1 Other types 2 Obsolete record types 3 Further reading 4 References

[edit] Other types

Other types of records simply provide some types of information (for example, an HINFO record gives a description of the type of computer/OS a host uses), or others return data used in experimental features.

The "type" field is also used in the protocol for various operations; type 255 is a request for "all cached records of all types", 252 (AXFR) is a request for transfer of a zone, TKEY and TSIG are used for transaction signing (which is different from record signing).

[edit] Obsolete record types

Progress has obsoleted some of the originally-defined record-types. Of the records listed at IANA, some have limited use, for various reasons. Some are marked obsolete in the list, some are for very obscure services, some are for older versions of services, and some have special notes saying they're "not right".

• Obsoleted by RFC 973: MD(3), MF (4), MAILA (254)
• Records to publish mailing list subscriber lists in the DNS: MB(7), MG(8), MR(9), MINFO(14), MAILB (253). The intent, as specified by RFC 883, was for MB to replace the SMTP VRFY command, MG to replace the SMTP EXPN command, and MR to replace the "551 User Not Local" SMTP error. Later, RFC 2505 recommends that both the VRFY and EXPN commands be disabled.
• Declared "not to be relied upon" by RFC 1123: WKS(11)^[1]
• Mistakes: NB(32), NBSTAT(33) (from RFC 1002); the numbers are now assigned to NIMLOC and SRV.
• Obsoleted by RFC 1035: NULL(10) (RFC 883 defined "completion queries", opcode 2, which used this record. RFC 1035 reserved this opcode.)
• Defined as part of early IPv6 but downgraded to experimental by RFC 3364: A6(38)
• Obsoleted by DNSSEC updates (RFC 3755): NXT(30). The domain of applicability for KEY and SIG was also limited to not include DNSSEC use.
• Part of the first version of DNSSEC (RFC 2230/RFC 2065), now obsolete: KX(36)
• Not in current use by any notable application: HINFO(13), RP(17), X25(19), ISDN(20), RT(21), NSAP(22), NSAP-PTR(23), PX(26), EID(31), NIMLOC(32), ATMA(34), APL(42)
• Defined by the Kitchen Sink internet draft, but never made it to RFC status: SINK(40)
• A more limited early version of the LOC record: GPOS(27)
• IANA reserved, no RFC documented them[1] and support was removed from BIND in the early 90s: UINFO(100), UID(101), GID(102), UNSPEC(103)

[edit] Further reading

• "IANA DNS Parameters registry". Retrieved on 2008-05-25..

[edit] References