DNS Resource Records

This is an alphabetical list of the DNS resource records in the IN class (used for Internet domain names, as usually understood). The record types NS, SOA, CNAME, and PTR form the basic infrastructure of DNS. These record types exist in all classes, not just IN.

See also the official IANA list of DNS parameters, which is ordered by numeric value. Note that the IANA list is not as up to date as it could be (for instance, several of its references to RFC documents are outdated).

A

Address, code 1. Used for storing an IP address (specifically, an IPv4 32-bit address) associated with a domain name. Defined in RFC 1035.

A6

IPv6 address, code 38. Relegated to Experimental status by RFC 3363, as AAAA records are now regarded as more generally useful. Defined in RFC 2874.

AAAA

IPv6 address, code 28. Used for storing an IPv6 128-bit address associated with a domain name. Defined in RFC 3596.

AFSDB

AFS Data Base location, code 18. Not widely used, rather use SRV records instead. Defined in RFC 1183.

CNAME

Canonical name for a DNS alias, code 5. Note that if a domain name has a CNAME record associated with it, then it can not have any other record types. In addition, CNAME records should not point to domain names which themselves have associated CNAME records, so CNAME only provides one layer of indirection. Defined in RFC 1035.

DNAME

DNAME, code 39. A way to provide aliases for a whole domain, not just a single domain name as with CNAME. Defined in RFC 2672.

DS

Delegation signer, code 43. A major change to the way DNSSEC operates. Defined in RFC 3658.

GPOS

Geographical position, code 27, obsolete. Defined in RFC 1712.

HINFO

Host Information, code 13. Not widely used. Defined in RFC 1035.

ISDN

ISDN address, code 20. Not widely used. Defined in RFC 1183.

KEY

Public key as used in DNSSEC, code 25. Defined in RFC 2535. See also RFC 3445.

KX

Key Exchanger, code 36. Defined in RFC 2230.

LOC

Location information, code 29. Associates a geographical location with a domain name. Defined in RFC 1876.

MB

Mailbox, code 7. Not widely used. Defined in RFC 1035.

MD

Mail destination, code 3, obsolete. Defined in RFC 1035.

MF

Mail forwarder, code 4, obsolete. Defined in RFC 1035.

MG

Mail group member, code 8. Not widely used. Defined in RFC 1035.

MINFO

Mailbox or mailing list information, code 14. Defined in RFC 1035.

MR

Mail rename domain name, code 9. Not widely used. Defined in RFC 1035.

MX

Mail Exchanger, code 15. Each MX record specifies a domain name (which must have an A record associated with it) and a priority; a list of mail exchangers is then ordered by priority when delivering mail. MX records provide one level of indirection in mapping the domain part of an email address to a list of host names which are meant to receive mail for that domain name. Critical part of the infrastructure used to support SMTP email. Defined in RFC 1035.

NAPTR

Naming authority pointer, code 35. Used mostly for Internet telephony infrastructure as in RFC 3263. Defined in RFC 3403.

NULL

Null record, code 10. Not widely used. Defined in RFC 1035.

NS

Authoritative name server, code 2. Specifies a host name (which must have an A record associated with it), where DNS information can be found about the domain name to which the NS record is attached. NS records are the basic infrastructure on which DNS is built; they stitch together distributed zone files into a directed graph that can be efficiently searched. Defined in RFC 1035.

NSAP

Network service access point address, code 22. Allows OSI-style NSAPs to be stored in the DNS. Defined in RFC 1706.

NSAP-PTR

NSAP pointer, code 23, obsolete. Defined in RFC 1348.

NXT

Next domain, code 30, obsolete. Defined in RFC 2065.

PTR

Domain name pointer, code 12. Provides a general indirection facility for DNS records. Most often used to provide a way to associate a domain name with an IPv4 address in the IN-ADDR.ARPA domain. Defined in RFC 1035.

PX

Pointer to X.400/RFC822 mail mapping information. Defined in RFC 2163.

RP

Responsible person, code 17. Defined in RFC 1183.

RT

Route through, code 21. Not widely used. Defined in RFC 1183.

SIG

Cryptographic public key signature, code 24. Defined in RFC 2931.

SOA

Start of authority, code 6. Marks the start of a zone. Defined in RFC 1035.

SRV

Server selection, code 33. Similar to MX records, generalised to any network service. Defined in RFC 2782.

TKEY

Transaction key, code 249. A way of distributing keys for TSIG records. Defined in RFC 2930.

TSIG

Transaction signature, code 250. Simple authentication for DNS transactions, using shared secret keys and hashing. Defined in RFC 2845.

TXT

Text string, code 16. Arbitrary binary data, up to 255 bytes in length. Defined in RFC 1035.

WKS

Well-known service, code 11. Information about which services are available at a host. Defined in RFC 1035.

X25

X25 PSDN address, code 19. Not widely used. Defined in RFC 1183.

EID             31 Endpoint Identifier                    [Patton]
NIMLOC          32 Nimrod Locator                         [Patton]
ATMA            34 ATM Address                            [Dobrowski]
CERT            37 CERT                                   [RFC2538]
SINK            40 SINK                                   [Eastlake]
OPT             41 OPT                                    [RFC2671]
APL             42 APL                                    [RFC3123]
SSHFP           44 SSH Key Fingerprint [RFC-ietf-secsh-dns-05.txt]
RRSIG           46 RRSIG [RFC-ietf-dnsext-dnssec-2535typecode-change-04.txt]
NSEC            47 NSEC [RFC-ietf-dnsext-dnssec-2535typecode-change-04.txt]
DNSKEY          48 DNSKEY [RFC-ietf-dnsext-dnssec-2535typecode-change-04.txt]
UINFO           100 [IANA-Reserved]
UID             101 [IANA-Reserved]
GID             102 [IANA-Reserved]
UNSPEC          103 [IANA-Reserved]