DNS Code & Description Records

Code	Number	Description	Function
A	1	address record	Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host, but also used for DNSBLs, storing subnet masks in RFC 1101, etc.
AAAA	28	IPv6 address record	Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.
AFSDB	18	AFS database record	Location of 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.
CERT	37	Certificate record	Stores PKIX, SPKI, PGP, etc.
CNAME	5	Canonical name record	Alias of one name to another: the DNS lookup will continue by retrying the lookup with the new name.
DHCID	49	DHCP identifier	Used in conjunction with the FQDN option to DHCP
DLV	32769	DNSSEC Lookaside Validation record	For publishing DNSSEC trust anchors outside of the DNS delegation chain. Uses the same format as the DS record.
DNAME	39	delegation name	DNAME will delegate an entire portion of the DNS tree under a new name. In contrast, the CNAME record creates an alias of a single name. Like the CNAME record, the DNS lookup will continue by retrying the lookup with the new name.
DNSKEY	48	DNS Key record	The key record used in DNSSEC. Uses the same format as the KEY record.
DS	43	Delegation signer	The record used to identify the DNSSEC signing key of a delegated zone
HIP	55	Host Identity Protocol	Method of separating the end-point identifier and locator roles of IP addresses.
IPSECKEY	45	IPSEC Key	Key record that can be used with IPSEC
KEY	25	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	Location record	Specifies a geographical location associated with a domain name
MX	15	mail exchange record	Maps a domain name to a list of mail exchange servers for that domain
NAPTR	35	Naming Authority Pointer	Allows regular expression based rewriting of domain names which can then be used as URIs, further domain names to lookups, etc.
NS	2	name server record	Delegates a DNS zone to use the given authoritative name servers
NSEC	47	Next-Secure record	Part of DNSSEC—used to prove a name does not exist. Uses the same format as the (obsolete) NXT record.
NSEC3	50	NSEC record version 3	An extension to DNSSEC that allows proof of nonexistence for a name without permitting zonewalking
NSEC3PARAM	51	NSEC3 parameters	Parameter record for use with NSEC3
PTR	12	pointer record	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, but other uses include such things as DNS-SD.
RRSIG	46	DNSSEC signature	Signature for a DNSSEC-secured record set. Uses the same format as the SIG record.
SIG	24	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	start of authority record	Specifies 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	SPF record	Specified as part of the SPF protocol, as an alternative to storing SPF data in TXT records. Uses the same format as the TXT record.
SRV	33	Service locator	Generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX.
SSHFP	44	SSH Public Key Fingerprint	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	DNSSEC Trust Authorities	Part of a deployment proposal for DNSSEC without a signed DNS root. See the IANA database and Weiler Spec] for details. Uses the same format as the DS record.
TXT	16	Text record	Originally for arbitrary human-readable text in a DNS record. Since the early 1990s, however, this record more often carries machine-readable data, such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework, DomainKeys, DNS-SD, etc.