DNS record types

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4 June 2008

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“A” record(address record) - returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host.

“MX” record(mail exchange record) - maps a domain name to a list of mail exchange servers for that domain.

“CNAME” record(canonical name record) - is an alias of one name to another, the DNS lookup will continue by retrying the lookup with the new name. This is useful when running multiple services (like an FTP and a webserver) from a single IP address. Each service can then have its own entry in DNS (like ftp.example.com. and www.example.com.). It is also used when running multiple HTTP servers, with different names, on the same physical host.

“NS” record(name server record) - delegates a DNS zone to use the given authoritative name servers

” TXT” record(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.

” SOA” record(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.

” PTR” record(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 addressd. 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.