Types of DNS records

Important categories of data stored in the DNS include the following:

* An A record or address record maps a hostname to its 32-bit IPv4 address.

* An AAAA record or IPv6 address record maps a hostname to its 128-bit IPv6 address.

* A CNAME record or canonical name record makes one domain name an alias of
another. The aliased domain gets all the subdomains and DNS records of the original.

* An MX record or mail exchange record maps a domain name to a list of mail
exchange servers for that domain.

* A PTR record or pointer record maps an IPv4 address to the canonical name for that host. Setting up a PTR record for a hostname in the in-addr.arpa domain that corresponds to an IP address implements reverse DNS lookup for that 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.

* An NS record or name server record maps a domain name to a list of DNS servers for that domain. Delegations depend on NS records.

* An SOA record or start of authority record specifies the DNS server providing authoritative information about an Internet domain.

* A SRV record is a generalized service location record.

* A TXT record allows an administrator to insert arbitrary text into a DNS record. For example, this record is used to implement the Sender Policy Framework specification.

Other types of records simply provide information (for example, a LOC record gives the physical location of a host), or experimental data (for example, a WKS record gives a list of servers offering some well-known service such as HTTP or POP3 for a domain).