Types of DNS records
The following categories of data (records) are stored in the DNS
Domain Name System:
An A record
or address record, maps a hostname to a 32-bit IPv4
An AAAA record
address record, maps a hostname to a 128-bit IPv6
A CNAME record
or canonical name record, is an alias of one name to another. The A record
that the alias is pointing to can be either local or remote - on a foreign name server. Useful when running multiple services from a single IP address
, where each service has its own entry in DNS
A 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 220.127.116.11, but a PTR record maps 18.104.22.168.in-addr.arpa to its canonical name, referrals.icann.org.
A NS record
or name server record, maps a domain name to a list of DNS servers authoritative for that domain. Delegations depend on NS records.
A SOA record
or start of authority record, specifies the DNS server providing authoritative information about an Internet domain, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.
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∞
("Naming Authority Pointer") are a newer type of DNS record that support regular expression based rewriting.
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
for a domain).