A, AAAA, CNAME e PTR

A, AAAA, CNAME, and PTR

A records map a name to an IPv4 address; AAAA records map it to IPv6. A CNAME says that one DNS name is an alias for another name. A PTR record supports reverse lookup: it maps a special reverse name back to a name.

Worked example

www.example.test. 300 IN CNAME edge.example.test.
edge.example.test. 300 IN A     192.0.2.20

The resolver follows the CNAME and then looks up the target. CNAME is not an HTTP redirect: it does not send a browser to a different URL or change the page path. An alias owner generally cannot also carry unrelated record types, with some protocol-defined exceptions at zone boundaries.

Reverse DNS is configured separately under in-addr.arpa for IPv4 and ip6.arpa for IPv6. A PTR record does not prove that the named host owns the address.

Check your understanding

Choose the best answer. This quiz runs locally and sends no DNS queries to real domains.