Details
DNS CNAME records are specified in RFC 1034 and clarified in Section 10 of RFC 2181.
CNAME records are handled specially in the domain name system, and have several restrictions on their use. When a DNS resolver encounters a CNAME record while looking for a regular resource record, it will restart the query using the canonical name instead of the original name. (If the resolver is specifically told to look for CNAME records, the canonical name (right-hand side) is returned, rather than restarting the query.) The canonical name that a CNAME record points to can be anywhere in the DNS, whether local or on a remote server in a different DNS zone.
For example, if there is a DNS zone as follows:
NAME TYPE VALUE -------------------------------------------------- foo.example.com. CNAME bar.example.com. bar.example.com. A 192.0.2.23When an A record lookup for foo.example.com is done, the resolver will see a CNAME record and restart the checking at bar.example.com and will then return 192.0.2.23.
Read more about this topic: CNAME Record
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