CNAME, A Record, and MX Record
Definitions of CNAMEs, A Records, and MX Records
This article applies to: DNS
CNAMEs
The CNAME (canonical name) record maps the aliases to the "official" name of a machine. The official name is stored in the A record. Aliases are most often used when a single machine hands out several different services. For example, one machine may be used for a Web server, an FTP site, and a mail server. Its CNAME would look something like this:
| wwwhost.cit.cornell.edu | 86400 | CNAME | myhost.cit.cornell.edu |
|---|---|---|---|
| ftphost.cit.cornell.edu | 86400 | CNAME | myhost.cit.cornell.edu |
| mailsvr.cit.cornell.edu | 86400 | CNAME | myhost.cit.cornell.edu |
A Records
An A (Address) record translates a hostname to an IP address. This is the base from which DNS works. An example of an A record would be:
www.webhost.cit.cornell.edu 86400 A 128.253.180.254
MX Records
An MX (Mail eXchange) record is put in place to redirect email sent to a user's machine to another designated mailhost. For a more detailed explanation, see the MX (Mail eXchange) FAQ.
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