Technical Library

Domain Name System

Introduction

Integration

Canonical Name (CNAME) records allow you to give aliases to machines already possessing a name. The CNAME record provides alternate host names for user convenience. It is also used to ease the transition from an old host name to a new host name.

The format of the CNAME records is:

The components of the CNAME record are described below.

alias: The nickname you wish to give to the canonical host name given in the host field.

host: The canonical name of the host is given here. This must be an official host name. It cannot be an alias.

An important thing to remember when creating CNAME records is to be sure the only resource record entered with the alias name is the CNAME record itself. All other resource records must be associated with the canonical name.

Here is an example of a correct way to use an alias:

conto           A       IP-address
                MX      5 conto
ed              CNAME   conto

This is valid because the only resource record entered with the alias name is the CNAME record. Therefore, ed would be an alias for conto, and mail for either name will be directed to the host, conto.

An INCORRECT usage of an alias may look like this:

conto           A       IP-address
ed              CNAME   conto
ed              MX      5 conto

This would cause an error because more than one resource record was entered with the alias name.

Remember that your domain name has a Start of Authority resource record associated with it, making your domain name an invalid alias name.