Records Explained: A, CNAME, NS, MX, and PTR.

A RECORDS

 

Address (A) records direct a hostname to a numerical IP address.  For example, if you want mycomputer.yourdomain.com to point to your home computer (which is, for example, 192.168.0.3), you would enter a record that looks like:

 

Important:  You must put a period after the hostname.  Do not put periods after IP addresses.                  

 

CNAME RECORDS

 

CNAME allows a machine to be known by one or more hostnames.  There must always be an A record first, and this is known as the canonical or official name.  For example:

 

yourdomain.com.  A  192.168.0.1

 

Using CNAME, you can point other hostnames to the canonical (A record) address.  For example:

 

ftp.yourdoman.com.  CNAME  yourdomain.com.

mail.yourdomain.com.  CNAME  yourdomain.com.

ssh.yourdomin.com.  CNAME  yourdomain.com.

 

CNAME records make it possible to access your domain through ftp.yourdomain.com,  mail.yourdomain.com, etc.  Without a proper CNAME record, you will not be able to connect to your server using such addresses.

 

Entering a CNAME record

 

If we wanted home.site-helper.com to point to site-helper.com, we could enter the record in two ways:

 

 

The first method allows you to simply enter the subdomain.  Do not put a period after the subdomain name.

 

 

The second method requires you to enter the entire hostname, followed by a period.

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