All About Subdomains

You have a domain name example.com.
A subdomain would look like sub.example.com.

The domain name system is a heirarchy of names, and include hostnames and subdomains.
For our purposes, there is not much difference between a hostname and a subdomain (there is a technical difference if you're running a network of servers).

You can login to Cpanel and click on "Subdomains".
Enter a new subdomain, for example, sub.example.com.

Cpanel will create a DNS entry (an A record) for that subdomain pointing to your IP address.

Advanced Uses of Subdomains

Cname Records

If you use a service like Google Apps for Domains, then you may need to create a Cname record in DNS to point something like:

To do this, you would submit a support ticket∞ requesting a Cname record.
You would not create a subdomain in Cpanel (which creates the A record). Cname records and A records cannot coexist in this manner.

Delegating Subdomains

You can delegate a subdomain to another ISP, webhost or network provider. This is not done through the Cpanel Subdomains.
You would need to submit a support ticket∞ with the remote network's DNS/Nameservers to have the Tech Staff create NS records delegating the subdomain.

Example:
You use DynDNS∞ to create a DNS record for your home IP address assigned to you by your DSL provider. If we created a hostname/subdomain for home.example.com and point it to your IP address at home, it would not work when your ISP changes your IP address.

Instead, you would register with DynDNS∞ to update a hostname home.example.com with your IP address everytime it changes.
In order for this to work, ASO will create a NS record, referring all requests for home.example.com to DynDNS∞.

Ultimately, ASO will answer requests regarding your website, email server, etc, and then for anything related to your home IP address, ASO will refer all requests to DynDNS∞ who then has the necessary information about home.example.com.

You can also do something similar with a mailling list∞.

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