Step-by-Step: Adding a Subdomain to Your Zone File at
Updated: May 4, 2001

This article assumes that you already looked at Registering Your Zone File at beforehand.  All we are going to do here is add a subdomain.

You might want a subdomain for several reasons.  You can use it to access a part of your website faster.  For example, leads to the main site and you can enter the forums by clicking on the icon labeled "forums".  However, the good people at DSL/Cable Webserver know that some people want to go directly into the forums without going through the main site so we created a subdomain called "forums".  This way, you can go into our forums by simply typing in  Pretty cool and handy.

Another reason you might want to use subdomains is so that you can host somebody's website under your domain name.  Something like this:

You could set it up so each of those subdomain + domain names go to each person's website.  Very nifty.

There are two ways we can setup subdomains.  We can set the subdomain to go to:

  • Option 1. The same IP address as the domain name.
  • Option 2. A different IP address than the domain name.
Most of us hosting websites on DSL or Cable only have 1 IP address so Option 1 is probably more applicable to us.  In order to host subdomains on the same IP address, your webserver software must be able to host multiple websites on a single IP address.  A list of the operating systems and webserver software that can do this can be found in Server Software.  After your DNS changes are complete, you must configure your webserver software to work with subdomains.

In each instance, you must add a new entry for each additional subdomain.

Here we go:

Go to:

Click on "Login" and type in your username and password.

If you have multiple zones hosted with, select the domain name that you want to edit.

You will then see the main page for your domain name.  It should look something like this.

There are two ways we can add a subdomain to our domain name.  We can either use the "IP addresses (A)" link or the "Aliases (CNAME)" link.  Both methods work, but we will use the "IP addresses (A)" method because it is more flexible in our case.  This isn't the way zone files are supposed to be written, but we'll let worry about that.  (That's why these things are web based and not text based!)

Click on the "IP addresses (A)" link.  You will then see this:

In the bottom box, fill out your new desired subdomain name in the first box.  In the second box, you can either type in the same IP number as your domain name or you can type in a different IP number than domain name.  Most likely, you will have only 1 IP address and should type this in the box.  A discussion about this topic is at the beginning of this article if your forgot already.

I'm going to be using the same IP address as my domain name.

Click on "Add New IP Address".  You will see this confirmatory message. Click "Yes".

Here is the screen that shows the subdomain listed with the proper IP number.  All modifications have been saved now and the DNS changes should appear almost instantaneously.

When I do a "nslookup", I get the proper answer.  I did this nslookup about 2 minutes after I finished the previous steps.  That's fast!

Now that your DNS changes are done, you must go and configure your webserver software to handle this new subdomain, otherwise, your visitors will simply get an error message when they try to use the new subdomain.

The error will look like this:

This is what it looks like when the webserver is configured correctly.

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