Sometimes it's possible you need other path for your URLs. For example, if your server name is DEMO_SERVER, all your paths will be called http://demo_server:[port]/....
If you want to change this situation you have to create an alternate access mapping in your Central Administration and afterwards you have 2 options: modify your 'hosts' file (not recommended) and the second option is create a new host in you DNS Server.
In my example I have a virtual machine with de MOSS Server and de DNS Server in the same machine, but it's the same situation.
First of all we edit our Alternate Access Mapping, and add an internal URL:
You must have this new link like this:
Now, you only need to add this new URL in the DNS Server to be recognized by all the machines:
In this example I've used localhost IP but in a normal situation you have to put your DNS IP.
Now you must have a row like this:
If all has gone well, you have to put the new URL in the browser and confirm the new mapping is working ok: