This has more to do with naming and the DNS/WINS system than your web
Basically, your users (their PC's) have to be able to recognize a URL / name
as 'pointing' to your server.
If you have a DNS server, for example, you can just add a record that says
'internal.mycorp.com' points to the IP address that myserver points to.
The WORST way to do this is to update their HOSTS files. A more elegant way
to do it is to install a DNS server, and setup the name records. If you
have a handfull of users, the HOSTS file entries will work. Otherwise, the
DNS server setup is faster, and will be a better infrastructure for you
== John ==