Firewalls: [no subject]

["A.Bygrave" <max @ buckscollege . ac . uk>]

I have heard that there is some software which can
sit on your server and allow one to operate an internal
addressing scheme and communicate with the internet on
another addressing scheme. I was told this was known as
'Firewalling' but I am not sure whether this is the correct term
for it. If you have any information on this can you please let me 
know. Thanks.