If you have a LAN and not two computers set to two Independent External IPs, it is probably a Modem/Router combo.
Which means that you probably saved a couple of bucks on a Switch and sooner or later you would not like this arrangment.:shocked:
When you had it with this setting, make the Modem/Router combo work as a Modem only, and buy yourself a nice "real" Router.:beer:
:sun: