It looks like all you want is just a Linux router. A gateway joins two or more disimilar networks, I believe. Like ethernet<->token ring or ATM<->FDDI. Check out the following packages :
zebra ipchains There are other ones that I can't think of right now. :) I'm pretty sure there is a linux router How-To as well. +-------------------------------------------------------------------+ | -=I T ' S P R I N C I P L E T H A T C O U N T S=- | |=- -=ALAN KEYES FOR PRESIDENT=- -=| | Balanced Budgets Personal Freedoms Morality Lower Tax | |=-- http://www.Keyes2000.com. --=| +———————————————————————————————————————————————————————————————————+