I’ve looked around for ages for a decent firewall generator script but I ran into problems with all of them. (No, I haven’t got time to learn about yet another firewall implementation! I gave up after ipfwadm!)
This script looks like it’ll do the business though! Just enter the network addresses of your internal lan(s), what ports you want to keep open, internal and external interfaces, and finally what networks to masquerade. Simple!
Update! Bah! Had to remove it again. It worked fine, except 2 users on our network had consistent problems connecting to our gateway for minutes at a time! Didn’t happen to anyone else though!