I am currently using a linux slackware box as a gateway to share my adsl internet connection with the other computers in my house. I currently have the following in my rc.local

ipchains -P forward DENY
ipchains -A forward -s 192.168.1.0/255.255.255.0 -j MASQ

This has mostly been working well except for a few problems. The main one is for directplay based games such as jdoom and total annihilation (probally the more main stream ones also), I cannot connect to any other servers, I might possibly be able to start my own server on the linux box (under wine), however this is quite anoying and not to many games will run like that.

Also i hear that ip tables is better, what would the equivilent of the one above be in iptables. Also what about security issues, what should i have setup. I am currently running a webserver and a ssh server.

iptables is better, look on google for the answers. What distro are you using?

You need some more masq helper modules.. eg

root@Box3~# lsmod
Module Size Used by
3c509 5996 2
ip_masq_pptp 5924 0
ip_masq_icq 13432 0 (unused)
ip_masq_ftp 3708 0
ip_masq_irc 2168 0 (unused)
ip_masq_quake 1448 0 (unused)

Have a read of this tutorial and then a look at Firestarter and Shorewall packages.. for iptables.