Manually configure routing for gateway

[retrogamer]

Hi, my family's going to get Cable internet soon, and I amd definitely going to need a router, and I've got a spare PC with Linux on it and two NICs, so it will be the router. I've been searching for information on how the heck to configure the routing, though. All of the docs I have found are for Red Hat or similar, and I'm using Slackware 10 (which does not have the nice GUI configs for internet) Can anybody tell me how to configure the routing table so that packets coming from the internal network go to the NIC that connects to the cable modem (keeping in mind that the NIC gets its IP from the ISP's DHCP server)? I mean, that stuff isn't automatically configured on bootup or something, is it?

[LondoJowo]

My router using the default setup has DHCP for the WAN (ISP) side and DHCP for the LAN side. The only thing I had to do was change the setting to enable "Filter IDENT(port 113)".