You should be able to find detail on this with a web search. I'd start by putting this line in a startup file
Code:
echo 1 >/proc/sys/net/ipve/ip_forward
Give some fixed IP to your local nic (which is beginning to sound more like a server than your server!) & run a dhcp server on it. You'll have to configure that. Add a fixed default route from your server to your own box, and connect them via dhcp. That might work, or at least give interesting errors