10.2 Server as router, bridge or gateway

I have 2 ethernet cards in an Xserve and I would like for computers attached to one card to be able to access computers attached to the other. I have turned on IP forwarding. My current configuration will let a computer on the second ethernet card ping the first ethernet card, but not ping anything attached it. The Xserve itself can ping anything attached to either card. What do I have to do? richard@illusion-arts.com