Game Server Not Visible

Have a DI-704 router and two computers behind a fire wall. Used port forwarding to punch a hole so that I can host games (Red Faction and SOF2). The problem is I can not see the server on my other machine. I can see it if I VPN to work and then start the game of choice. What I am doing there is going back out to the internet through work's internet connection.

Any ideas.

Thanks