Cant you set up a virtual server on the router for the relevant port? I have this capability on my home's D-Link 614 and the Cisco's I have at work. Both allow routing of game servers, even though we never have time to actually play the damn things
'Fraid I've never used Belkins, but if they are running a BSD, they should be willing to tell you how to access the routers configs and let you change things there.
Regards,
Ben