Well according to this
»
www.netgear.com/home/pro ··· 200.aspx
the Netgear DGN2200 *is* a combo modem+router. Most such devices dont expose a WAN port. The connection between the WAN port and the modem is INTERNAL! Thats one of the reasons these combo modems suck; they make reuse difficult (e.g., as just a router).
However, according to those specs, it says:
Ethernet WANEasy Upgrade to cable/fiber
That suggests to me that you probably can reconfigure one of the LAN ports to a WAN so you can reuse it!