windows server 2003 gateway

I have on my windows 2003 server only one network adapter, and I assigned to it 2 different ip from different subnet – 10.x.x.10 (lan) and 82.x.x.113 (wan static IP).
The clients are connecting with subnet of 10.x.x.x and they reach both of the server’s ip – 10.x.x.10 and 82.x.x.113, but they cannot go to the wan, even not to the gateway that the isp gave me, which is 82.x.x.1 (and the server can reach all the wan including gateway)

Maybe i have to use windows 2003 RRAS (routing and remote access service) to make all this working ?