To configure Windows Server 2003 to act as a router for your LAN:
1. Open the Routing and Remote Access snap-in from the Administrative Tools folder of your Start menu.
2. Right-click the server in the left-hand pane and press Configure and Enable Routing and Remote Access.
3. Follow the on-screen instructions.
NOTE: See Configure the Corporate Network which I extracted from Help and Support.
4. Right-click the server and press Properties.
5. Select the General tab and verify that the Router check box and option are set and correct.