this may help. quoted from
How to Setup A Site-to-Site VPN Connection
To setup a Site-to-Site VPN Connection , you may need to configure two windows servers for the Answering and Calling Routers. Here are the steps:
1. Run RRAS, on Configuration page, select LAN routing.
2. Configure VPN on the Answering Router.
3. Configure the Demand-dial Interface on the Answering Router.
4. Configure VPN on the Calling Router.
5. Configure the Demand-dial Interface on the Calling Router.
6. Confirm the Remote Access Policy Configuration on the Answering and Calling Routers.
Robert Lin, MS-MVP, MCSE & CNE
Windows, Network, Internet, VPN, Routing and How to at