Do you want to connect multiple LANs using Windows 2008 R2 Routing and Remote Access Service (RRAS)? This is the step by step tutorial.
First of all, you have to have multiple NICs connected to the different LANs. NICs should have an IP addresses of the LAN it is connected to. This IP address is the Default Gateway of that LAN.
On the server, go Server Manager. Right Click on Roles and select Add Roles.
Review the information and click Next.
Select check box next to Network Policy and Access Services and click Next.
Click Next on Introduction Network Policy and Access Services.
Select checkbox next to Routing and Remote Access Services. It will automatically select necessary services. Click Next.
Click Install on Confirm Installation Selection.
Click Close on Installation Results.
Go to Start, Administrative Tools, Routing and Remote Access.
Right click on your server and select Configure and Enable Routing and Remote Access.
Click Next on the Welcome screen.
Select Custom Configuration and click Next.
Select LAN Routing and click Next.
Click Finish to Complete Routing and Remote Access Setup Wizard.
Click Start Service.
Your Routing and Remote Access Server is ready. Your Private Networks should communicate now.