I set up a VPN on Windows Server 2008 through its routing and remote access services. I connected to the VPN, and configured the client to allow for split tunneling (Internet traffic goes to my default gateway, and traffic directed to the VPN server goes through the VPN gateway).
I had to adjust the routing table, adding an entry to ensure traffic to my VPN server goes through the tunnel by running the command "route add [VPN.IP] mask 255.255.255.255 [VPN.GATEWAY.IP] IF [VPN_INTERFACE_#]". Adding the correct route makes everything work flawlessly on all my machines, except for one.
The problematic machine is a laptop that's not directly connected to a network. It connects to WiFi, and then connects to a VPN to obtain internet access. Finally, it connects to the target VPN server for file sharing. The "route add" trick doesn't work for that laptop, I'm assuming because it's connected to two VPNs, and I'm getting the routing wrong. Can anyone familiar with routing explain what routes I may need to add?