Using Microsoft's built in VPN (in Windows 2000 or later) is NOT always a simple matter. Using a gateway/proxy server complicates it even further. I am using ProxyPlus, and it is not capable of routing the VPN, when the PPTP protocol is used. L2TP is strictly TCP oriented, so this one should not be a problem (but I have not tried it myself), but PPTP uses the GRE 47 protocol, which is unknown to Proxyplus.
But if the proxy server is a Windows 2000 Server, it can still be used to route VPN, without using Proxyplus.
First thing that must be done is to make sure the "Remote Registry" service (started by default) and the "Routing and Remote Access" service (disabled by default) are running.
On the server, the "Routing and Remote Access" administration program in administrative tools can now be opened. Right-click the server icon, and choose "Configure and Enable Routing and Remote Access". This will take you through a wizard, where you should choose to configure the server as an "Internet connection server". Then you should choose to "Set up a router with the Network Address Translation (NAT) routing protocol". Finally, choose the right connection to the internet when selecting "Internet connection". On the client, the gateway should of course be set as the default gateway. Note, it is not necessary to "share" the internet connection on the gateway.
That is basically it! Now you can create a new network connection, choosing "Connect to a private network through the Internet", and specifying the server ip address. Make sure the PPTP protocol is selected on the new connection.
Note, that the firewall will probably need some configuring the first time you connect. Note also, that this routing capability actually allows for a lot more traffic to go through the server than just the VPN, so be carefull. You ought to have a personal firewall on your client machine as well. You still have a privileged ip address though, so outsiders still cannot "see" your computer.
Last revised: 2006-04-01