Using Microsoft RRAS to setup a VPN server for PPTP is quite common; however, administrators have had a tough time configuring their RRAS Servers to enable L2TP VPN for their users. But the setup is actually quite easy once you know the exact steps to follow:
1. The ports needed to be open on your router and the Server's firewall for the L2TP protocol to work are as follows:
2. Be sure to use a different public IP address for your L2TP traffic as the primary WAN IP cannot be used for this purpose. This is mainly because if you do have VPN tunnels active on your router, the ports 500 and 4500 will be prioritized for the tunnels and won't be available to use for the L2TP traffic. So configure a secondary WAN address for all L2TP related connections.
3. You will need to add a registry key on your Server where you have configured your RRAS:
4. Login to your Server and open RRAS management console:
5. Configure your client side VPN configuration by choosing the VPN type as L2TP/IPsec and be sure to enter the Preshared secret in the step above
If you follow the above steps exactly as described, you should now be able to connect to your RRAS Server using L2TP protocol. You should also be able to have your PPTP connection working with the same RRAS server as well without any problems.