JSI Tip 1466. VPN/PPTP client can not see NetBIOS resources on RRAS server with one NIC.

The NetBIOS interface only binds to the first bound Internet Protocol (IP) on a NIC.

Example:

          RRAS/PPTP                         
          10.10.0.1                        
              |                   /        \          
  LAN(1) ------------ Router  ---- Internet ---- ISP ---- RAS/PPTP client
 10.10.0.0           Firewall     \        /  

When the client dials their ISP and then dials the PPTP connection, the router is configured to accept the PPTP traffic, so the connection is made.

This causes a host route to be entered in the host's route table, because the PPTP connection is the default gateway for the client computer. When the client tries to use NetBIOS resources on the RRAS server, the IP stack on the client sends the data to the static route, which is dropped by the router/firewall.

To resolve this difficulty, install a loopback adapter on the RRAS server and give it a different IP address:

              RRAS/PPTP                         
20.20.0.1 --- 10.10.0.1                        
                  |               /        \          
  LAN(1) ------------ Router  ---- Internet ---- ISP ---- RAS/PPTP client
 10.10.0.0           Firewall     \        /  

Use an LMHOSTS file on the client to resolve the name of the RRAS server to this new IP address. Change the RRAS static pool to give out addresses on this new network (20.20.0.0).

NOTE: This makes the RRAS server multihomed. See tips 0846, 1175, and 1192.