Local Network Access Fails Or Is Slow After PPTP Connection

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SYMPTOMS

You may experience slow connections and performance or even loss of connectivity on your local area network (LAN) after you have made a Point- to-Point Tunneling Protocol (PPTP) connection to a Windows NT 4.0 PPTP server.

CAUSE

Windows NT 4.0 PPTP clients add an incorrect local subnet route to their route tables when they connect to a PPTP server that is using the same IP network ID.

For example, the client and the server are both on LAN subnets of a class B address such as 172.16.0.0, using a 255.255.255.0 subnet mask. The server is on the 172.16.1.0 subnet and the client is on the 172.16.2.0 subnet. When the client connects through PPTP, it adds a route to the 172.16.0.0 network with a gateway of the PPTP server to its route table, which increases the time it takes to locate LAN resources.

NOTE: If the PPTP server has no route to the PPTP client's subnet, the client will not be able to connect to its local subnet.

RESOLUTION

To work around this issue, use the following steps:

1. Disable Use Default Gateway on Remote Network for the phone book entry that you use to dial the PPTP server.

   NOTE: If Use Default Gateway on Remote Network is not checked, the bad local subnet route is not added.

2. Delete the existing default gateway (if one exists) by typing the following at a command prompt:

         Route delete 0.0.0.0
   

3. Dial your PPTP phone book entry to make the connection to your PPTP server.

4. Add a new default gateway to the PPTP network by typing the following at a command prompt:

         Route add 0.0.0.0 mask 0.0.0.0 X.X.X.X
   

   Where X.X.X.X is your client's IP address assigned by the PPTP server.

5. After you disconnect, re-add your local default gateway by typing the following command at a command prompt:

         Route add 0.0.0.0 mask 0.0.0.0 Y.Y.Y.Y
   

   Where Y.Y.Y.Y is the IP address of the default gateway, or router, on your LAN.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.