Virtual Private Networks, Second Edition

Troubleshooting Problems

Problems with network services, especially those related to the Internet, are sometimes difficult to pinpoint. The AltaVista Tunnel is no exception. In addition to the common Internet problems, such as throughput issues, Internet or transit provider network problems, and end user education, you must add encryption and verification issues, virtual address resolution, and a host of other specifics which must be exactly right for the tunnel to function. Of course, common sense troubleshooting is still the name of the game. When you encounter a problem connecting the tunnel, do not forget to check the client and server machines’ configuration and the Internet connection on both ends. Sometimes, as anyone who’s solved a computer problem knows, it’s the simplest problems that are overlooked. Confirm that both ends have an Internet connection and that the tunnel client and server are running on the respective machines.

Once you’ve determined that both ends have Internet connectivity, there are four main areas where a problem may reside: the tunnel server configuration, the tunnel client configuration, the local network, or the Internet gateway configuration on the tunnel server’s network.

Tunnel Server and Client Configuration Checks

The tunnel server usually will experience the most problems, especially if this server is running other network services such as a mail server or web server. Should a client or group of clients fail to connect to the tunnel, first check ...