Making the Calls Configuring and Testing Layer 2 Connections

84 When dialing into an ISP that doesnt support PPTP, youll need to initiate a PPP call to the ISP using the Dial-Up Networking dialog box. Once the call has been connected, leave your PPP session up, select the PPTP entry you made in our case, its called Central Office VPN, and click the Dial button. This will initiate the PPTP call to the corporate RAS server over your PPP Internet connection.

5.6 Troubleshooting Problems

What do you do if your system doesnt connect? Is the trouble with your remote users ISP, the Central Offices ISP, with the Internet itself, or with the configuration on the RAS client or server? Because of all the factors involved, problems with VPN connections are some of the most difficult to track down.

5.6.1 Login problems

For dial-up RAS users, the most common problem in getting connected is working with the modem. In that case, all troubleshooting can be done on the client side. Authentication problems bad usernames or passwords, or incorrect authentication type follow shortly thereafter, and often require that someone look through the logs or watch the connection attempt at the destination RAS server. Windows NTs Event Viewer and Dial-Up Networking Monitor help you isolate such login problems.

5.6.1.1 The Event Viewer

The Event Viewer is the common logging system on all Windows NT machines. It can be found from the Start menu under Programs Administrative Tools. Lets say that Sara N. is having trouble dialing in—she seems to be having negotiation problems and isnt sure why. When you bring up the Event Viewer, look at the Source column for any RemoteAccess messages that occurred at the approximate time she was attempting to dial in. In the left-hand column, there are icons that distinguish informational messages an i encircled in blue, from warning messages an exclamation mark encircled in yellow, and from error messages a red STOP sign. You see a red STOP sign with the Source of RemoteAccess at the time Sara N. was attempting to dial in. Double-clicking on it will reveal the full error message see Figure 5-12 . The error appears to stem from a DHCP negotiation problem. The next logical step would be to make sure Sara N. is set up to obtain an IP address using DHCP, and to ensure that your DHCP server is configured correctly. 85 Figure 5-12. An unsuccessful VPN connection in the Event Viewer The Event Viewer can also be used to obtain useful information about successful logins, including username, port number, time connected, port speed, and bytes sent and received. Figure 5-13 shows some of the successful connection information reported by the Event Viewer. Figure 5-13. Logout information from a successful VPN session

5.6.1.2 The Dial-Up Networking Monitor

The Dial-Up Networking Monitor is found from the Start menu under Programs Administrative Tools. It can be used to watch the status of an incoming or connected call. Not only can you watch for authentication problems, you can also see if any packets are being sent or received, and look for any connectivity errors in the Device errors section. See Figure 5-14 for the information displayed.