Troubleshooting PPP

If you are having trouble getting PPP to work, here are a few suggestions for troubleshooting.

If the modem doesn't dial:

• Verify that you have selected the correct device for your modem. Remember that FreeBSD uses /dev/cuad # for its device names, not /dev/cuaa # as on some other systems.

• If you are using an older system, try reducing the speed to 57600 or 38400. Some older systems without high-speed UARTs cannot handle 115200.

• Verify your chat script or set dial line. Check your modem documentation to see whether you need to be sending it some initialization string other than the default one in the FreeBSD configuration files.

If the modem dials but fails to establish a connection:

• Verify that you are using the correct authentication type for your ISP (CHAP, PAP, or shell login).

• Verify that you are using the correct login name and password for your ISP.

• Verify your chat script or set dial line. Check your modem documentation to see whether there is an initialization string you have to send.

• If you are using user PPP, you might want to try kernel PPP instead. (I personally had a modem/ISP combination once where kernel PPP worked fine; but user PPP, for whatever reason, simply refused to work with this particular ISP.)

If a connection is made but attempts to access remote hosts by host and/or domain name fail:

• Verify that you have the correct DNS servers listed in /etc/resolv.conf. Also, verify the correct setup of the /etc/host.conf file. It should have a line that reads hosts followed by a line that reads bind.

If the preceding suggestions do not correct the problem, try turning on logging and then attempt to connect again. Logging can be enabled by adding a line to /etc/ppp/options that reads debug for kernel PPP and by changing the set log line in /etc/ppp/ppp.conf to read All for user PPP. Messages from kernel PPP will be logged to /var/log/messages, and messages from user PPP will be logged to /var/log/ppp.log. You can monitor the messages as they are being sent by typing tail -f /var/log/messages or tail -f /var/log/ppp.log. This will show you the last 10 lines of the file and also update the display each time the file changes.

The information logged is fairly technical. You might be able to spot the problem yourself. If you can't, the contents of the log can still be useful to your ISP if you can get them to help track down what's going wrong. If they can't figure it out either, they might be able to call their RAS vendor and let them look at your logs to diagnose the problem.

The information presented in this chapter should be enough to get most people up and running with their ISPs. However, both kernel PPP and user PPP are extremely esoteric, and this chapter cannot cover all the options available, especially considering the waning popularity of dial-up Internet access in favor of broadband solutions. If you need to do more advanced PPP configuration, both kernel PPP and user PPP have detailed man pages that describe all the options available. The kernel PPP man page can be accessed with man pppd, and the user PPP man page can be accessed with man ppp. In addition, sample configuration files are located in /usr/share/examples/ppp.