Q: PPP gives a "connection terminated" error message. How do I diagnose this situation?

Trying to get PPP work under Linux on my workstation, I run the following command:

pppd /dev/modem -detach 38400 debug crtscts connect "/usr/sbin/chat -f /root/ppp-hack/yale"

where "/root/ppp-hack/yale" is just my own chat scripts. The /etc/ppp/options file contains just the single "lock" option. The chat successfully establishes the serial connection, but then the configuration complains about the following:

Aug 13 01:17:18 duck pppd[2832]: pppd 2.2.0 started by root, uid 0
Aug 13 01:17:52 duck pppd[2832]: Connect: ppp0 <--> /dev/modem
Aug 13 01:18:22 duck pppd[2832]: LCP: timeout sending Config-Requests
Aug 13 01:18:22 duck pppd[2832]: Connection terminated.
Aug 13 01:18:22 duck pppd[2832]: Receive serial link is not 8-bit clean:
Aug 13 01:18:22 duck pppd[2832]: Problem: all had bit 7 set to 0
Aug 13 01:18:22 duck pppd[2832]: Exit.

A: The messages...

> Aug 13 01:18:22 duck pppd[2832]: LCP: timeout sending Config-Requests
> Aug 13 01:18:22 duck pppd[2832]: Connection terminated.
> Aug 13 01:18:22 duck pppd[2832]: Receive serial link is not 8-bit clean:
> Aug 13 01:18:22 duck pppd[2832]: Problem: all had bit 7 set to 0
> Aug 13 01:18:22 duck pppd[2832]: Exit.

...usually indicate that the connection was dropped by the other end. The most common cause for this is a security violation at the other end. For example, if the other end is using PAP or CHAP for authentication and you are not setting PAP or CHAP at your end.

Check with your PPP provider to make sure you are using the correct security protocol and passwords.

Another thing you can do is give the -v option to chat to make sure the login sequence is progressing as you expect. For example:

pppd /dev/modem -detach 38400 debug crtscts connect "/usr/sbin/chat -v -f /root/ppp-hack/yale"

This will cause chat to log the session to /var/log/messages. Try this and check that your chat script is proceeding as you expect.