[Sussex] modem connection

John Crowhurst fyremoon at fyremoon.net
Wed Oct 29 19:15:10 UTC 2003


> Hello sussex,
>
>   Well fellas I give up.  I cant find whats wrong (ive tried all the
> pppd faq's and man pages).  Can anyone help?

Try switching on debug so you can see what pppd is actually doing, it
could be the authentication phase is setup wrong.

Simply add the word debug to your /etc/ppp/options file, then try to
connect again. The debug will go to syslog (check your /etc/syslog.conf to
see where debug goes to, possibly in /var/log/debug.)

If the problem is in the authentication phase you may see something like
this example in the debug log:

sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x926a6327> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x82 <asyncmap 0xa0000> <auth pap> <magic 0xf622e6de>
<pcomp> <accomp>]
sent [LCP ConfRej id=0x82 <auth pap>]
rcvd [LCP ConfAck id=0x1 <asyncmap 0x0> <magic 0x926a6327> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x83 <asyncmap 0xa0000> <auth chap MD5> <magic
0xf622e6de> <pcomp> <accomp>]
sent [LCP ConfRej id=0x83 <auth chap MD5>

The LCP Conf bit is important, and in the above example:
1) The pppd initates a request to the server,
2) The server requests to use pap authentication,
3) The pppd rejects the request to use pap
4) The server acknowledges the pppd's response and attempts something else.
5) The server requests to use chap authentication,
6) The pppd rejects the request to use chap

Effectively, this connection will fail as it tries a few times to
authenticate then drops the connection.

The debug option provides lots of useful information to track down where
the problem lies in the connection stages.

-- 
John






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