I had something similar happen recently, where my modem would dial out,
but no useful connection resulted.  I turned on pppd's debugging, and
discovered that pppd was (correctly) rejecting my ISPs request for PAP
authentication, followed immediately by another request from the ISP's
side.  This went on indefinitely (not so correct).  (It seems my ISP had
enabled PAP on some of their dial in lines, but not all...)

Anyway, the moral here is to use the existing debug tools to see what's
happening.  In pppd's case, that means setting the debug option in your
/etc/ppp/options file, _and_ enabling daemon.debug mesages within your
/etc/syslog.conf file.  (Don't forget to restart syslog after making the
latter change.)

On 25 May 1998, John Darrow wrote:

> In article <Pine.NEB.3.96.980525172244.521B-100000@localhost>,
> Bjoern Labitzke <hermit@labitzke.isdn.cs.tu-berlin.de> wrote:
> 
> >Hello...
> 
> >Some time ago (May, 2nd according to the file checkin date)
> >src/usr.sbin/pppd/pppd/lcp.c got changed. Since then I have been unable to
> >connect to my provider correctly. The connection was established, sending
> >of data seemed to work, as the modem seemed to report answers (e.g. for
> >pings). The problem was, that no data came through the pppd back to th
> >system. So I didn't get ping-answers or anything else to see. I used an
> >old version of pppd to circumvent the problem. A few minutes ago I
> >stumbled across that problem again as I did another build. So I looked for
> >the problem and found the offending changes. Since May 2nd quite some time
> >has gone by and no other persons seem to experience that problem, so I
> >describe it here first, but will send-pr it, if needed. 
> 
> Actually, I've had a similar problem recently.  In my case it was pppd
> running on the receiving end (I dial into my office NetBSD machine), but
> the symptoms were the same - the modem connects fine, pppd runs, but I'm
> unable to make any useful connections through the link.  I ended up
> using the 1.3 pppd to bypass the problem, as I didn't have time to try
> to track down exactly which changes in pppd caused the trouble.  So go
> ahead and send-pr it, it's not just your setup.
> 
> >I have to point out, that I didn't try to understand the problem really, I
> >just backed out the most probable part and I found it to work again. Here
> >is the diff:
> 
> [ diff snipped ]
> 
> Unfortunately, I'm leaving this afternoon for the Black Hills, so I won't
> have a chance to test out your diff.
> 
> >Thanks in advance...
> >-- 
> >Bjoern Labitzke   | E-Mail: hermit@cs.tu-berlin.de
> >PGP-Key available | Use PGP! Or don't you use envelopes for your letters?
> 
> -- 
> John Darrow  (ISCA:  Jdarrow)  (ICQ:  1725164) <*>
> Lab Associate for Academic Computing, Science Division
> Wheaton College (IL)
> John.P.Darrow@wheaton.edu
> 
> -----BEGIN GEEK CODE BLOCK-----
> Version: 3.12
> GCS/M>AT d+ s:- a22 C++(++++) UBUH++++$/AS+++/L+ P+>+++ L- E--- W++
> N+++(*) o K++ w(+)(---) O? M(+)(--) V-- PS@ PE(+) Y+ PGP>++ t* 5+++
> X+ R tv+ b+>+++ DI++++ D+ G+ e++(*) h--(*) r y- 
> ------END GEEK CODE BLOCK------
> 
> 

-----------------------------------------------------------------------------
| Paul Goyette      | Public Key fingerprint:    | E-mail addresses:        |
| Network Engineer  |   0E 40 D2 FC 2A 13 74 A0  |  paul@whooppee.com       |
| and kernel hacker |   E4 69 D5 BE 65 E4 56 C6  |  paul.goyette@ascend.com |
-----------------------------------------------------------------------------