PPTP VPN Troubleshooting

I am having trouble connecting to an old client.  I had it working on a previous version of Ubuntu, and now they have turned my access back on for some more work.  Of course, it won’t work!

Here’s the troubleshooting story in case it helps anyone else:

I found this very helpful article that can help you through anything:

PPTP Client: Diagnosis Howto

I opened up the System Log Viewer and found some helpful error messages in the syslog.  The one that seemed most promising was this one: “pecan pppd[4367]: LCP: timeout sending Config-Requests”.

According to the Diagnosis Howto, I need to enable debugging logging to get a more specific error message.

First step was to check and make sure that I was getting debug messages in my log.  Easy enough to do:

skp@pecan:~$ logger -p daemon.debug skptest
skp@pecan:~$ tail -1 /var/log/syslog
Jun 16 16:41:20 pecan skp: skptest

Then, I opened up the options file:

cd /etc/ppp
sudo gedit options.pptp

And, I added “debug dump” at the bottom:
Adding Debug Option to PPTP

That didn’t work, so I tried the options file:

sudo gedit options

Adding Debug Dump to PPP Options file

That did the trick! Apparently, my problem is “No GRE received by PPTP Client” because I found these lines in the log:

pecan pppd[4713]: sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0xbc155d50> <pcomp> <accomp>]
pecan pppd[4713]: last message repeated 8 times

So, the next step is to “Check GRE Works”. I checked my network to make sure that it was eth1 that I was using with ifconfig (eth1 is the one with the IP address):


Then, according to instructions, I ran tcpdump:

sudo tcpdump -i eth1

At this point, it struck me that I should check the router. Sure enough it had PPTP Passthrough turned off. I enabled that and tried again.

PPTP Passthrough on Router

After clicking apply, I tried again and it worked!!!


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