[pptp-server] Error 650

[robert]

While trying to find the cause of my error 650 (see previous posts for 
details), I came across a reference to a GRE enabled version of traceroute.  
The reference didn't say where to get though.  I found the patch (and had to 
create a new patch to update the docs).  I have rpm versions available at my 
site http://home.swbell.net/berzerke/.  Both source and binary rpms are 
available.  Mirroring is permitted and encouraged.

Unfortunately, I haven't quite figured out how to properly interpret the 
results yet, or fix the problem.  Doing a traceroute to port 1723 succeeds (4 
hops, I'm using the same provider), put with GRE packets, it fails at the 
fourth (and last) hop.

If anyone can tell me what this means, I would appreciate it.  The obvious 
answer: "The last hop doesn't accept/return GRE packets." does work because 3 
other pptp clients can connect fine.  If GRE packets are blocked, they should 
not be able to connect either.