Re: PPTPD connect issue

I just now forwarded the reply I put together privately.  But I think
you already solved it.  You said you power cycled a switch and that
cured the problem for a while, right?  Was the switch at your PPTP
server site or a client site?  I'm guessing at your PPTP server site and
maybe GRE messes with this dumb switch's "mind".  We've seen stranger
things.

James thinks it's a broken consumer router - and this maybe what's going
on, and I've seen plenty of messed up consumer routers.  But you have 3
networks with 3 different routers suddenly showing the problem - right?
So look at what's common and that has to go back to the PPTP server
site.  

Unless I'm missing something, which also happens a lot. 

- Greg


-----Original Message-----
From: David Schulz [mailto:[email protected]] 
Sent: Tuesday, August 14, 2012 10:31 AM
To: [email protected]
Subject: Re: [Poptop-server] PPTPD connect issue

Hello there,

would you or anyone be so kind to forward "Greg's" reply? Its neither in
my Inbox nor in my Spam box :-(

I am happy to believe that the issue is related to client side
equipment, that would be supported by the troubleshooting and research i
have done so far. That said, is it really that simple? I have been using
a commercial PPTP VPN service for years behind NAT routers without this
kind of strange issue, and even while i could not connect to "my" VPN
when it was acting out - connecting to other PPTP VPN's was fine. I have
had this very issue in three different networks; one using a FreeBSD PF
Firewall router, one using Ubuntu with iptables, and then my own network
which uses a Linksys rv042 VPN router, nothing fancy. I would really
like to diagnose and figure out just what causes this sort of trip up,
and what do the other PPTP VPN servers have in their settings that is
different from mine?

Could you give a pointer as to what to look for during packet analysis
that would help further prove the problem to be on the client side?
Maybe a call id field with a missing value?


By the way - the log file message i am getting when things are suddenly
not working for new connections is LCP: timeout sending Config-Requests

I looked at pretty much everything that could cause the above, and
usually its related to GRE or firewall generally - or a Routers VPN
passthrough function (GRE again) - not in my case i think. 

with best regards,
D


On Aug 13, 2012, at 7:42 AM, James Cameron wrote:

> I agree with Greg, the problem is going to be in the firmware of the 
> router equipment, because it is failing to forward PPTP packets under 
> certain circumstances.
> 
> The call ID field gradually increments, and that may be a trigger, but

> so might available memory in the router.
> 
> Newer firmware is unlikely to be available for consumer routers, but 
> it may be worth checking to see if a fix is available.  Third-party 
> firmware may also be available.
> 
> You might also avoid the problem by switching to another VPN 
> technology.  PPTP requires very complex support within a router, if 
> that router performs IP address translation.  OpenVPN by comparison 
> requires no more router support than any UDP or TCP application.
> 
> --
> James Cameron
> http://quozl.linux.org.au/
> 
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Exclusive live event will cover all the ways today's security and 
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