Re: [pptp-devel] LCP: timeout sending Config-Requests

[James C. <jam...@hp...>]

On Sat, Oct 16, 2004 at 08:52:59PM -0700, Richard Gong wrote:
> I can't get the pptp client work. It has the following
> error:
>     sent [LCP ConfReq id=0x1 <asyncmap 0x0 <magic
> 0x8d2b2758> <pcomp> <accomp>]
> After trying several times, it terminated by timeout.

This shows an inability to send GRE packets to the server, or for the
GRE packets from the server to arrive back at the client.
http://pptpclient.sourceforge.net/howto-diagnosis.phtml#lcp_timeout

> The error is got when I run tcpdump -i ppp0
>     ioctl: No such device

At this stage, there is no ppp0 because the tunnel is not established.
To check the GRE data flow, run tcpdump against eth0 instead.
http://pptpclient.sourceforge.net/howto-diagnosis.phtml#tcpdump says
this "Give to tcpdump the name of the network interface that connects to
the PPTP Server, which for dial-up users would be ppp0, and for ADSL
users eth0."

We cannot make an assumption as to what it would be for you, so I don't
see that I need to change this.

On Sun, Oct 17, 2004 at 10:42:22AM -0700, Richard Gong wrote:
> I'm using Debian sid and have upgraded the kernel to
> the newest 2.6.8 with the mppe patch also. I do need
> the mppe to connect to the server. 

By the way, the problem you reported above (LCP timeout) has nothing to
do with MPPE.  It would happen regardless of whether the server or the
client required or didn't need MPPE support.  LCP is the link control
protocol.  MPPE is negotiated in the compression control protocol (CCP)
which occurs after LCP is successfully started.  Your error so far shows
that LCP is not working.

> Now the problem is like the pptp client doesn't emulate a ppp0
> interface I think.

No, I don't think this is the problem.

> I checked the config file in /etc/ppp/peers/{VPN}, and
> it seems there's no problem. The pppd is 2.4.2; the
> noauth parameter is being used.
> Any idea?

I would use tcpdump to prove that GRE packets are being emitted by the
client in the direction of the server.  I would also check to see if any
are coming back.  If none are coming back, then the possible causes are;

a) GRE packets are not reaching the server, because they are being
dropped by intervening equipment, such as ADSL modems (which are
routers),

b) GRE packets from the server are not reaching the client, because they
are being dropped by other equipment, or because the client's firewall
rules are preventing them from being accepted.

See http://pptpclient.sourceforge.net/howto-diagnosis.phtml#gre

-- 
James Cameron                         http://quozl.netrek.org/
HP Open Source, Volunteer             http://opensource.hp.com/
PPTP Client Project, Release Engineer http://pptpclient.sourceforge.net/