[pptp-server] Failing encrypted PPTPD connections

[Michael Kranz]

Hi,

we're facing serious problems connecting Win2K-clients over encrypted
PPTPD with our Linux boxes. We've seen similar entries in your
mailing-list. As we need a solution quickly and as we probably have to
evaluate possible alternatives, we need an answer to the following
question:

Is it definitely so, that a lost GRE-packet over an _encrypted_ VPN
connection makes the tunnel inoperable? Or do you know of a patch or an
intermediate solution?

Follows the problem description in detail:

(1) The PC is a Win2K box with 128-Bit Patch, the PPTPD server is
running SuSE 7.0, PPPD 2.3.11 and PPTPD 1.1.2.

(2) Configuration (see attached protocol): at 12:07 the direct analog
connection is established between:

PC <--> Cisco

An automatic forwarding establishes the VPN tunnel to our firewall,
which runs the PPTPD:

PC <--> Cisco <--> Firewall <--> Target

The connection has as IPs

172.20.70.3    (PC)
172.20.0.250   (Firewall / Interface to Target)
172.31.254.254 (Firewall / Interface to Cisco-Transfernet)
172.20.0.X     (Target)

(3) The connection is working. At 12:09 the client starts a webinterface
to mailserver (172.20.0.3); during the login process no response comes
back, s. attachment near 12:09:47, where you'll see the out-of-order
packets. From this time on, the tunnel is dead, despite the fact, that
packets continue to be exchanged, until the connection is ended by the
user at 12:32.

Many thanks in advance
Michael
-- 
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SuSE Linux Solutions AG          Mail:    Michael.Kranz at suse.de
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