[pptp-server] Accessing pptp over a Network behind a Firewall

Hauser Marcel marcel_hauser at gmx.ch
Mon Feb 25 10:19:52 CST 2002


Hi All

Hope this is not in any FAQ I din't read :) .... 

I'am new to this list... and I've currently successfully installed pptp
+ ppp on my Firewall which is based on RH 7.2.

Let me outline the Problem:
My Firewall is in a private network (172.16.224.0), which is my ISP's
Cable Modem Network. I have an external IP Address lets say 20.20.20.20
which is mapped to 172.16.224.30. At my Firewall I'am allowing port 1723
and Protocol 47 as explained in many FAQ's and HOWTO's.
If I put a winXP Notebook into the 172.16.224.0 Network, and try to
establish a vpn connection to 172.16.224.30 everthing is working just
fine !
BUT !! I can't connect from everywhere else on the internet.
I know it looks like a firewall issue... but that thing doing NAT at my
ISP isn't a firewall... it just does nat (allowing every kind of
traffic) !! 
The places where I try to connect to my firewall do have firewall's
aswell... but I know for sure, that they are allowing everything from
inside to outside !!

I know that IPSEC will not work in NAT Situations... but pptp isn't
using IPSEC.... what could be the problem here ??

In the logfiles I get

Sent [LCP ConfReq id=0x1 <mru 1490> <asyncmap 0x0> <auth chap 81> <magic
0x4328jfaal> <pcomp> <accomp>
Last message repeated 9 times
LCP: timeout sending Config-Requests
Connection terminated !

Any help would be very appreciated :)

Thanks in advance

Cheers Marcel






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