VPN connection thru linux firewall

After reading the how to's I am confused.
I need to connect to our sister company's VPN.
I will be connecting from a win98 thru our linux firewall (linux-mandrake 6.1 using ipchains). When I try the connection without the firewall it works. But from inside the firewall the connection can not be established.

Thanks in advance for any help

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babblegeek_Connect With a Mentor Commented:
The GRE protocol is not easily handled by a Linux firewall. For starters, you may want to check:


This talks about firewalling the PPTP protocol (typically used by Win 9x machines).
this will depend on how your VPNs are set up. does the firewall do the encryption or is this done by each single client? well, i know this is quite a stupid assumption, but we should know a bit more about your (virtual private) network topology.
try to execute this on the server:
(as root of course)

ipchains -A input -p tcp -s 0/0 -d localip/32 23 -j ACCEPT
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tfree112599Author Commented:
Sorry that did not work. I have tried various ipchains commands to no avail.

if I trace with a sniffer it appears to bomb when it should be starting to pass GRE traffic.
tfree112599Author Commented:
Encryption done by each single client
uhm. that's bad. try figuring out what packages your firewall is rejecting (iptraf).
tfree112599Author Commented:
solved by patching the 2.2.13 kernal with pptp patch. Then compiling pptp as module.
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