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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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
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.
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tfree112599Author Commented:
Encryption done by each single client
uhm. that's bad. try figuring out what packages your firewall is rejecting (iptraf).
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).

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tfree112599Author Commented:
solved by patching the 2.2.13 kernal with pptp patch. Then compiling pptp as module.
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