PPTP and Firewalls

[Simon Bland <angel@khaosse.net>]

I'm having some trouble setting up a PPTP VPN server behind a firewall.

Internet ----- Firewall ---- LAN (Including PPTP server)

At the moment I'm forwarding port 1723 back to the PPTP server. I can
see the logs of the client connecting to the server, but when the server
sends it's first LCP ConfReq there is never any reply. I'm guessing
there is some sort of routing issue involved, but can't seem to get it
set up.

The firewall and PPTP server are both running 2.4.18 kernels with iptables and GRE tunnels set up as modules and mppe patches for the kernel and for pppd, both are Debian stable.

I know the VPN configs are fine as I can get it working if the VPN runs
on the firewall, but I'd really rather not have the VPN running on the
firewall if I can get around it.

Thanks for any suggestions/help.