I have a RedHat 7.1 (2.4. kernels) acting as a firewall for a private IP
network, the firewall is done with iptables.
I want to enable incoming Microsoft VPN connections to a Microsoft VPN
server that is behind the firewall (in a private networks address, the
firewall does NAT). How do I configure iptables to do that ? The port that
need to be forwarded is 1723 but then there is a GRE packet (IP Protocol 47)
that also needs to be forwarded. This involves no ports, so can it be
forwarded based on its protocol.
The reason I can't use Linux PPTP server (PopToPoP or whatever) is that I
have an internal ADSL card on the linux box, and it's driver is precompiled
so I cannot do anything with the kernel.