Exposing Internal Host on Private network to Internet

[Bobby Hitt <Bobby.Hitt@bscnet.com>]

Hello all,

I have a network using Linux as a gateway/firewall running NAT. This works
perfectly to allow 5 internal hosts running Windows 2000/XP/Win98/Linux
access to the Internet. Also the Linux gateway is running openVPN which
allows me a secure connection to my Linux server in Connecticut for my
Windows machines.

I have setup a Windows 2000 Server on my network here running VPN server
that I want to be exposed to the the outside to allow Windows clients
running the VPN client to access the inside network here via the Windows
2000 server. I know I need to route ports 1723 47 for PPTP and 500 and 50-51
for IPSec to the Windows 2000 Server, but have no idea how to do this with
iptables.

I used to run a cable router that allowed one host to be exposed to the
Internet, which is how I want to setup the Linux router.

Any help is appreciated,

Bobby