PORT FORWARDING MINI HOWTO WITH LINUX 2.2.X

It's this easy... This is the script that I use to forward along HTTP traffic.

#!/bin/sh
## BEGIN port forwarding
SOURCE_IP=(your source IP goes here)
SOURCE_PORT=(your source port goes here)
DEST_IP=(your destination IP goes here)
DEST_PORT(your destination port goes here)
export SOURCE_IP SOURCE_PORT DEST_IP DEST_PORT
/usr/sbin/ipmasqadm portfw -a -P tcp -L $SOURCE_IP $SOURCE_PORT -R $DEST_IP $DEST_PORT
## END SCRIPT

This method works for SMTP, HTTP, or just about any other TCP/IP based protocal. If you want UDP, read the man page for ipmasqadm (hint.. it's -P). This simple script is only meant to get you started.