Understanding Alter Source IP

[Chew]

Hi All

Could you help us? We're attempting to understand 'Alter Source IP' in the Advanced Configuration page of GIT because we are exploring it as a solution to getting our Rome Total War games joinable. The evidence that the setup is almost working is that we can see games in the LAN list.

Please could somebody explain how to use the 'Alter Source IP' section of the advanced config page and maybe let us know if we're barking up the right tree?

Many thanks, in advance :)
_______________________
SITE A
game pc 1
laptop(XP sp2) connected to Win2K server (via switch),

- GIT [Client]

internet server
Win2k Server connected to Blueyonder Cable Modem
-ICS (forwarding port 213 TCP to laptop IP)
-ZoneAlarm (permitting TCP 213 in&out)
_______________________
SITE B
broadband router connected to blueyonder cable modem
-NAT forwarding TCP 213

game pc 2
PC (XP sp2) connected to broadband router

- GIT [server]

[Ark]

Alter Source IP does just that, it alters the source IP address of all packets matching the "from hostname", and changes the packet to the "to hostname". It does this to packets it captures on the LAN before tunneling them, so they come out the other side of the tunnel appearing to be from "to hostname" when they were really from "from hostname"
This *is* explained in the readme.txt that comes with the program.