Hmmm...sorry I wasn't able to come back to this last night...I've been very busy...
As far as your router goes...you shouldn't be having a hardware problem if you're getting on the Internet. Okay....so you tried forwarding ports 6112~6119, right? No go with that. Tried DMZ, no go with that...
Are your rigs set to get the IP address from DHCP server?
If so, then assign each computer an IP address. Go to your setup menu, I think it's in...look for the tab that lets you set the starting IP address and the number of clients.
Set the starting IP address to something like...192.168.1.130 with 10 clients (or more if you havemore than 10 rigs hooked up). Now you can assign your computers any unique IP address from 192.168.130~192.168.1.139. Normally your DHCP server within the router will do it, but it won't object to you manually setting them as long as they're all unique. To assign an IP address to a computer, just go into the network settings and manually enter the IP address. (Leave DHCP server on) Remember not to duplicate, remember which IPs are assigned to which rigs, and make sure that you don't connect until you have established them all...or turn off your router first. Try the port forwarding feature again and forward to the IP addresses of the rigs you want.
That's the best way to set up your network, IMO. If you don't want to go through this, you can just check your IP addresses on the DHCP client table to see which rigs have been assigned what IP. Then for the rigs you want the ports opened for, open the ports for thoseIP addresses. I believe that's what you were confused with earlier. Pick whichever one you want. Both should work...if not, then I'm stuck...