Ok guys, so by elimination I found out exactly what the issue is. On certain gateways you can put your gateway into modem or router mode. When in modem mode, it uses NAT only and the ISP assigns your modem an IP which is public to everyone. Your machine doesn’t get an IP, only the one the modem has. In this mode, there is no routing or port translation. GGPO and supercade both work fine in this mode.
The problem comes when you put your machine into routing mode using NATP, which is NAT with port translation. Basically, the ISP assigns your modem/router an IP, then your modem/router assigns your PC and other devices on your network an IP. These are internal IP’s that the modem should forward ports to. Trouble is, it seems to work and seems to not work. I’m not sure what is breaking the port translation on this device in particular.
As I stated before, I used a port checker tool from portforwarding.com to check my ports. If I turn on WAN blocking, my modem can’t be pinged since it’s hidden from the Wide Area Network, but my ports can be tapped as open or closed. The program reports they’re open, and of course, the ports that are closed are reported as closed, too. The program eMule has a port testing option too, open those ports and it tests positive. The thing about eMule is that it uses a browser to test your ports. Oh, and of course, both GGPO and supercade work with no problems at all in this mode. The problem is, ALL of your ports are open to everyone with a public IP that everyone can see. You basically have no security in this mode.
Then, there are other sites, like Shield’s Up which can only test TCP and of course, it tests negative and reports the ports as closed. It can’t even test UDP so there is no point in checking those ports. I used another client program called nmap, with the Zenmap GUI front end, to test my ports. They all test closed or unknown. On client programs, GGPO will work and won’t work, most often not working. Supercade doesn’t even get past the log in screen and will give you a time out error. Basically, you get security with this mode, but for some reason these programs aren’t working.
So, we have a strange situation here. I’ve emailed Motorola to see what they’ll say. I’m sure I’ll get some BS and they’ll probably blame it on the cable company, and of course, I’ll email them next.
Maybe I’ll get to figure this out. Who knows.