I run an Actiontec HD701D modem with NAT to an Airport extreme base station to laptop etc. As you might expect I get double NAT issues.
I tried a lot of different things to forward a port, but no luck.
Currently the airport is in bridge mode letting the modem handle the NAT, but still can't forward the port.
Also to note: firewall is off on the router, firewall is set to allow the application in OSX 10.6.3 and I did forward the port in the router. No luck.
http://192.168.0.1/. If you get the configuration for the AirPort at that address, you'll need to find its LAN IP address in the confiugration and change it to something like192.168.0.200so you can get through to the modem's configuration. – Patches Mar 13 '11 at 9:48