[olddude]

Found this:

There is a maximum of 20 Port Mapping entries that can be made in an Apple base station configuration. If you use an AirPort Extreme or AirPort Express base station there is an option which can be helpful in the case where you need many ports opened to a single computer. This is the Default Host option. When using this it is not necessary to use Port Mapping at all as all ports will be opened to the specified Default Host. This is found in Base Station Options. The default IP address for the Default Host is 10.0.1.253. You may change this IP address. The target computer must be Manually configured as specified above with the same IP address. Since all ports are now open to this computer, you should enable and configure the Mac OS X firewall on the default host computer to protect it from intruders.

I can't figure out from this if I can assign a private port, or if all are open, public and private. Any ideas?

Thanks!