Airport Extreme firewall? Opening ports?

[appletalk]

Hello,

I just installed an airport to our network and was reading on the apple site which said the airport comes with a nat firewall.

Is there a way to open ports, adjust, activate, or disable this firewall? Is there even a firewall built into my airport extreme?

If there is, can anyone explain how and where I would go to open up a few ports?

Thank you very much!