I have a network connection with a static IP and a headless Linux box with dual network cards between my LAN and the rest of the world. My laptop is using the OSX version of Limewire.

As I recall, the Windows version of the various Gnutella variants had an option for forcing your IP address that allows you to specify a hard-coded IP and port. The OSX version does not seem to have a place for the IP. For instance, I can select LimeWire -> Preferences -> Advanced -> Firewalls. In that dialog, I get simply a checkbox for "Force IP" and a text field for a port number, but there does not seem to be anywhere to enter the firewall's external IP address.

Is this functionality missing? Is there a different place to plug in my IP address? Is it "automagically" detected from packets and used by remote hosts?