Seth tells me that in the Linux world, people are accustomed to doing something called "one-armed routing." That's where you route on a single Ethernet interface, by creating a fake virtual interface that has an internal network address as well as the real interface with the real network address. I used to do this under OS 9 with IPNetRouter when I had a machine acting as a NAT/DHCP box running on a DSL modem in my old building.

Does anyone know how to do one-armed routing under OS X on Airport? This could be incredibly useful in situations where, for some reason (having paid a subscription fee, having an authenticated MAC address, having a superior antenna) one user has access to a WiFi network but others don't -- you could republish the network around your machine and share it with others. Right now, I usually accomplish this trick by connecting my Airport base-station to my iBook with an Ethernet cable and bridging whatever connection I can get onto down to the AP. It would be handy to pull this off without the Airport AP. Any ideas? Discuss