I have a Macbook Pro running Mountain Lion and a desktop computer with Ubuntu 12.04. The Macbook is connected to wifi, but I currently don't have a wifi adapter for the Linux box (nor is it anywhere near my router). I'm trying to temporarily ghetto-rig my system so that I can test some software I'm developing.
At the moment I have the two computers connected via ethernet, and I'm successfully using the Macbook's "internet sharing" to access the internet on the Linux box. However, to test my software I need to access the server remotely using my router's external IP, which means I need to forward a port to the Macbook, and then forward it again to the server.
My issue is I cannot get my Macbook to forward anything to the other computer. I tried using IceFloor and then tried a combination of ipfw and natd, as per tutorials I found online. But to be honest I actually know very little about these programs, so when the tutorials didn't work I was stumped.