Internet sharing over AirPort

Can't find anything definitive from Apple, but the detailed testing done here by Princeton University indicates that it's NAT (and that it's inappropriate for use on their campus, so might well be for your scenario too).

Type:

ps ax | egrep '[ /](PID|boo|nat)'

in a Terminal or xterm window. Fire InternetSharing from the System Preferences. Type the same command again.

You will be able to see the different daemons which InternetSharing spawns under 10.6 or 10.7 .

The answer is… InternetSharing does 3 things:

• address translation through natd,
• address distribution through bootpd,
• routing through route (but I got this information through other means of investigation).