How can I set up multihoming?
Got it. All you have to do is add multiple Ethernet interfaces in Network Preferences. And then just configure each one to the correct settings and you're set to go. I tested this by hosting two different websites on two different IPs by multihoming my iMac and it worked!


System Prefs -> Network dialog
Press the + button and select the interface you want to add to (you may need to go back  and identify which one if you have multiple Ethernet ports).
Name the service and press "Create"
Configure the new service as you would a static (manual) interface
Click "Apply"