This post was originally published in 2008
The tips and techniques explained may be outdated.
There are many legitimate reasons why someone would want to spoof a system’s MAC address. In my case, my University binds our network ports to a specific computer’s MAC address, and only allows you to reset that address once a week. My problems start when I want to switch my two computers for whatever reason, and connect my smaller iBook to the wall (let’s say I want to keep a web server online, but wish to take my MacBook Pro on the road).
In Tiger, it was very easy to spoof a MAC address:
sudo ifconfig en0 ether 00:00:00:00:00:00
en0 is the network interface you wish to change the MAC address of, and
00:00:00:00:00:00 is the target MAC address. With Leopard, that line no longer works. No matter how much I searched, I couldn’t find a solid alternative. Turns out, it’s extremely simple:
sudo ifconfig en0 lladdr 00:00:00:00:00:00
Note: This has been tested under 10.5.1 with both en0 and en1, and at least for the wired interface it works as advertised.