This is not a tutorial, it's more of a note so I'm going to remember how to do something the next time I stumble again on the problem.
The mac address uniquely identifies your hardware device on the network. At times you might want to change it and assign a custom address. Maybe to test some server component or to simulate a different machine.
On Mac OSX it's pretty easy to do. Open the terminal and run:
`sudo ifconfig en1 Wi-Fi xx:xx:xx:xx:xx:xx` replacing the x's with the desired MAC address.
Though, be sure to record your original address so you can set it back. A lot of applications will fail if your Mac address is different so don't lose your original address. Always save it for savekeeping before changing it and revert back to your original mac address after you finished to test whatever you were testing.
You can enter `ifconfig en1 |grep Wi-Fi` to see what your current address is (assuming you're using WiFi), or under the hardware tab of your Network Preferences panel.
Note: running if config on en1 assumes en1 is your current network. If it's not en1 and it's en0 or anything else instead change it accordingly.