If using Mac OS X you find yourself in a situation to test the correct functionality of a DHCP server or you need to force the lease af a different IP address from a DHCP server, you may want to change the MAC address of your ethernet network card so to be recognised as a new client of the network.
To change the Mac address with Mac OS X, you need to fire the following command:
$ sudo ifconfig en0 ether 00:xx:xx:xx:xx:xx (just modify the lat two digitas of your current MAC address)
