At one time or another, you may find it necessary to have two network interface cards (NICs) with the same physical network, or Media Access Control (MAC), address. This could be for a number of reasons including the testing of your internal network, software experimentation, or bypassing software protection mechanisms. This paper examines the design of typical NICs and the process used to change the MAC address stored in non-volatile memory on the card.

Paper: MAC Address Cloning

Originally released on the L0pht Heavy Industries website.