A Media Access Control (MAC) address is the physical address, also called the layer two address, configured in a Network Interface Card (NIC).

MAC address lock down: catalyst Ethernet switches block access to a MAC address that has not been configured or learned for the switch.
  • In a lock down, the port is disabled after the unauthorized MAC address attempts access.
  • The LED for the port changes from green to orange, which signifies a link down state and prevents anyone from putting an unauthorized PC on the network.