A MAC address uniquely identifies a network interface card (NIC) of a network device. A MAC address consists of 48 bits and is displayed as a 12-digit hexadecimal number. Bits 0 to 23 are assigned by the IETF and other institutions to identify vendors, and bits 24 to 47 are the unique ID assigned by vendors to identify their NICs.
MAC addresses fall into the following types:
Physical MAC address: uniquely identifies a terminal on an Ethernet network and is the globally unique hardware address.
Broadcast MAC address: indicates all terminals on a LAN. The broadcast address is all 1s (FF-FF-FF-FF-FF-FF).
Multicast MAC address: indicates a group of terminals on a LAN. All the MAC addresses with the eighth bit as 1 are multicast MAC addresses (for example, 01-00-00-00-00-00), excluding the broadcast MAC address. The multicast MAC address starting from 01-80-c2 is the BPDU MAC address, and is often used as the destination MAC address of protocol packets.
The MAC addresses of a switch are classified into the system MAC address and interface MAC addresses. The MAC addresses of an interface include the management interface MAC address, VLANIF interface MAC address, Layer 2 physical interface MAC address, Layer 3 interface MAC address, sub-interface MAC addresses, Layer 2 Eth-Trunk interface MAC address, and Layer 3 Eth-Trunk interface MAC address. The system MAC address is also called the device MAC address, which can be displayed using the display bridge mac-address command. The management interface MAC address, sub-interface MAC addresses, Layer 2 physical interface MAC address, and Layer 2 Eth-Trunk interface MAC address are the same as the system MAC address. The other interface MAC addresses are different from the system MAC address and can be displayed using the display interface command.