MAC = Media Access Control
Each Ethernet device has an assigned unique MAC address. This MAC address corresponds to the hardware unique name of the product. It may be compared with the DNA of a human.
This address is fixed during production by the manufacturer and can’t be changed.
Each Ethernet device inserts its unique “MAC” address into each message it sends out. The port on the switch used for a given MAC address is automatically learned when a frame is received from that address. Once an address is learned, the switch will route messages to only the appropriate port, instead of broadcasting messages out all ports like a hub. A time stamp is also placed in memory when a new address is learned. This time stamp is used with the aging feature, which will remove unused MAC addresses from the table after 300 seconds. If a device moves, the associated port on the switch will be changed (migrated) as needed.
In most switches, up to 2,048 MAC addresses can be stored and monitored at any time.