MAC Addresses

What is a MAC Address?

All hosts that have an IP address also have a MAC (Media Access Controller) address. Unlike IP addresses which are virtual, MAC addresses are fixed hardware based addresses that never change. They are programmed into a device when it is manufactured and all MAC addresses are globally unique. They are assigned and managed by the IEEE registration authority.

MAC addresses contain six eight-bit fields expressed as hex numbers.

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A switch has a Media Access Controller, but no MAC address. It is transparent to the network. It is never the final destination for network traffic, so it doesn’t need a MAC address. A router, however, has two MAC addresses: one used for the local network or LAN, and one used for the Internet or WAN.

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