2.1 MAC address:
MAC address (Short for Media Access Control) is assigned at the factory to a network device such as NIC. MAC address is protocol independent. Layer 2 devices such as switches, and bridges use MAC address to distinguish between different nodes in a network segment. Compare this with Layer 3 devices such as router that use IP address for transporting packets between different networks (or sub-networks).
Layer 3 addresses are logical addresses as they are assigned by the protocols, whereas Layer 1 addresses are physical addresses, and can't be changed without changing, for example, a network card (NIC).
2.1.1 MAC address Format:
A MAC address on a network is a 12-digit hexadecimal number (total 48 bits) in the format:
The first half of a MAC address contains the ID number assigned to the adapter manufacturer.
The second half of a MAC address is the serial number assigned to the adapter by the manufacturer.
You can find the MAC address on your computer by typing "ipconfig /all" at the command prompt of a Windows OS computer.
In the figure above, the value 00-C1-26-0D-DE-C9 represents the MAC address of the host named "system". Whichever higher layer protocol you use, the MAC address remains the same. In the MAC address given, 00-C1-26 is NIC manufacturer ID, and 0D-DE-C9 is the serial number given to the adapter by the manufacturer.
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