Question 1

What is a MAC address?

Accepted Answer

A MAC (Media Access Control) address is a 48-bit hardware identifier assigned to every network interface. Written as 6 colon-separated hex pairs (AA:BB:CC:DD:EE:FF), it is used for device identification on local networks. Unlike IP addresses, MAC addresses are assigned by manufacturers — though modern devices can randomize them.

Question 2

What is a locally administered MAC address?

Accepted Answer

The second-least-significant bit of the first byte indicates administration: 0 = globally unique (manufacturer-assigned), 1 = locally administered (overridden by software). Generated/test MAC addresses should set this bit to 1 (e.g. x2:xx:xx:xx:xx:xx) so they don't conflict with real hardware MACs.

Question 3

What is a unicast vs. multicast MAC address?

Accepted Answer

The least-significant bit of the first byte: 0 = unicast (sent to one recipient), 1 = multicast (sent to a group). FF:FF:FF:FF:FF:FF is the broadcast address (sent to all devices on the segment). Generated MACs should use a unicast address (first byte ends in 0 or 2, not 1, 3, etc.).

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