MAC Addresses and the Address Table

Every network interface has a MAC address (Media Access Control address), a unique hardware identifier burned into the device by its manufacturer. While IP addresses can change as a device moves between networks, the MAC address normally stays fixed with the hardware. Switches rely entirely on MAC addresses to forward frames, so understanding them is essential to understanding how a LAN works.

A MAC address is 48 bits long, usually written as twelve hexadecimal digits in six pairs, like 00:1A:2B:3C:4D:5E. Each pair represents one byte. The colons (or sometimes hyphens or dots) just separate the pairs for readability. This format gives a vast number of possible addresses, enough to uniquely identify network hardware worldwide.