MACAddress

• This is a physical address as opposed to a logical address
• cf IPAddress
• Also referred to as hardware addresses, physical addresses, burned-in addresses or less commonly MAC-48 or EUI-48.
• 48 bit address usually written in hex form hh:hh:hh:hh:hh:hh where h is a hex digit
• Left-most 24 bits are the OUI
• Right-most 24 bits are the Device ID - a unique code given to each device manufactured by that organisation
• Some network interfaces allow for their MAC address to be changed
• In theory, they’re unique to the network card installed on a device, but the number of device-identifying bits is limited, which means manufacturers do reuse them. Each manufacturer has about 17 million available addresses (16^6), so when it burns a device with a MAC address ending in ff:ff:ff, it starts again at 00:00:00. This approach assumes it is highly unlikely two devices with the same address will end up in the same local network segment.