Ethernet and ARP
MAC address
The 48-bit address of a network card, used to deliver frames within one network.
Written as six hex bytes, 02:42:0a:00:01:0a. Frames on Ethernet and Wi-Fi are addressed by MAC; IP addresses
are only looked at once the frame arrives. A MAC address never leaves its own network: a router rewrites both MAC
addresses at every hop, while the IP addresses stay the same end to end.