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I am trying to understand how MAC addresses work and what their purpose is. I believe them to work like this:
Each computer on a LAN has a MAC address which can be used to identify each. When a packet goes out, my router replaces my MAC address with its own, and each step around the network the next device replaces the MAC address with its own.
If I am plugged into a modem via cable, does the modem still replace my MAC address with its own, or does my MAC address go all the way to the website that I am communicating with?
Each computer on a LAN has a MAC address
Almost: Each network card has a unique 48 bits value to identify itself. Not the computer. The distinction is moot if you only have a single network card in the computer, but it gets relevant if you have multiple network cards. – Hennes – 2013-01-01T18:00:46.033