Q & A on The origin of Ethernet addresses Q: Where do Ethernet addresses come from, and who actually put one in my computer? A: An organization known as IEEE now administers Ethernet addresses. When a company decides to manufacture Ethernet interface cards (i.e., the circuit board that plugs into a computer and connects the computer to an Ethernet, the company must obtain enough addresses from the IEEE so it can burn one address onto each card. So, if your computer contains an interface card manufactured by 3Com Corporation, then 3Com put the address on the card. Note: have an address stored on each interface card means that if you change the interface card in your computer, the computer's Ethernet address changes. An interesting fact: when IEEE assigns addresses to a given company, the values are not picked at random. Instead, the first 24 bits of all addresses (3 octets) identify the company, and the last 24 identify a particular interface card made by that company. Thus, given an Ethernet address, it is possible to determine the company that manufactured the interface card. You can find information about Ethernet addresses on: http://www.cavebear.com/CaveBear/Ethernet/ For a list of manufacturers and corresponding address prefixes on that site, look under ``vendor codes''.