MAC address stands for Media Access Control address. The MAC address is the hardware layer address. MAC addresses are supposed to be unique and non-repeated--often referred to as a "Burned-In" address.
Once the MAC address is programmed into an ethernet card, it can not be reprogrammed. MAC addresses consist of a 6 byte address separated by colons (eg.) aa:bb:cc:dd:ee:ff (these bytes can also be referred to as octets since they are 8 bit hex numbers). The first three bytes are assigned to ethernet hardware manufacturers as a prefix. Every ethernet product that a company makes will use that company's registered 3-byte MAC address prefix. ETC's registered prefix is 00:c0:16.
Understanding the way Obsession displays MAC address information can greatly help in troubleshooting device and network problems. Obsession displays MAC addressing in a few different ways. Obsession displays MAC addresses in the diagnostic display, ETCNet seft-test menu, and the Multiuser configuration screen. The Obsession code has a tendency to abbreviate MAC addresses heavily.
For example, the following numbers all refer to the same MAC address:
Also, Obsession II processors and some other products use third-party ethernet cards. These cards will have the MAC address prefix of their manufacturer, not ETC's. For example, Obsession II processors may have a prefix of 00:50:04, which is one of the many prefixes registered to 3Com, the ethernet card's manufacturer.