The ethernet hardware address (or MAC) is a 12 hexadecimal digit number that uniquely identifies a network interface (and usually a computer) on a given subnet. We describe how to determine this number for several operating systems, including Windows, MacOS X and Linux.

## The Ethernet Hardware (MAC) Address

MAC addresses have nothing specifically to do with Apple Macintosh or MacOS computers, although most Apple Macs will have a MAC as described below.

A media access control (MAC) address is a unique number associated to an ethernet card, by the card vendor. Proper communication on any subnet requires that each networked host interface have a unique MAC. In general, it will be unique over an entire large site such as a University and is thus useful for uniquely identifying a typical computer.

The MAC address is generally presented in one of 3 ways, as shown in the examples below:

• colon-delimited (typical Unix style) 09:00:07:A9:B2:EB
• dash-delimited (Windows style) 09-10-4A-B9-E2-A4
• non delimited: 080007A92BFC

The numbers are hexadecimal, meaning they cover the range of decimal values 0 to 15 and are represented by members of the set { 0123456789ABCDEF }.