A MAC address is a unique identifier burned into equipment capable of connecting with a network, such as PC network cards. Media players with network connectivity, such as digital video recorders, have MAC addresses as well. The short answer to the title question is, no, MAC addresses do not simply change.
The Purpose of MAC Addresses
A network-capable item requires a unique identifier for much the same reasons as any other item receives a serial number. It is occasionally necessary to identify not just a model number, but an actual unit.
Finding MAC Addresses
The MAC address is a set of six pairs of characters incorporating digits and the letters A through F. To ascertain the MAC address of all network-capable elements in a computer, Windows users may enter "ipconfig /all" (without quotes) into a command windows (press "Start," then type "cmd" into the "Run" box), then scan for "Physical Address." Mac OSX users will find this information in the Network area of System Preferences.
MAC addresses are a useful element of network security, as networks may be configured to allow only certain MAC addresses to join.
Identifying Nodes' Activity
A MAC address may be used to identify which equipment performed which network activity. For example, a network with several PCs attached will have evidence that one specific PC visited one specific website.
A MAC address does not simply change, but users may "spoof" their MAC address, changing the ID it broadcasts to the network. Spoofing is accomplished in different ways depending on operating system, and there are utilities to spoof as well.
- Photo Credit Image by Flickr.com, courtesy of Vivek Patankar
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