Last updated: 2/2/02
Q. What is an Ethernet MAC address?
A. MAC = Media Access Control. Each
and every Ethernet device interface to the network media (e.g., network adapter,
port on a hub) has a unique MAC address, which is "burned" into
the hardware when it is manufactured. MAC addresses uniquely identify
each node in a network at the Media Access Control layer, the lowest network
layer, the one that directly interfaces with the media, such as the actual
wires in a twisted-pair Ethernet. In modern Ethernets the MAC address
consists of six bytes which are usually displayed in hexadecimal; e.g.,
The first three bytes (e.g., 00-0A-CC) are the manufacturer's
code and can be used to identify the manufacturer. The last three are
the unique station ID or serial number for the interface. One can determine
the MAC address of an operating Network Interface Card (NIC or network adapter)
in Windows 9X/Me with Start, Run, enter winipcfg, and select the adapter. In
Windows NT, 2000, and XP it can be determined by opening a DOS Window/Prompt
(Start, Programs, Accessories...) and typing:
The MAC address/station ID may be printed on the NIC.
Many broadband routers can clone a NIC MAC address. That
is, make the Wide Area Network (WAN) Ethernet interface going to a cable
or DSL MODEM look like a NIC in a PC. This is useful in that many MODEMs
marry themselves to a specific MAC address when they are first installed
and it can be rather difficult to get them to marry themselves to a new MAC
address. The WAN port MAC address on some routers can be manually changed
(e.g., the SMC7004ABR).
It is possible to change/override the MAC address
with Windows, etc.
A vendor/Ethernet MAC address lookup service is available