MAC Address

 A MAC (Media Access Control) address is a 48 bit unique ID assigned to every internet-connected machine that allows it to be identified when connected to a specific network. Also known as Hardware Address or physical address of machine on network.

A MAC address is a hardware identification number that uniquely identifies each device on a network. The MAC address is manufactured into every network card, such as an Ethernet card or Wi-Fi card, and therefore cannot be changed. 

MAC is divided into The vendor ID (24 bit) and other NIC identifier 24 bit.

Because there are millions of networkable devices in existence, and each device needs to have a unique MAC address, there must be a very wide range of possible addresses. For this reason, MAC addresses are made up of six two-digit hexadecimal numbers, separated by colons. For example, an Ethernet card may have a MAC address of 00:0d:83:b1:c0:8e. Fortunately, you do not need to know this address, since it is automatically recognized by most networks.

Finding Your MAC Address

windows

1. Click Start then Run (in Windows 7, Start and type in the Search Programs and Files box.)
2. Enter: cmd
3. Enter: ipconfig /all
   If the output scrolls off your screen, and it will on Vista and Windows 7, use: ipconfig /all | more
4. The Physical Address is your MAC address; it will look like 00-15-E9-2B-99-3C. You will have a physical address for each network connection that you have.

 Linux

Linux

1. Become root, using su.
2. Enter: ifconfig -a

   # ifconfig -a
   eth0      Link encap:Ethernet  HWaddr 00:09:3D:12:33:33  
             inet addr:10.248.155.17  Bcast:10.248.255.255  Mask:255.255.0.0
             inet6 addr: fe50::234:3dff:fe12:7d73/64 Scope:Link
             UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
             RX packets:3489041718 errors:0 dropped:0 overruns:0 frame:0
             TX packets:3259212142 errors:0 dropped:0 overruns:0 carrier:0
             collisions:0 txqueuelen:1000 
             RX bytes:2732221481 (2.5 GiB)  TX bytes:4065716672 (3.7 GiB)
             Interrupt:185

3. The ethernet devices are called eth0, eth1, and so on The MAC address is in the first line of the output, labeled HWaddr, it is 00:09:3D:12:33:33.