MAC addresses


Martin McBride, 2017-10-12
Tags mac address
Categories networks network hardware

Every networked device has a unique number, called a MAC address. This number is assigned to the device by the manufacturer. Normally it never changes, and is completely unique - no other device in the world has the same MAC address.

MAC stand for Media Access Control.

A MAC address is not the same as an IP address, see IP address vs MAC address.

A MAC address is 48 [[bits]] long (equivalent to 6 bytes). It is normally written as 12 hexadecimal digits, for example:

84-3A-4B-4C-A7-CA

The first six digits show the manufacturer of the device. For example 84-3A-4B is Intel. The next six digits uniquely identify the device. A particular manufacturer will ensure that these digits are unique for every individual device they make.

Network hardware

The MAC address is normally hard-wired into the network hardware. If you have a PC with a separate [[Network Interface card]], it will contain the MAC.

For phones, tablets, or even some PCs and laptops, the network hardware will be built into the main board.

Many devices these days have several ways to connect to other devices - for example, a wired Ethernet connection, a wireless connection, and maybe a Bluetooth connection. Each of these separate connections will have a different MAC address.

Finding your MAC address

You can find the MAC address of a Windows PC using the Command Prompt window, sometimes called the cmd window. Simply type in:

ipconfig /all

You should see a lot of information about your network connection. What you are looking for is the Physical Address - this is another name or the MAC address.

You might see more than one address, and noted above, for the Ethernet, wireless and Bluetooth connections if you have them.

There are similar commands for Linux and Mac computers.

Changing the MAC address

We said earlier that the MAC address is unique and unchanging, and that is usually the case. There are exceptions.

  • If you change the network interface card on a computer, the MAC address will also change (because the MAC address is built into the card).
  • It is possible to change the MAC address of a device using special software, though that is not something you would normally want to do.

It is the manufacturer's job to make sure every MAC address is unique, but there is no guarantee that some manufacturers might not make a mistake and give the same address to more than one device.

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