What Is A MAC Address & Why Do We Need It? (Cisco Certification)
There’s a good question. What IS a MAC address? In this post I will take you though everything you need to know about this address and it will give you some really good foundational knowledge on how computers communicate with each other over our wifi networks at home, over the internet and everything in between!
If you don’t know what hexadecimal is and would like to know how the MAC address looks like how it does, then I would certainly recommend checking out the hex section of my other post ‘How to convert between binary, hex and decimal?‘ along with this.
If you really don’t care about why the MAC address looks like it does then you will still be fine to carry on reading this. All you would need to know at this point is that it has 12 digits (yes, digits. Not characters as a,b,c,d,e and ‘f’ is a hex number), which are in pairs.
The MAC address digit-pairs are separated by usually either a dash/hyphen “–” or also commonly seen as separated by a colon “:“.
Names, names, names and names
Sometimes we like to mix things up a little bit in technology as sometimes everything might seem a little too easy. That’s why the MAC address has about six names. 🙂
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Common MAC address Names
- MAC is probably the most common term, meaning Media Access Control.
- BIA or Burned-In Address is another.
- Hardware Address
- Physical Address
- Ethernet Address
- Layer 2 / L2 Address
Where is the MAC address located?
Any device connected to a network will have a network interface. This is usually referred to as the NIC or Network Interface Card. In older PC’s it was on it’s own card but now it’s all integrated into the electronics but the term ‘Network Interface CARD’ has stuck.
 The MAC address is burned in to a chip (integrated circuit) that exists on the NIC.
How the MAC address works
There are literally billions of of mobile phones in the world today and this number is growing every day. These phones, along with laptops, PC’s, tablets and any other networked device all need their very own unique MAC address.
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OUI
The first half of a MAC address is what is called the OUI or Organizationally Unique Identifier. So if we had a MAC address of 11:22:33:44:55:66 for example, then the 11:22:33 part of the MAC would be the OUI.
Vendors such as Samsung are given their own identifier. But a company as big as Samsung will more than likely own more than just one OUI.
The second half of the MAC address (44:55:66 in this example) is created by the vendor themselves. The vendor MUST make sure that every device they make has a unique MAC address.
Here you can find a list of OUI’s that are assigned to their respective vendors. There are many online tools which can also be found by doing a simple search which can be used to lookup a vendor by using the OUI of the MAC.
Check out the wiki for OUIÂ here.
How is the MAC address used?
In my other post ‘What is TCP/IP and how does it work?‘ I explain that there are many protocols in the suite. One of those protocols is ARP (Address Resolution Protocol).
As the name suggests, ARP resolves a hosts IP address from it’s MAC address.
I will cover ARP in another post and I will return here and provide a link.
Also in the TCP/IP section I mention the OSI model. If you don’t know about the OSI model yet then I will have a post on that subject too which I will be linking here.Â
The MAC address can be found at the ‘Data Link Layer’ of the OSI model. Network switches operate at the Data Link Layer and so switches deal with MAC addresses.
Conclusion
Now we know what a MAC address is, where it’s located on a device, what it is made up of and how it is used.
Computer networks are made up of many different components and the MAC address is just one of those components. To truly understand how this address works, further knowledge of TCP/IP networking is needed. But don’t worry, that’s why I started creating this site.
