Networking 101: MAC Addresses

Hello Guys,

So last time we talked about IP Addresses which make up layer 3 (Network Layer) of the OSI Model and are also useful in routing.
Today, we are going to talk about MAC Addresses which make up layer 2 (Datalink Layer) of the OSI Model.

MAC stands for Media Access Control. MAC address is a 48-bit physical address that is embedded into the NIC (Network Interface Controller).
These 6 sections are actually 6 octets.


(FIGURE A)





                                                                        (FIGURE B)

The address that you see just next to ether is the MAC Address. This address is used by switches to communicate and know what the device really is.

MAC address has the first 3 octets as their identifiers. These 3 octets or 24 bits form the OUI (Organisationally Unique Identifier) and the remaining 3 octets or 24 bits are NIC specific i.e. they depend on the NIC installed.
Thus, we can say that (from figure B) the first 6 characters i.e. 98-28-A6 will be denoting the Organization which built the NIC, and the last 6 characters i.e. 3C-02-BA will be the NIC specific number which your vendor would assign to you.

Here are some OUIs for your reference
CC:46:D6 - Cisco 
3C:5A:B4 - Google, Inc. 
3C:D9:2B - HP
00:9A:CD - HUAWEI

Also from our earlier discussion, we know that the first 24  bits are for OUI, now, the first 2 bits are assigned to denote the unicast or broadcast and global or locally administered functioning of the MAC.

MAC Addresses can be represented in 3 types of notations:
1. Hyphen-Hexadecimal notation in Windows.             [seperated by "-"] 
2. Colon-Hexadecimal notation in Linux.                     [seperated by ":"] 
3. Period-Hexadecimal notation in Cisco Systems.      [seperated by "."]

Token-Ring and Ethernet are some LAN technologies that use MAC as a physical address whereas technologies like AppleTalk do not use a MAC Address.
      

If you have the IP address of a device, you won't be able to figure out what is the device whether it's a PC or a smartphone or a laptop, etc. 
On the other hand, if you have a MAC address, you'll be able to get information about the device.

Want to check yours?

If you're in windows, type "ipconfig /all"  or "ifconfig" if on kali.
Copy your MAC address.
Go to https://dnschecker.org/mac-lookup.php
Put in your MAC address
You'll get to know the details about your MAC address
Here's how the details of the MAC on our Kali Linux look like


Let's have a look at the type of MAC addresses now.
There are 3 types of MAC addresses
1. Unicast
2. Multicast
3. Broadcast

Unicast

In unicast, the data frame is sent to only a specific device. If the LSB (Least Significant Bit) of the first octet of MAC is set to zero, then it means that the device will act in unicast mode and will send a frame that has only one destination address.
Generally, the MAC address of the source machine is unicast. Let's understand this with an example;
Let's say you want to request a page from google.com. Now your device will generate a request. Thus it becomes a source of that request and so it will act in unicast mode with only the address of google.com and not any other address.


Multicast

In multicast, the data frame is sent to only a specific group of devices. Here, the LSB of the first octet is set to 1.



Broadcast

In Broadcast, the Ethernet frames have all ones in their destination address. Thus the frames designed with the ff:ff:ff:ff:ff:ff address will be sent to all devices which are in the same network as that of the source device.


If you like the content then do consider connecting with me and pour your knowledge into my DM!!😇 

Instagram: bhavak_29

LinkedIn: https://www.linkedin.com/in/bhavak-kotak-3b6b071b1/

:NOTE:

All the images belong to their respective owners.

I am a learner so I learn things from different sources and I DO NOT claim that any of the content(if it does) belonging to someone else as mine.

Also a huge thanks to Heath Adams(AKA The Cyber Mentor). It is because of his course that I am motivated to put this content here and I have taken inspiration from his videos to a considerable amount of extent and tried to convey what I understood in the best way possible.


 





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