Hey what's up guys welcome to CertBros. In this video we're going to be looking
at MAC addresses
So we're getting closer to the end of our journey through the tcp/ip model
In this video we're going to be looking at the data link layer the data link
Ethernet standards operate here. It's also responsible for adding another type of
address called a MAC address. So what is a MAC address? Well first, MAC stands for
Media Access Control. It's a unique identifier that is assigned to a network
interface card aka a NIC
and this is what a mac address looks like. The first thing to know is that
unlike an IP address which can be changed, MAC addresses are described as
being physical addresses. Think of them like they're set in stone. Burnt into the
NIC by the manufacturer. They are unique and cannot be changed
...well you can spoof a MAC address. The address itself is 48 bits long or 6
bytes. Bits and bytes are binary value.s There are 8 bits in a byte and to
remember the difference think off eating binary. You take a bite and you will have
a mouthful of bits. Anyway the address has two sections. The
first 24 bits, or 3 bytes, is called the organizationally unique identifier or OUI
It identifies the vendor. The last 24 bits is a unique value that was
assigned by the vendor that makes this address unique
There are three types of mac-address. Unicast which means a particular unique
MAC address like the one we have here. Multicast which is a MAC address used
for an application or protocol. This will be sent to all devices but only those with
that application or protocol will listen to it. And we have something called a
broadcast address. Now this is sent to all devices within a network and a
broadcast address looks like this. It's all F's. So back to our unicast MAC
address. It's important to note that there is more than one way to show a MAC
address and it changes depending on where you're looking at it. Here are
three ways to display the same MAC address
The top one is six groups of two digits separated by colons, this is typically
how Linux or Apple will display their MAC addresses. The middle one is again
six groups of two digits but this time separated by dashes. This is how
Microsoft display their MAC addresses. Lastly the bottom displays the address
as three groups of four digits this is how Cisco displayed their MAC addresses
Although you'll likely see the bottom Cisco format when going through the exam
you need to be able to look at all three of these and think that is a MAC address
Ok so I know what you're probably thinking, we already have IP addresses so
why do we need MAC addresses? Well let's look at an example. We have four
computers and a switch. Switches are commonly layer 2 devices. When computers
are talking to each other in the local area network or LAN, this is layer 2
communication and layer 2 communicates using MAC addresses
But when we leave our network this is where IP addresses are mainly used
Routers are layer 3 devices and they mainly focus on IP addresses to get the
data to the destination. So in summary you can think about MAC addresses as a
local communication and IP addresses as global communication
We'll cover this more when we go into more in depth switching and routing
topics. Before we finish this video, I will show you how to check your own MAC
address at home. On Windows you simply open up a command prompt or PowerShell
type ipconfig /all to see your interface settings. Find your interface and
Remember you might have more than one if you have a wireless interface
and look for something called the physical address
If you're using Linux or Apple open up a terminal
and type in ifconfig and look for the ether address
This video is part of our full CCNA course which can be found in the
description. So please feel free to go and check that out. If you like this
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this helped and thank you for watching