Original subtitles

You need to know how to read.

MAC addresses and what they mean and to help us do that.

Let's make this practical and use Packet Tracer.

So please open packet tracer and follow me and make sure that you see something similar.

The numbers that you get may be different but we'll manually configure MAC addresses in Packet Tracer

because it's easy to do that.

So make sure that you can view the MAC addresses and then gonna show you how to work with hexadecimal

and how to convert numbers from binary to hex hexadecimal to decimal and so forth.

So the first thing is let's get a switch and I'll get a 35 60 switch and drag that into the topology.

I'll go the end devices.

Grab a P.C. grab a laptop add that to the topology go to network connections and get a straight through

cable and connect the pieces Ethernet interface to the switch on gigabit 001.

You don't have to use exactly the same interfaces it's really up to you but what I've done here is connect

the pieces to the switch to make it easier to follow.

I'll go to preferences and I'll show the port labels in my diagram so fast.

Ethan at 0 in the piece he is connected to gigabit 1 0 1 on the switch.

I'll connect to the second gig interface to the laptop on fast ethernet zero so we've got our devices

in our topology.

The switch needs a power supply so grab a power supply and add that to the switch.

And as you can see the switch is now booting up.

But now let's view the MAC addresses on the devices it's on P.C. one go too fast ethernet a zero.

This is the MAC address of the P.C. by default.

I'm gonna give it an IP address of 10 1 1 1 with a subnet mask of slash 24 or 2 4 5 2 4 5 2 4 5 0.

If you don't understand that yet don't worry too much we'll talk a lot about submitting in later videos

but for the moment I've configured the P.C. with those details.

I'll go to desktop.

Command prompt and if we type IP config like you would on a Windows computer.

Notice there's the IP address of the P.C. IP config slash all.

There is the MAC address of the P.C. not easy to read.

Will change that in a moment but for the moment I want to show you that the switch will learn those

MAC addresses so hence it's important for you to learn hexadecimal on the laptop go to config first

Ethan at 0.

I'll configure this laptop with an IP address of 10 dot one that wanted to add a subnet mask of that

2 4 5 2 4 5 2 4 5 0.

There's the MAC address of this P.C. so if I go to command prompt on the laptop and TCP IP config slash

all there's the IP address there's the MAC address back on the P.C..

P.S. 1 P.S. starts with 0 0 0 4 laptop starts with triple 0 6 the first half of this address is the

vendor code.

Second half is a unique identifier for the MAC address but notice please when I type a command such

as Opp dash a.

It says there are no op entries.

OP is used to find the MAC address of another device in the network.

It's basically a broadcast sent out into the network saying who has this IP address and then that device

will reply back with its MAC address.

So back on the laptop.

If I type OP dash a notice it says no op entries are found OP is used to discover the MAC address of

a another device in ethernet devices have mac addresses allocated to them by vendors.

If I want to talk to your device I need to know what your MAC address is to be able to send the traffic

onto the ethernet network.

So if the laptop pings the P.C. it's basically going to send a broadcast into the network saying who

has this IP address and then that P.C. will reply back.

Notice now when we type up dash a we see that this IP address is using this MAC address and that's correct.

Per the information on P.C. one back on the P.C. IP config slash all shows us that the P.C. has this

IP address and this MAC address the laptop has learnt the MAC address of the P.C. and in the same way

the P.C. has learnt the MAC address of the laptop.

So that's an example where hexadecimal values are used but it's not only there.

If I have a look at the switch I'm going to bypass the initial configuration on the switch.

Now don't worry too much if you don't know the commands on Cisco switches in a lot of detail yet you'll

learn as we go along.

Enable takes us to privilege mode and I can type show MAC address table to see the MAC address table

on the switch the switch has learned to where the devices are the whole idea with a switch is when it

receives traffic on one port it needs to switch that traffic out of another port needs to know where

the devices are so that it can efficiently send the traffic to only the correct ports.

So in other words if traffic arrives on this interface going to the laptop we only want to send it out

of this interface.

Now the switch doesn't have other interfaces connected at the moment but if we did we wouldn't want

to send that traffic out of all interfaces we would want to limit it to this one interface.

So the switch learns where devices are in the network.

If we change the MAC address of the P.C. so going back to the pieces config will click on fast ethernet

zero.

I could as an example set the MAC address to 0 0 C0 and then just make it a number like that a whole

bunch of ones notice a MAC address consists of six hexadecimal values this is hex which is the vendor

code and then six hexadecimal values which is the unique identifier for the mac address a hex value

is for binary bits and I'll explain that in more detail in a moment.

This is a forty eight.

But no we've got twelve hexadecimal values and a MAC address twelve times for 48 bits each number has

a hexadecimal number.

What I'll do now is change the MAC address of the laptop so go to config Foster Ethan 0.

Let's make that 0 0 C0 2 2 2 2 and a bunch of twos.

So I've changed the MAC address of the laptop as well if I type IP config that's the IP address to slash

all.

Make this bigger that shows us the MAC address of the P.C. has changed or the laptop in this case has

changed.

So now OPP dash a the OP cache has timed out or has been flushed in this example there are no op entries.

If the laptop pings the P.C. and type OPP dash e now you can see that the Mac address of value has been

updated.

So the laptop has learnt the new mac address associated with the P.C. and in the same way the P.C. has

learnt that was the previous entry but P.C. has learnt the new mac address of the laptop and the switch

will have learnt the new mac addresses.

Now it still has the old mac addresses in its MAC address table they will time out after a period of

time but for the moment it's got both the old mac addresses and the new mac addresses in its MAC address

table a switch learns where the MAC addresses of devices are in the network and then basically switches

the traffic from one MAC address to another depending on who's talking to who.

So as you can see here MAC addresses are used in a lot of places you need to know how to read MAC addresses

you need to know what that means.

If I tell you that that's a 48 but no you need to know that.

Why why is it 48.

So let's talk about the theory and I'll show you how to do conversions from one numbering system to

another.

Don't forget that IP version 6 also uses hexadecimal.

So if I type IP conflict slash all on the.

P.S. notice link local IP version 6 address DHEA P client identifier.

These are all hexadecimal numbers.

We've got a Bluetooth hexadecimal number hexadecimal is used in multiple places you need to know how

to work with hexadecimal.

So now let's talk about the theory of hexadecimal and how to do conversions.