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I'll go through this in more detail later.

Let's just look briefly at some of the devices that we had in the past and then some modern devices.

The original Ethernet was 10 base five using this really big yellow cable.

So this cable was restricted and distance the signal would attenuate from one end of the cable to the

other.

And what they developed were repeaters.

This is an example of a very early repeater.

This would repeat the signal from one port to another.

We could use ten base five here or ten base two.

So this amplified the signal basically didn't understand the actual signal but it just amplified the

signal from one port to another.

Now you'll notice it doesn't have many ports on it.

We've only got two ports.

So it was simply repeating from one port to another.

So example of a repeater.

They then developed what was called a multiple port repeater.

This is a Cisco fast hub 400 series.

So we've got RJ 45 connectors on the front.

We've got power on the back.

But the idea is a hub is essentially a multi port repeater.

We've got multiple ports and we are simply repeating the signal.

We would connect RJ 45 until the twisted pairs an example to these ports.

And what a hub does is once again it simply repeats the signal without understanding what's going on.

So it doesn't understand the frames that it receives or the information that it receives.

It simply amplifies it.

So a repeater here would amplify the signal amplified from one port to another.

Here we've got a multiple repeater.

It's repeating the signal from one port to multiple other ports.

So if traffic was received on port one on this hub it would simply amplify the signal out of all of

those ports.

So it repeats the signal out of every other port without understanding any of the details.

Here's an example of a net gear hub on the front.

We have 24 RJ 45 ports and on the back.

We've got 10 base two as well as 10 base five.

So again this would allow me to connect different cable types on the back we could connect 10 base five

as an example.

And then on the front we could have UDP RG 45 cabling as we know today.

This has no intelligence.

There's no intelligence in the hub.

There's no intelligence in the repeater.

Remember this is just repeating the signal from one port to another.

This is a multiple repeater.

If something is received on this port it just amplifies it.

Out of all the other ports or repeats it out of all the other ports.

Otherwise we get attenuation of signals and the signals degrade over a period of time which restricts

the length of a cable.

This allows me to increase the length of the cable.

Now the problem in those days is the more devices that you have on the network the more collisions that

you're going to have which causes problems and slows the network down.

I'll talk more about that later.

But the idea is that this is a hub.

This is a repeater.

We don't worry too much about these days.

A lot of people say David don't even show me hubs because they're pointless but they forget that wireless.

This is an example of a wireless access point very modern wireless access point supports Wi-Fi sex the

latest version of Wi-Fi at the time of this recording a Wi-Fi network or a wireless network is essentially

a hub in the air.

We are sharing the air.

So whatever I'm saying can be heard by you if you're within range.

Both of us can speak at the same time because it's a shared medium.

We are sharing the air now Wi-Fi six does try and implement some very clever stuff to allow multiple

devices to talk at the same time.

So it kind of approaches a switch but it's still acting as a hub.

So what is a switch.

Here's an example of a switch.

This is an older switch that is 750 very popular for doing labs.

Cisco labs noticed lots of ports on the switch we got 48 ports on the switch.

The number of ports on your switch varies.

You can have very small switches you could have larger switches.

Here's an example is a five Port switch T.P. linked switch very small switch.

Has another four port switch from TB link so you don't necessarily have lots of ports but in an enterprise

environment you typically will you'll have a lot of ports on a switch.

These are smaller switches.

The point is is that the form factor or the way that these devices look varies.

But the big difference between a switch and a hub is a switch has intelligence a switch actually reads

what are called the frames received on Ethernet when you send data into Ethernet we're sending what's

called a frame.

So this device uses what's called a MAC address table.

It's the same as these devices of the top here.

They basically receive frames and they have the intelligence to only forward the frames out of the correct

ports.

So if there was a device with a certain MAC address on this port and traffic was received on this port

going to that MAC address it would only be sent out of that port rather than out of all ports a hub

or multiple repeater is done when a when traffic is received on one port it just simply amplifies it

or floods it is the term out of all ports so everyone receives that frame here.

A switch has a MAC address table it has some intelligence and it learns where MAC addresses are in the

network and then it will only forward the traffic out of the relevant ports.

Based on the destination MAC address and a frame.

So if traffic comes into this port it's going to you based on your mac address it's learned that you're

connected to this port when traffic arrives in this port going to your mac address it's only going to

be sent out of this port whereas if it arrived on a hub it would send it out of all ports.

So a big difference between a switch and a hub is a switch has intelligence.

It works at what's called Layer 2.

We'll talk about that later in a moment.

So it has some intelligence and it'll only forward the frames out of the correct ports.

Now some people would say but hold on a minute David what is a bridge.

A bridge.

You can think of as an intermediate device between a switch and a hub.

So we had repeaters first.

Then we've got hubs and then we had bridges which basically did things in software they learned where

the MAC addresses were of devices in the network and then someone rebranded their devices as switches

because they could learn MAC addresses in hardware.

So they use something called an application specific integrated circuit or a sec.

So the lines are a little bit blurred but for the CCMA you don't have to worry about that a switch learns

where devices are learns where their MAC addresses are and then we'll only forward the traffic out of

the relevant ports a bridge was an intermediate device between a switch and a hub.

So historically we had repeaters that we had hubs and we had bridges software switches if you like and

then we have switches today.

Now notice the number of ports on the switch there many many ports on the switch.

So that's one of the features of switches they allow us to connect many devices in our local area network.

They are essentially useful sending traffic within a local area network or LAN.

We're not going to try and send it from one network to another.

These operate on mac addresses using what's called Layer 2 in the OSA model or TCE IP model hubs or

layer 1 devices they are basically dumb devices they don't understand what they receive.

These are called Layer two devices because they use Ethernet frames and then we have routers which use

IP addresses to rot from one network to another.

They are called Layer three devices.

We'll talk about those terms in a separate video layer one layer to layer three layer 4 and layer five

to seven you need to know those layers you need to know the TTP IP and we say models so don't worry

too much about that for the moment just get an understanding dumb device repeats everything that receives

on one put out of all of the ports more intelligent device uses mac addresses learns where devices are

and then we have writers.

Now your home device might look something like this teepee link.

This is a little tepee link right.

It allows us to root from one network to another.

Typically little routers like this allow us to go from our Ethernet LAN local area network onto the

Internet.

So to what's called a one wide area network.

So Ethernet ports this is how we connect our devices to the broader wireless and then we've got a connection

to the Internet.

He has a Cisco router what you'll notice is the shroud it is as big as the switch but it has far fewer

ports on it.

We've only got a few Ethernet ports and then we've got other types of ports.

These are what are called serial ports.

Now fortunately in the new CCMA you don't have to learn about these serial interfaces.

They were very slow.

Older interfaces.

The most common when technology and land technology tonight today is Ethernet so Ethernet is what you

need to know.

So that's why I'm spending so much time discussing Ethernet these older interfaces aren't that important

today.

But think of your home broader.

How do you connect to the Internet.

Maybe you've got an A DSL connection.

So your service provider mine here in the U.K. is British Telecom.

They've given me an A DSL connection.

Now some of you may be fortunate enough to have fibre to your home.

So in actual fact your one connection is Ethernet.

In that case but in the old days it might have been something like the serial interface.

But notice this right here this is an interesting road.

Eighteen hundred series right.

This is an older router that would be used in small medium business or in a remote branch office of

a large corporate.

This device does a lot of things.

It has all telephone connections here where you could put old analog phones in.

So these ports share these f access ports would allow you to connect an old analog phone to the rudder

and then this would allow you to make telephone calls to your service provider like AT&T or British

Telecom etc..

It's also got a way an interface.

So one of these interfaces could go here.

It also allows us to connect to the Internet.

It's also got like a switch part to it.

So the idea here is this is kind of like a hybrid device writers today mix a lot of switching with them.

Like I said nothing is as simple as it seems in its purest form.

A router will rot from one network to another.

So as an example we are routing from Ethernet to serial or we are routing from physical Ethernet to

wireless or we are writing from one connection type to another.

So as an example this writer could support voice over IP.

We could have IP phones talking to analog phones but this is where it gets a little bit less clear cut.

This is what you need to remember a router has writing functionality in its most basic form.

A writer writes from one IP network to another.

So here we are talking about IP addresses such as IP version for IP version 6 addresses.

We are routing from one network to another as in one IP network to another in a lot of cases.

We would be routing from one physical media to a different physical media.

This is typically used for connections to the Internet or to wide area networks.

So we are connecting from a local area network to a wide area network switches are typically used in

the local area networks are local within the building as an example local at your home you're not going

to use this to write to the Internet or write to other sites.

A router does that function so it rots from one network to another layer to switch as this is called

uses Mac addresses but switches today have routing functionality so switch like this is called a layer

3 switch because it has routing capabilities built into it and then it'll rot from one VLAN or virtual

local area network to another virtual local area network.

Basically from one subnet to another subnet we'll talk about that later.

Thing to remember is basic definition routing switching dumb device so no intelligence here.

Intelligence based on Mac addresses intelligence based on IP addresses.