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I'll go through this in more detail later.
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Let's just look briefly at some of the devices that we had in the past and then some modern devices.
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The original Ethernet was 10 base five using this really big yellow cable.
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So this cable was restricted and distance the signal would attenuate from one end of the cable to the
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other.
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And what they developed were repeaters.
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This is an example of a very early repeater.
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This would repeat the signal from one port to another.
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We could use ten base five here or ten base two.
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So this amplified the signal basically didn't understand the actual signal but it just amplified the
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signal from one port to another.
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Now you'll notice it doesn't have many ports on it.
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We've only got two ports.
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So it was simply repeating from one port to another.
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So example of a repeater.
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They then developed what was called a multiple port repeater.
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This is a Cisco fast hub 400 series.
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So we've got RJ 45 connectors on the front.
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We've got power on the back.
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But the idea is a hub is essentially a multi port repeater.
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We've got multiple ports and we are simply repeating the signal.
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We would connect RJ 45 until the twisted pairs an example to these ports.
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And what a hub does is once again it simply repeats the signal without understanding what's going on.
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So it doesn't understand the frames that it receives or the information that it receives.
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It simply amplifies it.
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So a repeater here would amplify the signal amplified from one port to another.
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Here we've got a multiple repeater.
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It's repeating the signal from one port to multiple other ports.
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So if traffic was received on port one on this hub it would simply amplify the signal out of all of
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those ports.
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So it repeats the signal out of every other port without understanding any of the details.
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Here's an example of a net gear hub on the front.
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We have 24 RJ 45 ports and on the back.
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We've got 10 base two as well as 10 base five.
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So again this would allow me to connect different cable types on the back we could connect 10 base five
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as an example.
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And then on the front we could have UDP RG 45 cabling as we know today.
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This has no intelligence.
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There's no intelligence in the hub.
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There's no intelligence in the repeater.
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Remember this is just repeating the signal from one port to another.
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This is a multiple repeater.
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If something is received on this port it just amplifies it.
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Out of all the other ports or repeats it out of all the other ports.
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Otherwise we get attenuation of signals and the signals degrade over a period of time which restricts
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the length of a cable.
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This allows me to increase the length of the cable.
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Now the problem in those days is the more devices that you have on the network the more collisions that
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you're going to have which causes problems and slows the network down.
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I'll talk more about that later.
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But the idea is that this is a hub.
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This is a repeater.
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We don't worry too much about these days.
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A lot of people say David don't even show me hubs because they're pointless but they forget that wireless.
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This is an example of a wireless access point very modern wireless access point supports Wi-Fi sex the
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latest version of Wi-Fi at the time of this recording a Wi-Fi network or a wireless network is essentially
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a hub in the air.
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We are sharing the air.
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So whatever I'm saying can be heard by you if you're within range.
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Both of us can speak at the same time because it's a shared medium.
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We are sharing the air now Wi-Fi six does try and implement some very clever stuff to allow multiple
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devices to talk at the same time.
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So it kind of approaches a switch but it's still acting as a hub.
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So what is a switch.
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Here's an example of a switch.
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This is an older switch that is 750 very popular for doing labs.
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Cisco labs noticed lots of ports on the switch we got 48 ports on the switch.
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The number of ports on your switch varies.
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You can have very small switches you could have larger switches.
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Here's an example is a five Port switch T.P. linked switch very small switch.
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Has another four port switch from TB link so you don't necessarily have lots of ports but in an enterprise
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environment you typically will you'll have a lot of ports on a switch.
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These are smaller switches.
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The point is is that the form factor or the way that these devices look varies.
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But the big difference between a switch and a hub is a switch has intelligence a switch actually reads
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what are called the frames received on Ethernet when you send data into Ethernet we're sending what's
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called a frame.
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So this device uses what's called a MAC address table.
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It's the same as these devices of the top here.
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They basically receive frames and they have the intelligence to only forward the frames out of the correct
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ports.
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So if there was a device with a certain MAC address on this port and traffic was received on this port
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going to that MAC address it would only be sent out of that port rather than out of all ports a hub
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or multiple repeater is done when a when traffic is received on one port it just simply amplifies it
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or floods it is the term out of all ports so everyone receives that frame here.
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A switch has a MAC address table it has some intelligence and it learns where MAC addresses are in the
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network and then it will only forward the traffic out of the relevant ports.
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Based on the destination MAC address and a frame.
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So if traffic comes into this port it's going to you based on your mac address it's learned that you're
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connected to this port when traffic arrives in this port going to your mac address it's only going to
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be sent out of this port whereas if it arrived on a hub it would send it out of all ports.
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So a big difference between a switch and a hub is a switch has intelligence.
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It works at what's called Layer 2.
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We'll talk about that later in a moment.
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So it has some intelligence and it'll only forward the frames out of the correct ports.
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Now some people would say but hold on a minute David what is a bridge.
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A bridge.
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You can think of as an intermediate device between a switch and a hub.
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So we had repeaters first.
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Then we've got hubs and then we had bridges which basically did things in software they learned where
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the MAC addresses were of devices in the network and then someone rebranded their devices as switches
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because they could learn MAC addresses in hardware.
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So they use something called an application specific integrated circuit or a sec.
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So the lines are a little bit blurred but for the CCMA you don't have to worry about that a switch learns
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where devices are learns where their MAC addresses are and then we'll only forward the traffic out of
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the relevant ports a bridge was an intermediate device between a switch and a hub.
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So historically we had repeaters that we had hubs and we had bridges software switches if you like and
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then we have switches today.
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Now notice the number of ports on the switch there many many ports on the switch.
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So that's one of the features of switches they allow us to connect many devices in our local area network.
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They are essentially useful sending traffic within a local area network or LAN.
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We're not going to try and send it from one network to another.
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These operate on mac addresses using what's called Layer 2 in the OSA model or TCE IP model hubs or
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layer 1 devices they are basically dumb devices they don't understand what they receive.
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These are called Layer two devices because they use Ethernet frames and then we have routers which use
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IP addresses to rot from one network to another.
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They are called Layer three devices.
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We'll talk about those terms in a separate video layer one layer to layer three layer 4 and layer five
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to seven you need to know those layers you need to know the TTP IP and we say models so don't worry
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too much about that for the moment just get an understanding dumb device repeats everything that receives
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on one put out of all of the ports more intelligent device uses mac addresses learns where devices are
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and then we have writers.
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Now your home device might look something like this teepee link.
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This is a little tepee link right.
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It allows us to root from one network to another.
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Typically little routers like this allow us to go from our Ethernet LAN local area network onto the
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Internet.
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So to what's called a one wide area network.
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So Ethernet ports this is how we connect our devices to the broader wireless and then we've got a connection
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to the Internet.
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He has a Cisco router what you'll notice is the shroud it is as big as the switch but it has far fewer
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ports on it.
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We've only got a few Ethernet ports and then we've got other types of ports.
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These are what are called serial ports.
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Now fortunately in the new CCMA you don't have to learn about these serial interfaces.
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They were very slow.
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Older interfaces.
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The most common when technology and land technology tonight today is Ethernet so Ethernet is what you
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need to know.
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So that's why I'm spending so much time discussing Ethernet these older interfaces aren't that important
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today.
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But think of your home broader.
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How do you connect to the Internet.
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Maybe you've got an A DSL connection.
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So your service provider mine here in the U.K. is British Telecom.
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They've given me an A DSL connection.
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Now some of you may be fortunate enough to have fibre to your home.
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So in actual fact your one connection is Ethernet.
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In that case but in the old days it might have been something like the serial interface.
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But notice this right here this is an interesting road.
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Eighteen hundred series right.
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This is an older router that would be used in small medium business or in a remote branch office of
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a large corporate.
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This device does a lot of things.
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It has all telephone connections here where you could put old analog phones in.
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So these ports share these f access ports would allow you to connect an old analog phone to the rudder
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and then this would allow you to make telephone calls to your service provider like AT&T or British
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Telecom etc..
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It's also got a way an interface.
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So one of these interfaces could go here.
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It also allows us to connect to the Internet.
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It's also got like a switch part to it.
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So the idea here is this is kind of like a hybrid device writers today mix a lot of switching with them.
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Like I said nothing is as simple as it seems in its purest form.
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A router will rot from one network to another.
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So as an example we are routing from Ethernet to serial or we are routing from physical Ethernet to
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wireless or we are writing from one connection type to another.
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So as an example this writer could support voice over IP.
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We could have IP phones talking to analog phones but this is where it gets a little bit less clear cut.
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This is what you need to remember a router has writing functionality in its most basic form.
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A writer writes from one IP network to another.
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So here we are talking about IP addresses such as IP version for IP version 6 addresses.
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We are routing from one network to another as in one IP network to another in a lot of cases.
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We would be routing from one physical media to a different physical media.
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This is typically used for connections to the Internet or to wide area networks.
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So we are connecting from a local area network to a wide area network switches are typically used in
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the local area networks are local within the building as an example local at your home you're not going
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to use this to write to the Internet or write to other sites.
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A router does that function so it rots from one network to another layer to switch as this is called
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uses Mac addresses but switches today have routing functionality so switch like this is called a layer
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3 switch because it has routing capabilities built into it and then it'll rot from one VLAN or virtual
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local area network to another virtual local area network.
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Basically from one subnet to another subnet we'll talk about that later.
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Thing to remember is basic definition routing switching dumb device so no intelligence here.
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Intelligence based on Mac addresses intelligence based on IP addresses.
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