this is day one of my free ccna course and a huge shout out to boson software the official sponsor of the ccna course they are the reason this can be made available for free so i highly encourage you to go check them out they have the absolute best ccna ccnp labs and practice exams day one we're not wasting any time we're getting right into what is this it's a switch how does it work why is it amazing because it is amazing and we'll even get a chance to lab what does labing mean well you'll find out we're going to use cisco packet tracer to analyze frames and packets going across the network and you're going to get a chance to enter your first cisco cli command let's get started [Music] in my last video we talked about what a network is and we followed a call of duty bullet when i shot it from my computer how it goes through my home network to my brother's network and shoots his character and we went high level like router switch firewall access point what are those things but we didn't go too deep but now are you ready we're gonna go just a little bit deeper it's just like one of those red pill blue pill situations from the matrix after this there is no turning back you take the red pill you stay in wonderland and i show you how deep the rabbit hole goes you take this pill there's no going back we're going deep into the networking rabbit hole you're going to fall in love and never look back okay i warned you you're still watching this that means you want to keep going let's do this okay let's talk about switches first what are they and what are they doing and here's one right now this is a switch it's beautiful isn't it look at this oh love it now if you watched our last video you have a high level view of what a switch is for what's it doing well it's helping our computers to connect to each other and talk and hang out and chat send data we connect using these ethernet cables and we plug them into our ports oh love that sound here listen to this up close asmr version uh one of my favorite sounds so we connect one computer connects another computer and assuming we have computers on the other ends of these they're talking they're having fun they're playing games but what's really going on inside of here let's pop the hood let's take a look oh by the way switches can come in many different sizes like this is an 8 port and this big boy is a 48 port he's beautiful [Music] why do you need 48 ports well so you can connect 48 different devices to each other that's why now let's first look at this guy the ethernet cable all it is is a bunch of metal wires like check it out your computer communicates with the other computers via electrical signals and these electrical signals go down these wires through the cable to the switch and then it goes to the other computer it's amazing it's just electrical signals going in and out of these ports it's isn't that cool now switches are amazing but for you to really appreciate how amazing they are you need to look at their predecessor the one that came before them the hub he's disgusting he's dumb he doesn't have any smarts the switch is smart the hub is not but before we had switches hubs are all we had and here's what they did and why they're dumb now i want you to actually see how dumb this is and experience it for yourself so right now what i want you to do is go download cisco packet tracer i've got a link below sign up for a free account through netacad and you'll be able to download it what is this it's a tool that lets you build and play with networks and so much more it's amazing so go download and install that it's on windows mac linux and once you install packet tracer i've got another link below for a pack a tracer file which is a lab i built that we can play with right now so go ahead and download that and launch it do not get overwhelmed with all the buttons and options here i'll walk you through every step right now if you zoom in right here i've got two networks i got this one here which is a switch and my laptops if i scroll over i've got another network and it's not nearly as smart because i'm rocking a hub now a hub and a switch physically kind of look the same they look like this they have ports where you can plug ethernet cables into but they're so so different actually we can look at a hub right now let me click on the physical button up here i can click on my home city my corporate office and then jump into my wirelink wiring closet and there it is so you can see switch it's got ports hubs got ports okay but why are they different how would you like this if when you sent a text to your friend it didn't just go to your one friend it went to all your friends and then when your friend responded back to you it only went to you but it went to all your friends as well that's stupid right like that i would never use that texting platform that's what a hub does check this out and i want you to do this with me so click on simulation down here at the bottom right this is what makes packet tracer so cool we can analyze the network traffic slowly as it goes through the electrical wires it's oh it's powerful anyways so don't touch that leave it there i want you to click on harry potter up here laptop harry then click on desktop and then click on command prompt this is very similar to a windows command prompt it kind of is a windows command prompt and what we're going to do is we're going to have mr harry here talk to ron over here through the hub we're going to send a message that we use in networking all the time called a ping message what is that for we use it to see if other computers or servers are up and can be reached kind of like this ping reply now you may have noticed i've got a couple things right here layer two address and layer three address now what's an address well if i wanted to send you a message i might send it to your email address if i want to send you a letter i might send that to your mailing address it's something unique to you that allows me to send something to you data whatever and in the networking world it's the same thing now what does layer 2 and layer 3 mean we'll cover that here in a bit but just know that when i'm going to send a ping message to ron i'm going to be looking at his layer 3 address that might look familiar to you what is that well that's an ip address you're probably familiar with that right harry knows that when he wants to talk to ron that's his address that's his phone number that's his mailing address that's how he gets information to ron his ip address so here we go we're about to ping ron now please make sure you have the simulation button checked not real time you want simulation here we go get your command prompt open we're going to ping ron so i'll type in ping and the ron's ip address 10. 1. 2 now watch what happens when i hit enter boom a little envelope popped up a little message we're going to send to ron and then notice over here we have a little event timeline where that message is popped up we can see the play-by-play here as we get more advanced and go deeper and deeper into what's happening which actually happen in the next video we can click on these and look at some hairy details like what's happening don't worry about that yet we'll get into it but it's amazing so harry wrote his letter he's ready to send it and if we click on this little advanced button right here it'll take a step forward in time let's go ahead and do that click advanced boom let's do it one more time boom there it goes it's going across the network electrical signals firing so now the hub has the message in an ideal world in a perfect world the hub's like okay well this message is for ron i'm going to send it to ron but the hub's an idiot he's dumb watch what happens watch what happens click next and why did you do that mr hob you sent the message to everyone harry's just trying to talk to his buddy ron and now hermione knows and and malfoy knows that's that's bad right now watch what happens next remember in a ping situation harry's gonna send a ping hey you there ron iran's gonna go yes i'm here but watch this click next ron does reply perfect but then watch what the hub does the dummy hub he since ron's replied out to everyone why hub why well again the hub has no smarts he's got no brain his job is just to repeat that electrical signal whenever your computer sends down this wire the hub is going to go and send out to everyone this is how we did things for a long time now notice that over here harry potter's got a green check mark going yes yes yes that message is for me yes yes yes but then down here malfoy and hermione have this x which means that most the time in a hub environment if a computer got a message that wasn't meant for them it would just ignore it but you know that's if you're a good person if you're a hacker like i'm learning hacking right now if you get a message like that if you're able to see everyone's traffic you're like yes yes give me more i'm gonna hack all you guys not a very safe and secure environment you don't want to text your buddy something secret and all of a sudden all your friends know the secret but now let's look at the switch he fixes everything go ahead and click on reset simulation you can close out harry potter there and let's scroll on over to the better environment the switch environment now here the switch has the same goal as the hub just to connect these computers together so they can talk so they're doing the same job just one's really really good at it so over here let's walk through the same situation johnny right here is gonna ping mark oh hi mark and we'll see what happens and i'll explain how it happens here in a moment so go ahead and click on johnny click on the desktop tab and then jump into your command prompt we're going to type in ping and then mark's ip address right here is 10.
1. 1. 2 we're going to hit enter and bam johnny's got a message ready for mark let's click on next and see what happens next next okay there it goes the switch has it what's it gonna do boom so much better only mark got it and then when mark responds it only goes to johnny that's how it's supposed to work thank you mr switch and if you look back at our command prompt you can see that we sent a ping message and then we got a reply from mark from the ip address everything's good mark's alive he's like hey yeah yeah johnny i'm here and if we click on real time it'll just complete it like it normally should bam bam bam really fast because these electrical signals are going really really fast down these wires but that's what's cool about this packet tracer we can slow down time bullet time and watch it happen okay we're about to go deeper we're about to learn more about how this guy does things are you ready let's take a deeper look the switch can do all this magic because it has a brain a brain that can remember things like hey on my port fa02 that's where johnny lives and on my port fa01 that's where mark lives and the same thing goes for denny and lisa and anyone else who connects to the switch he'll remember where they are so when you send a message he'll go oh well i know exactly where johnny is he's over here port fa02 he stores that information in something called the cam table which stands for content addressable memory don't worry about that too much right now we'll cover a lot of that later now the switch doesn't know johnny as johnny the switch knows johnny as 00d097528936 that's how the switch knows johnny has a layer 2 address that's how the switch knows mark he doesn't know mark's name but he doesn't know zero zero e0b0590897 love that guy what are these things that's called a mac address often referred to as a layer two address every single device that you connect to the internet has a mac address every one of them like go ahead and look get your laptop out look for it like on this phone here that i would connect to the switch look right here there's my phone's mac address right there it's often referred to as the burned in address because this address should never change that's how your device is identified it's unique identifier so when i connect my phone to this switch and my phone tries to talk to somebody boom the switch learns hey that phone which that phone's name is 9c57803844a he lives on port 1.
so if anybody wants to talk to him it's gonna be part one now we'll cover more about layers here in a moment i'm kind of building up to that but this right here doing this and that wonderful beautiful sound yes that's this is layer one anything physical the the electrical wires the metal wire that send electrical signals down into the switch that's layer one so layer one electrical signals firing at light speed down ethernet cable physical and then we get to our switch and now we're thinking about layer two that's where our layer two address comes in that's where the mac address comes in layer two is often referred to as the data link layer but we won't cover too much on that right now i have to stop i don't wanna give you too much right now now you may be wondering why isn't the switch just using the layer three address like what we used when we pinged 10. 1. 1.
2 why isn't the switch no marked by that number well the simple answer is that the switch can't even see that number it has no idea what it is you see the switch is a layer 2 device and doesn't know anything about layer 3 or ip addresses or anything that's why we're dealing with mac addresses right now now watch this let's get back to our packet tracer we're going to do a couple things here real quick let's click on simulation mode once more and let's open up mark we'll go to his desktop go to his command prompt and we're going to ping lisa down here so we'll do ping 10. 1. 1.
5 and hit enter the message was built now go and click the forward message real quick and i want you to click on this this message right here we have click on it now as you can see we have seven layers we're going to be talking about here very soon but don't don't think about anything above layer three right now don't think about that but notice this message we're sending to the switch notice what's not there layer three is missing it's just layer two because that's all the switch understands and also notice the two and from so right here we have the from which is the mac address of mark over here and then the two is to lisa's mac address down here and if we go ahead and step forward in time boom the switch receives it if we click on that message again we see that switch receives it and he knows exactly where to send it because he remembers where lisa is and then if we click on that button bam it goes to lisa now i'm not sure if i want to show you this yet yeah let's go ahead and do it so click on that envelope right there the message that just arrived to lisa you can see here that instead of just having layer one and layer two we now have layer three involved because that's a layer that mark and lisa are talking on layer three you see we pinged from mark's ip address 10. 1. 1.
2 to lisa's ip address of 10. 1. 1.
5 and then lisa is sending out a message see out to mark at 10. 1. 1.
2 from herself 10. 1. 1.
5 and then we step forward in time once more boom we see this message go to the switch but then if we open that message oh layer three is gone again it's just layer two because that's all the switch cares about is layer two and that's how he knows where things are that's where devices are based on their mac address now go and click on real time let that finish out and we're gonna jump into the switch's command line interface and this might be your first cisco command kind of exciting so let's let's open it up what we're going to do is we're going to look inside the switch's brain so go and click on him and jump to the cli tab this is a whole new world for you yes okay now hit enter then type in enable and hit enter now you should have a hashtag sign right there next to your switch here's a command i want you to enter show mac dash address dash table we're looking inside the switch's brain and looking at his cam table where he keeps the mac addresses and how they are assigned to the ports because mark and lisa just talked the switch knows that mark which is referred to as blah blah blah mac address lives fa01 and then lisa lives at fa03 and then if we go to denny over here and we go to desktop and command prompt and we try to ping johnny 10. 1. 1.
3 it's going to go through it's being successful awesome if we jump back into the switch and hit the up arrow to enter the same command hit enter well now the switch knows where everyone is he knows where johnny is where denny is or mark and lisa he learned it stored it in his brain and now whenever someone sends a message he goes i know exactly where they are boom right there the hub just doesn't do that and that's the job of the switch he learns where everyone is by learning their mac address they're burned in address and stores that in his brain is cam table and marks where they are so whenever he receives a message he can forward those messages to the appropriate people and not to anyone else that shouldn't hear about it now when we're talking about layer two this message right here is referred to as a frame all the messages going through this switch right here are frames boom boom boom frames just going around like crazy because it's layer two when you think layer two think switch think frames switch frames layer two switch frames layer two is it working is it going in there but then when the message goes to lisa and we're talking about ip addresses in layer three do you know what it becomes this message is now a packet now just so you know when you're talking to network engineers and other folks they might refer to layer two messages the frames they might call those packets as well we just get in the habit of it if it's going across the network and it's going to people and it's a message we often just refer to it as packet it just happens but technically it's frames layer 2 frames switch layer 2 frames switch okay now we're gonna talk a little bit about wireless um here's a wireless access point little baby cisco one here's a bigger cisco one the reason i wanna talk about them now along with switches is because they're basically doing the same job as a switch but what's funny what's funny is they're more like a hub than a switch they're kind of dumb i mean they're amazing but they're kind of dumb like a hub let me show you looking back at packet tracer if i scroll down just a little bit you can see i have a little wireless network here let me add the uh ip addresses here real quick now what i want you to do real quick is down here at the bottom click on the lightning bolt or harry potter esque and then click on the lightning bolt again this is a connection it's like plugging an ethernet cable and we're going to plug it into the access point here and then plug it into our switch we talked a little bit about wireless in the first video but it's just an extension of the switch so it connects to the switch with an ethernet cable and then it connects all the other devices via wireless which we know to be airwaves or radio waves so most of our devices like our phones and everything else connect to this access point which is connected to a switch now even though this access point is connected to a switch he's actually more like a hub and it's all about these connections right here let me show you real quick i'm gonna have mr denny here i'm gonna click on denny and launch his laptop we're going to go into his desktop and go to his command prompt and we're going to ping let's say the first tablet down here 10. 1. 1.
11 so i'll do ping 10. 1. 1.
11.
