CCNA Day 1: How Switches Work vs Hubs & Hands-On Packet Tracer Lab

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. oh and i forgot to go into simulation mode let's go to simulation mode down here

bring denny back up and boom so as you can see denny's got his packet ready and he sends

this frame to the switch now if we open up that frame what do we see well we see that the

source is indeed denny over here based on his mac address and then the destination

well what is that matching let me scroll down here we can see yeah it does match the first tablet here so the switch

knows that he lives on this port connected to the access point but it's what the access point does with it

that's so stupid but it's just how wireless is right now let's skip forward in time

the access point has it now but now let's see what happens click next boom and once more

boom the message was sent to everyone like a hub now we'll cover

wireless in more detail here later in this course but just know for now that's why people tell you plug into an

ethernet cable at all cost if you can because a wireless connection is more like a hub and the

fact that all the messages are going to each device isn't the worst part with hubs it's just a traffic jam collisions

all the time which is why switches are great and we'll cover more on that later but yeah

always prefer ethernet cable a hardline connection to a wireless connection if you can

now later versions of wi-fi like wi-fi 6 do help out with this i actually made a video on wi-fi sticks that you can check

out up there and then as we step forward a time when the first tablet sends here's a reply

back the access point will then send it to the switch and then the switch like it's

supposed to we'll just send that to denny but then we had the same process happen

again when denny does send another ping hey hey first tablet are you there the

access point will still broadcast that doubt out to everyone all right hope you have your coffee

ready time for a quiz time to test your knowledge and what we just covered in this video the questions i'm

about to ask you are not easy i pulled them from boson xm the best ccna

practice exam you can find they are world renowned and they are sponsoring this video so check out the link below

for that exam anyways let's see what you know question number one

which of the following addresses will a switch use to populate the cam table select the best answer

if your answer was b source ip address you are wrong because the answer is in fact

d source mac address remember switches layer 2 mac address switches layer 2 mac address

let's select our answer and get the deep down dive from boson so right off the bat because we know

we're talking about a switch in the cam table we can mark out a and b because those are talking about

ip addresses and the switch doesn't know anything about ip addresses but what we're talking about now is mac addresses

now it could have been source or destination a switch will learn a mac address and

add it to its cam table when a device sends a frame to that port and in that frame the

source mac address will be this guy's mac address so that makes sense destination would be

who he's sending that frame to which might be a person over here and you wouldn't want to add this guy's mac

address to this guy's port confusion it wouldn't work if you got that right that's

amazing you're just a little bit closer to passing your ccna next question

which of the following addresses will a switch use to make forwarding decisions select the best answer

[Music] if your answer was destination mac address then you are absolutely

correct let's select the answer and see if boson thinks i'm right here is boson's

wonderful explanation i encourage you to pause the video and read that but looking at the question it's talking

about a switch making forwarding decisions well we can automatically say you know

what source ip addresses out destination ip address is out because again switches

don't know anything about ip addresses now when a switch receives a frame from a device this

frame will have a source mac address let's just say zero zero zero one and a destination

zero zero zero two the source is coming from this guy that's his mac address he's trying to

send it to the destination mac address this guy who is probably over here and this question explanation is perfect

because it piggybacks off the previous question the switch will not use a source mac

address to make forwarding decisions however it will use it to populate the cam table again if you got

that right congrats you are even closer to getting your ccna and if you didn't it's fine

go back and watch the video learning is a process it's a day by day thing adding to your knowledge you'll get

there trust me didn't i tell you switches are amazing and we i know i keep saying this

have just scratched the surface and in this video we covered some ground on how switches work

you even got to work in packet tracer and watch packets and frames go across the network you may have even

issued your first cisco cli command which is amazing write that down today was your first command

show mac address table you looked inside the switch's brain inside his cam table to see the mac address to

switch port assignment that's huge and guys that's about it we just covered day one switches

in the coming videos we'll be talking about routers and we'll be talking about the other layers

of the osi model which we kind of talked about layers one two and three today we'll cover the rest soon and you're

gonna love it trust me if you like this stuff you will love love that stuff and again huge

massive shout out to bozon software for sponsoring this ccna series they're making it free

so i encourage you go check them out they have amazing labbing software so what i

showed you today was cisco packet tracer it's great for demonstrating to you how a network works

boson netsim is a great lab software that will allow you to go through labs and once we

get deeper into like cisco command line stuff where it gets pretty pretty

sophisticated pretty complex they have fantastic labs that walk you through things they'll grade you on how

you do and they'll even explain everything it's it's awesome and then of course the

practice exam questions i showed you today that's from their practice exam and ask

around their exams are golden if you can pass their exams uh you can probably pass the ccna many

people say bosons is actually harder than the real ccna

so links below for that again they have their summer sale it's 25 off if you have any questions or

comments please let me know below and if you like this video like it hit that subscribe button and

hit that bell notification icon to be notified when i post stuff this was ccna

day one see you on day two [Music] you