Hello, Siberians. I'm Kelly Hander Han. And welcome back to session Wednesday. This week we're gonna talk about network devices and we're gonna look at the different type of devices that were going to use for network connectivity. And even though this is somewhat of a basic topic, I find that many people really don't know the ins and outs. So
what, We're gonna start with this? We're gonna talk about
first of all, what a hub does and really, what a hub did. And, yes, I totally understand We're not using hubs today, but I want to talk about what they did, because it's easier to explain what a switch does if we look at what a hub does. My hub isn't relevant today.
Okay, so let's go back
5 10 years ago. And let's say that we have
all our hosts connected into a hub.
Okay, Now the thing about a hub is a hub, Since all data out all ports all the time,
that's all the hub does. Ah, Hub doesn't do any addressing. It doesn't have any decision making. A hub isn't aware of the data where it's going up doesn't care.
So when computer a has data descend a computer? Be
what ports does it go out? Goes out all ports on the hub matter. Fact hubs haven't always even required power. At one point in time, hubs were just racks that provided, you know, metal rack that provided a conduit for the signal. So you know, hubs again. No decision making. So a sense to be goes out. All the ports
C and D have access to that data.
Now what? Keep see Andy from picking up that data is the network card looks at the Mac. Address the Mac address on that frame and says, This is for me or it isn't for me and that's a default configuration. We'll talk in a little while about how, ah, we can configure Nick so it can pick up all traffic. That's what turns
a regular system into a sniffer, but that's a little bit ahead of where we want to be right now.
All right, so all data out all ports all the time, and what used to happen
is F as my network would grow and get larger and larger and larger. We go hub to Hub Hub now, when a sens traffic to be Who sees that traffic?
It goes everywhere on the network right now. If I'm an attacker
and I plug a sniffer into this port on the hub
and all of sniffer is is it's a computer or host with the network card in a mode called promiscuous mode and promiscuous mode means that that network card can capture any traffic on the network, regardless off with the Mac address is okay. But
if I plug a sniffer in here and I can capture any traffic on the network, regardless of where it's destined,
what traffic will this sniffer have access to
every bit of traffic on this network? That's a real problem. So not only were Hub's not efficient because they didn't do any sort of directing or addressing hubs also were pretty big security vulnerability because all traffic from everybody's on the network at all times.
the other big problem is
the way Ethernet networks work, and most of us are on Ethernet networks.
Every computer is competing with every other computer for time on the cable
A and on Lee one system can have it stat out on the cable at a time or you have collisions. So a isn't just completely competing with B and C and D. It's competing with all
Now, if you've just got a couple of systems plugged into a hub, that's fine, right? You're not really gonna have a problem. But as my network grows and grows and grows and grows, I'm gonna have a lot of collisions. And if you think about traffic on the highway, collisions really slow things down.
So what was the point of a hub? You know, honestly, the best thing ah hub ever did for us was to be cheap.
Ah, Hub was cheap. That was the biggest reason I said, Oh, I'll put a hub here because I was tight with money. Okay, I knew it didn't do a dressing or any of those problems, but it was a quick, easy way to connect some computers. But now all of a sudden, I'm having a lot of collisions on my network. We don't want collisions. People are complaining
So what we used to do
is we would bring in a switch.
Now a switch does too big things that ah hub did not do.
first of all, a switch
uses Mac addresses, so that switch is able to determine
Hey, Traffic four, computer. Why goes out this port traffic destined for computer B goes out This port
traffic destined for Computer J goes out this port as well.
So that's good. It's sort of acts like a police officer at an intersection When the lights are down, you go this way, you go that way, right, speeds things up. But another big thing that switch does to help with performance
is it creates what we refer to his collision domains. Or we could talk about that isolating collision traffic. So what that means is, every port on the switch is its own collision domain.
a is just competing with other systems on this port
for time on the cape. Okay, J and K are just competing with each other. Why and Z are just competing with each other. So what we've done is we've taken one large collision domain where everybody's fighting with everybody else for time to communicate. And we've created three smaller collision domains. That's good. That helps with traffic. Okay, but
go back to what hubs
did for us. What was the biggest benefit of a hub?
So in the past, this is how we connected. However,
with the advent today of links ISS, Netgear and some of the other switches that are so very cheap,
they've really taken away the job of a hub. And because they provide better performance and greater security, we've now
replaced our hubs with switches.
Okay? And maybe we'll go switch to switch
Traffic for B goes out. Just this port
traffic for J goes out this port Really? On this switch, this port and then this port on the switch. So what we've done now think about how many collision domains we've created. We've created every port on the switches, its own collision domains. So what can you tell me about collisions in a modern switched network?
We've all been eliminated them right again. Huge benefit from a security perspective. Also, something to think about.
Now if I plug my sniffer
into this port on the switch what? Traffic is coming out. This port
shouldn't really be anything. I mean, things like Matt broadcasts and stuff that we're not really concerned about right now, But no meaningful traffic should be coming out that poured on the switch, so that helps a tremendous amount in the realm of security. So switch much better than Hub, which is really why we're not using hubs at all today. I could get a switch for 30 bucks,
which is what hubs used to cost.
There's no reason for a hub.
Okay, so we're going switched to switch to switch. And that's very handy.
As an attacker, I would much rather you have used to switch a hub on your network switches. Give us the security benefit,
but here's a problem that switches don't solve for me.
J a N K. There in the sales report
and the salespeople have an application they've installed that requires on broadcasts. It has a lot of broadcast. Now, if you think about a broadcast, where does a broadcast go on? The network
goes everywhere, right? So when J broadcasts and specifically broadcast something that on Li Ke needs, that broadcast goes all the way across the network.
Now it's not that all broadcaster bad because they're not.
It's just that unnecessary broadcasts are very negative thing. A switch doesn't help me with that
Okay. What do I need to help me? I need a router. That's the primary job of a router.
Okay, Now, for those of you, a little bit Maurin advanced in networking and you're going, Oh, but a switch blah, blah, blah. I am building for dramatic effect, so be patient. I probably know what you're getting ready to say. Just build with me. Okay? So
when I bring in a router,
arounder does two things.
Okay, First of all, a router uses I p addresses, which means I have logical separation of my domains. Okay, I can group domains based on logic. I can put the sales domain. Aiken, regardless, where the computers are located, I can have the production domain. The
voice over I p domain, whatever it is that I want to have.
I p addressing I assign Mac addressing is bound to the network court, so we don't generally change the Mac address, but I p addresses can change based on my configuration. All right, so this will be the sales to Maine.
And let's say this is the 10 network.
Okay, This might be my production network,
and maybe they're the 17 to 16 network, and this is,
Let's say this is my human resource is
Okay, so a router is ableto understand
that traffic to the sales network goes out this port on the router
router to the production network goes here
and router to HR. Traffic for the HR network goes out this port A routers able to look at those I p addresses and make decisions. Switches cannot switches used Mac addresses, so that's a big benefit. Okay, so when you hear the idea of routing of traffic, that's what's happening. Also, the understanding
that a router has, and the ability to connect different network ideas is a big part of what around does
now. The other thing that a router does
is it isolates broadcasts.
Okay, so what that means is, each port on the router is its own broadcast of May. So when J. Has that sales broadcast now, it's isolated to this port on the router, and it doesn't carry through, doesn't goto other networks, so that's a big benefit as well.
Routers also provide those basic service is with switches with isolation of collision domains.
So you get further collision domain isolation at each of those ports as well, so that's very helpful. So we have a hub that was just cheap, right? We have a switch that gave us greater capability, used Mac addresses in order to direct traffic and isolated collisions to help us with traffic.
the next step, and they also isolate broadcasts as well. And they allow different network ID's to communicate.
The downside of a router, though, is that a router is very expensive. And I'm not talking about Alexis and Netgear routers I'm talking about like grown up routers. Riel routers you would use in production are very, very pricey on Dhe when we talk of them being very pricey, we're really trying to think about things in terms of a port
So, for instance, if I go out and I buy switch, I'm gonna get switched. That has 36 ports, 24 ports, 48 ports. I get a lot of ports on the switch when I go out and I buy a router going to get one port
or maybe two ports for the local area network, so when it comes to port by port basis on a router. Very, very expensive. So if you tune into the next sessions next Wednesday, we will talk about what we do to get
the functionality of a router, but still save money. And your cliffhanger have you running back next week is we're gonna bring up the idea of the lands. Layer three Switch layer three switches as well. I hope you tune in. We look forward to seeing you next Wednesday.