Hello, Siberians. I'm Kelly Hander Han, and I want to welcome you back to sessions Wednesday. Last week we talked about network connectivity but devices and we looked at what hubs used to do. Forest versus switches versus routers. Just a quick review. We said a hub
was a cheap way too easily connect devices together,
but a hub didn't do. Addressing it didn't control traffic, and everybody was fighting with everybody else for time on the network. Okay, so switches gave us a tremendous benefit because with switches, those devices are able to read Mac addresses off the network card and determine where traffic should go,
right? Sort of again. We talked about it acting like a police officer directing traffic.
The other thing that a switch did force was toe isolate, collision traffic so that everybody wasn't competing with everybody else. Each system had its own sort of pathway onto the network. Almost, if you will s Oh, that was great. But we said switches did not isolate broadcast traffic.
And when you've got a lot of broadcasts and there are a lot of applications today that still rely very heavily on broadcasts,
well, switches don't help us with broadcast traffic. We need a router and a routers job was to isolate broadcast traffic and to also connect networks of different I p addresses toe. Understand that routers can understand. This is the 10 network. This is the 17 to network. This is the 192168 network,
and a switch can't do that because by default, switch looks at Mac addresses.
If you're a big OS I model person switches operated layer two of the S I model routers operated layer three. So layer two, we have Mac addresses, switches or layer to they look at Mac and trusts routers. Air layer three I p addresses Air Layer three. So that's what routers could use.
But we did say the problem with a routers that they're expensive, especially if you look at a port by port basis.
Usually, when you go out and purchase a router, you get one land port, one port for your internal network. And if we were to set it up like this, what? We're already using three ports on a router, so this becomes very, very costly. So, he said, This
is fine, but it's not really the way things work. So we've got a couple of ideas here.
One of the things that we can do, and probably the thing that we most commonly do is we bring in, yes, a switch. But
we use a special feature on the operating system of the switch
called the Villain. And what does a villain do?
It isolates broadcasts,
but what's significant about that
is it isolates those broadcasts on a switch. So here we've got a very inexpensive switch that we can get a lot of the functionality we could have had on the wrapper.
Hey, so we do that by creating villains now. The reason I said just a few minutes ago that switches don't isolate broadcast traffic is a switch in and of itself. Natively does not deal with broadcasts. A switch deals with collision domains and Mac addresses. That's what a switch does,
however higher in switches,
you can create the lands on these and honestly, villains are so popular day that a lot of even the lower end villains you can create one or two of those. But I just want to stress, especially for any of you that might be taken to some tests. Ah, any sort of certification test switches are layer to.
They divide traffic into collision domains and they use mac addresses
because that's how they are natively. All right, But I can take that broadcast isolation feature of a router and implemented through what we refer to as a villain. So what I could do is I can connect the sales,
the land to certain ports on the switch
and a sign those a grouping of 1,000,000,000 won or I can call it sails the land.
Hey, I can use this port for my production. The land
and I can use this port
So what have I done? I've created three separate broadcast remains on a switch. Just like I would do is a router. And look at all these beautiful ports I have left. I can create lots of other villains. I can plug other devices into them. And this again, it's just a feature that you can use and you set up through the operating system on a switch. Great.
So why not just do this? Well, in some ways, we do, but we still have an inherent problem with this configuration,
we still have a switch that is a layer to device that can on Lee understand Mac addresses.
So the problem with this is when I do create a villain and let's say I just assign these ports
to the sales Phelan, let's just say I sign a couple of ports there.
I'm gonna go a little crazy here and color code. So hold tight.
They will say those are the production villain. I'm out of colors. So there goes color coded. And this is the sales feeling or I'm sorry, the HR villain. So that's great. I've created three different broadcast domains,
but a switch uses Mac addressing.
So what the switch doesn't understand is that traffic for 17216.1 dot one
goes out the sports.
Okay, were traffic for 10 111 goes out. These ports were trafficked for 192168 goes out this port.
Okay, a switch doesn't have knowledge of I p addresses.
Okay, so that's the big difference. So what we have in this situation is we do not get inter villian communication,
okay? We don't get that, because what does a host do when it doesn't know how to reach an I P address. When the first things it does is it broadcasts out right, and then it looks to a default. Gateway, a gateway of last resort, might be called when we were switching. So one of the ways that we could enable
interval and communication
we could bring around her in here.
and we have that extended might hear people talk about villain trunk ing when you're connecting a villain on a switch to another device. And this router would enable routing in between. Why? Because the router understands Layer three addressing I p address. Okay,
we actually used to call this roast
But remind me again,
what was the problem with the route?
So this doesn't help me a whole lot from what we had before.
So for those of you playing along at home,
whether or not you've been on
layer three, switch or not,
if we do spend the extra money and instead of buying a standard layer to switch, we spend a little more money and we pay for a layer three switch. What function do you think a layer three switch has that a layer to switch doesn't have
uses I p addressing and acts as a router again, cheaper, more efficiently.
That's a great deal. So what we're looking at is if you go in the server rooms now with the ah, you know all the devices you will see for internal communications. Most organizations have gotten rid of their internal routers in favor of layer three switches set up with villains.
It's cheaper. It's easier to logically configure.
It's just all around, really a better process for
so I want to stress again that this is not true of all switches. Not all switches can read. Layer three addresses. It has to be specifically you might hear multi layer switch MLS. Or you might hear people talk about a manage switch. So a layer three switch has this capability that allows inter veal in,
Um, so then that becomes the question becomes, well, routers obsolete? No,
However, routers air now primarily used to get off the local network for our internal. For our land networks were primarily using switches with villains. However, we want to connect up to the Internet. We want to connect across on NPLs link.
We want to connect to our local office via VPs. You know any of those other means
We're still going to need a router to get off of our network, so we're not done with routers. But routers have really shifted into becoming more like when devices and we're using Layer three switches with fi lands for internal device. Okay, so I hope that clears things up. I find that even people that have been in networking for quite a bit of time
don't always know exactly why we used hubs and why we don't today
what benefits of a switch versus a router versus later three switch versus villain and all these different things. So hopefully that's cleared up A little bit of mystery for you. Thanks for watching, and I hope you come back next week. Decisions Wednesday