Intro and Topologies

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9 hours 49 minutes
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will continue on into module three of our network plus course
module three is going to cover network infrastructure.
As we move into the objectives, I want to give a heads up that this is a lengthy section because there's so much network infrastructure.
First, we'll discuss network topology
from a bird's eye view. That's how everything is connected. Together. The physical network topology
will cover logical topology as well,
which is more about how data moves on the network and how individual systems are able to communicate.
Then we'll focus on wired communication and media that we use.
We'll discuss twisted pair co axial, cable and fiber optic as well.
From there, we'll move into wireless communication and its specifics and wireless security.
Next, we'll look at network connectivity devices, how we connect these elements together and the fact that different devices are going to provide different functionality.
We'll try to remove some of the mystery about switches, routers, layer three switches, V lands and dip various devices.
We'll also get a little bit deeper into switch and villa and configuration.
Then we'll move on to looking at routing configuration firewalls and how, if we create these network segments we protect traffic flowing from segment to segment. Last but not least, we'll talk about W. A N Technology,
as promised, will jump right into network topology.
First, we'll discuss physical topology, which is how the systems are arranged on the network and how they communicate with each other.
Then logical topology will cover how they communicate, who gets time on the cable, when and how. That's determined.
starting out with physical topology will begin with the bus network.
This was a topology that was common when I first got into networking.
A bus network involves a central segment of cable or a central trunk, and usually that was thinks co axial cable.
You see the individual nodes or host connected directly into the cable and use devices called vampire tops that would literally crime pierce into the coaxial cable to provide the connection with the termination. On each end,
termination was there to prevent something called signal bounce, where the signal just kind of stays on the line and bounces throughout the network. We had to have a termination on our cable
When looking at this diagram, be sure to realize that everybody is connected into the cable. There is no central point of connectivity other than the cable. What that means is, if the cable goes down, our network goes down.
One of the things about co axial cable needing to be terminated is if there's any sort of break in the cable. There's a break in the termination and therefore you have a signal bounce.
A single break in the cable could send the entire network down.
The other thing was, it was difficult to trace that break in the cable. You've got this long segment of cable, and knowing where the break happened could be very challenging.
As for how these hosts communicate, it was a free for all because there is no device to direct traffic. And this was with early Ethernet networks.
If you'll remember from previous chapters, we said Ethernet uses a media access mode called C S. M. A. C D carrier sense multiple access with collision detection, meaning every host is going to sense the cable, determine if somebody else's transmitting and if so, put their message out there.
But other notes could be listening at the same time, and everybody put their message on the cable at the same time.
If that's the case, we have collisions
in this environment because we're all in one giant collision domain. We're going to have a lot of collisions. It was just something that we dealt with using bust apologies.
In this diagram, we have a physical bus. You can tell it by the central strand of cable or the central trunk of cable. It's also a logical bus, and a logical bus means a single collision domain. Everybody fighting for time on the cable. This is one of those few instances where the logical meets the physical.
Moving into ring topology. It's not difficult to figure out why it's called a rain. It's because each note is connected to each other and is connected in a ring and ring out fashion
node one would connect to ring one on No. Two. Then No two would use ring out to connect to Node three and so on. In a true bring environment, any break in the cable would take the network down, and so would any no that was malfunctioning because no one job is to pass the ring to know, too.
If we have a malfunctioning no, that can also bring the network down, so that gets up very tricky
and most ring to apologies. You have a single frame that traverses. The network host has to grab or capture that frame in order to communicate.
There's only one frame, and you can't communicate without it. So typically we would have no collisions again, exactly as it is. This is a ring topology because there's a token traversing this ring. It's a ring from both the physical and logical perspective. A concern here is that there's way too much dependent on single points of failure.
Often, what we do is bringing a device called a multi station access unit. Rather than physically connecting those nodes to this idea of a ring, we would connect it into the central device that, when put in the middle, look like a star.
If you can envision a device in the middle that all nodes connect directly to that, that's going to give you a star physically. But a ring logically
here is our star. It looks like a star, and you can see why. What we have is notes connecting into a hub as our central point of connectivity. Here's the thing about a hub. It sends all data out all ports all the time. So we really have a physical star but a logical bus because we're one giant collision domain.
If we change that device in the middle to a switch, then we would have a physical star and a logical star, because the switch is going to direct traffic out of the appropriate ports.
If you think about the main star bus rang, you have the physical topology, which I show they look in the diagram and then you have the logical topology, which is really more about how traffic is directed.
There are other types of topology specifically mesh with the mesh. Every node is connected to every other node that can be expensive so many times. For redundancy, we might use a partial mesh, which is going to allow multiple paths to get traffic from one spot to another.
You can see partial mesh compared to a full mesh and see Yeah, there's going to be a lot more expensive because we have all these connections, from node to node to node that's extremely fault tolerant. We might need that if we're talking about w and connectivity for multiple offices. But as far as seeing something like that in L. A and probably not,
we also have hybrid technologies. You might see a star bus or star ring or any sort of combination. Of the two apologies
that would be considered a hybrid.
The idea is, it's really about what meets your needs best as far as how communication is going to happen.
Word of realism we don't really use a lot of the ring topology is today. That's back in the day when we had a token ring, and that's something that's gotten off the L. A. N.
You may still see some of the ring topology is for Metropolitan area networks, but it's not really something we see on the Elliott.
The start technology is very popular, of course, because we have various devices connected into switches.
Sometimes we might have a long, trunk connecting switch to switch, which would be a star bus.
The truth is, somewhere in the middle, we mix and matched apologies as we need them.
The bottom line. Don't forget physical and logical. I think on the exam will ask you to know the difference
when you're looking at a diagram The first thing you want to look at is its shape, so to speak. If it's a central trunk or cable, you've got a bus. If it's connected, ring, you've got a ring.
If you're connected to essential device, that's a physical star.
When it comes to logical topology, though, it's more about how data is moved on the network and how traffic is directed and controlled to provide access for the individual nodes.
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