Network Topologies – N10-008 CompTIA Network+ : 1.2

There are many different network types and topologies. In this video, you’ll learn about star, ring, bus, mesh, hybrid, and wireless topologies.

When you’re designing, building or troubleshooting a network, you’ll be using a network topology type that can vary depending on the technology you’re using. If you’re looking to understand the way the data is flowing or you want to plan to create a new type of network, then it’s useful to understand what these topologies might be. This is also useful during the troubleshooting process, because you’ll know exactly what flow the traffic takes to get between point A and point B.

One of the most popular types of topologies is the star topology. You might also hear this referred to as a hub and spoke, where the hub is in the middle and the spokes are along the outside. This is a topology that you’ll find on almost any network regardless of the size of the network. And you’ll also find that most devices are connecting back to the central hub of the star.

For example, a switched ethernet network has the ethernet switch in the middle of the star. And then all of the devices run directly back to this particular switch. They’re not connecting to each other. They’re instead connecting back to the central switch in this star topology.

Although we don’t often see a ring topology used on our local area networks, it’s still a topology type that’s used quite often for wide area networks. So although many people will remember the older token ring technologies that we used to run inside of our local area networks, we don’t generally find those ring networks any longer. But if you’re connecting over a metropolitan area network or a wide area network, we use ring networks extensively.

It’s not because a ring technology somehow lends itself to work better over a wide area network. It’s because we can create additional redundancy using the ring topology. For example, a very common way to send traffic over a ring network is to have the traffic simply go in a circle. Now if we’re on this wide area network and there’s construction going on and someone happens to sever a fiber connection that’s being used for this metropolitan area network, then we’re not going to be able to send that traffic through the rest of that ring.

But the devices that are on either side of that severed link recognize that traffic is no longer able to traverse that connection and instead will loopback the connection on those individual endpoints. So instead of having data go around a ring, the data will instead go to as far as it can around the ring and then loopback to get to the other side of the ring, maintaining uptime and availability even in the case where part of that ring may be severed. Early types of ethernet networks were not switched ethernet, but were instead run over coax. And this coax was quite simply a cable that was run down the middle of the room very similar to this cable.

This is a bus network. And although it was commonly used on those early ethernet networks, we can still find modern networks that use the same bus topology. One problem with bus networks is that it is a single cable that is running either through the walls or down the center of the room. And if we happen to have a break in this cable, you can see immediately that it would suddenly segment the network into different pieces. Or in some cases, cause no data to be transferred across the network.

That’s one of the reasons we moved away from bus networks for our local area networks, because one single disconnect could cause an outage for everybody else on the network. In our modern automobiles, we have bus networks that we use extensively. These are controller area network buses, or CAN bus connections. And they’re used to connect all of the different sensors and controllers inside of our automobiles to be able to make all of our cars much safer to drive on the roads.

Another popular topology, especially in larger networks, is to create a mesh between devices or a mesh between sites. We may have devices that are connected in different locations. And we might want to connect them all together. But instead of having a single connection to a particular site, we may want to create multiple connections to mesh these together. That way if we do lose any one of these network links, we’re able to work around that problem by simply using one of the redundant connections.

You’ll commonly use this type of mesh design if you’re creating redundancy or fault tolerance or perhaps you’re designing a load balance network and you can use different parts of the network to share that load. Probably the most common place to find a wired mesh network is over a wide area network where you can create multiple links to other sites so that you can have a primary connection from one site to the other and then a backup or secondary connection that you can use if you run into problems.

When you start combining these different typologies together, you create a hybrid network. A hybrid network is more than one of these topology types all working together. For example, you might have three remote sites all connecting devices together using a switched ethernet or star network. And then you may be connecting those together over a wide area network that uses a ring topology.

If you’re using a wireless network, you may be communicating in a number of different ways. If you’re using an access point, you’re probably communicating over an infrastructure connection. This means that all of the devices on your network are communicating through an access point. This is probably the most common way to use wireless connections, but it’s not the only way to communicate over a wireless link. If you just have two devices and there’s no access point that you can use, you can connect directly from one device to another using ad hoc networking.

You don’t need an access point or any other type of wireless infrastructure. You simply have one device communicate directly to another device over this wireless connection. And if you’ve added internet of things devices, which are commonly wireless devices that control our lights, our door locks, or the air conditioning systems, then you’re probably using a mesh network where all of these devices can communicate to all the other devices simultaneously to create an interconnected mesh of communication between all of these IoT devices.

One of the advantages of these mesh wireless networks is that it allows many devices to communicate to each other even if those devices are very far apart from each other. This also allows the mesh network to self-heal. So if you turn off one of those IoT devices, the remaining devices will self-heal and redesign themselves into a mesh network that will allow them to continue the communication.