Discovering computer networks: hands on in the Open Networking Lab
Discovering computer networks: hands on in the Open Networking Lab

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Discovering computer networks: hands on in the Open Networking Lab

9.1 Connecting devices

So far, you have been using network simulators to learn how to connect and configure network devices. Computer simulations are really useful tools for learning about computer networks, but it is also helpful to see the physical devices that these simulated components represent.

Knowing what these devices look like and, for example, where to plug the cables in, should help you associate the computer representations with the real thing.

In this first video, you will see what a server room is like. You will see network devices, such as switches, routers and servers, in action. A server is simply a computer, but as it usually serves a single function, or a limited set of functions. It doesn’t have a user driving it, so it doesn’t need a monitor, keyboard or mouse.

Watch the video now, which is about 2 minutes long.

A server room

Download this video clip.Video player: 55_a_server_room.mp4
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Hi. I’m Andrew Smith from the Open University.

As you can tell, it’s really noisy in here because of all the networking equipment in this server room. In a little while I’m going to be introducing you to all the equipment in this room and its purpose and why we use it in networks and running the internet.

So it should be a little quieter now. We are actually looking at what’s called a patch panel. This is all the cable connections between the server room and the computers in the network, whether it’s your school computer, a teacher’s computer or an employee’s computer. Each of the flashing lights show data that’s travelling on the network now whilst I was taking this video. Some of these lights are very, very busy and some of them are not so busy.

This cable run here shows the run from the patch panel across the building to all the other computers.

We use this server room to teach Cisco networking. In this cabinet are switches that are used to run large buildings. You may discover that banks, other corporations use these switches to make sure that all their employees are connected and they can run their daily business.

We’re also looking at a series of routers. These connect networks. These connect buildings together or organisations together or different nodes on the internet. These are some very powerful routers. At the back we can see they are cabled differently. These blue cables are serial cables for wide area network links.

Finally, we get to look at some servers. These could be web servers, file servers. They could be telephony servers. They could be streaming your videos to you now. We run a number of servers in our labs offering a considerable amount of storage as well as many other services. Hopefully, you’ll find it’s very useful. You’ll discover in Open Networking Lab all the equipment that I’ve described. The cables, the routers, the switches and the servers exist as part of the PT Anywhere simulator.

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Activity 1 Think about

5 minutes

  • 1. In the video you saw many switches and routers. What is the difference between a switch and a router?

  • A switch connects devices in a single network; a router connects networks to other networks.

  • 2. The video also showed lots of flashing lights on the devices. What were these indicating?

  • The flashing lights indicate that data is being transferred.

  • 3. At the end of the video you saw some servers. What kind of servers were mentioned? Do you know what these different kinds of servers do?

  • Web servers host websites; file servers store files, telephony servers offer digital phone services.

Now watch the video below, which is about 3 minutes long. It starts by showing a lab environment where two laptop computers are being connected to a switch using Ethernet cables, and the switch is connected to a router.

Connecting devices together

Download this video clip.Video player: 56_connecting_devices_together.mp4
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In this demonstration we’re going to look at how devices are connected together. We will use Packet Tracer to set up a small network. Before we do this, we’re going to show you the same network connected up with real devices in the lab. so that you can equate them to the equivalent in Packet Tracer.

To save time we have already positioned the devices on the desk and obtained all the cabling required. The diagram of the network topology we are using is here.

Firstly I’m going to take a network cable and connect it to the data socket on the wall. This is the internet feed. The other end of his cable connects to gigabit 0/1 of the router.

Next I’m going to put a cable between the left-hand laptop’s fast ethernet port and the port fast ethernet 0/1 of the switch. Then I’m going to put the cable in between port fast ethernet 0/2 of the switch and the right-hand side laptop. Finally, I’m going to take a network cable and connect the router’s port gigabit 0/0 to port fast ethernet 0/24 of the switch. Now we have our finished network. OK. So not everybody has a nice pile of equipment available to set up a real network. In order to help people learn networking without having access to real equipment, Cisco have developed the Packet Tracer network simulator. This allows students to learn about networking without the need for real kit.

Now we’re going to create exactly the same network in Packet Tracer. When we open up Packet Tracer, we start off with an empty page. The beauty of Packet Tracer is that we can pretty much do whatever we like, and make networks with many devices and combinations. We are going to construct the same network as we set up in the lab. Firstly we will go to the WAN emulation section and select the PT Cloud. This will represent the Internet. Next we will go to the routers section; select a 2900 series router, as this is what we had available in the lab. at the time.

Next we will go to the switches section and select a suitable switch.

Finally we go into the end-user devices and select a laptop. We can simply drag and drop two of the laptops onto the page: one for the left, and one for the right.

We now have all of our devices positioned on the diagram. Now we need to connect them all up. Using standard ethernet cables we now connect the devices up. When you take the relevant cable, and click it over the device, a list of port numbers will be displayed. All you need to do is click the right port number, and the Packet Tracer will connect one end of the cable to that port. Go to the second device with the same cable, click the device, ands select the correct port for the end of the cable. We now have the internet connection connected to gigabit 0/1 of the router. Next, take the same type of cable and connect up port gigabit 0/0 of the router to port fast ethernet 0/24 of the switch. Finally, we take a cable and connect fast ethernet 0/1 of the switch to the left-hand laptop, and another from fast ethernet 0/2 to the right-hand laptop. Now we have our network connected up. This is all of our hardware sorted out, but it’s not going to work until we program it all. We will be doing that in a later session.

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The video also shows an equivalent network being created in the Packet Tracer network simulator. Later in this session you will have a go at building the same network using PT Anywhere.

Activity 2 Think about

5 minutes

  • 1. Could you make out how many ports the Packet Tracer switch had? How did this compare to the physical switch in the lab? What about the router – did it have many ports?

  • In Packet Tracer you may have been able to see that there were 24 Fast Ethernet ports on the switch, whereas the switch in the lab had 48. The router (both simulated and physical) had just a few ports (which is typical), but these provide Gigabit Ethernet connections. In fact the router used in the Packet Tracer network is actually a representation of the same model of router (2900 series Cisco router) used in the first video.

  • 2. In the video, which devices were connected to the switch?

  • The laptops and the router were connected to the switch.

  • 3. What was the router connected to and why?

  • The router was connected to the switch and also connected to a socket on the wall which provided access to the internet. Routers are needed to connect a network to the internet.

Activity 3 Try it out

10 minutes

As a revision exercise, use PT Anywhere [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] to create the same network that you saw in the video. You will need to drag into the main screen the devices that will make up the network, and also the cloud symbol that represents the internet. Just build the network for now making the necessary connections between the devices. You don’t need to configure any devices (unless you want to do this to practise what you have learned earlier in the course).

Hint: when making the connection between the cloud and the router, choose the Cloud’s Ethernet interface.


Here is an image of the finished version of the network.


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