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

1.3 Packet Tracer Anywhere

As part of your work in this course, you will be building networks in a simulator called Packet Tracer Anywhere. This part introduces you to the simulator.

There are two short videos to watch followed by an activity. When you’ve completed this part you should be able to use the ipconfig and ping commands in Packet Tracer Anywhere.

Watch the video below, which is about 2 minutes long. It introduces you to Packet Tracer Anywhere.

Introduction to Packet Tracer Anywhere – What is it?

Download this video clip.Video player: 07_intro_to_packet_tracer_what_is_it.mp4
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Transcript

In this course we use two network simulators.

This one uses Cisco’s Packet Tracer software, which you might be familiar with. Cisco make a lot of network hardware, and a small amount of domestic network hardware. But they’re also involved in network education and training, which is why they’ve produced the Packet Tracer simulation software.

We’ve also got this much simpler network simulator, which is based on Packet Tracer but has a much simpler interface. It can be viewed on a browser. This simulator is called Packet Tracer Anywhere, or PT Anywhere for short. I’m going to give you a quick introduction to Packet Tracer Anywhere.

As Packet Tracer Anywhere is viewed in a browser, you get to it by clicking on a link. We’ve provided a few links on this site. Depending which link you click, you might get a preloaded network or a blank screen to construct a network in. Here I’ve got a preloaded network.

The switch is a device we haven’t met yet, although we’ll look at it in more detail in later sessions. The name ‘switch’ probably gives the impression it’s something like a light switch. Actually, it’s very different from an electrical switch. The name comes from the American word for a set of railway points. In the USA, points are called ‘switches’. A set of points, or a switch, is used to divert a train from one track to another, depending on the destination. You can think of the router and switch here as forming a unit that’s a bit like the home gateway. In fact, the Ethernet sockets on the back of a home gateway are the switch part of the device. The router and the switch here are actually based on large-scale commercial devices, and they’re more complicated than domestic devices. Packet Tracer Anywhere hides some of this complication, but not all of it. But we’re not going to go into that yet. That’s for much later in the course. The PCs in Packet Tracer Anywhere, though, are standard PCs. so I’ll concentrate on them in this part.

End transcript
 
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Having seen how Packet Tracer Anywhere looks in a browser now watch the video below, which is about 4.5 minutes long. It shows you the basics of using Packet Tracer Anywhere.

Introduction to Packet Tracer Anywhere – How to use it

Download this video clip.Video player: 08_intro_to_packet_tracer_how_to_use_it.mp4
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Transcript

Now here’s a basic network. None of these devices has an IP number attached, so I’ll give them some IP numbers. I’ll start with this computer, RightHandSide. We select it, then go to ‘Edit device’, and choose ‘Interfaces’. I’m going to give it an interface address of 192.168.1.100. And for the subnet mask, the usual one for a home network: 255.255.255.0. And now the last bit, which is vital but easily missed because it’s off the bottom: ‘Submit’. So that’s sorted out that device.

Now I’ll set this one up: LeftHandSide. I’ll select it, then do ‘Edit device’, ‘Interfaces’. I’m giving this one an address of 192.168.1.105, and the usual subnet mask: 255.255.255.0. Again, the vital stage is easily missed because it’s off the bottom: ‘Submit’.

OK. Those computers now have IP addresses. So I’ll check them by pinging.

An easy way to get to the command prompt is just by double-clicking on the device, like that. And there’s the command line. I’ll do ping 192.168.1.100, which was the IP address of the other computer. Let’s see what happens. Good! That shows there’s a connection there between those two computers.

Now, I can add another device to this network, and I’m going to add another PC. I just drag this one up here like that. Then, with that selected, I do ‘Connect devices’, and drag this down here to the switch. There’s a choice of interfaces here. This one, PC0 ‘FastEthernet’, is the PC. And then ‘MySwitch’ – that’s the switch, naturally.

The PC actually has only one interface; so that’s selected by default anyway. On the switch I’m going to take this one, Fast Ethernet 4, and ‘Submit’. And I’ll give this an IP address. So ‘Edit device’, ‘Interfaces’, ‘IP address’ 192.168.1, and 110 for the last number.

For the subnet mask, the usual one: 255.255.255.0. And again – so easily missed – ‘Submit’. And there we are.

Now, I’m going to check that all those are all talking to each other. I’ll go back to the one I started with, RightHandSide, and its command prompt. Type ping. And I want to check that this PC can reach the others.

By now I’m probably forgetting what IP addresses I gave them, so I’ll ping this one: 192.168.1.255. That 255 at the end makes this IP number special. It’s for broadcasting the same message to all devices on the local network. We can see we’ve got replies from number 105, that was the LeftHandSide computer; and from number 110; that was the one I added.

So those are the basics of PT Anywhere, and you’re welcome to have a play with it; and there’s an activity following this part.

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Activity 7 Try it out

5 minutes

  • Open PT Anywhere [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] in a new tab or window so you can read these instructions. One of the PCs on this PT Anywhere network is not working properly. From PC0, send a ping to its network broadcast address and use the reply to find out which of PC1 and PC2 is malfunctioning. (Hint: First you will need to discover PC0’s IP address to work out what the network broadcast address is. When you send a ping to the network’s broadcast address, the reply from the address ending with ‘.1’ is from the router.)

  • The malfunctioning PC is PC2 with an IP address of 192.167.2.150.

    To reach this conclusion you need to discover PC0’s IP address by selecting it and then going to ‘Edit device’, then ‘Interfaces’. You should have found that its IP address is 192.168.2.50 and therefore the network broadcast address is 192.168.2.255. The next step was to double-click on PC0 to open the command prompt and enter ping 192.168.2.255. The reply shows that PC0 can only talk to the device with IP address 192.168.2.1 (which is the router, as indicated in the hint to the previous question) and to the PC with IP address 192.168.2.100. It’s easy to discover that 192.168.2.100 is PC1 by checking PC1’s ‘Interfaces’ settings. Therefore it is PC2 that is malfunctioning. This PC has an IP address of 192.167.2.150.

  • Change the IP address of PC2 to 192.168.2.150 then resend the ping to the broadcast address from PC0. What is the result?

  • The ping returned replies from 192.168.2.1, 192.168.2.100 and 192.168.2.150.

  • What can you deduce from this?

  • PC2’s original IP address of 192.167.2.150 was inappropriate for this network. (In Session 2 you will find out why this address was inappropriate.)

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