ITCN PT Introductory Lab

Introduction to Computer Networking

Laboratory Work – Packet Tracer 5.3

Introduction

The object of today's laboratory work is to learn to use Packet Tracer. This is a visual application that allows you to design a network and run simulations of the network traffic. Once you have learnt to use the application, you will use it to test various network designs and draw conclusions regarding the delivery of frames.

Follow the instructions below and use a pen and paper to keep a record of your responses to the questions.

This work will be assessed informally during the lab period and formally at the end of term.

Method

Run the tutorial for the Packet Tracer application. The tutorial can be found in Packet Tracer under the Help menu.

This application is only available via the NAL window.

When you have finished the tutorial, complete the TWO exercises below and answer the questions in red and also the questions at the end (Further Questions to answer). This laboratory work is intended to allow you to see the effect of congestion on an Ethernet network.

When configuring the delivery simulations, you need to change the Packet Tracer mode from Realtime to Simulation. You can observe the passage of packets of information around the network using the Auto Capture/ Play button.

Exercise 01 - Hubs

Hubbed Network

Your network should appear similar to that shown below

Build phase

· Make a network with 3 PCs connected to a hub

· You will need to choose the appropriate link between PC and hub. This is a Copper straight through cable.

· Choose a /24 IP address. Add identities to all PCs i.e. an IP address from the chosen network and default subnet mask.

1. What network topology have you created?

Run phase

· Give one PC a frame at time = 1 whose destination is one of the other PCs

· Run the simulation

· Watch the events taking place with the frame during delivery

2. Make a note of how many PCs this frame was delivered to. *

Save in the simulation window with an appropriate name

*You may take a screen dump of this and edit it using Paint [Alt Gr+print Scrn; Start; Run; pbrush]. It is better to save this type of picture as a gif to save disk space.

· Now add a second frame to another PC also at time = 1 whose destination is any one of the other PCs

· Run the simulation

· Watch the events taking place with both of the frames during delivery

3. Make a note of what happens.

Save in the simulation window with an appropriate name

4. What do you need to do to ensure both frames get delivered (apart from replacing the hub with a different networking component)? Hint: could you send the frames one after the other instead of all at once?

5. How many intervals for all 3 PCs to send one message each?

Save in the simulation window with an appropriate name

Hubbed Networks connected with a Router

Build phase

Save the entire project as [your-name]01

· Duplicate your network using a different network number for each of the 3 extra PCs

· Put a router in between each network

· You will need to choose the appropriate link between the hub and the router

· Add suitable IP addresses to the router interfaces

· Remember that the router interfaces must be on different IP networks

· Each PC connected to a particular router will have the default gateway that is the same as the router interface

· Make sure IP identities have been applied to all PCs and interfaces

· Make sure that all PCs on your network have the correct default gateway configured otherwise the frames will not reach the router

Your network should be something like that shown below

Run phase

· Give one PC a frame on each of your two networks whose destination is one of the PCs on the other network

· Run the simulation

· Watch the events taking place with the frames during delivery

6. Make a note of how many PCs each frame was delivered to and the other events during delivery

Save in the simulation window with an appropriate name

· Now add a second frame to two other PCs whose destination is any one of the other PCs

· FOUR frames in total should be ready to send at time = 1

· Run the simulation

· Watch the events taking place with both of the frames during delivery

· Adjust the sending time so that all of the frames eventually get delivered

7. Make a note of this and how many intervals this event took to complete.

Save in the simulation window with an appropriate name

8. How many intervals for all 6 PCs to send one message each?

Save in the simulation window with an appropriate name

Build phase

Save the entire project as [your-name]02

Exercise 2 - switches

Switched Networks connected with a Router

Build phase

· Now replace both of the hubs with switches

· Add IP identities to all PCs if needed

Your new network should look something like the one below

Run phase

· Give one PC a frame whose destination is any one of the other PCs on its own network

· Run the simulation

· Watch the events taking place with both of the frames during delivery

9. Make a note of this and how many intervals this event took to complete

Save in the simulation window with an appropriate name

· Now add a second frame to another PC whose destination is any one of the PCs on the network that is the other side of the router

· You should have 2 frames to begin delivery at time = 1

· Run the simulation

· Watch the events taking place with both of the frames during delivery

10. Make a note of the events during delivery and how many intervals this event took to complete

Save in the simulation window with an appropriate name

· Give one more PC a frame on each of your networks whose destination is any one of the other PCs the other side of the router

· You should now have 4 frames to be delivered starting at time = 1

· Run the simulation

· Watch the events taking place with both of the frames during delivery

11. Make a note of this and how many intervals this event took to complete

Save in the simulation window with an appropriate name

· Now add a frame to the remaining PCs on each network whose destination is any one of the other PCs so that each PC has one frame to send

· All PCs should now have a frame to deliver starting at time = 1

· Run the simulation

· Watch the events taking place with both of the frames during delivery

12. Make a note of this and how many intervals this event took to complete

Save in the simulation window with an appropriate name

Build phase

Save the entire project as [your-name]03

Further Questions to answer

13. What difference in delivery times did you notice when switches were used instead of hubs?

14. Which PCs do transmitted frames reach in a network connected entirely with hubs?

15. During your simulations, in which network devices did queues develop?

16. What type of computer hardware does this suggest must be present in these devices?

17. What difference in network performance would there be if a Switched network were connected to a Hubbed network using the above conditions?

18. What is the term used to express the condition when only one PC is connected to each switch port?

If you complete these exercises and wish to experiment, build TWO large networks, one with hubs and one with switches and for each network attempt to calculate the average interval time required for any PC to send a message at times of high network usage. Document your experiment and your results. Which network gives the best service to the end users?

Keep a record of this work in your log book. Show it to your lab demonstrator before you leave.