Lab 1: Network from Scratch

Overview

In this lab you will work with your classmates to construct a local area network (LAN) from basic principles. First, you an a partner will work together to network two machines via such that you can run the chat server/client software provided. Following, you will join your small, two-person network with the rest of the classes network, and, finally, we will create a gateway such that Internet traffic can exit the LAN.

Oh, and you also have to crimp your own cables!

Deliverables

One working RJ45 standard cable
Lab write-up and answers to all associated questions to be turned in hard copy on Tuesday 9/11 to Bridget Rothera in Science 239

You may consult the Internet, your classmates, or your book to answer the lab questions.

Associated Files

Group Work

Part 1 and 2 of this lab is to be done with a lab partner. Be sure to indicate your lab partner in your lab write-up. Part 3 and 4 will be done class-wide.

Part 1: Cat-V Cables and RJ-45

In this part of the lab you will crimp your own cable with your lab partner. Individually, you and your lab partner you will each crimp a standard RJ-45 cable and a single single RJ-45 cross-over cable. A wiring chart will be provided to you in lab, as well as requisite equipment, such as a cable crimper.

Questions:

What is the order of RJ-45 A wiring? How is it different for RJ-45 B?
What is a cross-over wire and where are they used? What exactly is "crossed over"?
Why do Cat-V wiring consist of twisted pairs of wires?

Part 2: Two-Person Network

In this part of the lab, you and were partner must setup a two-person network that connect your computers together using the cross-over cable from part 1. To accomplish this task, you must manually configure your wired network interface.

On your computer, you must first turn off DHCP, and instead select manual setup. Next, you and your partner need to choose different IP addresses in the 10.0.0.X range. Finally, provide a netmask of 255.255.255.0. You can ignore the gateway/router setting for now.

Once your network is setup, test it using the ping command, ensuring that each of you can ping the other computer at the choose 10.0.0.X address. To run ping, open a terminal and issue the command:

shell> ping 10.0.0.x

Following, run the chat_client/server software and have a chat with across your little local network. To start a chat, each person must first start the chat server:

shell> python chat_server.py

And next, in a separate terminal, run the chat client

shell> python chat_client.py 10.0.0.x

Where 10.0.0.x is replaced with the IP address of the server destination. Additionaly, these programs have other options, which we can discuss if needed.

Questions:

What is the subnet mask and what is its role in the LAN?
What happens when you and your lab-partner choose the same IP address?
Provide a trace of a conversation between you and your lab partner using the chat_client.py and chat_server.py scripts.

Part 3: LAN

In this part, you will expand your local network to include another group, a total of four computers. Grab a switch and using the standard RJ-45 cable, everyone connect to the switch. Make sure that everyone selects a unique IP address. Run the chat_server/client program again and ensure that everyone can communicate with each other.

Once completed, continue to expand your local network to include other groups by connecting switches to switches until everyone in the lab is on the same local network. To see who is connected, you can ping the broadcast address like so:

shell> python chat_client.py 10.0.0.255

Questions:

Did everyone need to be on the same switch? Or could you connect switches to other switches? What happens when you connect a swtich to another switch?
What was the ip address selection strategy used when expanding the LAN to everyone in the class?
What is a broadcast address? And how is it selected?

Part 4: Gateway to the Internet

Finally, we will setup a gateway/router connecting the class-wide LAN to the Internet. I will provide the gateway/router on IP address 10.0.0.1.

Questions:

How can everyone on the LAN share a single IP address?
How does your computer know to send traffic to the gateway, as opposed to machines on the local network?