*** = write down and submit answers to these questions/problems. I recommend you use a google doc to record your answers. ***
In this exercise, you will create your own private LAN out of 3 computers and a hub, and then change the LAN's configuration a few times.
Record your answers to the questions marked *** for submission.
"Trio up" with 2 others to form a group of 3 people, each with a computer. Boot each computer into Linux with the flash drive. On each computer, login as mradmin, and open a terminal window. Get 3 Sticky Notes from your prof.
On each computer, do the following:
ip addr and note the name of the interface that has the 153.106.*.* IP address. ip addr again. It should not have an IP address now. ip addr to see if the interface is up and see that it has no IP address. *** Q1 How does ip addr indicate that an interface is up -- i.e., attached to a cable? ***sudo service network-manager stop
If we left this daemon running, it will keep reconfiguring the interfaces over the top of what we are doing.Assign IP addresses to each machine. To assign an IP address, use sudo ip link set and sudo ip addr add, as shown below:
sudo ip link set eth1 up
sudo ip addr add 15.0.0.200/24 broadcast 15.0.0.255 dev eth1
For the other 2 machines, replace .200 with another value (like .201 or .199) and eth1 with the appropriate network interface name on that machine.
*** Q2. Document how you have set up your computers, including your IP addresses and MAC addresses on the 3 machines. ***
Make sure all machines can ping each other.
Designate one computer as "computer1" and run wireshark on it. In a terminal, start pinging "computer2". Start capturing packets in wireshark. Watch the packets going by for a few seconds.
*** Q3. Document the source and destination MAC addresses and IP addresses in the captured ping packets. Also, document what protocol ping actually uses. In that protocol, document the type value for a ping request vs. a ping response. ***
Run arp -n on each machine (including "computer3") to see the arp table (the arp table holds the mapping between an IP address and its MAC address). *** Q4. Note what values are in each ARP table. ***
Now, try this. Stop all pings. Then, do a ping from computer 2 to computer 3. On computer 1 (where wireshark is running), do you see the ping packets ? *** Q5. If so, what can you learn from this about the operation of a hub? ***
Next, set up 2 hubs in your little network: Connect computer 1 to hub 1, then hub 1 to hub 2, then hub 2 to computer 2 and computer 3. Make sure all computers can ping each other. When connecting hub 1 to hub 2 make sure the little green lights come on.
If the lights don't come on, make sure you are using port 4 for the ethernet cables that connect the 2 hubs together. If the lights still don't come on, check out this website (if you can get to it on your cellphone, perhaps) that talks about needing, or not needing, a crossover cable.
*** Q6. What did you have to do to get the hubs to communicate with each other? ***
Now ping between computer 2 and computer 3. *** Q7. Do you see the ping packets in wireshark on computer 1? Should you? ***
Remove the 2nd hub and reconnect all computers to hub 1. Make sure all computers can ping each other.
Replace your hub with a switch. Does communication still work?
*** Q8. How does the amount of traffic you see on wireshark change when you use a switch instead of a hub? ***
Use arp -n to look at each machine's arp table again.
*** Q9. Has anything changed? Does a switch have MAC addresses on its ports? ***
Remove all your ethernet cables and wrap them up nicely. Put your hubs and switches and their power cords back in the cabinet.
Connect your machines to the orange lab network, and run
sudo service network-manager start
Make sure the machine has a 153.106.*.* address again. Now, shutdown each machine.
Submit your answers to this lab via Moodle.
Turn in the answers to the questions marked *** by submitting the file via Moodle.
20 points total:
5 points: All questions are answered
5 points: Depth of information/investigation.
10 points: Correctness.