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CSIS 330 – Lab 9:  Packet Tracer

Examining a MAC Address Table

[Adapted from Cisco Networking Academy Network Fundamentals]

Background:

Switches maintain a table of MAC addresses and associated switch ports.  When a switch receives a frame, the destination MAC address is checked against the table, and the corresponding port is used to route the frame out of the switch.  If a switch does not know which port to use to route the frame, or the frame is a broadcast, the frame is routed out all ports except the port where it originated.

Access to Cisco devices can be accomplished through several means.  A console port can be used if the Cisco router or switch is within proximity of a computer.  Using the Windows hyperterm utility, a serial connection can be established.  For devices physically distant from the network engineer, network on the AIX port enables telephone access.  For secure networks, the Cisco device can be configured for a Telnet session.  In this lab, you will connect to the switch using the Command Line Interface provided within Packet Tracer.

Assignment Instructions:

1.  Open the Packet Tracer file that accompanies this assignment. (Lab_9.pkt)

The logical topology is shown below.

2. 
Determine IP and MAC addresses of devices

In the Logical Workplace, mouse over each of the following device interfaces and record the IP and MAC addresses that are shown in the popup.  Record your answers in the template provided.

PC-PT (1A)

PC-PT (1B)

PC-PT (11A)

PC-PT (11B)

Switch 2960-24TT (S1-Central) VLAN1 interface

Router 1841 (R2-Central) - FastEthernet0/0 interface

Router 1841 (R2-Central) - Serial0/0/0 interface

Router 1841 (R1-ISP) - FastEthernet0/0 interface

Router 1841 (R1-ISP) - Serial0/0/0 interface

Server-PT (Eagle Server)

Answer the following questions in the template provided.

a. Are PC-PT (1A) and PC-PT(11A) in the same network?

b. Are PC-PT (1A) and Eagle Server in the same network?

c. How do you know?

d. Which device interfaces display <not set> for their MAC address?

e. Why do these interfaces not have MAC addresses?

3. Examine the MAC address table of the switch

Click on the S1-Central switch. Click on the CLI tab.  Press the [Enter] key to enter User EXEC mode.

Type enable at the prompt.  This puts you in Privileged  EXEC mode.

Type show mac-address-table at the prompt.

Take a screen shot of your output and paste it into the appropriate section (Screenshot #1) of the Word Answer Template provided.

Type exit at the prompt.  This will return you to User EXEC mode and clear your screen of the output.  Close out of the window.

4. Ping a computer within the same network.

[Before you try to ping a device on this network, make sure you see green lights on each of the cables that are connecting the devices to each other.  If you do not see green lights, click back and forth between Simulation mode and Realtime mode until you see the green lights.]

When you ping a device that is within the same network, an entry is made in the switch’s MAC table for both devices.  By default, this entry is stored for only 2 minutes.  If you ping that same device again, the length of time the entries are stored is extended to 10 minutes.  Therefore, in this assignment, whenever you are told to ping a device, issue the command two times in order to extend the amount of time that you can examine the MAC address table.

Click on the PC-PT (1A) computer.  Click the Desktop tab and the Command Prompt button.  At the command prompt, ping PC-PT (1B).  

To do this, type ping 172.16.1.2 and press enter.

Repeat this command to extend the amount of time the entries are stored in the MAC table.

Take a screen shot of your output and paste it into the appropriate section (Screenshot #2) of the Word Answer Template provided.

5. Examine the switch’s MAC address table again.

It is important to note that MAC address entries in your switch’s MAC address table are stored for only a short period of time (2 or 10 miniutes).  As you proceed through this assignment, you will be instructed regarding how many entries to expect in your MAC address table.  If fewer entries than expected are present, you will need to return to Step 4 and begin again from that point.

Click on the S1-Central switch. Click on the CLI tab.  Press the [Enter] key to enter User EXEC mode.

Type enable at the prompt.  This puts you in Privileged  EXEC mode again.

Type show mac-address-table at the prompt.

Take a screen shot of your output and paste it into the appropriate section (Screenshot #3) of the Word Answer Template provided.

Type exit at the prompt.  This will return you to User EXEC mode and clear your screen of the output.  Close out of the window.

At this point, you should see exactly two rows in your MAC address table.  If you see more than two rows, close out of Packet Tracer WITHOUT SAVING, and reopen the pkt file.  Wait until the green lights appear on the connectors and resume this assignment starting with Step #4 above (Ping A Computer within the same network).

Once you have exactly two rows in your MAC address table, answer the following questions in the template provided.

Questions:

a. What device belongs to the MAC address listed in the first row of the MAC address table?

b. What device belongs to the MAC address listed in the second row of the MAC address table?

6. Ping a device in a different network.

Following the same procedure that was outlined in Step #4 above, click on PC-PT(1A) again and try to ping Server-PT (Eagle Server).

[Note that you will have to use the IP address for the Eagle Server that you determined in Step 1.  ]

Issue this command again to extend the amount of time the entries are stored in the MAC table.

Take a screen shot of your output and paste it into the appropriate section (Screenshot #4) of the Word Answer Template provided.

7. Examine the switch’s MAC address table one last time.

Click on the S1-Central switch. Click on the CLI tab.  Press the [Enter] key to enter User EXEC mode.

Type enable at the prompt.  This puts you in Privileged  EXEC mode again.

Type show mac-address-table at the prompt.

Take a screen shot of your output and paste it into the appropriate section (Screenshot #5) of the Word Answer Template provided.

Type exit at the prompt.  This will return you to User EXEC mode and clear your screen of the output.  Close out of the window.

At this point, you should see three rows in your MAC address table.

Answer the following questions in the template provided.

a. To which device does the new MAC address in the table belong?

b. Why is the MAC address of the Eagle Server not among the addresses in the switch’s MAC address table?

Deliverables:

Save your Answer Template using the convention of [your first initial] + [your last name] + “_Lab9”.

For example:   Joe Smith will save his file template as  JSmith_Lab9.doc .

Submit your Answer Template to Blackboard by attaching it to the appropriate assignment link.