3.1.1.5 Packet Tracer Examining A Redundant Design Instructions

3.1.1.5%20Packet%20Tracer%20-%20Examining%20a%20Redundant%20Design%20Instructions

3.1.1.5%20Packet%20Tracer%20-%20Examining%20a%20Redundant%20Design%20Instructions

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Packet Tracer – Examining a Redundant Design

Topology

Objectives

Part 1: Check for STP Convergence

Part 2: Examine the ARP Process

Part 3: Test Redundancy in a Switched Network

Background

In this activity, you will observe how STP operates, by default, and how it reacts when faults occur. Switches

have been added to the network “out of the box”. Cisco switches can be connected to a network without any

additional action required by the network administrator. For the purpose of this activity, the bridge priority was

modified.

Part 1: Check for STP Convergence

When STP is fully converged, the following conditions exist:

 All PCs have green link lights on the switched ports.

 Access layer switches have one forwarding uplink (green link) to a distribution layer switch and a blocking

uplink (amber link) to a second distribution layer switch.

 Distribution layer switches have one forwarding uplink (green link) to a core layer switch and a blocking

uplink (amber link) to another core layer switch.

Part 2: Examine the ARP Process

Step 1: Switch to Simulation mode.

Packet Tracer – Examining a Redundant Design

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Step 2: Ping from PC1 to PC6.

a. Use the Add Simple PDU tool to create a PDU from PC1 to PC6. Verify that ARP and ICMP are selected

in the Event List Filters. Click Capture/Forward to examine the ARP process as the switched network

learns the MAC addresses of PC1 and PC6. Notice that all possible loops are stopped by blocking ports.

For example, the ARP request from PC1 travels from A1 to D2 to C1 to D1 and then back to A1.

However, because STP is blocking the link between A1 and D1, no loop occurs.

b. Notice that the ARP reply from PC6 travels back along one path. Why?

c. Record the loop-free path between PC1 and PC6.

Step 3: Examine the ARP process again.

a. Below the Scenario 0 drop-down list, click New to create Scenario 1. Examine the ARP process again

by pinging between two different PCs.

b. What part of the path changed from the last set of pings?

Part 3: Test Redundancy in a Switched Network

Step 1: Delete the link between A1 and D2.

Switch to Realtime mode. Delete the link between A1 and D2. It takes some time for STP to converge and

establish a new, loop-free path. Because only A1 is affected, watch for the amber light on the link between A1

and D1 to change to green. You can click Fast Forward Time to accelerate the STP convergence process.

Step 2: Ping between PC1 and PC6.

a. After the link between A1 and D1 is active (indicated by a green light), switch to Simulation mode and

create Scenario 2. Ping between PC1 and PC6 again.

b. Record the new loop-free path.

Step 3: Delete link between C1 and D3.

a. Switch to Realtime mode. Notice that the links between D3 and D4 to C2 are amber. Delete the link

between C1 and D3. It takes some time for STP to converge and establish a new, loop-free path. Watch

the amber links on D3 and D4. You can click Fast Forward Time to accelerate the STP convergence

process.

b. Which link is now the active link to C2?

Step 4: Ping between PC1 and PC6.

a. Switch to Simulation mode and create Scenario 3. Ping between PC1 and PC6.

b. Record the new loop-free path.

Step 5: Delete D4.

Switch to Realtime mode. Notice that A4, A5, and A6 are all forwarding traffic to D4. Delete D4. It takes

some time for STP to converge and establish a new, loop-free path. Watch for the links between A4, A5, and

A6 to D3 transition to forwarding (green). All three switches should now be forwarding to D3.

Packet Tracer – Examining a Redundant Design

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Step 6: Ping between PC1 and PC6.

a. Switch to Simulation mode and create Scenario 4. Ping between PC1 and PC6.

b. Record the new loop-free path.

c. What is unique about the new path that you have not seen before?

Step 7: Delete C1.

Switch to Realtime mode. Notice that D1 and D2 are both forwarding traffic to C1. Delete C1. It takes some

time for STP to converge and establish a new, loop-free path. Watch for the links between D1 and D2 to C2 to

transition to forwarding (green). Once converged, both switches should now be forwarding to C2.

Step 8: Ping between PC1 and PC6.

a. Switch to Simulation mode and create Scenario 5. Ping between PC1 and PC6.

b. Record the new loop-free path.

Suggested Scoring Rubric

Activity Section

Question

Location

Possible

Points

Earned

Points

Part 2: Examine the ARP

Process

Step 2b

5

Step 2c

15

Step 3

5

Part 2 Total

25

Part 3: Test Redundancy

in a Switched Network

Step 2

15

Step 3

5

Step 4

15

Step 6b

15

Step 6c

10

Step 8

15

Part 3 Total

75

Total Score

100