Packet Tracer – Investigate a VLAN Implementation
Addressing Table
Device Interface IP Address Subnet Mask Default Gateway
S1 VLAN 99 172.17.99.31 255.255.255.0 N/A
S2 VLAN 99 172.17.99.32 255.255.255.0 N/A
S3 VLAN 99 172.17.99.33 255.255.255.0 N/A
PC1 NIC 172.17.10.21 255.255.255.0 172.17.10.1
PC2 NIC 172.17.20.22 255.255.255.0 172.17.20.1
PC3 NIC 172.17.30.23 255.255.255.0 172.17.30.1
PC4 NIC 172.17.10.24 255.255.255.0 172.17.10.1
PC5 NIC 172.17.20.25 255.255.255.0 172.17.20.1
PC6 NIC 172.17.30.26 255.255.255.0 172.17.30.1
PC7 NIC 172.17.10.27 255.255.255.0 172.17.10.1
PC8 NIC 172.17.20.28 255.255.255.0 172.17.20.1
PC9 NIC 172.17.30.29 255.255.255.0 172.17.30.1
Objectives
Part 1: Observe Broadcast Traffic in a VLAN Implementation
Part 2: Observe Broadcast Traffic without VLANs
Background
In this activity, you will observe how broadcast traffic is forwarded by the switches when VLANs are
configured and when VLANs are not configured.
Instructions
Part 1: Observe Broadcast Traffic in a VLAN Implementation
Step 1: Ping from PC1 to PC6.
a. Wait for all the link lights to turn to green. To accelerate this process, click Fast Forward Time located in
the bottom tool bar.
b. Click the Simulation tab and use the Add Simple PDU tool. Click PC1, and then click PC6.
c. Click the Capture/Forward button to step through the process. Observe the ARP requests as they
traverse the network. When the Buffer Full window appears, click the View Previous Events button.
Questions:
Were the pings successful? Explain.
Type your answers here.
Packet Tracer – Investigate a VLAN Implementation
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Look at the Simulation Panel, where did S3 send the packet after receiving it?
Type your answers here.
In normal operation, when a switch receives a broadcast frame on one of its ports, it forwards the frame
out all other ports. Notice that S2 only sends the ARP request out F0/1 to S1. Also notice that S3 only
sends the ARP request out F0/11 to PC4. PC1 and PC4 both belong to VLAN 10. PC6 belongs to VLAN
- Because broadcast traffic is contained within the VLAN, PC6 never receives the ARP request from
PC1. Because PC4 is not the destination, it discards the ARP request. The ping from PC1 fails because
PC1 never receives an ARP reply.
Step 2: Ping from PC1 to PC4.
a. Click the New button under the Scenario 0 dropdown tab. Now click on the Add Simple PDU icon on the
right side of Packet Tracer and ping from PC1 to PC4.
b. Click the Capture/Forward button to step through the process. Observe the ARP requests as they
traverse the network. When the Buffer Full window appears, click the View Previous Events button.
Question:
Were the pings successful? Explain.
Type your answers here.
c. Examine the Simulation Panel.
Question:
When the packet reached S1, why does it also forward the packet to PC7?
Type your answers here.
Part 2: Observe Broadcast Traffic without VLANs
Step 1: Clear the configurations on all three switches and delete the VLAN database.
a. Return to Realtime mode.
Open configuration window
b. Delete the startup configuration on all 3 switches.
Questions:
What command is used to delete the startup configuration of the switches?
Type your answers here.
Where is the VLAN file stored in the switches?
Type your answers here.
c. Delete the VLAN file on all 3 switches.
Question:
What command deletes the VLAN file stored in the switches?
Type your answers here.
Step 2: Reload the switches.
Use the reload command in privileged EXEC mode to reset all the switches. Wait for the entire link to turn
green. To accelerate this process, click Fast Forward Time located in the bottom yellow tool bar.
Close configuration window
Step 3: Click Capture/Forward to send ARP requests and pings.
a. After the switches reload and the link lights return to green, the network is ready to forward your ARP and
ping traffic.
b. Select Scenario 0 from the drop-down tab to return to Scenario 0.
Packet Tracer – Investigate a VLAN Implementation
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c. From Simulation mode, click the Capture/Forward button to step through the process. Notice that the
switches now forward the ARP requests out all ports, except the port on which the ARP request was
received. This default action of switches is why VLANs can improve network performance. Broadcast
traffic is contained within each VLAN. When the Buffer Full window appears, click the View Previous
Events button.
Reflection Questions - If a PC in VLAN 10 sends a broadcast message, which devices receive it?
Type your answers here. - If a PC in VLAN 20 sends a broadcast message, which devices receive it?
Type your answers here. - If a PC in VLAN 30 sends a broadcast message, which devices receive it?
Type your answers here. - What happens to a frame sent from a PC in VLAN 10 to a PC in VLAN 30?
Type your answers here. - In terms of ports, what are the collision domains on the switch?
Type your answers here. - In terms of ports, what are the broadcast domains on the switch?
