15 Hubs and Switches

Hubs are not often used in modern network environments, but learning how they operate still provides a solid foundation to enterprise networks.  Alternatively, switches are ubiquitous in network implementations.  Finally, learners can use this exercise to gain more experience with GNS3 and VirtualBox.

Estimated time for completion: 15 minutes

Learning Objectives

• Understand how hubs function in a network
• Understand how switches function in a network
• Gain further experience using GNS3
• Introduce the use of Wireshark

Prerequisites

• Chapter 2 – Setting Up a GNS3 Environment
• Chapter 14 – Your First Network

deliverables

Six screenshots are required:

• GNS3 workspace
  • With Hub
  • With Switch
• Wireshark capture between PC3 and the specified network device
  • PC1 pinging PC2 (hub)
  • PC2 pinging PC3 (hub)
  • PC1 pinging PC2 (switch)
  • PC4 pinging PC3 (switch)

Resources

• NOTE: Each source will referenced with its corresponding number in superscript (EX: ¹  ) at the end of a step 
• 1.“Wireshark Introduction.” Chapter 1. introduction. Accessed May 27, 2024. https://www.wireshark.org/docs/wsug_html_chunked/ChapterIntroduction.html.
• 2. Bombal, David. “GNS3 Tips: Using the GNS3 Hub and Switch with Wireshark (Part 1).” YouTube, November 28, 2016. https://www.youtube.com/watch?v=lHcF6KXMPJ0.
• 3. Bombal, David. “GNS3 Tips: Using the GNS3 Hub and Switch with Wireshark (Part 2).” YouTube, November 28, 2016. https://www.youtube.com/watch?v=27KdkT0yIxg&t=2s.
• 4. Bombal, David. “GNS3 Tips: Using the GNS3 Hub and Switch with Wireshark (Part 3).” YouTube, November 28, 2016. https://www.youtube.com/watch?v=kgFxGM9E3tI&t=1s.

Contributors and testers

• Sawyer T. Hansen, Cybersecurity Student, ERAU Prescott
• Quinton D. Heath Van Horn, 7th grade
• David Reese, Mathematics Major, SUNY Bridgeport
• Stephen Torres, 9th grade
• Jacob M. Christensen, Cybersecurity Student, ERAU-Prescott
• Dante Rocca, Cybersecurity Student, ERAU-Prescott

Phase I – Setup

We complete the setup first so that we can focus on the learning activities later on. Your network should look like the following image:

1. Start GNS3
   1. Create a new blank project: LAB_02
   2. Verify the GNS3 VM is running by looking for the green light under the Servers Summary section
      

      

2. Add a hub to the GNS3 workspace ²
   1. Click on Browse all devices 
   2. Drag the Ethernet hub device into the workspace

      NOTE: When given the option, remember to always choose GNS3 VM as the server to host devices.

3. Add the PCs to the network
   1. Click on Browse all devices  ²
   2. Drag a VPCS device to the main workspace ²
   3. Repeat this three more times so you have four VPCS devices in the workspace ²
4. Add labels and change device symbols as you see fit
   

   

1. Our network space for this lab is 192.168.1.0/24
2. Click Start/Resume all nodes to power on all devices
3. Assign an IP address to PC1 ²
   1. Right-click on PC1 and select Console ²
   2. At the PC1 prompt, assign it an IP address with a Class C subnet mask ²

      > ip 192.168.1.1/24

      

   3. At the PC1 prompt type “save” to keep the IP configuration the next time the PC is rebooted

      > save

   4. After a few seconds, the newly entered IP address will be assigned to PC1

      > show ip

      

   5. In the GNS3 workspace add a text label of “192.168.1.1” next to PC1
4. Repeat the step 3 to configure IP addresses for the remaining PCs (Figure 6)

1. Connect PC1
   1. On the left side of the GNS3 workspace click the Add a link option ²
   2. Click on PC1 and select Ethernet0 port in the sub-menu ²
   3. Click on the hub and select any open Ethernet port available ²
   4. Click the Show/Hide interface labels to view the connections
2. Repeat  step 1 for the remaining PCs
   

   

   NOTE: You can right-click anywhere in the workspace to de-select the cable.

1. Start a Wireshark capture between PC2 and the hub
   1. Hover your mouse over the connection between the two devices ³
   2. Right-click the cable between the two devices and select Start capture ³(Figure 8)
   3. A new Wireshark window will open  ³ (Figure 9)
   4. A magnifying glass will appear on the wire to show you where the network sniffing is taking place
2. Now open the PC1 console and ping the IP address for PC2

   > ping 192.168.1.2

   

3. Now watch for the ICMP ping requests and replies in the Wireshark window ^1,3
   

   

1. Ensure you have an active Wireshark capture on the PC1-Hub connection ³
2. Open the console on PC2 and ping PC3

   > ping 192.168.1.3

3. In Wireshark, observe the packets between PC2 and PC3 ^1,3
   

   

4. Feel free to experiment; try capturing packets between any PC and the hub and then ping different PCs

1. Replace the hub with an Ethernet switch
   1. Right-click on the hub and delete it from the workspace ⁴
   2. Click on Browse all devices 4
   3. Drag the device labeled Ethernet switch to the workspace ⁴
2. Reconnect the computers to the switch by attaching cables

   NOTE: Again, don’t worry about what interfaces to use. I personally use interface 1 for PC1, and interface 2 for PC2, etc., but it doesn’t matter for this lab.

3. Start a Wireshark capture between the PC3-Switch connection ⁴
4. From the PC1 console, ping PC3

   > ping 192.168.1.3

   1. On Wireshark, you should see the same ICMP request and reply packets as you did earlier ^1,4
5. From the PC1 console, ping PC2

   > ping 192.168.1.2

   1. Notice how, unlike the hub, you will not see the ping conversation between PC1 and PC3 in the Wireshark capture ^1,4
6. Feel free to experiment by watching different connections and pinging different devices

End of Lab

List of Figures for Print Copy