CCNP ENCOR // Layer 2 Forwarding (LAB) // ENCOR 350-401 Complete Course

Introduction

This tutorial provides a step-by-step guide to Layer 2 Forwarding as part of the CCNP ENCOR 350-401 course. It covers practical lab configurations, including packet capture and MAC address management, enabling you to gain hands-on experience with network traffic management and analysis.

Step 1: Configure the Linux Server

1. Set Up the Server: Ensure your Linux server is properly configured to act as a packet capture tool.
2. Install Necessary Tools: You may need tools like tcpdump or Wireshark for capturing network packets.
3. Network Interface Configuration: Make sure the network interfaces are configured correctly to capture the desired traffic.

Step 2: Start Packet Capture

1. Open Terminal: Access the terminal on your Linux server.
2. Run Capture Command: Use the following command to start capturing packets on the appropriate interface:

   sudo tcpdump -i [interface_name] -w capture.pcap
   

   Replace [interface_name] with your actual network interface name.
3. Verify Capture: Ensure that the capture is running by checking the output in the terminal.

Step 3: Generate Traffic on R1

1. Access Router R1: Log into your router R1 via console or SSH.
2. Create Traffic: Use the following command to generate traffic:

   ping [destination_IP]
   

   Replace [destination_IP] with the IP of the target device.
3. Monitor Capture: Check your packet capture tool to see if the ping traffic is being recorded.

Step 4: Generate Unknown Unicast Traffic

1. Identify Unknown Unicast: Configure a device to send packets to a MAC address that is not in the MAC address table.
2. Testing: Use a tool or script to send unknown unicast packets.
3. Capture Verification: Verify that the unknown unicast traffic is being captured in your packet capture file.

Step 5: Examine Packet Capture

1. Open Capture File: Use Wireshark or a similar tool to open the capture.pcap file.
2. Analyze Traffic: Look for specific patterns in the packets, such as source and destination MAC addresses.
3. Filters: Apply filters to isolate the unknown unicast traffic for better analysis.

Step 6: Disable MAC Aging

1. Access Switch Configuration: Connect to your switch.
2. Disable MAC Aging: Enter the following commands in the configuration mode:

   interface [interface_name]
   no mac-address-table aging-time
   

   Replace [interface_name] with your switch interface.
3. Verify Changes: Check the MAC address table to confirm that aging is disabled.

Step 7: Configure Static MAC Addresses

1. Enter Configuration Mode: Access your switch's configuration mode.
2. Add Static MAC Address: Use the following command to add a static MAC address:

   mac-address-table static [mac_address] vlan [vlan_id] interface [interface_name]
   

   Replace [mac_address], [vlan_id], and [interface_name] with your specific values.
3. Verification: Check the MAC address table to ensure that the static entry is present.

Conclusion

In this tutorial, you learned how to configure a Linux server for packet capture, generate various types of traffic, and manage MAC addresses on a switch. These skills are essential for understanding Layer 2 forwarding in network environments. For further practice, consider exploring additional scenarios and configurations related to Layer 2 protocols and traffic analysis.