The Configure, Verify, and Troubleshoot Interswitch Connectivity module provides you with the instructions and Cisco hardware to develop your hands on skills in understanding the configuration of trunks as well as of associated protocols. This module includes the following activities:

  • Creating Trunk links using DTP and VTP
  • Applying 802.1q encapsulation
  • Understanding Native VLANs

Exercise 1 - Trunk Configuration and Dynamic Trunking Protocol - Part I

A trunk is a link, usually between two switches, that transmits frames belonging to two or more VLANs. It is because of trunks that you are able to distribute multiple VLANs throughout multiple switches.

Exercise 2 - VLAN Trunk Protocol

VTP is a protocol that functions in a client server model. One device, in this case, NYCORE1, will be configured as the server where all VLAN configurations are made. Client devices, in this case, NYACCESS1 receive the information about the VLANs created and automatically create them in their own VLAN databases.

Exercise 3 - Trunk Configuration and Dynamic Trunking Protocol - Part II

In Exercise 1 you partially configured a trunk link between NYCORE1 and NYACCESS1. The configuration was completed on the NYCORE1 side, however, not on the NYACCESS1 side. You configured VTP in Exercise 2 so that NYCORE1 will automatically share its VLANs with NYACCESS1.

Now that NYACCESS1 has the appropriate VLANs configured, you can finish the trunk configuration.

Exercise 4 - Native VLAN Configuration

Frames that are placed on a trunk are tagged with the VLAN ID that they belong to. What happens if a frame without a tag is placed on a trunk link? The answer is, the frame is placed on the Native VLAN.

Each trunk is configured with a Native VLAN. If it is not configured properly, it could be a source of network vulnerabilities that attackers can take advantage of.

Exercise 5 - Adding and Removing VLANs from a Trunk

As a network evolves, new VLANs must be created to accommodate the needs of the network. As a result, these VLANs often have to be propagated to multiple switches. Sometimes, VLANs are removed from networks or renumbered.

You currently have a trunk between NYCORE1 and NYACCESS1. You are required to add two more VLANs to the trunk, specifically, VLAN 30, Marketing and VLAN 40, Research to the trunk, but you must remove VLAN 20, Sales.

In this section, you will learn how to add and remove VLANs from trunks.