Chapter 3. VLANs, Trunks, and VTP

Terms you'll need to understand:

• Virtual LAN (VLAN)

• Static and dynamic VLANs

• Local and end-to-end VLANs

• VLAN Membership Policy Server (VMPS)

• InterSwitch Link (ISL)

• IEEE 802.1Q and 802.1Q tunneling

• Native VLAN

• Dynamic Trunk Protocol (DTP)

• VLAN Trunk Protocol (VTP)

• VLAN Pruning

Techniques you'll need to master:

• Understanding the advantages of VLANs

• Comparing dynamic and static VLANs

• Configuring static VLANs and associating ports to them

• Troubleshooting VLAN configurations

• Comparing IEEE 802.1Q and ISL trunking protocols

• Tunneling 802.1Q VLAN information in a Metro network

• Knowing the DTP modes and when a trunk is formed

• Configuring and troubleshooting trunks and pruning

• Understanding the three different VTP modes

• Comparing VTP versions 1 and 2

• Configuring and troubleshooting VTP

There are many definitions for a virtual LAN (or VLAN, for short). A VLAN can be described as a grouping of ports on a switch or a grouping of ports on different switches. It can also be characterized as a group of related users in a data network or as a group of users at the same geographic location (which is the most common). In the simplest terms, a VLAN is a broadcast domain. In a bridged network, all devices are in the same broadcast domain. One of the problems of using bridges for LAN segmentation is that they solve bandwidth problems, but not broadcast problems. Switches, even though they act like bridges, have some additional features that make them more robust in solving your networking problems.

The remainder of this chapter focuses on three areas: VLANs, trunking, and the Virtual Trunk Protocol (VTP). All three of these areas play an integral part in the setup of VLANs in your network.