4.6 VLAN Trunking Protocol (VTP)
4.6.1 VTP benefits
The role of the VLAN Trunking Protocol (VTP) is to maintain VLAN configuration consistency across the entire network. VTP is a messaging protocol that uses Layer 2 trunk frames to manage the addition, deletion, and renaming of VLANs on a network-wide basis. Further, VTP allows you to make centralized changes that are communicated to all other switches in the network.

VTP minimizes the possible configuration inconsistencies that arise when changes are made. These inconsistencies can result in security violations because VLANs crossconnect when duplicate names are used; they also could become internally disconnected when they are mapped from one LAN type to another (for example, Ethernet to ATM or FDDI).

VTP provides the following benefits:

  • VLAN configuration consistency across the network
  • Mapping scheme that allows a VLAN to be trunked over mixed media; example: mapping Ethernet VLANs to a high-speed backbone VLAN such as ATM LANE or FDDI
  • Accurate tracking and monitoring of VLANs
  • Dynamic reporting of added VLANs across the network
  • Plug-and-play configuration when adding new VLANs

Before creating VLANs on the switch, you must first set up a VTP management domain within which you can verify the current VLANs on the network. All switches in the same management domain share their VLAN information with each other, and a switch can participate in only one VTP management domain. Switches in different domains do not share VTP information.

Using VTP, each Catalyst Family Switch advertises the following on its trunk ports:

  • Management domain
  • Configuration revision number
  • Known VLANs and their specific parameters