VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that propagates the definition of Virtual Local Area Networks (VLAN) on the whole local area network.
To do this, VTP carries VLAN information to all the switches in a VTP domain. VTP advertisements can be sent over 802.1Q, and ISL trunks. VTP is available on most of the Cisco Catalyst Family products. Using VTP, each Catalyst Family Switch advertises the following on its trunk ports:
- Management domain
- Configuration revision number
- Known VLANs and their specific parameters
There are three versions of VTP, namely version 1, version 2, version 3.
The comparable IEEE standard in use by other manufacturers is GVRP or the more recent MVRP.
On Cisco Devices, VTP (VLAN Trunking Protocol) maintains VLAN configuration consistency across a single Layer 2 network. VTP uses Layer 2 frames to manage the addition, deletion, and renaming of VLANs from switches in the VTP client mode.
VTP is responsible for synchronizing VLAN information within a VTP domain and reduces the need to configure the same VLAN information on each switch thereby minimizing the possibility of configuration inconsistencies that arise when changes are made.