What is VLAN Trunking Protocol (VTP) Pruning

VLAN Trunking Protocol (VTP) is used to communicate VLAN information between switches in the same VTP domain. VLAN Trunking Protocol (VTP) pruning is a feature in Cisco switches, which stops VLAN update information traffic from being sent down trunk links if the updates are not needed. If the VLAN traffic is needed later, VLAN Trunking Protocol (VTP) will dynamically add the VLAN back to the trunk link.

In normal operation a switch needs to flood broadcast frames, multicast frames, or unicast frames where the destination MAC address is unknown to all its ports. If the neighboring switch doesn’t have any active ports in the source VLAN, this broadcast is unnecessary and excessive unwanted traffic may create problems on the network.

VLAN Trunking Protocol (VTP) pruning helps in increasing the available bandwidth by reducing unnecessary flooded traffic. Broadcast frames, multicast frames, or unicast frames where the destination MAC address is unknown are forwarded over a trunk link only if the switch on the receiving end of the trunk link has ports in the source VLAN.