VTP V3 Pruning
The VLAN architecture requires all flooded traffic for a VLAN to be sent across a trunk port even if it leads
to switches that have no devices that are active in the VLAN. This method leads to wasted network bandwidth.
VTP V3 Pruning optimizes the usage of network bandwidth by restricting the flooded traffic to only those
trunk ports that can reach all the active network devices. When this protocol is in use, a trunk port does not
receive the flooded traffic that is meant for a certain VLAN unless an appropriate join message is received.
A join message is defined as a new message type in addition to the ones already supported by version 1 of
the VTP V3 protocol. A VTP V3 implementation indicates that it supports this extension by appending a
special TLV at the end of the summary advertisement messages that it generates. In VTP V3 transparent mode,
VTP relays all VTP packets, and pruning requires that the switch processes TLVs in the VTP V3 summary
packets.
VTP V3 Per Interface
VTP allows you to enable or disable the VTP protocol on a per-port basis to control the VTP traffic. When a
trunk is connected to a switch or end device, it drops incoming VTP packets and prevents VTP advertisements
on this particular trunk. By default, VTP is enabled on all the switch ports.
VTP V3 Pruning and Spanning Tree Protocol
VTP maintains a list of trunk ports in the Spanning Tree Protocol (STP) forwarding state by querying STP at
bootup and listening to the notifications that are generated by STP.
VTP sets a trunk port into the pruned or joined state by interacting with STP. STP notifies VTP V3 when a
trunk port goes to the blocking or forwarding state. VTP V3 notifies STP when a trunk port becomes pruned
or joined.
Default VTP Settings
This table lists the default settings for VTP parameters.
Table 10: Default VTP Parameters
Default
Parameters
Disabled
VTP
Transparent
VTP Mode
blank
VTP Domain
1
VTP Version
Disabled
VTP Pruning
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Configuring VTP V3
VTP V3 Pruning