What’s VTP Pruning? VLAN Trunking Protocol Pruning

VTP Pruning is the important thing aspect of VTP (VLAN Turning Protocol). It assist improves community efficiency and community bandwidth by lowering pointless flooded site visitors i.e. broadcast, multicast, unknown and flooded unicast packets. In regular operation, a swap must flood broadcast frames, multicast frames, or unicast frames the place the vacation spot MAC deal with is unknown to all its ports. If the neighboring swap doesn’t have any lively ports within the supply VLAN, this broadcast is unnecessary and extreme undesirable site visitors might create issues on the community.

Associated- VTP Interview Questions

This is disabled by default in Cisco switches. VTP pruning Cisco helps to ship broadcasts solely to these trunk hyperlinks that truly wants the knowledge i.e. with VTP pruning enabled, when the vacation spot MAC deal with is unknown, frames are forwarded over a trunk hyperlink provided that the swap on the receiving finish of the trunk hyperlink has ports within the supply VLAN pruning. It ought to solely be enabled on VTP servers, all of the purchasers within the VTP area will robotically allow VTP pruning. VLAN 1 can’t be pruned as a result of it’s an administrative VLAN.

All of the model of VTP i.e. VTP model 1, VTP model  2 and VTP model 3 assist VTP pruning. To allow VTP pruning on a Cisco IOS swap, use the VTP VLAN pruning configuration command. As soon as VTP pruning is enabled, you possibly can optionally configure a prune eligible listing if you wish to restrict the VLANs that may be pruned.

Instance State of affairs: VTP Pruning

A situation will assist perceive the idea of VTP pruning in a extra detailed approach. Beneath is a setup of 4 Switches (SW1, Sw2, Sw3 and Sw4) with SW1 being the VTP Server and connecting to every Swap in a STAR topology over trunk hyperlinks.Sw1 has configured 5 VLANs (VLAN 1,10,20,30 and 40) and the VLANs have been robotically configured through VTP on remainder of Switches.

Assigned Entry Ports

Every swap has entry ports assigned as beneath –

• SW2 has 2 entry ports each in VLAN 10
• SW3 has 2 entry ports,1^st in VLAN 10 and a couple of^nd in VLAN 20
• SW3 has 2 entry ports,1^st in VLAN 30 and a couple of^nd in VLAN 40

All of the Swap to Swap connectivity is on trunk hyperlinks with all VLANs allowed on trunk ports.

Beneath Diagram exhibits no VTP pruning is enabled on all of the 4 Switches although all being members of similar VTP area.

No VTP Pruning

Now let’s say system connection of one of many entry port of Swap 2 (SW2) sends broadcast. This broadcast shall be acquired on following –

• All of the Entry ports and trunk ports of SW2 besides the supply port.
• SW1 receives the VLAN 10 broadcasts on trunk port related to SW2 and forwards the identical on trunk ports related to SW3 and SW4.
• SW3 acquired the published and forwards to a related Entry port on VLAN 10.
• SW4 acquired the published on trunk port however doesn’t ahead to entry port since no entry port with VLAN 10 membership.

VTP Pruning Enabled

Now, after enabling VTP pruning on all of the switches, let’s see what change occurs from the earlier situation.

• As soon as it’s enabled, the published on VLAN 10 from SW2 is forwarded to SW1 nonetheless, it isn’t relayed to all trunk ports.
• Seeing that no Entry port membership is there on SW4, the Broadcast of VLAN pruning is barely relayed to trunk port of SW3 and never in the direction of SW4.

Within the Nutshell, VTP pruning saves the bandwidth and pointless flooding of hyperlinks by not sending broadcast / unknown unicast site visitors out of interfaces not required.

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