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Re: Confusion on VTP pruning. posted 11/10/2008
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Yes - it sounds like you understand this concept pretty well. If SW1 is the server and SW2 and SW3 are the clients, you enable VTP Pruning on the server device - SW1. Now, if you have VLAN 20 client off of SW1 only, then VLAN 20 traffic will be dynamically "pruned" off of the trunk links that lead to SW2 and SW3.

Pruning is dynamic, so if at any point you add clients to SW2 or SW3 for VLAN 20, pruning will adjust and send traffic to those switches via the trunk links.

If you were to make VLAN 20 prune ineligible, then you could force this VLAN traffic over links where it would have been pruned under the normal operation.

Anthony J. Sequeira, CCIE #15626, CCSI #23251
Senior CCIE Instructor


Internetwork Expert, Inc.
Toll Free: 877-224-8987
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On Nov 10, 2008, at 4:09 AM, Shahnawaz Khot wrote:

Hi experts,

I have confusion on pruning. Please help with your expert suggestions.

Let's suppose for following topology.

SW1 - - - - - - - -


All three switches are interconnected by trunk links.

If SW1 is VTP server and I am enabling a pruning on server, it does mean it
will enable in the entire VTP domain. SW2 and SW3 are clients in that VTP

Suppose SW1 has vlan 20 and I want to prune that vlan traffic to its
clients. Clients don't have any ports assigned to vlan 20.

I think the topology is pretty clear now.

So as the link is trunk carries all vlan traffic between SW2 and SW3. Does
VTP pruning will change anything by enabling on server (SW1)?

I think, it won't affect anything because both VTP clients have trunk ports.

In such lab scenarios, configuring VTP pruning eligibility list on server
trunks connected to other clients will be an idea to resolve this?

I am talking about *switchport trunk pruning vlan* command on SW1 trunk
links to SW2 and SW3.

I have no idea how can we enable pruning with such topology Please suggest.

Warm Regards,


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