Take the 2-minute tour ×
Network Engineering Stack Exchange is a question and answer site for network engineers. It's 100% free, no registration required.

This question is a literal repost of the same question asked on The Cisco Learning Network. Answers are unique to Stack Exchange.


Why does VTP pruning require the switch to be in server mode?

I am trying to understand why a client switch can't run vtp pruning.

any insight would be helpful..

Thanks.

share|improve this question

2 Answers 2

up vote 6 down vote accepted

That’s because VTP functions on a client/server model, not a distributed model. The server effectively controls everything that happens inside the VTP domain. When a switches directly connected port/downstream port, it sends a VTP Join message indicating participation in that VLAN.

If you wanted something similar to a distributed model that supports VLAN pruning across links, you would be looking at something similar to GVRP, which is pretty difficult to come by in the Cisco world these days (aside from CatOS). I would assume this is because they’re trying to push VTP a lot harder.

I am trying to understand why a client switch can't run vtp pruning.

Keep in mind that every switch running VTP (client or server) will prune if told to do so. This is not default behaviour, VTP comes disabled. Otherwise, scenarios like below would not function as expected.

Cisco VTP Pruning Scenario

If Switch 4 was the only device pruning, all other downstream switches would be needlessly spammed when expected not to.

share|improve this answer

VTP pruning is enabled on the server because the server decides if pruning is used in the domain or not.

For pruning to be effective it needs to be enabled in the entire domain. If a client was to enable pruning then it would only have effect locally. This would not have any positive effect in the domain except for the device that you had configured it on.

Also the point of using VTP is to have a single/few points of administration where you send the VLANs. Enabling pruning on all devices individually would go against the idea of VTP.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.