Why vtp pruning is a bad idea


A while ago I considered implementing VTP with pruning on a client network. But it’s a bad idea because of the following (from Cisco documentation)

(In vtp v3) VTP pruning still applies only to VLANs 1 to 1005, and VLANs 1002 to 1005 are still reserved and cannot be modified.


VTP pruning is not designed to function in VTP transparent mode. If one or more switches in the network are in VTP transparent mode, you should do one of these:

Turn off VTP pruning in the entire network

Turn off VTP pruning by making all VLANs on the trunk of the switch upstream to the VTP transparent switch pruning ineligible.

There is a funny cornercase scenario related to this: if you have switch A>switch B>switch C, where switch B is a transparent vtp switch while A and C have vtp enabled with pruning, switch C may request (through B) to prune a vlan. Switch A will prune the vlan from the trunk to switch B (which may have needed it!)

In other words: avoid…


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