We have a VTP domain with one master switch connected to several downstream switches. The domain has vtp pruning enabled.
One switch wrongly prunes back vlans from the trunk which are active on the switch.
I am having trouble finding an in-depth explaination of how pruning works, but from my understanding the choice of which VLANs to prune off is made based on the join requests from the neighboring switch. Meaning the wrong information is actually being generated by the master switch and not the switch which is wrongly pruning these vlans? The master switch's pruned vlans IS correct.
All other switches are pruning the correct VLANs. All obvious steps have been taken ie; reload, reconfigure, reset vtp domain yet the problem still remains.
Does anyone have an in-depth document explaining the process vtp pruning uses to generate and process join messages so I can troubleshoot this further?
For now, I have configured vtp on the trunk interface to inform it that the active VLANs are not eligable for pruning, this fixes the symptoms, but does not resolve the underlying issue.
Many thanks in advance.