Pruning on 3500 and 3550 series switches

VLAN pruning is intended to prevent Broadcast and Unknown traffic from being needlessly flooded along trunks in the case where the VLAN has no active ports on the far side of the trunk from the source of the traffic.

In that case pruning would be inappropriate since the traffic is required to cross the link.

For what it's worth I have never liked the idea anyway.

- Few such links are likely in (most) well designed networks. - Process sounds complex and potentially problem prone. - I expect that few people use it so you will be a beta tester.

Good for a class though, you need to know

addressing (L2) learning forgetting forwarding decisions flooding vlans trunking more?

If they can get their little heads well enough round this to correctly predict behaviour then they will be ahead of . . . some professors.

I doubt though if the educational potential was a consideration for Cisco when they spent the money to put it in.

Maybe the VLAN Policy Server thing was put in just for such an eventuality too? I suspect that it though has gone.