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Suppose you have a big switch with several VLANs. What is the recommend best practice with regards to spanning tree? I see you can configure global spanning tree, and there is per-VLAN spanning tree. What is the preferred best practice in this configuration?

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Sounds like you only have a single switch? Spanning-Tree shouldn't be necessary unless you are concerned someone will cable it wrong and create a switching loop.

Per-VLAN spanning tree is useful when you have redundant links between multiple switches. Instead of having the redundant links sit idle (blocked state), you can maximize the available bandwidth by having different VLAN's take different routes to the root switch.

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Thanks for the info. This is single Foundry (now Brocade) switch but has other switches attached, spread out in some ad-hoc topology that nobody knows. It is not a redundant configuration. It seems that running single instance spanning tree should be fine in this case. –  Keith Mar 29 '11 at 1:33

Per-VLAN spanning tree tends to be more implementation-specific than traditional STP, Rapid STP, or multi-instance (MST). In particular, (at least as far as I'm aware), only Cisco does rapid per-VLAN spanning tree -- rpvst+ -- so if you are concerned about interoperability, you'll need to use MST (preferred for traffic engineering controls), or ordinary rapid STP.

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