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Showing posts from June, 2009

Spanning tree limits

I'm compiling a list of spanning tree and VLAN limits on different switches. This is what I've come up with so far. I don't have an authoritative source for these, but in many cases this is hard to get from specs. If you go over these limits, bad things will happen! (broadcast storms, VLANs disappearing, cats and dogs living together. That sort of thing) A "STP instance" is "a tree" in a spanning tree. So this only applies to PVST/PVST+ and similar. MST has a way lower limit (like 16), and you shouldn't need more than a couple. But you know that if you're using MST. So in most cases I would say this is the limit of the number of VLANs you can have since if you have 50+ VLANs then you're probably running some form of spanning tree. Switch Max STP instances Max number of VLANs Cisco 2900XL 64 64 Cisco 2950/2955 ...