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I have a Cisco 5505 switch running CatOS connected to a number of Cisco 2950 switches running IOS. The 5505 switch supports a large number of vlans (I'm guessing 1005), yet the 2950s only support a max of 64 STP instances.

We have around 70 vlans configured on the 5505, which is the VTP server, and the 2950s are all VTP clients. The 2950s all have far fewer than 64 vlans in active use on them (something like max 20 each). Yet I keep still getting:

%SPANTREE_VLAN_SW-2-MAX_INSTANCE: Platform limit of 64 STP instances exceeded.

on the 2950s. Yes, we have more than 64 STP instances running, but that is in total, and not per 2950 switch. The vlan trunks between the 5505 and the 2950s are all restricted using 'allowed vlan' to reduce the number of vlans going to each 2950.

Any ideas on this? I don't really want to have to put the 2950s into transparent VTP mode as this increases the admin when adding new vlans.

I can confirm on the 2950s when doing 'show spanning-tree vlan X' that we only have STP instances for the vlans in active use on the switch itself, and no more.

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What about show spanning-tree summary output ? –  radius Dec 17 '10 at 11:04

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