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Switch automatically disables STP

Quite a few of our IOS Catalyst switches have quite a few 'no spanning-tree vlan <number>' statements in their running configs. As we didn't add them ourselves, we suspect the switch added them by itself for some reason. Removing them doesn't work, as they're immediately added again.

Does anyone know what might be the cause of this behaviour?

What the command does is obvious, why it is added eludes me.

We've seen it so far on 2924XL, 3524XL, and 2950 switches, with various IOS versions. The disabled vlans do seem to be the same on most switches, regardless of them actually being used.

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Accepted Solutions
Cisco Employee

Re: Switch automatically disables STP

Catalyst 3500 series XL and most Catalyst 2900 series XL switches support a total of 250 VLANs and 64 spanning-tree instances. If you have more than 64 VLANs, STP will run only 64 VLANs.

http://www.cisco.com/univercd/cc/td/doc/product/lan/c2900xl/29_35wc9/ol256205.htm#702466

1 REPLY
Cisco Employee

Re: Switch automatically disables STP

Catalyst 3500 series XL and most Catalyst 2900 series XL switches support a total of 250 VLANs and 64 spanning-tree instances. If you have more than 64 VLANs, STP will run only 64 VLANs.

http://www.cisco.com/univercd/cc/td/doc/product/lan/c2900xl/29_35wc9/ol256205.htm#702466

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