If someone is absolutely sure that there is no possibility for layer2 loops to form then he/she can disable spanning tree.
The benefit you can gain from it is less processor utilization and less bandwidth utilization, as the switch will not send bpdus on the disabled vlans and will not have to process the spanning-tree algorithm for those vlans.
Personally i would be extremely reluctant to turn off STP on any switch just in case of a misconfiguration either accidental or malicious.
You could turn it off if you have designed a network that has no redundant L2 links, a good example being a L3 routed network in both the access/distribution and core network but i would still leave STP on to be honest.
Thank you. Just at a quick glance most of them do appear to be C2950 switches. There are 89 vlans defined and 64 VLANs reflected in the sho spanning-tree summary. Just to double check; can I assume that means that each VLAN is equivalent to one instance of STP. The information that you have provided is greatly appreciated, I didn't realize that this could occur without someone intentionally configuring it that way. Good to know.
you wrote "In a device like this vlans created /learned after having reached the limit are automatically in STP off and you see lines as the ones you have placed in your post. " in your previous meassage.
Several years ago I noticed an even worse behaviour of Cisco 3500XL switches:
After reaching the STP instance limit, one VLAN has disabled its STP. But not the VLAN last created, just one random VLAN :-(
This was terrible that time, I hope it's fixed in current IOS.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...