Multiple spanning-tree root devices.

[paulhowlett_2]

Hi, I have been alerted, by Ciscoworks LMS, that I have multiple spanning-tree root devices on my network. I have configured one of our 6509s (CatOS) to be root for all devices and the priority was ato set to 8192. However I have 8 devices that are reporting being roots for all but the default (vlan 1) vlan. I've checked their priorities and hey are predominantly set at 61443 or at least a lot higher than 8192. They are different models of devices, 2950, 3750 etc and I have upgraded them to the latest IOS and rebooted all with no change. All devices running either PVST or PVST+. Anybody have any ideas?

Thanks.

[Jon Marshall]

Hi

Are you using the same VTP domain across all your switches ?

Have you set your 6500 to be spanning-tree root for all the vlans.

If you log on to one of the switches and do a

sh spanning-tree for one of the vlans what does it show and what is the priority for this vlan on the 6500.

Jon

[markwgallagher · Accepted solution]

Check to ensure that the VLANs in question exist in all devices from the access device with the incorrect root all the way back to the actual root 6509. If each instance of spanning tree can't talk directly to the root, it will elect a root from among the instances that it can communicate with.

[paulhowlett_2]

You are spot on, thank you. This was caused due to some sloppy VLAN pruning configuratiuon.

Thank you very much.