Our server guys got two new c7000 blade enclosures, and I set up the blade switches (3120X) that came w/ them.
I set them up as a single VBS.
After connecting the switch stack to our DC aggr 6513, it somehow says it's the root of EVERY vlan!
Checked the priority of the new switch, it's got the higher number than the actual root.
I hardcode the priority to 64400 (or something close to it), same thing.
Has anyone seen anything like this?
You are only allowing vlans 3,6 & 13 across the trunk link from the 6500 switches. So if you look at the spanning-tree for these vlans on the 3120's they should be reporting the 6500's as STP root.
But for all the other vlans by not allowing them across the trunk you stop STP running across the trunk for those vlans so both will think they are root.
Solution depends on what you are trying to achieve
1) By only allowing 3,6,13 on the link it sounds like these are the only vlans present on the 3120 switches. If so you could make the 3120 switches VTP transparent and only have those vlans created on the switches.
2) Rather than using allowed you can prune the trunk link. If you prune then STP will still run across the link for the pruned vlans so the 3120's should see the 6500 switches as root for all vlans. Be careful not to use a list of vlans with the prune command though as this has the same effect as using the "allowed" keyword ie. it stops STP for vlans not in the list.