Wired Intelligent Edge

Hello,

(Please feel free to ask for more info)

My switches keep flip flopping when it comes to being an STP root. At first I noticed nearly all of them had default priority so I started to raise the priority on the ones I definitely do not want to become root. And I added admin edge on my access ports. The root should be a cisco switch and ironically it does say it is the root but the hp switches keep fighting with eachother.

Image stamp: /sw/code/build/sbm(t4a)
Nov 5 2009 18:02:07
W.14.38
51
Boot Image: Primary

I check the logs and they are still becoming root. What gives?

spanning-tree
spanning-tree 3 admin-edge-port
spanning-tree 3 bpdu-protection
spanning-tree 5 admin-edge-port
spanning-tree 5 bpdu-protection
spanning-tree 6 admin-edge-port
spanning-tree 6 bpdu-protection
spanning-tree 8 admin-edge-port
spanning-tree 8 bpdu-protection
spanning-tree 10 admin-edge-port
spanning-tree 10 bpdu-protection
spanning-tree 15 admin-edge-port
spanning-tree 31 admin-edge-port
spanning-tree 31 bpdu-protection
spanning-tree 33 admin-edge-port
spanning-tree 43 admin-edge-port
spanning-tree 46 admin-edge-port
spanning-tree 48 admin-edge-port
spanning-tree Trk1 priority 4
spanning-tree priority 13 force-version stp-compatible

here is the cisco spanning tree info:

VLAN0035
Spanning tree enabled protocol ieee
Root ID Priority 20515
Address 001c.b086.1200
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 20515 (priority 20480 sys-id-ext 35)
Address 001c.b086.1200
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/7 Desg FWD 19 128.7 P2p
Gi0/9 Desg FWD 4 128.9 P2p
Gi0/35 Desg FWD 4 128.35 P2p
Gi0/51 Desg FWD 4 128.51 P2p
Gi0/52 Desg FWD 4 128.52 P2p
Po2 Desg FWD 3 128.72 P2p
Po5 Desg FWD 3 128.96 P2p

Greetings!

What is the STP mode on the Cisco switch — is it running PVST+ or MSTP/RSTP? The default spanning tree mode on the 2910 is MSTP, which does not recognize PVST+ BPDUs. From the Cisco output in your post, it looks like this is the STP status for VLAN 35, implying it is running PVST+.

You need to change the STP mode on the Cisco switch to MSTP, as the 2910 does not support RPVST (required for interoperability with PVST+).

Hello,

The STP mode on Cisco is PVST:

I have read there shouldn't be interoperability issues between MSTP and PVST since MSTP has the feature PVST simulation mechanism.

Since the other day I have also read that MSTP switches need to be configured with matching mstp config-name, config-revision, and instance number, at that time none of my switches had this configuration set. I have applied it to 3 out of 8 switches so far. After I doing this to all the HP's should they begin to see the Cisco as the root?

HP Buswash Switch

HP Fuel Island

HP Community Room

After adjusting the priority for all switches the root was appropriately chosen. But I had an issue where my Aruba AP's would randomly go into a blocking state/forwarding state. I enabled bpdu-filtering on those ports and havent had those AP's go down since. 

We think it may be a bug in the HP Procurve OS that had the switch thinking the AP was sending superior BPDU's even though the STP function was turned off on the AP's.