01-04-2011 02:00 PM - edited 03-06-2019 02:49 PM
Has anyone came accorss the following situation in Nexus 7K with vPC.
NEXUS1# sh spanning-tree vlan 3871
VLAN3871
Spanning tree enabled protocol rstp
Root ID Priority 36639
Address 0022.557a.7641
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 36639 (priority 32768 sys-id-ext 3871)
Address 0022.557a.7641
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po10 Desg FWD 1 128.4105 (vPC peer-link) Network P2p
Po171 Altn BLK 1 128.4266 (vPC) P2p
Po172 Altn BLK 1 128.4267 (vPC) P2p
Po173 Altn BLK 1 128.4268 (vPC) P2p
Po174 Altn BLK 1 128.4269 (vPC) P2p
VLAN1936
Spanning tree enabled protocol rstp
Root ID Priority 34704
Address 0022.557a.7641
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 34704 (priority 32768 sys-id-ext 1936)
Address 0022.557a.7641
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po10 Desg FWD 1 128.4105 (vPC peer-link) Network P2p
Po20 Desg FWD 1 128.4115 (vPC) P2p
Po110 Desg FWD 1 128.4205 (vPC) P2p
Po173 Desg FWD 1 128.4268 (vPC) P2p
Nexus2# sh span vlan 3871
VLAN3871
Spanning tree enabled protocol rstp
Root ID Priority 36639
Address 0022.557a.7641
Cost 1
Port 4105 (port-channel10)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 36639 (priority 32768 sys-id-ext 3871)
Address 0026.51c9.35c1
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po10 Root FWD 1 128.4105 (vPC peer-link) Network P2p
Po171 Altn BLK 1 128.4266 (vPC) P2p
Po172 Altn BLK 1 128.4267 (vPC) P2p
Po173 Altn BLK 1 128.4268 (vPC) P2p
Po174 Altn BLK 1 128.4269 (vPC) P2p
As you can see for one vlan the port channels are blocked by STP. I have exactly same configuration for both vlans on all switches.
show vpc consistancy-parameter vpc 173 does not show any of this vlan went into suspended mode in fact shw show vpc brief shows vlans are actually active.
Solved! Go to Solution.
01-18-2011 10:52 AM
This is not necessarily a bug. The ports are all in Altn BLK state.
This implies they are all connected to the same layer2 i.e. they are all receiving bpdu's from the same designated port which is also on the root bridge.
The link below explains this state:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml#states
regards,
Leo
01-10-2011 11:45 PM
What release are you running? Might want to check out CSCtf94815 After double failure recovery, root port-channel goes int blk state. It is triggered by dual-active scenario and is fixed in 4.2(6).
zz
01-11-2011 06:31 AM
Actually switch is running 4.2(6) code.
01-11-2011 05:16 PM
Let me check on that.. the release info seems to be incorrect in the bug record. I'll get back to you shortly.
zz
01-12-2011 11:17 PM
So developer confirmed that the bug is fixed in 4.2(6) -- appears to be a new bug to me. It should not have a BKL ports on a root, though it is possible to see ports in BKL state in transitioning state.
zz
01-18-2011 10:26 AM
Down stream switches are HP switches. I am attaching some show comands when issue was occuring. The BLK state of this vlan, did not recover after bouncing the ports.
01-18-2011 10:52 AM
This is not necessarily a bug. The ports are all in Altn BLK state.
This implies they are all connected to the same layer2 i.e. they are all receiving bpdu's from the same designated port which is also on the root bridge.
The link below explains this state:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml#states
regards,
Leo
01-18-2011 11:05 AM
Hi,
are you sure the Down stream switches are participating in STP?
If not, they might simply forward STP BPDUs to other ports returning them to the Cisco switches finally.
BR,
Milan
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