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Cisco Bug: CSCut68375 - STP BLK and forward change when one of VPC peer is down

Last Modified

Apr 12, 2017

Products (12)

  • Cisco Nexus 9000 Series Switches
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 9396PX Switch
  • Cisco Nexus 9396TX Switch
  • Cisco Nexus 9504 Switch
  • Cisco Nexus 3164Q Switch
  • Cisco Nexus 3172TQ-XL Switch
  • Cisco Nexus 9508 Switch
  • Cisco Nexus 9332PQ Switch
  • Cisco Nexus 93128TX Switch
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Known Affected Releases

6.1(2)I3(2) 6.1(2)I3(4) 7.0(3)I1(1)

Description (partial)

Symptom:
When using a Nexus 9508 and vPC peer-links created on different modules, the STP status of the vPCs change to BLK and then FWD when one of the modules is shut down.

-  Nexus 9508 

  N9K-1 ======= N9K-2 
        |                        |
         ----vpc----------
         N9372 

 VPC peer-link : 1/35,1/36,2/35,2/36 on both N9Ks

With the above topology, if the customer shutdown module 2 in N9508#1, N9508#2's Po212 STP status is changed BLK and then remained as BLK.
> > Po212            Desg BLK 1         128.4307 (vPC) P2p
To recover this, partner tried to do following thing on N9508#1.
> > - no spanning-tree vlan 16
> > - spanning-tree vlan 16

Additionally, after recovering this issue, partner tried to do shutdown the slot2 in N9508#1 several times..
then the #2 chassis port-channel STP status was changed BLK and then FWD by itself in short.

Conditions:
- Version : n9000-dk9.7.0.3.I1.1.bin 
- Hardware : cisco Nexus9000 C9508

-  Nexus 9508 

  N9K-1 ======= N9K-2 
        |                        |
         ----vpc----------
         N9372 

 VPC peer-link : 1/35,1/36,2/35,2/36 on both N9Ks
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