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Cisco Bug: CSCuo22348 - port-state request triggers burst of bpdu's from VPC primary switch.

Last Modified

Oct 22, 2019

Products (8)

  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7000 10-Slot Switch
  • Cisco Nexus 7000 4-Slot Switch
  • Cisco Nexus 7700 6-Slot Switch
  • Cisco Nexus 7000 18-Slot Switch
  • Cisco Nexus 7700 18-Slot Switch
  • Cisco Nexus 7000 9-Slot Switch
  • Cisco Nexus 7700 10-Slot Switch

Known Affected Releases

6.2(6) 6.2(6a) 6.2(8) 6.2(8a)

Description (partial)

Symptom:
Nexus 7000 switch may exhibit excessive TX inband traffic rates affecting control-plane services after attempting to collect show interface trunk command output.

Bug is not specific to show int trunk command. It can happen anytime port state info request event is processed.
Request may come via SNMP request or another show command.

Check output of "sh hardware internal cpu-mac inband stats" for TX packet rate. With this bug, TX rate shoots up very high. 

N7K1# sh hardware internal cpu-mac inband stats | in rate
Packet rate limit ........... 64000 pps
Rx packet rate (current/max)  1 / 16 pps
Tx packet rate (current/max)  15215 / 18753 pps   <<====

AND

Check for below logs in the output of "show spanning-tree internal interactions". 

+++++++++++++++++++++
1080) Event:(null), length:87, at 988005 usecs after Wed Oct 29 10:26:46 2014
stp_send_bpdu_now(4995): Start: reason During handling of port state info request

1081) Event:(null), length:85, at 980152 usecs after Wed Oct 29 10:26:46 2014
stp_send_bpdu_now(5017): End: reason During handling of port state info request
++++++++++++++++++++++

Conditions:
Nexus 7000 running 6.2(2) or later release with a high VLAN count. Whenever a port-state request is sent to STP, there are additional BPDUs sent out for each STP logical port in the system.
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Bug Details Include

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