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Cisco Bug: CSCuj55178 - Layer 3 traffic loss upto 165 sec after restoring from vpc split-brain

Last Modified

Jan 29, 2017

Products (7)

  • Cisco Nexus 5000 Series Switches
  • Cisco Nexus 5548P Switch
  • Cisco Nexus 5596UP Switch
  • Cisco Nexus 6004 Switch
  • Cisco Nexus 6001 Switch
  • Cisco Nexus 5548UP Switch
  • Cisco Nexus 5596T Switch

Known Affected Releases

6.0(2)N1(2a)

Description (partial)

Symptom:
see traffic loss of up to 165 sec for Layer3 southbound traffic until vPC is completely recovered from split-brain scenario.

Conditions:
The issue here is that when VPC peers are brought up the secondary will suspend all VPC legs for a delay restore timer. The secondary will see the peer-link as up and forwarding however, so the SVIs will come online and start advertising local routes to the L3 protocols upstream. However, any traffic the secondary VPC receives is blackholed since we cannot forward down VPC legs, and when we send over the peer-link the VPC primary drops the traffic. The VPC primary will receive a BPDU from the secondary with the emulated bridge ID for VPC and move the port into a Backup / BLK state for a 'delay restore' timer. This causes all traffic received over the peer-link to be dropped.
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Bug Details Include

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