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Cisco Bug: CSCus97195 - Nexus 5K/6k - FEX HIF port down delay when FEX Fabric member links down

Last Modified

Feb 13, 2018

Products (10)

  • Cisco Nexus 6000 Series Switches
  • Cisco Nexus 5548P Switch
  • Cisco Nexus 5596UP Switch
  • Cisco Nexus 6004 Switch
  • Cisco Nexus 6001 Switch
  • Cisco Nexus 5672UP Switch
  • Cisco Nexus 5548UP Switch
  • Cisco Nexus 56128P Switch
  • Cisco Nexus 5696Q Switch
  • Cisco Nexus 5596T Switch

Known Affected Releases

7.0(2)N1(1) 7.0(5)N1(1)

Description (partial)

Symptom:
FEX Host Interfaces (HIF's) may take ~6-8 seconds to go down, while the Network Interfaces (NIF's) have already gone down.
This may cause extended packet loss as the connecting devices still have link operational with the FEX host ports which has lost it's uplink Network interfaces to parent N5k/6k switch.

Conditions:
When a shutdown for all physical member ports for the FEX Fabric Port-channel is performed.

Traffic loss happens as downlink devices in vPC or in NIC teaming (Active/Standby) would continue sending traffic towards this FEX which has no uplinks available causing blackholing of traffic. Once the host interfaces are down, neighboring device detects link down and moves traffic to redundant link.
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Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
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