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Cisco Bug: CSCup64606 - FCoE packet drops with Nexus N6004, N5696Q, and N56128P

Last Modified

Aug 14, 2018

Products (7)

  • Cisco Nexus 6000 Series Switches
  • Cisco Nexus 5596UP Switch
  • Cisco Nexus 5548P Switch
  • Cisco Nexus 6004 Switch
  • Cisco Nexus 6001 Switch
  • Cisco Nexus 5548UP Switch
  • Cisco Nexus 5596T Switch

Known Affected Releases


Description (partial)

Slow FC or FCOE Performance with Nexus N6004, N5696Q, or N56128P.Selective Retransmission Request (SRR) may be logged on host or storage.

Drops on the egress on a Nexus 5600/6000, for a no-drop class of traffic. Possible in both 10G & 40 G fabric modes, higher probability with 40G fabric mode. This can be verified by seeing counter increments in show hardware internal bigsur asic <global-asic-num> reg match .*wo_cr and via RX_FRM_DROP counter increments in show platform software qd info counters bm-fabric asic <global-asic-num>

The slowness observed in the application is due to the FCoE packet drops, which triggers retransmission from the application

On a Nexus 5600/600, when multiple ingress ports send data to one egress port for a no drop class of traffic and the egress buffer occupancy reaches the xoff threshold, this is indicated by observing the output of show hardware internal buffer info pkt-stats asic-num <global-asic-num> and verifying it to cross the xoff value for pool1 in Egress buffer allocation with the show platform software qd info command
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