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Cisco Bug: CSCvs44170 - N5K/N6K: FCoE-based system queuing policy overrides FEX host interface queuing policy

Last Modified

Jan 20, 2020

Products (1)

  • Cisco Nexus 6000 Series Switches

Known Affected Releases

7.3(5)N1(1) 7.3(6)N1(1)

Description (partial)

Symptom:
Queue scheduling configured as part of an outbound queuing policy applied to a FEX host interface with a Nexus 5000 or 6000 parent device may not function as expected when one of the default FCoE queuing policies is configured system-wide.

Conditions:
1. Nexus 5000 or 6000 device connected to a FEX
2. Outbound queuing policy is applied to one of the host interfaces located on the FEX
3. Default FCoE queuing policy is applied to the system (as shown below)

N6K# show running-config ipqos | section system.qos
<snip>
system qos
  service-policy type qos input fcoe-default-in-policy
  service-policy type queuing output fcoe-default-out-policy    <<<
  service-policy type queuing input fcoe-default-in-policy      <<<

4. In an oversubscribed scenario on the FEX host interface, traffic is not scheduled as expected. For example, if the outbound queuing policy on the FEX host interface configures 90% of the interface bandwidth to the default queue (qos-group 0) and 10% of interface bandwidth to a different queue (for example, qos-group 1), then scheduling will be applied evenly among traffic in both qos-groups instead of applied as configured.
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