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Cisco Bug: CSCvt37793 - WRED values lost during downgrade-upgrade

Last Modified

Oct 03, 2020

Products (1)

  • Cisco Application Policy Infrastructure Controller (APIC)

Known Affected Releases

4.2(3n)

Description (partial)

QoS values not respected, values are replaced with 0 for min and max thresholds.

Symptom:
Packet loss is observed across the spine switches for unicast traffic.

Conditions:
This issue occurs under the following conditions:

1. Make changes to WRED values in release 4.x.
2. Downgrade to a release where WRED is not supported.
3. Upgrade to release 4.x, where WRED is supported again.

These changes kept the WRED algorithm. However, it removed the max and min thresholds and applies the default values for WRED. This configuration blocks all unicast traffic over the spine switches.

    qos parameters level3
      algo wred
        maxThreshold 0
        minThreshold 0
        probability 0
        weight 0
        ecn disabled
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