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    Detecting and Logging Transit Traffic Packet Drops in the Forwarding Plane

    A detector logic is implemented in ES2 4G LM, ES2 10G LM, ES2 10G ADV LM, ES2 10G UPLINK LM, and GE/FE line module to monitor and report transit traffic packet drops for each sub-reason in the ingress and egress forwarding plane.

    The detector logic takes snapshots of monitored sub-reason specific drop counters over a polling interval of 60 seconds. The logic compares the latest snapshot of a particular drop counter with the previous snapshot of the drop counter to check the drop counter difference. If the drop counter difference is greater than the threshold value configured for the sub-reason, then a warning message is logged in the DataPlanePacketEngineering event log. The warning message contains the following information:

    • Line module slot number
    • Line module type
    • Packet drop sub-reason and number of dropped transit traffic packets
    • Direction of the dropped packet
    • Threshold value configured for the sub-reason


    • The logic detects and logs only the forwarding plane problem. It does not reset and restore the forwarding plane—that is, no recovery flow is invoked.
    • You cannot configure or modify the polling interval.
    • You can configure the logic to monitor only 25 sub-reasons.
    • The logic does not take into account the drops occurring before the first polling interval.

    To set a threshold level for the minimum number of sub-reason specific packets to be dropped for logging a warning message:

    • Issue the packet-drop-monitoring command in Global Configuration mode.
      host1(config)#packet-drop-monitoring linecard-type LM4 direction ingress sub-reason ARFMIS threshold 1000

      Use the no version to disable logging of warning messages (that is, the threshold value is set to 0).

    The packet drop monitoring configuration is applied for all existing line modules and also for any new line modules inserted in the chassis, based on the line module for which the configuration is done. The configuration is not removed even after issuing the slot erase command.

    Published: 2014-08-12