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Troubleshooting Guide

CloudEngine 16800, 12800, 12800E, 8800, 7800, 6800, and 5800 Series Switches

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Packets Are Discarded on an Outbound Interface

Packets Are Discarded on an Outbound Interface

Keywords

Outbound direction, packet discarding, switch

Abstract

Packets are discarded on an outbound interface.

Problem Description

When devices on the network forward packets, some packets are discarded on the outbound interface.

Procedure

  1. Check the statistics on an interface. If Discard under Output has a value, packet loss occurs on the interface. The possible causes are as follows:
    • CE12800, CE6870EI, and CE6875EI: Traffic policing is configured on the device, and packets exceeding the rate limit are discarded.
    • A PFC deadlock occurs on the device. The packets buffered before the deadlock and the packets received during the deadlock are discarded.
    • Queue congestion occurs on the device, and excess packets are discarded.
    <HUAWEI> display interface 10ge 1/0/3
    10GE1/0/3 current state : UP (ifindex: 7)
    Line protocol current state : UP
    Description:
    Switch Port, PVID :    1, TPID : 8100(Hex), The Maximum Frame Length is 9216
    Internet protocol processing : disabled
    IP Sending Frames' Format is PKTFMT_ETHNT_2, Hardware address is 58f9-8709-e691
    Port Mode:     COMMON FIBER,     Port Split/Aggregate:         DISABLE
    Speed:                10000,     Loopback:                        NONE
    Duplex:                FULL,     Negotiation:                  DISABLE
    Input Flow-control: DISABLE,     Output Flow-control:          DISABLE
    Mdi:                      -,     Fec:                             NONE
    Last physical up time   : 2018-11-01 15:52:39
    Last physical down time : 2018-11-01 15:49:12
    Current system time: 2018-11-05 12:10:20
    Statistics last cleared:2018-11-05 12:10:02
        Last 10 seconds input rate: 0 bits/sec, 0 packets/sec
        Last 10 seconds output rate: 10000000000 bits/sec, 8445974 packets/sec
        Input peak rate 0 bits/sec, Record time: -
        Output peak rate 10000000000 bits/sec, Record time: 2018-11-05 12:10:20
        Input :                  0 bytes,                  0 packets
        Output:         7581922025 bytes,           51225582 packets
        Input: 
          Unicast:                      0,   Multicast:                       0 
          Broadcast:                    0,   Jumbo:                           0 
          Discard:                      0,   Frames:                          0
          Pause:                        0
    
          Total Error:                  0
          CRC:                          0,   Giants:                          0
          Jabbers:                      0,   Fragments:                       0
          Runts:                        0,   DropEvents:                      0
          Alignments:                   0,   Symbols:                         0
          Ignoreds:                     0
    
        Output:
          Unicast:               51225696,   Multicast:                       1
          Broadcast:                    0,   Jumbo:                           0
          Discard:               57203902,   Buffers Purged:                  0
          Pause:                        0
    
        Input bandwidth utilization threshold : 90.00%
        Output bandwidth utilization threshold: 90.00%
        Last 10 seconds input utility rate:  0.00%
        Last 10 seconds output utility rate: 100%
  2. Determine the cause of packet loss using the following methods:
    • CE12800, CE6870EI, and CE6875EI: Traffic policing is configured on the device, and packets exceeding the rate limit are discarded.

      Run the display current-configuration | include car command in the user view to check for traffic policing configurations on the device. If traffic policing is configured on the device and packets match the traffic policing configuration and are forwarded through the interface with packet loss, stop the corresponding service and check whether the number of lost packets increases on the specific outbound interface. If the number of lost packets does not increase, packets are discarded on the outbound interface due to the traffic policing configurations on the device.

    • A PFC deadlock occurs on the device. The packets buffered before the deadlock and the packets received during the deadlock are discarded.

      In versions earlier than V200R005C00, run the display dcb pfc command in any view to check the statistics on PFC frames. If the numbers of incoming and outgoing PFC frames are large and increase continuously on multiple interfaces including the outbound interface with packet loss, and traffic is forwarded between these interfaces, a PFC deadlock occurs on the outbound interface.

      In V200R005C00 and later versions, if the QOS_1.3.6.1.4.1.2011.5.25.32.4.1.11.75 hwXQoSPfcDeadLockAlarm alarm is generated on the device and the alarm contains the interface with packet loss, a PFC deadlock occurs on the outbound interface.

      When a PFC deadlock occurs, the interface discards packets buffered before the deadlock and the packets received during the deadlock.

    • Queue congestion occurs on the device, and excess packets are discarded.

      Run the display qos queue statistics interface interface-type interface-number command in any view to check queue-based traffic statistics on the outbound interface with packet loss. If the Dropped field has a value, packet loss occurs on the outbound interface due to queue congestion.

      The possible causes are as follows:
      • The device receives packets from multiple interfaces and forwards them through only one interface. The size of the received packets on the multiple interfaces exceeds the forwarding capacity of the outbound interface.
      • A microburst occurs on the device. That is, a large amount of burst data is received in milliseconds, so that the burst data rate is tens or hundreds of times higher than the average rate or even exceeds the port bandwidth. For details, see What Is a Microburst?.

Root Cause

  • CE12800, CE6870EI, and CE6875EI: Traffic policing is configured on the device, and packets exceeding the rate limit are discarded.
  • A PFC deadlock occurs on the device. The packets buffered before the deadlock and the packets received during the deadlock are discarded.
  • Queue congestion occurs on the device, and excess packets are discarded.

Solution

  • If packets are discarded due to traffic policing configurations on the device, no action is required.
  • If packets are discarded due to a PFC deadlock or queue congestion, configure links that work in load balancing mode or increase the bandwidth of the outbound interface to optimize the network traffic scheme.

Suggestion

Properly plan the network traffic forwarding paths to prevent any PFC deadlock or queue congestion on the network.

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Updated: 2020-01-07

Document ID: EDOC1000060766

Views: 607825

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