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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).
Irregular Packet Loss Occurs on VMs Connected to a VXLAN Gateway

Irregular Packet Loss Occurs on VMs Connected to a VXLAN Gateway

Problem Description

On the VXLAN network shown in Figure 19-2, server leaf nodes are CE6860EI switches. Packets are discarded irregularly on different VMs connected to the server leaf nodes.
Figure 19-4 VXLAN networking

Root Cause

A VXLAN gateway learns a large number of MAC addresses. When a hash collision occurs in MAC addresses and rate limit on unknown unicast packets is configured, packets whose rate exceeds the threshold are discarded.

Solution

Perform the following steps to locate and rectify the fault:

  1. Determine the VXLAN gateway to which the VM with packet loss is connected based on alarm information.
  2. Check whether a MAC address hash collision occurs on the device.

    Run the display mac-address hash-conflict command to check the MAC addresses that cannot be added to the MAC address table on the chip due to hash collisions. The Conflicting MAC Address field shows conflicting MAC addresses. A MAC address with an asterisk (*) indicates a current conflicting MAC address, and a MAC address without an asterisk (*) indicates a historical conflicting MAC address.

    <HUAWEI> display mac-address hash-conflict 0010-1100-3710 bridge-domain 10
    Flags: * - Current MAC address in the hash bucket of the chip
           _ - Internal bridge domain resource
    BD   : bridge-domain
    -------------------------------------------------------------------------------
    Slot: 1         Chip: 0
    -------------------------------------------------------------------------------
    MAC Address     VLAN/BD        Conflicting MAC Address   Time
    -------------------------------------------------------------------------------
    0010-1100-3710    -/10         0010-1100-7bd2*            -
                                   0010-1100-6bd7*            -
                                   0010-1100-08a7*            -
                                   0010-1100-20c9*            -
                                   0010-1100-7bd2             2018-02-01 14:32:23
                                   0010-1100-6bd7             2018-02-01 14:32:23
                                   0010-1100-08a7             2018-02-01 14:32:23
                                   0010-1100-20c9             2018-02-01 14:32:23
    -------------------------------------------------------------------------------
  3. Check whether unknown unicast suppression is configured in a BD.

    Run the display current-configuration configuration bridge-domain 10 command to check the configuration of the BD. The command output shows that the storm suppression unknown-unicast cir command has been configured to enable unknown unicast suppression. Because MAC address hash collisions occur and rate limit on unknown unicast packets is configured, service traffic is considered as unknown unicast traffic after MAC address learning fails. As a result, packets whose rate exceeds the threshold are discarded, causing packet loss.

    <HUAWEI> display current-configuration configuration bridge-domain 10
    #                                                                               
    bridge-domain 10                                                                                              
     ... ...  
     storm suppression unknown-unicast cir 1000 kbps cbs 1048576 bytes    
     ... ...                                                                                          
    #                                                                               
    return   
  4. Delete the configuration of unknown unicast suppression in the BD.
    Run the undo storm suppression unknown-unicast command in the BD view to delete the rate limit configuration for unknown unicast packets.
    <HUAWEI> system-view
    [~HUAWEI] bridge-domain 10
    [~HUAWEI-bd10] undo storm suppression unknown-unicast
    [*HUAWEI-bd10] commit
  5. Run the display mac-address hash-conflict command again to check the MAC addresses that cannot be added to the MAC address table on the chip due to hash collisions. If no conflicting MAC address exists and packet loss does not occur on VMs, the fault is rectified.
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Updated: 2020-01-07

Document ID: EDOC1000060766

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