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Troubleshooting Guide

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

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A Loop Occurs When VBST Specifications Are Exceeded

A Loop Occurs When VBST Specifications Are Exceeded


On the CE6851HI, VLANs 31 and 40 to 4000 have been created, and VBST is used.

Figure 13-12 Diagram of the networking on which VBST specifications are exceeded

Problem Description

After VLAN 35 is created on the CE6851HI and Eth-Trunk1 and Eth-Trunk2 are added to VLAN 35, a loop occurs on the network.

Cause Analysis

  1. Check the STP configuration on the device. The device runs VBST.

    <HUAWEI> display current-configuration | include stp
    stp mode vbst

  2. Run the display alarm active verbose command in any view to check for abnormal alarms on the device.

    <HUAWEI> display alarm active verbose
    Sequence    : 20  
    AlarmId     : 0xA772002             AlarmName : hwVbstVlanNumExceeded    
    AlarmType   : quality_of_service    Severity  : Warning          State : active 
    RootKindFlag: Independent                          
    StartTime   : 2017-03-21 15:52:40+09:00   
    DDescription : The number of VLANs running VBST has exceeded the upper limit, and the VBST function may not take effect on some VLANs. (hwVbstMaxVlanNum=128)

    In the preceding information, the value of AlarmName indicates that the number of VLANs supported by VBST reaches the upper limit, and the VBST function is unavailable in some VLANs.

  3. Check the VLAN configuration. The command output shows that the number of VLANs created on the device exceeds 128.

    <HUAWEI> display current-configuration | include vlan
    vlan batch 31 35 40 to 4000

  4. Check VBST instance information. The instance corresponding to VLAN 35 is not displayed in the command output.

    <HUAWEI> display stp vlan instance
    Instance Mode    VLANs Mapped
           0 default 2 to 30, 166 to 4094
           1 dynamic 1
           2 dynamic 31
           3 dynamic 40
           4 dynamic 41
           5 dynamic 42
         127 dynamic 164
         128 dynamic 165


Replace VBST with MSTP.



Updated: 2020-01-07

Document ID: EDOC1000060766

Views: 612085

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