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After adding Vlan, looping occurred

Publication Date:  2018-02-15 Views:  119 Downloads:  0
Issue Description

Product: CE6810LI V100R006C00SPC600

VLAN 31 of the existing setting operated normally without looping. After adding VLAN 35 to eth-trunk1 and eth-trunk2, looping occurred.

 

Configuration

#

vlan batch 31 35 40 to 4000

#

stp mode vbst

#

 

#

interface Eth-Trunk1

 description ## to SMBS01 port-channel2 ##

 port link-type trunk

 port trunk allow-pass vlan 31

 stp no-agreement-check

 mode lacp-static

#

interface Eth-Trunk2

 description ## to SMBS02 port-channel2 ##

 port link-type trunk

 port trunk allow-pass vlan 31

 stp no-agreement-check

 mode lacp-static

#





Handling Process

1. Check configuration

#

stp mode vbst

#

 

We found that the stp mode was VBST.

 

 

2 check the alarm

 

===============================================================================

                 display alarm active verbose

===============================================================================

 

Sequence    : 1590     

AlarmId     : 0xA772002             AlarmName : hwVbstVlanNumExceeded                                          

AlarmType   : quality_of_service    Severity  : Warning          State : active

RootKindFlag: Independent          

StartTime   : 2017-03-21 15:52:40+09:00               

Description : The number of VLANs running VBST has exceeded the upper limit, and the VBST function may not take effect on some VLANs. (hwVbstMaxVlanNum=128)

 

After check the alarm, we found that there was an active abnormal alarm, it shown that the number of VLANs running VBST has exceeded the upper limit, and the VBST function may not take effect on some VLANs

 

3. Check the vlan configuration

 

#

vlan batch 31 35 40 to 4000

#

We found there were more 128 VLANs created in the device

 

4 check the VBST instance information

===============================================================================

                 display stp vlan instance

===============================================================================

 

--------------------------------------------------------------------------------

Instance Mode    VLANs Mapped                                                  

--------------------------------------------------------------------------------

       0 default 2 to 30, 32 to 39, 166 to 4094                                

       1 dynamic 1                                                             

       2 dynamic 31                                                            

       3 dynamic 40                                                             

       4 dynamic 41                                                            

       5 dynamic 42 

     127 dynamic 164                                                           

     128 dynamic 165        

 

We found that there were 128 instances in the device. And there was no instance for VLAN35.

 

And now the problem is clear. The number of VLANs running VBST has exceeded the upper limit, there was no instance for VLAN35. So after adding VLAN 35 to eth-trunk1 and eth-trunk2, looping occurred.

Root Cause

The number of VLANs running VBST has exceeded the upper limit, there was no instance for VLAN35. So after adding VLAN 35 to eth-trunk1 and eth-trunk2, looping occurred.

Solution

Using MSTP to Replace the VBST.

END