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[All About Switches] Two Master Devices Exist in a VRRP Group in VRRP+MSTP Networking

Latest reply: Mar 9, 2018 00:39:10 2077 1 0 0

Involved Products and Versions

All products and versions


As shown in Figure 1-1, terminals are connected to SwitchC and SwitchD, and Switch C is connected to the Internet through SwitchA and SwitchB in the upstream direction. MSTP is deployed on the network to remove loops. VRRP is configured on both SwitchA and SwitchB to implement reliability and load balancing.

Figure 1-1 Networking diagram of two master devices in a VRRP group in VRRP+MSTP networking



Fault Symptom

Both SwitchA and SwitchB are VRRP master devices, and some network segments cannot access the Internet in wireless and wired services.

Cause Analysis

A loop occurs on SwitchD.

Troubleshooting Procedure

                          Step 1     Run the display cpu-defend statistics all command. It is found that a large number of VRRP packets are sent to the CPU while a large number of VRRP packets are discarded.

<HUAWEI> display cpu-defend statistics all
 Statistics on slot 2:
Packet Type          Pass(Packet/Byte)   Drop(Packet/Byte)  Last-dropping-time  
vrrp                          47876567          1856471019  2017-06-21 02:46
                            3255606556          126240029k

                          Step 2     Run the display trapbuffer command to check alarm information on the switch. An alarm indicating MAC address flapping is generated.

#Jun 21 2017 10:36:14 HX-1 L2IFPPI/4/MFLPVLANALARM:OID MAC move detected, VLANID = 28, MacAddress = 12b7-c3d0-9070, Original-Port = XGE2/0/0, Flapping port = XGE2/0/10 and XGE2/0/6. Please check the network accessed to flapping port.

Check that a loop occurs on SwitchD based on Original-Port and Flapping port in the alarm information. After the loop is removed, the fault is rectified.


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Created Mar 9, 2018 00:39:10 Helpful(0) Helpful(0)

thanks for your sharing!
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Come on!


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