Hello all,

Find below some steps to check if there are MAC flapping records in your network. Hope to be useful.

Procedure:

Use a command to determine the interface where MAC address flapping occurs.

Run the display mac-address flapping record command to check all historical records of MAC address flapping on the switch.

NOTE:

This command has been available since V200R001C00.

<HUAWEI> 
 S  : start time
 E  : end time
(Q) : quit vlan
(D) : error down
------------------------------------------------------------------------------
Move-Time             VLAN  MAC-Address      Original-Port Move-Ports   MoveNum
-------------------------------------------------------------------------------
S:2011-08-31 09:22 300   0000-0000-0007   Eth-Trunk1    Eth-Trunk2   81
E:2011-08-31 09:22

-------------------------------------------------------------------------------
Total items on slot 2: 1

Original-Port: indicates the interface that learns the MAC address first. The value of Original-Port is Eth-Trunk1.

Move-Ports: indicates the interface that learns the MAC address later. The value of Move-Ports is Eth-Trunk2.

Determine the interface where MAC address flapping occurs based on alarms.
Run the display trapbuffer command to check alarms to determine whether MAC address flapping occurs.

Modular switches and fixed switches of V200R001C00 and later versions support global MAC address flapping detection, and global MAC address flapping detection is enabled on them by default. Fixed switches of V100R005 and V100R006 do not support global MAC address flapping detection, and support only VLAN-based MAC address flapping detection. By default, VLAN-based MAC address flapping detection is disabled. You can run the loop-detect eth-loop alarm-only command in the VLAN view to enable VLAN-based MAC address flapping detection.

Differences on alarms of fixed and modular switches in different versions:
- Modular switches of V100R002, V100R003, and V100R006:
```
L2IF/4/MAC_FLAPPING_ALARM:OID 1.3.6.1.4.1.2011.5.25.42.2.1.7.12The mac-address has flap value . (BaseTrapSeverity=0, BaseTrapProbableCause=0, BaseTrapEventType=4, L2IfPort=549,entPhysicalIndex=1, MacAdd=0000-0000-002b,vlanid=1001, FormerIfDescName=Ethernet3/0/2,CurrentIfDescName=Ethernet3/0/3,DeviceName=S9306-169).
```
- Fixed andmodular switches of V200R001C00 and later versions:
```
L2IFPPI/4/MFLPVLANALARM:OID 1.3.6.1.4.1.2011.5.25.160.3.7 MAC move detected, VLANID = 200, MacAddress = 0800-0000-0001, Original-Port = Eth0/0/12, Flapping port = Eth0/0/17. Please check the network accessed to flapping port.
```
- Fixed switches of V100R005 and V100R006:
```
L2IFPPI/4/MFLPVLANALARM:OID 1.3.6.1.4.1.2011.5.25.160.3.7 Loop exists in vlan 1001, for flapping mac-address 0000-0000-002b between port GE0/0/24 and port GE0/0/23. 
```
NOTE:
MAC address flapping between interfaces may be not caused by network loops. MAC address flapping may occur on an aggregation switch in specific scenarios, for example, users roam between APs and a PC goes online through different access switches.