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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).
WLAN User Roaming Triggers MAC Address Flapping

WLAN User Roaming Triggers MAC Address Flapping

This section provides a troubleshooting case that WLAN user roaming triggers MAC address flapping.

Networking

The aggregation device CE12800 connects to two access devices (CE5800s), and the CE5800s provide network services for WLAN users through the connected APs.

Problem Description

The alarm about MAC address flapping is reported on the CE12800 sometimes. Alarms are displayed as follows:

Aug 29 2013 16:41:04 slot1 %%01FEI_COMM/4/hwMflpVlanLoopAlarm_active(l):CID=0x807f0467-alarmID=0x095e0012;MAC flapping detected, VlanId = 1, Original-Port = 10GE1/0/1, Flapping port = 10GE1/0/2,-. Check the network connected to the interface learning a flapping MAC address: 0000-c055-0102.

Cause Analysis

Generally, Layer 2 loops cause MAC address flapping. However, traffic switching also triggers the alarm about MAC address flapping in some networking. Analyze the cause for MAC address flapping according to the network.

  • Check whether a loop exists on the network.
    1. In the alarm about MAC address flapping, 10GE1/0/1 on CE5800-1 learns the MAC address, and then 10GE1/0/2 on CE5800-2 learns the MAC address.
    2. Check alarm records on CE5800-1 and CE5800-2. MAC address flapping does not exist on CE5800-1 and CE5800-2, that is, no loop occurs on CE5800-1 and CE5800-2.
    3. According to the flapped MAC address 00000-c055-0102 in the alarm about MAC address flapping, query the MAC address on CE5800-1 and CE5800-2. Hosts corresponding to this MAC address connect to the network through GE1/0/1 on CE5800-1 and GE1/0/2on CE5800-2. GE1/0/1 connects to AP1 and GE1/0/2 connects to AP2, and no loop occurs between AP1 and AP2.

    According to the preceding analysis, the alarm about MAC address flapping is not caused by loops.

  • Determine the cause for MAC address flapping.

    GE1/0/1 connects to AP1 and GE1/0/2 connects to AP2, so MAC address flapping on STAs. WLAN users go online from AP1 first and then AP2, that is, WLAN users roam between AP1 and AP2. On the CE12800, the outbound interface corresponding to the MAC address of WLAN users changes from 10GE1/0/1 to 10GE1/0/2, that is, MAC address flapping occurs.

    When WLAN users roam, the alarm about MAC address flapping is generated.

Procedure

The alarm about MAC address flapping is a normal situation and does not affect services, so the alarm can be ignored.

Suggestion

  1. In the networking where the aggregation device connects to access devices and access devices connect to APs, if the alarm about MAC address flapping is generated on the aggregation device sometimes, the alarm can be ignored.
  2. If MAC address flapping occurs multiple times in a short time, Layer 2 loops may occur. The occasional MAC address flapping is often caused by traffic switching, which can be ignored.

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Updated: 2020-01-07

Document ID: EDOC1000060766

Views: 603961

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