What are the common causes for STP flapping

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The packet change and timer timeout repeatedly trigger recalculation and make network switches constantly repeat the following process: 1. Root bridge selection; 2. Port role switch; 3. Port status migration. Repetition of this process for many times is called STB flapping, which cannot be converged.

The common causes are as follows:
Link fault: The link attributes such as the port status, rate, and duplex mode of a port on the network constantly change.
Node fault: A switch has high CPU usage and cannot send or process STP packets at specified intervals.
Network fault: The network is congested, making the STP packets in the direction of root port be discarded in the process of forwarding. L2PT transparently transmits STP packets of other networks, making the STP convergence mistakenly occur on the device where the STP packets are discarded. The multicast suppression function is incorrectly configured on the network, making STP packets be discarded occasionally.
Modify configuration or optimize the network design based on different causes to rectify the STP flapping.

Other related questions:
What are common causes for AP faults
The common causes are as follows: - The AP does not have an IP address. - The AP's IP address conflicts with that of a device on the local LAN. - The network between the AP and AC is faulty. - The AP fails to be authenticated. - The number of APs connected to the AC reaches the upper limit. - The parameters such as the MAC address and SN on the AP conflict with the parameters on other APs. - The radio environment deteriorates. - The AP fails due to hardware problems.

What are the common causes of the failure to initiate a SiteCall?
Common causes of the failure to initiate a SiteCall: An endpoint can initiate a SiteCall only after registering with the GK server through the allocated account and password. Log in to the web interface, choose System > Admin > Call > H.323, and set the following parameters: Register on GK: Select Enable. GK IP: Enter the GK/SC address. (The management platform can be the MCU's built-in web interface or SMC1.0/2.0.) Site number: Enter the site ID allocated by the platform. User name: The value must be the same as that specified on the management platform. Password: The value must be the same as that specified on the management platform. HUAWEI GK: Select Enable.

In which situation does MAC address flapping occur on CE switches
MAC address flapping occurs when a MAC address is learned by two interfaces in the same VLAN and the MAC address entry learned later replaces the earlier one. MAC address flapping is usually caused by Layer 2 loops.

How to clear MAC address flapping alarms on an AC
The possible causes for MAC address flapping alarms are as follows: - The interfaces where a loop occurs are added to the same VLAN. - Cables are connected incorrectly. - A loop occurs on the network. Troubleshooting procedure: 1. Connect cables on the interfaces correctly and check whether the alarm persists. If so, go to step 2. If not, go to step 6. 2. Check whether the two interfaces that learn the same MAC address can be added to different VLANs based on the network topology. If yes, go to step 3. If not, go to step 4. 3. Add the two interfaces to different VLANs, and check whether the alarm persists. If so, go to step 4. If not, go to step 6. 4. Disable loop detection and enable STP. Check whether the alarm persists. If so, go to step 5. If not, go to step 6. 5. Contact Huawei technical personnel. 6. End.

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