The packet change and timer timeout repeatedly triggers recalculation and makes 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 of the port converge mistakenly. The multicast suppression function is incorrectly configured on the network, making STP packets be discarded occasionally.
