What is and how to implement STP slow convergence

STP slow convergence is a concept relative to the fast convergence of RSTP and MSTP point-to-point links. It is not a new function but the initial convergence mode of the STP protocol.

The STP port is blocked by default. After the STP root bridge is selected and the port role calculation is performed, the port enters the listening state.

After the first ForwardDelay, the status switches from listening to learning. This ForwardDelay takes 15 seconds, during which the port is in the listening state.

After the second ForwardDelay, the status switches from learning to forwarding. This ForwardDelay takes 15 seconds, during which the MAC address learning is completed.

The two ForwardDelay takes total 30 seconds during which STP port enters the forwarding process. This whole process is called slow convergence.

NOTE:
During the 30 seconds' slow convergence, the port is blocked, and the sent DHCP packets are discarded for multiple times, making the DHCP protocol run abnormally. In this case, modify configuration to prevent slow convergence.

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