Why does the STP convergence fail for a switch


The switch STP calculation, convergence, and damage are implemented using BPDUs. The BPDU processing capacity must be enabled for the port. Otherwise, the switch discards the BPDUs by default, making the STP convergence fail.

Globally run the bpdu enable command for the S2700 switch. Run the bpdu enable command on the port for other devices.

Other related questions:
Why does a subcard fail to register on a switch
The possible causes are: The switch does not support the subcard. The subcard is not hot swappable and can register successfully only after the switch restarts. The subcard is not in a good contact with the backplane. The system version of the switch needs upgrading. NOTE: When this occurs, send the bar code of the subcard and switch version information to Huawei technical personnel so that Huawei can fix the problem quickly.

Why is the convergence for multiple MST regions slow
When a specified interface of the root bridge is faulty, the two packets that contain different root bridge information in an MST region may interact with each other continuously. The root bridge selection flaps for a period. As a result, the negotiation time is long and the network convergence is slow. Using the stp max-hops command, you can properly limit the maximum number of hops as required. Thus, the root bridge can be quickly confirmed and the convergence time can be shortened.

Convergence fails on the Huawei switch connected to the wireless CG device in STP mode. Why
When the switch encapsulates STP BPDUs, the Length field in the 802.3 Ethernet frame header contains 8-byte filling bits. However, the wireless CG device performs strict check for the Length field, and directly discards STP BPDUs sent by the switch. Convergence fails.

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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