MSTP/4/LOOPBACK_DETECTED

Message

MSTP/4/LOOPBACK_DETECTED:The port [port-name] was blocked because it received the BPDU packets sent by itself.

Description

STP detected a self loop when an interface received the BPDUs sent by itself.

Parameters

Parameter Name	Parameter Meaning
port-name	Name of the port where loopback detection is enabled

Possible Causes

An STP-capable interface received BPDUs with the designated bridge ID as the local bridge ID and the designated interface ID as the local interface ID, indicating that a self loop occurs.

Procedure

Run the display current-configuration interface interface-name command to check whether the interface generating this alarm has been configured with the loopback function.
- If so, go to Step 4.
- If not, go to Step 2.
Check whether there is a loop formed by hubs and devices that are connected to the interface.
- If so, go to Step 5.
- If not, go to Step 3.
Collect log information and configuration information, and then contact technical support personnel.
Run the undo loopback command in the interface view to delete the local loopback configuration.
Remove the self-loop network cable from the hub to resolve the problem.