ALM-303046935 The MSTP Process's Port has been set to discarding state because of detecting loopback

Description

MSTP/4/PROLBDETECTGED:OID [OID] The MSTP Process's Port has been set to discarding state because of detecting loopback. (ProcessID=[INTEGER], InstanceID=[INTEGER], PortID1=[INTEGER], PortID2=[INTEGER], PortID3=[INTEGER], PortID4=[INTEGER], PortIDFlag=[INTEGER], IfIndex=[INTEGER], PortState=[INTEGER], PortName=[STRING])

When port detected loopback, block the port and arise trap.

Attribute

Alarm ID	Alarm Severity	Alarm Type
303046935	Warning	Communication alarm

Parameters

Name	Meaning
OID	Indicates the MIB object ID of the alarm.
ProcessID	Indicates the MSTP process ID
InstanceID	Indicates the instance ID.
PortID1	Indicates ID 1 of the port in the MSTP process.
PortID2	Indicates ID 2 of the port in the MSTP process.
PortID3	Indicates ID 3 of the port in the MSTP process.
PortID4	Indicates ID 4 of the port in the MSTP process.
PortIDFlag	Indicates the port flag.
IfIndex	Indicates the port index.
PortState	Indicates the port state.
PortName	Indicates the port name.

Impact on the System

After detecting a port blocked by local loopback, the system considers that a network storm occurs and blocks the local port to prevent the network storm from affecting services of the entire network. Services on the block port will be interrupted.

Possible Causes

When the STP port of the equipment receiving BPDU with the same designated bridge ID and designated port ID as this equipment and port, STP blocks this port and arises this trap for loopback detection will lead loop.

Procedure

Check whether the port where the alarm is generated is configured with local loopback.
- If so, go to Step 4.
- If not, go to Step 2.
Check whether there is a loop formed by a hub and devices, one of which is connected to the port.
- If so, go to Step 5.
- If not, go to Step 3.
Collect alarm information and configuration information, and then contact technical support personnel.
Delete the local loopback configuration to solve the problem.
Remove the self-loop network cable from the hub to solve the problem.
End.