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Alarm Handling

S9300, S9300E, and S9300X V200R010C00

This document provides the explanations, causes, and recommended actions of alarms on the product.
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LDT_1. hwLdtPortLoop

LDT_1. hwLdtPortLoop


LDT/4/DetectLoop: OID [oid] The port detected loop. (InterfaceIndex: [INTEGER] InterfaceName: [OCTET] VlanListLow: [OCTET] VlanListHigh: [OCTET])

If the packets that a port sends is returned to the port through the local VLAN, the packets are looped. A loop may cause a broadcast storm.

A loop was detected.


Alarm ID Alarm Severity Alarm Type warning equipmentAlarm (5)


Name Meaning
[oid] Indicates the ID of the MIB object.
hwLdtInterfaceIndex Indicates the index of a port, that is, the index of a physical port at the link layer.
hwLdtInterfaceName Indicates the name of a port.
hwLdtPortLoopVlanlistLow Indicates the lower ID of the VLAN to which the alarmed port belongs. The value ranges from 0 to 2047. The value 0 is not used.
hwLdtPortLoopVlanlistHigh Indicates the higher ID of the VLAN to which the alarmed port belongs. The value ranges from 2048 to 4095. The value 4095 is not used.

Impact on the System

Packets sent from the interface are sent back to the interface through another interface in the same VLAN. This loop may cause broadcast storms in the VLAN.

Possible Causes

The network where the device locates had a loop.


  1. Run the display loop-detection command in the system view or interface view to check information about loop detection on the interface. The following operations are performed according to the workmode field:

    • If the value of workmode is trap, the port sends the trap and records logs without processing a detected loop. You need to clear this alarm manually. Run the display this command in the interface view to view the VLAN to which the port belongs. Go to step 2.
    • If the value of workmode is block, the port sends the Trap alarm, records logs, blocks the port, and deletes the MAC address forwarding entry. Go to step 3.
    • If the value of workmode is nolearning, the system sends the trap, records logs, disables the port from learning MAC addresses, and keeps the normal packet forwarding function of the port. Go to step 3.
    • If the value of workmode is shutdown, the system sends the trap and records logs. The port is disabled automatically. Go to step 3.
    • If the value of workmode is quitvlan, the system sends the trap, records logs, and deletes the interface from the VLAN where a loop occurs. Go to step 3.

  2. Remove the loop manually.

    Do as follows to remove the loop manually:

    • Disconnect the alarmed port manually.


      • Remove the connection cable on the port where the loop alarm was generated.
      • Run the shutdown command in the interface view to set the port to down state.
    • Run the loop-detection mode command to set the port to a working mode other than Trap. The system then processes the alarm automatically.

  3. Wait until the interface recovery time expires, and check whether a clear alarm is received.

    • If a clear alarm is received, no further action is required.
    • If no clear alarm is received, contact technical support personnel.

Updated: 2019-08-21

Document ID: EDOC1000142054

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