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AR Router Troubleshooting Guide

This Product Documentation provides guidance for maintaining AR Enterprise Router, covering common information collection and fault diagnostic commands, typical fault troubleshooting guide, and troubleshooting.
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LDP LSP Flapping

LDP LSP Flapping

Common Causes

This fault is commonly caused by one of the following:

  • The route between LSP peers is flapping.

  • The LDP session flaps.

Troubleshooting Flowchart

This section describes the troubleshooting flow of LDP LSP flapping.

After an LDP LSP is established, the LDP LSP flaps.

The troubleshooting roadmap is as follows:
  • Check that the routes do not alternate between unreachable and reachable.

  • Check that the LDP session flaps.

Figure 24-3 shows the troubleshooting flowchart.

Figure 24-3  Troubleshooting flowchart for LDP LSP flapping

Troubleshooting Procedure

This section describes the troubleshooting procedure of LDP LSP flapping.



Saving the results of each troubleshooting step is recommended. If your troubleshooting fails to correct the fault, you will have a record of your actions to provide Huawei technical support personnel.


  1. Check that the routes alternate between unreachable and reachable.

    Run the display ip routing-table command to check information about the routes to the destination of the LSP. Run this command at 1-second interval. If routes exist, routing information is displayed. If no routes exist, no routing information is displayed. If sometimes routing information is displayed but sometimes not after the command is run several times, the routes alternate between unreachable and reachable.

    • If routes alternate between unreachable and reachable or no route is displayed, see The Ping Operation Fails and rectify the fault in IGP routes.

    • If the routes are always reachable, go to Step 2.

  2. Check that the LDP session flaps.

    Run the display mpls ldp session command to check the Status field. Running this command every second is recommended. If Operational and Initialized are displayed alternatively, the LDP session flaps.

    • If the LDP session flaps, see LDP Session Flapping.

    • If the LDP session does not flap, go to Step 3.

  3. Collect the following information, and contact technical support personnel.

    • Results of the preceding troubleshooting procedure
    • Configuration files, logs, and alarms

Updated: 2019-05-10

Document ID: EDOC1000079719

Views: 447858

Downloads: 4305

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