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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 Goes Down

LDP LSP Goes Down

Common Causes

This fault is commonly caused by one of the following:

  • Routes become unreachable.

  • The LDP session goes Down.

  • Resources are insufficient. The number of resources defined in the PAF/license file, the number of tokens, or the number of labels reaches the upper limit, or memory is insufficient.

  • The policy for establishing an LSP is configured.

Troubleshooting Flowchart

After an LDP LSP is established, the LDP LSP goes Down.

The troubleshooting roadmap is as follows:
  • Check that the routes exist.

  • Check that the LDP session is successfully established.

  • Check that resources are insufficient. The number of resources defined in the PAF/license file, the number of tokens, or the number of labels reaches the upper limit, or memory is insufficient.

  • Check that a policy for establishing LSPs is configured.

Figure 24-4 shows the troubleshooting flowchart.

Figure 24-4  Troubleshooting flowchart for the fault that an LDP LSP goes Down

Troubleshooting Procedure

Context

NOTE:

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.

Procedure

  1. Check that routes exist.

    Run the display ip routing-table ip-address mask-length verbose command to check information about the route to the destination of the LSP.

    ip-address mask-length specifies the destination address of the LSP.

    If routing information is displayed and the value of the State field is Active Adv in the command output, a route reachable and is in the active state. If the route is a BGP route of a public network, check the Label field in the command output. If a value is displayed, not NULL, routing information carries a label.

    • If no route appears, the routes are not in the active state, or the BGP routes do not carry labels, see The Ping Operation Fails.

    • If BGP routes are reachable and in the active state, they carry labels. Go to Step 2.

  2. Check that the LDP session is successfully established.

    Run the display mpls ldp session command to check the Status field. If Operational is displayed, the LDP session is established and is Up. If Initialized is displayed, the session is in Initialized state.

    • If the LDP session fails to be established, see LDP Session Goes Down.

    • If the LDP session is established properly, go to Step 3.

  3. Check that resources are insufficient. The number of resources defined in the PAF/license file, the number of tokens, or the number of labels reaches the upper limit, or memory is insufficient.

    Perform the following steps to check that resources are insufficient.

    1. Check whether the number of LSPs reaches the upper limit defined in the PAF/license file.

      Run the display mpls lsp statistics command to check the Total field subject to the LDP LSP field. If the value is greater than that defined in the PAF/license file, resources are insufficient.

    2. Check that tokens to establish ingress LSPs or transit LSPs are used up.

      Run the display tunnel-info statistics command to view token statistics. The Global-1 Avail Tunnel-ID Num field shows the total number of available tokens, and the Global-1 Allocated Tunnel-ID Num field shows the number of used tokens. If the values of these two fields are the same, the tokens are used up and resources are insufficient.

    • If resources are insufficient, increase the upper limit of the resources or delete unwanted LSPs.

    • If resources are sufficient, go to Step 4.

  4. Check that a policy for establishing LSPs is configured.

    • Run the display this command in the MPLS view. If the following information is displayed, an IP-prefix-based policy has been configured to trigger the establishment of LSPs. The policy name (abc in the following example) depends on the real-world situation. Then, check that some LSPs are not included in the IP-prefix-based policy.
      lsp-trigger ip-prefix abc
    • Run the display this command in the MPLS LDP view. If the following information is displayed, an IP-prefix-based policy has been configured to trigger the establishment of LSPs. The policy name (abc in the following example) depends on the real-world situation. Then, check that some LSPs are not included in the IP-prefix-based policy.
      propagate mapping for ip-prefix abc 
    • Run the display ip ip-prefix command in the system view. If the following information is displayed, only routes to 1.1.1.1/32 and 2.2.2.2/32 can be used to trigger the establishment of LSPs. The IP addresses (1.1.1.1/32 and 2.2.2.2/32 in the following example) depend on the real-world situation.
             index: 10               permit  1.1.1.1/32
             index: 20               permit  2.2.2.2/32 

    • If one of the policies for establishing LSPs is configured, add the route to the destination of the required LSP to the policy.

    • If no policy is configured, go to Step 5.

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

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

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Updated: 2019-05-10

Document ID: EDOC1000079719

Views: 451204

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