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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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The SPT on a PIM-SM Network Fails to Forward Data

The SPT on a PIM-SM Network Fails to Forward Data

Common Causes

This fault is commonly caused by one of the following causes:

  • The downstream interface on the multicast device does not receive any (S, G) Join messages.

  • PIM-SM is not enabled on the interface.

  • The RPF route to the multicast source is incorrect. For example, the unicast route contains a loop.

  • Configurations are incorrect. For example, the configurations of the TTL, MTU, switchover threshold, or multicast boundary are improper.

Troubleshooting Flowchart

After the PIM-SM network is configured, the SPT fails to forward data.

Figure 20-5 shows the troubleshooting flowchart.

Figure 20-5  Troubleshooting flowchart: the SPT on a PIM-SM network fails to forward data

Troubleshooting Procedure

NOTE:

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

Procedure

  1. Check that the PIM routing table contains correct (S, G) entries.

    Run the display pim routing-table command on the device to check whether the PIM routing table contains correct (S, G) entries.

    • If the PIM routing table contains correct (S, G) entries, check whether the downstream interface list contains downstream interfaces to forward data to all group members.
      • If the (S, G) entries exist and are all correct in the PIM routing table, run the display multicast forwarding-table command to view the (S, G) entries in the forwarding table and check whether the value of the Forwarded field in the command output keeps increasing. The value of the Matched field is not updated in time. Therefore, after running the display multicast forwarding-table command, you need to wait for several minutes.
        • If the value of the Matched field keeps increasing, it indicates that the upstream device can normally forward multicast data to the current device but the current device fails to forward the data downstream. Go to Step 9.

        • If the value of the Matched field remains unchanged, do as follows:
          • If the current device is not a source's DR, it indicates that the current device has not received any multicast data. The fault may be caused by the upstream device. Then check whether the PIM routing table on the upstream device contains correct (S, G) entries.
            • If the PIM routing table on the upstream device does not contain correct (S, G) entries, troubleshoot the upstream device following the preceding steps.

            • If the PIM routing table on the upstream device contains correct (S, G) entries, but the value of the Matched field still remains unchanged, go to Step 9.

          • If the current device is already a source's DR, it indicates that SPT has been set up but the source's DR fails to forward the multicast data along the SPT. Go to Step 9.

    • If the PIM routing table does not contain correct (S, G) entries, go to Step 2.

  2. Check that the downstream interface has received Join messages.

    NOTE:

    If the current device is a receiver's DR, skip this step.

    If the downstream interface does not receive any (S, G) Join messages, the possible causes may be as follows:
    • A fault occurs on the downstream interface.

    • PIM-SM is not enabled on the downstream interface.

    Run the display pim control-message counters interface interface-type interface-number message-type join-prune command to check whether the number of received Join/Prune messages on the downstream interface keeps increasing.

    • If the number of received Join/Prune messages on the downstream interface does not increase, run the display pim control-message counters interface interface-type interface-number message-type join-prune command on the downstream device to check whether it has sent Join/Prune messages upstream.
      • If the command output shows that the number of sent Join/Prune messages keeps increasing, it indicates that the downstream device has sent Join/Prune messages. The fault may be caused by a failure in PIM neighbor communication. In such a case, go to Step 9.

      • If the command output shows that the number of sent Join/Prune messages does not increase, it indicates the downstream device experiences a fault. Then locate the fault.

    • If the number of received Join/Prune messages on the downstream interface keeps increasing, go to Step 3.

  3. Check that PIM-SM is enabled on interfaces.

    The following interfaces are easy to be ignored in enabling PIM-SM:
    • RPF neighboring interface to the multicast source

    • RPF interface to the multicast source

    NOTE:

    In PIM-SM network deployment, you are recommended to enable the multicast function on all the devices on the network and enable PIM-SM on all the interfaces.

    Run the display pim interface verbose command to check PIM configurations on the interface. Focus on checking whether PIM-SM is enabled on the preceding interfaces.

    • If the command output does not contain information about an interface of the device or the PIM mode of an interface is dense, you need to run the pim sm command on the interface.

      If the system prompts that "Warning: Please enable multicast routing first" when you configure PIM-SM on the interface, run the multicast routing-enable command in the system view to enable the multicast function first and run the pim sm command in the interface view to enable PIM-SM on the interface.

    • If PIM-SM has been enabled on all the interfaces on the device, go to Step 4.

  4. Check that an RPF route to the multicast source is available.

    Run the display multicast rpf-info source-address command on the device to check whether there is an RPF route to the multicast source.

    • If the command output does not contain any RPF route to the RP, check the configurations of unicast routes. Run the ping command on the device and the RP to check whether they can ping each other successfully.

    • If the command output contains an RPF route to the multicast source, do as follows:
      • If the command output shows that the RPF route is a static multicast route, run the display current-configuration command to check whether the static multicast route is properly configured.

      • If the command output shows that the RPF route is a unicast route, run the display ip routing-table command to check whether the unicast route is consistent with the RPF route.

    • If the command output contains an RPF route to the RP and the route is properly configured, go to Step 5.

  5. Check that the interface that forwards multicast data is the receiver's DR.

    Run the display pim interface interface-type interface-number command on the device to check whether the interface that forwards multicast data is a receiver's DR.

    • If the DR information in the command output is not marked with local, troubleshoot the involved DR following the preceding steps.

    • If the DR information in the command output is marked with local, go to Step 6.

  6. Check whether a multicast boundary is configured on the interface.

    Run the display current-configuration interface interface-type interface-number command on the device to check whether a multicast boundary is configured on the interface.

    • If the configuration of the interface contains multicast boundary, it indicates that a multicast boundary is configured on the interface. Then you need to run the undo multicast boundary { group-address { mask | mask-length } | all command to delete the configuration of the multicast boundary or re-plan the network to ensure that no multicast boundary is configured on the RPF interface or the RPF neighboring interface.

    • If no multicast boundary is configured on the interface, go to Step 7.

  7. Check whether a source policy is configured.

    Run the display current-configuration configuration pim command to view the current configurations in the PIM view.

    • If the configuration contains source-policy acl-number, it indicates that a source filtering rule is configured. If the received multicast data is denied by the ACL rule, the multicast data is discarded. Then you need to run the undo source-policy command to delete the configuration of the ACL rule or reconfigure an ACL rule to ensure that demanded multicast data can be normally forwarded.

    • If no source policy is configured, go to Step 8.

  8. Check whether the PIM routing table contains correct (S, G) entries.

    Run the display pim routing-table command on the device to check whether the PIM routing table contains (S, G) entries. For details, see Step 1.

  9. Collect the following information and contact technical support personnel.
    • Results of the preceding troubleshooting procedure

    • Configuration files, log files, and alarm files of the devices

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Updated: 2019-05-10

Document ID: EDOC1000079719

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