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Configuration Guide - IP Multicast

S7700 and S9700 V200R010C00

This document describes IP multicast basics and how to configure IP multicast features, including IGMP/MLD, PIM (IPv4&IPv6), MSDP, multicast VPN, Layer 3 multicast CAC, Layer 2 multicast CAC, IGMP/MLD snooping, and multicast VLAN, IPv4&IPv6 multicast route management, static multicast MAC address, multicast network.
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SPT on a PIM-SM Network Fails to Be Established

SPT on a PIM-SM Network Fails to Be Established

Fault Symptom

The shortest path tree (SPT) fails to be established on a network. User hosts cannot receive multicast data.

Fault Analysis

This fault is commonly caused by one of the following:

  • The downstream interfaces of multicast devices do not receive any (S, G) Join message.
  • PIM-SM is not enabled on the interface.
  • The RPF route to the multicast source is incorrect (for example, a unicast routing loop occurs).
  • Configurations (such as the MTU, switchover threshold, and multicast boundary) are incorrect.

Procedure

  1. 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.

    • If the PIM routing table contains (S, G) entries, the entry has an RPT flag, and the multicast group is in the ASM group address range, the upstream interface is the RPF interface to RP but not the SPT interface to the multicast source, the SPT fails to be established.

      Run the display current-configuration configuration pim command on the receiver's DR to check the current configuration in the PIM view. If the command output contains "spt-switch-threshold traffic-rate" or "spt-switch-threshold infinity", run the undo spt-switch-threshold command to delete the configuration or run the spt-switch-threshold traffic-rate command to reconfigure a proper traffic rate.

    • If the PIM routing table contains (S, G) entries and the entry has an SPT flag, run the display multicast forwarding-table command to check (S, G) entries and check whether the value of Matched field keeps increasing. Wait a few minutes for the value of Matched field to update after running the display multicast forwarding-table command.
      • If the value of Matched field keeps increasing, the data forwarding on the upstream devices is normal but the data cannot be forwarded to downstream devices.

      • If the value of Matched field stops increasing and the current device is not the source's DR, the current device fails to receive multicast data. In this case, check whether the PIM routing table of the upstream devices has correct (S, G) entries.

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

  2. Check whether downstream interfaces receive Join messages.

    NOTE:

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

    Downstream interfaces fail to receive (S, G) Join packets if a fault occurs on these interfaces or PIM-SM is not enabled.

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

    • If the number of Join/Prune messages received by downstream interfaces does not increase, run the display pim control-message counters interface interface-type interface-number message-type join-prune command to check whether the downstream devices send Join/Prune messages to upstream devices.
      • If the number of Join/Prune messages increases, the downstream devices send Join/Prune messages. In this case, check whether PIM neighbors can communicate with each other.

      • If the number does not increase, the downstream devices are not working properly. In this case, locate and rectify the faults.

    • If the number of Join/Prune messages received by downstream interfaces increases, go to step 3.

  3. Check whether PIM-SM is enabled on the interface.

    The fault usually occurs when PIM-SM is not enabled on the RPF interface connecting to the multicast source.
    NOTE:

    When deploying a PIM-SM network, you are advised to enable multicast on all switches and the PIM-SM protocol on all interfaces.

    Run the display pim interface verbose command on the device to check PIM information on interfaces. Check whether the PIM-SM function is enabled on the preceding interfaces.

    • If the command output indicates that PIM-SM is not enabled on the interface or the PIM mode on an interface is Dense, run the pim sm command on the interface.

      If "Error: Please enable multicast in the system view first." is displayed when you enable PIM-SM on interfaces, run the multicast routing-enable command in the system view to enable the multicast function. Then, run the pim sm command in the interface view to enable PIM-SM.

    • If PIM-SM is enabled on all interfaces, go to step 4.

  4. Check whether the RPF route to the multicast source is available.

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

    • If the command output does not contain the RPF route to the multicast source, check the configuration of the unicast route. Run the ping command on the device and on the multicast source to check whether they can ping each other.

    • If the command output contains the RPF route to the multicast source,
      • If the RPF route is a static multicast route, run the display current-configuration command to check whether the static route configuration is correct.

      • If the command output indicates 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 the RPF route to the multicast source and the configuration of the route is correct, go to step 5.

  5. Check whether the interface forwarding multicast data is the receiver's DR.

    Run the display pim interface interface-type interface-number command to check whether the interface forwarding multicast data is the receiver's DR.

    • If there is no local flag in the command output, the device is not the receiver' DR. In such a case, you can locate the receiver's DR based on the DR address that is displayed in the command output and go to step 6.

    • If there is a local flag in the command output, go to step 6.

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

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

    • If the command output contains multicast boundary, the multicast boundary is configured on the interface. In this case, you can run the undo multicast boundary { group-address { mask | mask-length } | all } command to delete the multicast boundary configuration or replan the networking to ensure that the multicast boundary is not configured on the RPF interface or the RPF neighbor interface.

    • If the multicast boundary is not configured on the interface, go to step 7.

  7. Check whether the source policy is configured.

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

    • If the command output contains the "source-policy acl-number" or the "source-policy acl-name", source-based filtering rules are configured. If the received multicast data does not match ACL rules, the multicast data is discarded. In this case, you can run the undo source-policy command to delete the configuration or reconfigure the ACL rules to ensure that the multicast data can be forwarded normally.

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Updated: 2019-08-21

Document ID: EDOC1000141903

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