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Resolution Guide - EX - Troubleshoot Multicast issue with EX device configured as Layer 2 switch

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Article ID: KB21585 KB Last Updated: 06 May 2020Version: 5.0
Summary:

This article explains how to troubleshoot Multicast issues with the EX device configured as a Layer 2 switch.

For configuration information or if your EX device is configured as a Layer 3 switch, refer to KB21990-Resolution Guides and Articles - Junos OS - Troubleshoot Multicast.

 

Symptoms:
  • Multicast is not working on EX device that is configured as a Layer 2 switch.

  • The Multicast client is not receiving data from the Multicast source, where the EX Layer 2 switch is in the path.

 

Solution:

Perform the following steps to troubleshoot a Multicast issue with EX Series Ethernet switches configured as a Layer 2 switch:

Note: For the flowchart version of these steps, click the flowchart icon:
 

step1  Map out your Network Topology and identify the following. For an example with definitions, refer to KB21591 - Sample Multicast Network Topology with Junos OS devices.

  • Multicast Client (Receiver) and the EX port to which it is connected
  • Multicast Server (Source) and the EX port to which it is connected
  • Multicast Group (the group address not working)
  • VLANs on the ports of the EX switch

step2  Confirm that Unicast traffic connectivity is working between the Multicast Client (receiver) and Server (source).

  • Unicast traffic must be working before continuing to troubleshoot Multicast.
  • One way is to test Unicast traffic is to ping from the Multicast client to the Multicast server. (Check if ping is permitted on the devices.)
  • If the ping response fails between the Multicast client and server, then narrow down the issue to the immediate next-hop connected device to test if Unicast routing is working.
  • Similarly from the upstream neighboring devices, follow the above step along the path taken by each next-hop device to reach the server.

Do you have Unicast connectivity working between the Multicast Client and Server?

  • Yes - Jump to Step 4
  • No - Continue to Step 3

step3  Ping from the EX switch to the Multicast Server. Do you have Unicast connectivity working between the EX switch and the Multicast Server?

  • Yes - Continue to Step 4
  • No - Troubleshoot environment for Unicast connectivity. Unicast traffic must be working before continuing to troubleshoot Multicast.

step4  Confirm that the EX switch is receiving Multicast traffic (stream) sent by the Multicast Server to the Client. 

  • To do this, create a Firewall Filter specifying the destination-address of the Multicast Server group address. For an example of how to do this, refer to KB21589 - Firewall Filter Examples to verify Multicast traffic is reaching the EX switch.
  • Apply the Firewall Filter on the EX switch interface to the ingress interface where the Multicast Server stream is expected.
  • Check if the Firewall Filter counters increment. This helps to understand if the traffic sent by the Multicast server is being received by the EX switch or not.

Is the EX switch receiving traffic (stream) from the Multicast Server (source), that is, is the Firewall Filter counter incrementing?

  • Yes - Continue to Step 5
  • No - If there is no traffic from the Multicast server (source) identified on the EX interface, narrow down the issue towards the Multicast source and the path, traversing each next-hop device reaching the source. 

step5  On the EX switch, is igmp-snooping enabled on the VLAN in which the Multicast Client and Server are connected? (It is enabled by default.) For more information about igmp-snooping, refer to KB21735 - Verify Multicast client is listed in IGMP Snooping Database.

  • To check, run the configuration command:  show protocols 

    The following output shows that igmp-snooping is enabled for all the VLANs of the EX device. It can also be enabled on a specific VLAN.

root@Juniper-L2_EX# show protocols
igmp-snooping {
vlan all;
  • Yes - igmp-snooping is enabled - Continue to Step 6
  • No - Packets are flooded to all the ports when igmp-snooping is not enabled. Configure port mirroring to see if Multicast stream is being forwarded by the switch. For more information about port mirroring, refer to Understanding Port Mirroring on EX Series Switches. Continue to Step 9, if still not resolved.

step6  On the EX switch, is the Multicast Receiver (client) in question listed in the IGMP snooping table? For more information and an example of how to do this, refer to KB21735 - Verify Multicast client is listed in IGMP Snooping Database.

  • No - Continue to Step 7
  • Yes - Jump to Step 9

step7  Confirm that the EX switch is receiving IGMP reports from the Multicast Client.

  • To do this, create a Firewall Filter specifying the source-address of the Multicast client and the destination-address of the Multicast Server Group address. For more information and an example of how to do this, refer to KB21589 - Firewall Filter Examples to verify Multicast traffic is reaching the EX switch.
  • Apply the Firewall Filter to the EX switch interface connected to the Multicast client (receiver).
  • Check if the Firewall Filter counters are incrementing; this confirms that the EX switch is receiving the client's IGMP reports.

Is the EX switch receiving IGMP reports from the Multicast Client?

  • No  - Continue to Step 8
  • Yes - Jump to Step 9 and open a case

step8  Are the Multicast clients configured to send IGMP reports?  

Note: Not all clients are intentionally configured to send IGMP reports.

  • No - Clients are NOT configured to send reports:

    The EX switch is monitoring for IGMP packets when igmp-snooping is enabled. It requires IGMP reports for the specific Multicast traffic from the Multicast receiver client.
    If the clients do not send IGMP reports, then the EX switch will not send the Multicast traffic towards them.
    If the client is NOT supposed to be configured for sending IGMP reports, then the igmp-snooping configuration on the EX switch should be disabled for that particular VLAN.

    Note: Caution should be taken when disabling igmp-snooping on a VLAN, since all devices connected to the VLAN will receive the Multicast traffic once IGMP is disabled.

    Continue to Step 9, if still not resolved.

  • Yes - Clients are configured to send reports:

    Check the configuration on the Multicast Client. 

    Confirm all groups are properly configured.

    Also try another Multicast Client. 

    A packet capture on the client interface can be taken to confirm the client is sending the correct report.

    Continue to Step 9, if still not resolved.

step9  If the above steps do not resolve the problem, then collect the following and open a case with your technical support representative:

  • Network Topology

    - Multicast Client (Receiver) and the EX port to which it is connected

    - Multicast Server (Source) and the EX port to which it is connected

    - Multicast Group (the group address not working)

    - VLANs on the ports of the EX switch


  • IGMP Snooping logs and data: (only if Clients are configured to send IGMP Reports)

    root@Juniper-L2_EX# set protocols igmp-snooping traceoptions file igmp-snooping-reports.log
    root@Juniper-L2_EX# set protocols igmp-snooping traceoptions file size 1m
    root@Juniper-L2_EX# set protocols igmp-snooping traceoptions flag all
    
    root@Juniper-L2_EX# run clear igmp-snooping membership
    root@Juniper-L2_EX# run clear igmp-snooping statistics
    
    [wait for next report...approx 120 seconds]
    
    root@Juniper-L2_EX# run show igmp-snooping membership detail
    root@Juniper-L2_EX# run show igmp-snooping membership vlan <vlan name> detail
    root@Juniper-L2_EX# run show igmp-snooping statistics
  • Collect all the logs on the EX device using the 'file archive' command.  For instructions, refer to KB20569 - Collecting Logs from EX series devices using the 'file archive' command.


  • Request Support Information:

    root@Juniper-L2_EX# run request support information all-members | no-more

 

Modification History:

2020-05-06: Updated all links and verified the remaining content, all are active and valid; added port mirroring information link for reference

 

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