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Configuring Multicast Forwarding with MLD Snooping in an EVPN-MPLS Environment

 

You can configure multicast forwarding with MLD snooping on MX Series routers with MPCs, vMX routers, and EX9200 switches serving as provider edge (PE) devices in an Ethernet VPN (EVPN) over MPLS environment. Starting in Junos OS Release 18.4R1, statements in the [edit protocols mld-snooping] configuration hierarchy can be configured in this environment on PE devices to enable IPv6 multicast traffic forwarding for receivers that are multihomed to EVPN provider edge (PE) devices with all-active multihoming.

The MLD snooping configuration is not automatically synchronized among all the multihoming peer PEs, so similar configurations must be committed for each multihomed peer PE device.

In addition, to handle Layer 3 multicast forwarding, PEs with hosts in multicast groups that span bridge domains or VLANs use PIM distributed designated router (PIM DDR) mode to route multicast traffic between bridge domains or VLANs through IRB interfaces. With PIM DDR configured, a PE device routes the traffic to any local IRBs configured for bridge domains or VLANs in the multicast group with interested receivers, even if the IRB is not the elected PIM designated router (DR).

IGMP snooping and multicast forwarding operation ensures that multicast traffic reaches all subscribed receivers within and between bridge domains or VLANs, and preserves bandwidth on the access side by reducing the amount of multicast control and data traffic being forwarded.

Configuring MLD Snooping for Default Any-source Multicast (ASM) Membership Group Processing with MLDv1 or MLDv2

By default, the EVPN-MPLS network processes only (*,G) (any-source multicast [ASM]) membership reports with IGMPv2, MLDv1, and MLDv2.

To configure MLD snooping on PE devices in an EVPN-MPLS network:

user@device# set protocols mld-snooping

You can also configure MLD snooping for a particular routing instance:

user@device# set routing-instances routing-instance-name protocols mld-snooping

PE devices cannot process both (*,G) ASM reports and (S,G) SSM reports at the same time, but you can alternatively configure PEs to process only (S,G) (source-specific multicast [SSM]) membership reports. See Configuring MLD Snooping with MLDv2 to Process Source-Specific Multicast Membership Reports Only.

Configuring MLD Snooping with MLDv2 to Process Source-Specific Multicast Membership Reports Only

By default, the EVPN-MPLS network processes only (*,G) (any-source multicast [ASM]) membership reports with IGMPv2, MLDv1, and MLDv2. You can alternatively configure PEs to process only MLDv2 (S,G) (source-specific multicast [SSM]) membership reports using the evpn-ssm-reports-only option in the [edit protocols mld-snooping] hierarchy when you configure MLD snooping.

You can enable SSM-only processing for one or more bridge domains in the EVI, or for all bridge domains in a virtual switch instance. When this option is enabled, ASM reports are not processed and are dropped.

To configure MLD snooping with MLDv2 to process only SSM membership reports:

user@device# set protocols mld-snooping evpn-ssm-reports-only

Viewing IGMP Snooping Multicast Information for EVPN-MPLS in the CLI

The following EVPN commands are supported to view MLD snooping multicast information in an EVPN-MPLS environment. The output of these commands includes information learned from native MLD snooping on a PE device and learned from EVPN Type 7 Join Sync Route and Type 8 Leave Sync Route messages.

  • show evpn mld-snooping database

  • show evpn multicast-snooping next-hops

  • show mld snooping evpn database

  • show mld snooping evpn membership