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Support for EVPN Type 6 Selective Multicast Ethernet Tag Route

Contrail Release 5.1 and later supports EVPN Type 6 selective multicast Ethernet tag (SMET) route to selectively send or receive traffic based on the presence or absence of active receivers on a compute node. The EVPN Type-6 SMET route helps build and use multicast trees selectively on a per <*, G> basis.

The length of the route update is NLRI (Network Layer Reachability Info) size, which is calculated as follows:

NLRI = Min.size (23 bytes) + 2 * IP_Address_Size + 1 (router_type) where,

The minimum size for the SelectiveMulticastRoute (TYPE-6) = RD (16 bytes) + Ethernet_Tag (4 bytes) + 3 = 23 bytes.

Based on number of prefixes carried, the NLRI length varies. The length of the update when transported through BGP is (NLRI Size * 8).

Currently, all broadcast, unknown unicast, multicast (BUM) traffic is carried over the inclusive multicast ethernet tag (IMET) routes. This results in flooding of all compute nodes irrespective of whether an active receiver is present or not on each of those compute-nodes.

Configuring EVPN Type-6 SMET Routes

EVPN Type-6 SMET routes capability attaches a specific BGP community attribute Ethernet Multicast flags Community (MF) to the IMET routes. This community is advertised by default in Contrail Release 5.1 and later. You must enable IGMP on the network as shown in Figure 1 as well as on the QFX device to which the multicast source is connected. You can configure IGMP at the global system configuration-level, at virtual network-level, or at VMI-level. Configuring ERB-UCAST-Gateway role enables IGMP snooping on the QFX device.

Figure 1: Configure IGMPConfigure IGMP

You can allow or deny multicast traffic by attaching a policy at the virtual network-level as shown in Figure 2.

Figure 2: Define Multicast PolicyDefine Multicast Policy

In Contrail Release 5.1 and later, the receivers are always inside the contrail cluster and sender is always outside the cluster. This feature is supported only with <*, G> /igmpv2. The SMET feature is supported only on QFX10000 and QFX5110 devices running Junos OS Release 18.4R1 and later.