OISM with M-VLAN IRB method for external multicast connectivity (also called L2 uplink with EVPN-enabled IRB interfaces)

With optimized intersubnet multicast (OISM) in an EVPN-VXLAN network, you can connect the OISM border leaf (BL) devices to an external PIM domain using one of a few supported methods. When you use regular OISM, these platforms now support the multicast VLAN (M-VLAN) integrated routing and bridging (IRB) method, which establishes a Layer 2 (L2) uplink on the BL devices to the external PIM router. The BL devices use the M-VLAN and associated IRB interfaces in the EVPN instance to exchange multicast control and data traffic with external multicast sources and receivers. In the EVPN instance, configure the pim-evpn-gateway irb statement with the M-VLAN IRB logical interface at either the [edit protocols evpn oism] or the [edit routing-instances name protocols evpn oism] hierarchy level.