OISM with symmetric bridge domain configuration in EVPN-VXLAN fabrics

Optimized inter-subnet multicast (OISM) in an EVPN-VXLAN edge-routed bridging overlay fabric supports and optimizes routing multicast traffic across VLANs in an EVPN tenant domain. This feature runs on on leaf devices and border leaf devices in the fabric. OISM uses a supplemental bridge domain (SBD) and a multicast VLAN (MVLAN) to route multicast traffic from or to devices outside of the fabric. This feature also works with existing IGMP snooping and selective multicast (SMET) forwarding optimizations to minimize replication and forwarding in the EVPN core when bridging within tenant VLANs. With the OISM symmetric bridge domain model, you configure the SBD and all of the tenant VLANs on all of the OISM leaf devices in the fabric.