Replication Types Supported in Underlay Network Optimized Layer 2 Overlay Multicast (OL2OM) supports the following replication types: • Ingress Replication • Underlay Multicast with Default MDT Ingress Replication Ingress replication, or headend replication, is a unicast approach to handle multidestination Layer 2 overlay broadcast, unknown unicast, and multicast (BUM) traffic. For more information, see Ingress Replication in the “Configuring EVPN VXLAN Layer 2 Overlay Network“ chapter. OL2OM uses the ingress replication mechanism to send the Layer 2 overlay multicast traffic only to those VTEPs where receivers have joined the multicast group.
If ingress replication is already configured as part of initial Layer 2 VNI configuration, OL2OM uses the same mode of replication, without the need for extra configuration steps. Using ingress replication to handle OL2OM traffic can result in scaling issues because an ingress device must replicate the multicast traffic as many times as the number of VTEPs that are associated with the Layer 2 VNI. Use ingress replication in a network that has fewer receivers. Underlay Multicast with Default MDT A multicast distribution tree (MDT) is a multicast tunnel that transports multicast traffic.
Traffic through the Default MDT is flooded to all remote VTEPs, irrespective of whether the VTEP has any receivers or not. For more information, see Underlay Multicast in the “Configuring EVPN VXLAN Layer 2 Overlay Network“ chapter. For a large scale fabric network, we recommend Underlay Multicast Replication. Optimized Layer 2 Overlay Multicast traffic can take advantage of the underlying multicast network for data replication to support better scale and performance. How to Configure Optimized Layer 2 Overlay Multicast Configure Optimized Layer 2 Overlay Multicast in the fabric and also on the host-facing or Layer 2 access devices.
Prerequisites for Configuring Optimized Layer 2 Overlay Multicast Before configuring Optimized Layer 2 Overlay Multicast, ensure that the EVPN VXLAN Layer 2 Overlay network has been configured by performing all the procedures that are listed in How to Configure EVPN VXLAN Layer 2 Overlay Network . Configure Optimized Layer 2 Multicast in EVPN VXLAN Layer 2 Overlay Enable Optimized Layer 2 Overlay Multicast in BGP EVPN VXLAN Fabric Follow these steps to enable Optimized Layer 2 Overlay Multicast in the EVPN VXLAN fabric: Configuring Optimized Layer 2 Overlay Multicast Replication Types Supported in Underlay Network Configuring Optimized Layer 2 Overlay Multicast 5