1. CGW sends EVPN route type 6 (*, *) to all the Layer 2 VTEPs in EVPN VXLAN fabric. 2. Receiver R4 in VLAN 20 sends (*, G) IGMP join to VTEP 2. (*, G) is created in IGMP snooping table on VTEP 2. 3. VTEP 2 sends EVPN route type 6 (*, G) to the CGW and all other Layer 2 VTEPs. (* , G) is also created in Layer 3 multicast on the CGW. 4. Source S1 in VLAN 10 starts streaming data. VTEP1 forwards the multicast traffic. 5. Layer 2 multicast traffic is switched through L2VNI to the CGW, based on the default EVPN route type 6. In the CGW, multicast data packets are processed by Layer 3 Multicast and routed to access SVI20 where the receiver R4 is connected. 6.
Multicast traffic is forwarded to VTEP 2 through L2VNI. On egress VTEP 2, Layer 2 Overlay Multicast switches the data packets to the port where the receiver R4 is connected. Optimized Layer 2 Overlay Multicast Handoff with External Network Figure 3: Topology to show Layer 2 Overlay Multicast Traffic Handoff to an External Network In this topology, either the multicast receiver or sender exists on an external network. The Centralized Gateway is configured to route the multicast traffic between the EVPN VXLAN fabric and the external network. The leaf VTEPs in the VXLAN fabric perform only bridging.
If a source device that is connected to a Layer 2 VTEP starts streaming multicast traffic, the traffic is bridged from the Layer 2 VTEP to the Centralized Gateway VTEP. The Centralized Gateway VTEP then routes the multicast traffic to the interested receivers in the external network. The Rendezvous Point (RP) is located outside the fabric. Configuring Optimized Layer 2 Overlay Multicast Optimized Layer 2 Overlay Multicast Handoff with External Network Configuring Optimized Layer 2 Overlay Multicast 4