The multicast source sends traffic to a multicast group –or physical/virtual network interface controller (NIC) outside AWS –through its ENI. An AWS Transit Gatewaywith the multicast domain configuration and registered source and members forwards the packet to the virtual router. The virtual router deployed in an Amazon VPC receives the multicast packets. The virtual routers are responsible for delivering the multicast packets between different network segments, Protocol Independent Multicast (PIM*) being a popular choice. In this example, the multicast packets are forwarded via a Generic Routing Encapsulation (GRE**) tunnel established between the virtual routers in AWS and the multicast router in the corporate data center. The on-premises router receives packets via the tunnel and decapsulates them. Decapsulated packets are sent over the downstream multicast
