A router uses multicast domain (MD) to implement multicast VPN in Any-Source Multicast (ASM) mode, and in this situation multicast data of private networks can be transmitted over public networks.
MD VPN only supports IP multicast in ASM mode on the public network. PIM tunnels are set up on the public network to transmit multicast data between sites in a VPN.
Before transmitting multicast data in a VPN, ensure that this VPN functions properly. To allow a PE to receive data from multiple VPNs, configure a public network instance and multiple VPN instances on the PE. The public network instance is responsible for the communication with the P, and the VPN instances are responsible for the communication with their connected Customer Edges (CEs).
A share-MDT needs to be set up to forward multicast packets in an MD VPN. Or, a special switch-multicast distribution tree (MDT) can be set up to switch multicast data of private networks flowing to the public network from the share-MDT to the switch-MDT for transmission. Multicast data can therefore be transmitted on demand, and the pressure on Provider Edges (PEs) is reduced.