Multicast in BGP/MPLS IP VPN
Applicable Scenario
Figure 7-12 shows the typical BGP/MPLS IP VPN networking. Multicast in BGP/MPLS IP VPN allows private multicast traffic to be forwarded on the BGP/MPLS IP VPN. VPN users at each site receive multicast data from the users of the same VPN. PEs at the public network edge support multi-instance, and multicast traffic in VPN instances is isolated.
Implementation
As shown in Figure 7-13, the device transmits private multicast traffic over the GRE tunnel deployed between PEs.
To deploy multicast in BGP/MPLS IP VPN network, create a tunnel interface on the PE and bind the tunnel interface and the interface connecting the PE and the CE to the same VPN instance. The private routing protocol process on the PE advertises IP addresses of network segments where the tunnel interface and the interface connecting the PE and the CE are located. After multicast packets reach the PE, the next hop in the VPN instance routing table is the tunnel interface. The PE encapsulates a GRE header to multicast packets and sends it to the remote PE over the GRE tunnel. The remote PE decapsulates the multicast packets.
When configuring multicast in BGP/MPLS IP VPN network, note the following points:
- There must be a reachable route between the source address and destination address of the tunnel interface. The tunnel interface can use the loopback interface address as the source address. The loopback interface binds to the same VPN instance as the tunnel interface. In addition, there must be a reachable route between the loopback interface and the source address of the peer tunnel interface.
- IP addresses of tunnel interfaces at both ends of the GRE tunnel must be located on the same network segment.
- Interfaces including tunnel interfaces in a VPN instance must use the same PIM protocol. PIM can be not configured on the source interface of tunnel interface.
- All the PEs bound to the same VPN instance must establish a GRE tunnel.