Advanced Topics in BGP/MPLS mVPNs
The previous chapter described the original PIM/GRE-based solution for providing multicast, explored its shortcomings, and introduced the basic concepts for the alternative BGP/MPLS mVPN architecture, also referred to as NG mVPN. In this chapter, we discuss advanced topics related to BGP/MPLS mVPNs. We cover inter-AS operations, PIM Dense-Mode (DM), RP discovery, extranets, migration from PIM/GRE to BGP/MPLS mVPNs, and scaling. Finally, we conclude by looking at achieving high availability for video traffic using mVPNs and leveraging some of the BGP/MPLS mVPN mechanisms for delivering Internet multicast over an MPLS core.
11.2 BGP/MPLS mVPN – INTER-AS OPERATIONS
The discussion in the previous chapter was limited to a scenario in which all the sites of a given VPN are connected to the PEs that are in the same AS. However, as we saw in Chapter 9 (Hierarchical and inter-AS VPNs) for the unicast case, sites of a given VPN can be connected to PEs that are in different ASs. To allow operation in such a case two things must happen: an inter-PE tunnel must be set up across multiple ASs, and multicast routing information must be exchanged between the PEs in the different ASs.
Let us see how this is done in the simple context of a deployment spanning two ASs, AS1 and AS2, by looking at the inter-PE tunnel establishment and the multicast information distribution separately. Figure 11.1 shows two ASs, AS1 and AS2, connected at ASBR1 and ...