Configuring Multicast with MPLS and GETVPN
This paper covers the configuration of IP Multicast with Multiprotocol Label Switching (MPLS) including the basics of Multicast with the Group Encrypted Transport VPN (GETVPN).
This paper describes how to configure IP Multicast with Multiprotocol Label Switching (MPLS). Using only MPLS the configuration will not include encryption and is described first. Next the paper will add encryption for Multicast with the Group Encrypted Transport VPN (GETVPN).
The key to using MPLS for multicast is for MPLS routers inside the core use the existing Layer 3 routing information for multicast replication. This replication inside the MPLS core improves multicast efficiencies and network performance.
With multicast core replication a Protocol Independent Multicast (PIM) adjacency is made between the Customer Edge (CE) and Provider Edge (PE) routers. PE routers maintain PIM adjacencies with CE routers, other PE routers, and with Provider (P) routers. No PIM adjacency is needed between CE devices not directly connected. This allows for a lot more scalable configuration than using CE to CE tunnels.
Multicast-enabled VPNs will create a VPN multicast routing table (MVRF). To support VPN-aware multicast systems, PIM Spare Mode, Spare Mode Bi-Directional, (Bi-Dir), or Source Specific Multicast SSM capability must be enabled on all affected P and PE routers. This addition results in a global multicast routing table being created in the provider network routers. The PE routes that have been configured to run PIM (global instance) will establish a PIM adjacency with neighboring P routers. The MPLS core and the enterprise network connected to it have separate instances of multicast routing with different rendezvous points.
There is no requirement to run the same multicast protocols in the customer and provider network. For example: Sparse mode in the enterprise; SSM in the MPLS Core; PIM Bi-Dir in the enterprise; and Sparse mode in the MPLS Core, etc. If PIM is configured as the CE-to-PE multicast protocol, the PE devices maintain PIM adjacencies with CE devices. No PIM adjacency will be established between CE devices that are not directly connected.