In this case study, you will examine the multicast architecture in a large network corresponding to an Internet service provider, ISPnet. The large network encapsulates many regional networks, each with the architecture shown in Figure 13-16. The overall network multicast architecture is shown in Figure 13-17.
For simplicity, you can enable ip pim-sparse-dense-mode on all interfaces within the network and on customer interfaces, as requested by the customer. Therefore, if the customer wants multicast service, IP PIM sparse-dense mode is enabled on the interface leading to that customer.
At least one core router in every regional network is configured as both an RP and an RP mapper. A full mesh of IMSDP and IMBGP peering is maintained among all backbone routers. EMSDP peering is enabled for customers running their own RP and for peer ISPs at the regional public NAP. For non-MSDP customers, auto-RP advises routers in the customer's network of available RPs in the provider's network.
The regional NAP includes two peering infrastructures: one optimized for multicast and another for unicast. MBGP is enabled on the multicast infrastructure and enables interdomain multicast routing that is incongruent to unicast. MBGP is also used in instances in which customers want separate links for unicast and multicast traffic.
Figure 13-16. Multicast Architecture within an ISPnet Regional Network
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