With multicast multi-topologies, IPv6 multicast services can run in a specified topology, which isolates IPv6 multicast services from unicast services.
On the current network, multicast services highly depend on unicast routes. During multicast routing, a router searches a unicast routing table for an optimal route. If the unicast optimal route, shared by both multicast services and unicast services, is faulty, the multicast services and unicast services will be interrupted and users will fail to receive the multicast data.
With multicast multi-topologies, IPv6 multicast services can run in a specified topology, which isolates IPv6 multicast services from unicast services.
When configuring multicast multi-topologies, you can configure a multicast topology instance or a unicast topology instance. A multicast topology can be used in both PIM-SM intra-domain and inter-domain scenarios, but a unicast topology instance can be used only in a PIM-SM intra-domain scenario.