A network engineer must design a multicast solution based on these requirements:interactive communicationmust not use...

BIDIR-PIM is the correct multicast solution for interactive many-to-many communication with many sources when source trees must not be used. Bidirectional PIM is specifically designed for applications where receivers can also be senders and where the number of sources can grow without creating per-source multicast state throughout the network. Instead of building shortest-path trees for each source, BIDIR-PIM uses a shared tree rooted at the rendezvous point and forwards traffic bidirectionally along that tree. This reduces multicast routing-table growth and control-plane churn in environments with many active sources. PIM dense mode is not appropriate because it floods and prunes traffic and is inefficient at scale. Any-source multicast with PIM-SM may create source trees, which violates the requirement. MSDP is used to exchange source information between PIM-SM domains and is not itself the forwarding mode for this campus or WAN multicast design. Reference topics: BIDIR-PIM, many-to-many multicast, shared tree, multicast source scaling, PIM design.