Quick Answer

The answer is that PIM Bootstrap messages elect the RP in PIM Sparse Mode, while Hello discovers neighbors, Join requests membership, Prune leaves a group, and Assert resolves duplicate forwarding on a multi-access network. This is correct because each PIM message type serves a distinct function in building and maintaining multicast distribution trees: Hello establishes neighbor adjacencies, Join and Prune signal interest or disinterest in a multicast group, Assert breaks ties when multiple upstream routers forward the same traffic onto a shared segment, and Bootstrap carries RP-set information to all routers. On the ENCOR 350-401 exam, this topic often appears as a drag-and-drop question testing your ability to match each message to its role, with a common trap being confusion between Bootstrap and Assert—remember that Bootstrap is about RP election, not forwarding conflict. A useful memory tip: “Hello finds friends, Join says yes, Prune says no, Assert fights duplicates, Bootstrap picks the RP.”