Which of the following descriptions of RP in PIM-SM are correct? (Multiple choice)

Question

Options

• ADynamic RP election will involve two types of roles, C-BSR and C-RP.
• BRP is used to process join and exit messages from hosts and join or member joining requests
• COnly one RP can specify which multicast groups the RP provides services for.
• DNot all PIM devices in the network need to know the address of the RP

• A
  70% (21)
• B
  30% (9)

Explanation

A is correct because PIM-SM's dynamic RP mechanism relies on exactly two candidate roles: C-BSR (Candidate Bootstrap Router), which collects and distributes RP information across the domain, and C-RP (Candidate RP), which advertises willingness to serve as an RP for specific group ranges - both roles are required for the election process.

C is correct because while multiple C-RPs can exist in a domain, for any specific multicast group, only one RP is ultimately selected and active; each RP defines the group ranges it serves, and the BSR ensures no two RPs compete for the same group.

D is correct because only PIM routers that participate in active multicast distribution trees (i.e., DRs for receivers or routers on the source/receiver path) functionally need the RP address - routers uninvolved in any multicast forwarding for a group have no operational requirement to hold that mapping.

B is wrong because the RP does not process join/leave messages from hosts - that is handled by the local Designated Router (DR) via IGMP. The RP only processes PIM Join/Prune messages from other routers in the PIM domain, not directly from end hosts.

Memory tip: Picture the RP as a lobby in a hotel - guests (receivers) and visitors (sources) meet there, but it's the front desk (DR) that handles individual guest check-ins (IGMP). The hotel manager (BSR) runs the election to pick which concierges (C-RPs) staff which floors (group ranges).

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