In the PIM protocol, which of the following packets have destination addresses that are unicast addresses? (Multiple choice)

Question

Options

• ARegister Stop
• BHello
• CBootstrap
• DGraft

• A
  79% (11)
• B
  7% (1)
• C
  14% (2)

Explanation

Register Stop and Graft both use unicast destination addresses because they target a single, specific router. Register Stop is sent by the Rendezvous Point (RP) directly back to the Designated Router (DR) that originated a Register message - a one-to-one reply. Graft (used in PIM-DM) is sent unicast to the upstream neighbor to rejoin a previously pruned branch.

Hello is wrong because it's sent to the ALL-PIM-ROUTERS multicast address (224.0.0.13) for local neighbor discovery - it must reach every PIM router on the link, so multicast is required. Bootstrap is also wrong for the same reason: Bootstrap messages flood RP-set information to all PIM routers domain-wide using the 224.0.0.13 multicast address.

Memory tip: Ask "Is this message talking to everyone or one specific router?" Hello and Bootstrap are announcements to the crowd (multicast), while Register Stop and Graft are direct replies/requests to a known individual neighbor (unicast). If it's a targeted response or a hop-by-hop upstream message, it's unicast.

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