What is the role of the RP in PIM sparse mode?

Question

Options

• AThe RP responds to the PIM join messes with the source of requested multicast group
• BThe RP maintains default aging timeouts for all multicast streams requested by the receivers.
• CThe RP acts as a control-plane node and does not receive or forward multicast packets.
• DThe RP is the multicast that is the root of the PIM-SM shared multicast distribution tree.

• A
  2% (1)
• B
  5% (2)
• C
  2% (1)
• D
  91% (39)

Explanation

PIM Sparse Mode – Role of the Rendezvous Point (RP)

Option D is correct because in PIM Sparse Mode (PIM-SM), the Rendezvous Point serves as the root of the shared distribution tree (also called the *,G tree), meaning all multicast traffic initially flows through the RP, allowing receivers and sources to find each other before potentially switching to a shorter source-specific path.

Option A is wrong because the RP does not respond to Join messages by contacting the source directly - instead, sources register with the RP via unicast Register messages, and the RP builds the tree by accepting Join messages from receivers toward itself.

Option B is wrong because maintaining aging timeouts is a general multicast function distributed across routers, not a defining or exclusive role of the RP.

Option C is wrong because the RP is not a control-plane-only device - it actively receives and forwards multicast packets, at least until the network can switch to a source-specific shortest-path tree (SPT).

Memory Tip: Think of the RP as a "meeting point" - sources and receivers rendezvous (meet) there, just like the name suggests. If you remember "Rendezvous = meeting root of the shared tree," option D will always stand out.

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