300-320 Question #277: Real Exam Question with Answer & Explanation

The correct answer is B: There is reduced congestion in the network.. PIM Dense Mode (PIM-DM) works on a flood-and-prune model: multicast traffic is initially flooded everywhere, and routers then send Prune messages to stop unwanted traffic. This causes significant bandwidth waste, especially in large networks with sparse receivers. PIM Sparse Mode

Question

Which option is an advantage of using PIM sparse mode instead of PIM dense mode?

Options

ANo RP is required.
BThere is reduced congestion in the network.
CIGMP is not required.
DIt floods all multicast traffic throughout the network.

Explanation

PIM Dense Mode (PIM-DM) works on a flood-and-prune model: multicast traffic is initially flooded everywhere, and routers then send Prune messages to stop unwanted traffic. This causes significant bandwidth waste, especially in large networks with sparse receivers. PIM Sparse Mode (PIM-SM) uses an explicit join model - traffic is only sent down paths where receivers have joined, drastically reducing unnecessary traffic and congestion (B). Option A is wrong because PIM-SM requires a Rendezvous Point (RP); it is PIM-DM that has no RP. Option C is wrong because both modes use IGMP for host membership. Option D actually describes PIM-DM behavior (flooding), not an advantage of PIM-SM.

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