Which protocol uses a pull model, enabling multicast traffic to be sent only where it is requested?
- MP-BGP
- PIM-DM
- PIM-SM
- OSPFv3
Explanation: Protocol Independent Multicast - Sparse Mode (PIM-SM) is based on an explicit pull model, meaning that multicast traffic is forwarded only to the specific parts of the network that have requested it. In this operation, receivers signal their interest via IGMP, and the last-hop routers send PIM join messages toward a Rendezvous Point (RP) to "pull" the data stream down the shared distribution tree.
In contrast, PIM-DM (Dense Mode) uses a push model, which floods multicast traffic to every corner of the network and then requires routers with no interested receivers to prune the unwanted traffic. PIM-SM is the optimal choice for production networks because it efficiently conserves bandwidth and router resources by avoiding this unnecessary flooding. Other protocols like OSPFv3 and MP-BGP are primarily unicast routing protocols used to populate the routing table rather than managing the multicast distribution "pull" logic.
Related exam: Modules 8 – 13: Checkpoint Exam: Network Routing Answers (CCNP ENCOR v9)
