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Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureMedium

A large-scale data center network uses OSPF as its interior gateway protocol. Due to an increase in multicast video streaming services, the network team needs to ensure efficient delivery of multicast traffic to specific receivers across the OSPF domain. The receivers dynamically join and leave multicast groups. Which multicast routing protocol should be configured to support this sparse mode multicast environment?

  1. AMulticast Source Discovery Protocol (MSDP)
  2. BPIM-Sparse Mode (PIM-SM)
  3. CDistance Vector Multicast Routing Protocol (DVMRP)
  4. DPIM-Dense Mode (PIM-DM)
Show answer & explanation

Correct answer: B. PIM-Sparse Mode (PIM-SM)

PIM-Sparse Mode (PIM-SM) is designed for environments where multicast receivers are numerous but sparsely distributed across the network, and they dynamically join and leave groups. It explicitly builds distribution trees from receivers back to the Rendezvous Point (RP) and then to the source, making it efficient for sparse multicast traffic.

Why the other options are wrong

  • A. MSDP (Multicast Source Discovery Protocol) is used to discover multicast sources in other PIM-SM domains and advertise them to RPs, not for core multicast routing within a single domain.
  • C. DVMRP (Distance Vector Multicast Routing Protocol) is an older, less efficient multicast routing protocol that is rarely used in modern networks and operates in dense mode fashion.
  • D. PIM-Dense Mode (PIM-DM) operates by flooding multicast traffic throughout the network and then pruning branches where no receivers exist, which is inefficient for sparse environments.

PIM-Sparse Mode (PIM-SM)

A multicast routing protocol used in IP networks where multicast receivers are sparsely distributed and dynamically join/leave multicast groups, building distribution trees only where necessary.

  • Designed for sparse receiver environments.
  • Uses a Rendezvous Point (RP) to discover sources and receivers.
  • Builds shared trees (RPT) and source trees (SPT).
  • More scalable than PIM-DM for large networks.

Memory trick: Multicast: Efficiently sending data to many.

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