300-420 Question #160: Real Exam Question with Answer & Explanation

Question

An engineer is designing a multicast network for a financial application Most of the multicast sources also receive multicast traffic (many-to-many deployment model). To better routing tables, the design must not use source trees. Which multicast protocol satisfies these requirements?

Options

• ABIRDIR-PIM
• BPIM-SM
• CMSDP
• DPIM-SSM

Explanation

{"question_number": 6, "correct_answer": "A", "explanation": "BIDIR-PIM (Bidirectional PIM) is designed specifically for many-to-many multicast deployments and exclusively uses shared (RP-based) trees-it never builds source-specific shortest-path trees (SPTs). In BIDIR-PIM, traffic flows bidirectionally along the shared tree: from receivers toward the RP and from sources toward the RP, then out to receivers. This keeps routing tables small and manageable because only one tree per group exists regardless of the number of sources. PIM-SM (B) starts with shared trees but switches to source trees (SPTs) after a threshold is reached, violating the 'no source trees' requirement. PIM-SSM (D) always uses source-specific trees and requires receivers to know the source address-not suitable for many-to-many. MSDP (C) is an inter-domain protocol for RP source discovery between AS domains, not a multicast forwarding protocol choice for avoiding source trees.", "generated_by": "claude-sonnet", "llm_judge_score": 5}

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