MSDP Connects PIM-SM Domains to Deliver VoD Across ASes

300-420 By islever Editorial Last updated

Design multicast services (SSM, PIM bidirectional, MSDP, service-reflection)

Short answer

C MSDP connects separate PIM-SM multicast domains so the RP in AS5373 can advertise the VoD source to clients in AS65773 across the WAN.

Question

Refer to the exhibit. A company specializing in VoD content creation has two offices in a separate multicast domain connected by a WAN link. BGP communication has been established between the offices. Clients are inside the LAN in each office. In AS5373, R2 has been selected as RP. What must the network architect design to deliver VoD content to clients in AS65773? - Exhibit: MSDP Connects PIM-SM Domains to Deliver VoD Across ASes
  1. PIM SSM
  2. PIM ASM with BSR
  3. MSDP Correct Answer
  4. PIM ASM with Auto-RP

Key Takeaways

Different multicast domains + own RP = MSDP. SSM/BSR/Auto-RP stay within a single domain; MSDP is what links PIM-SM domains for inter-domain source discovery.

The two offices are in separate multicast domains with their own RPs. MSDP (Multicast Source Discovery Protocol) peers the RPs across the domains so a source registered with the RP in AS5373 is discovered by the RP in AS65773, delivering the VoD content to the remote clients.

Common mistake: Picking B/D (BSR/Auto-RP): those elect an RP inside ONE domain; they do not bridge separate multicast domains. PIM SSM (A) uses no shared tree/RP at all, so it cannot leverage the existing ASM RP setup.

Expert Analysis

Why the Answer Is Correct

C is correct. MSDP peers the RPs of the two PIM-SM domains across the WAN, so the VoD source registered with the RP in AS5373 is advertised to the RP in AS65773 and the remote clients can join it.

Why the Other Options Are Wrong

B (BSR) and D (Auto-RP) are RP-election mechanisms that operate within a single domain; they cannot connect separate domains. A (PIM SSM) builds source trees with no shared RP, so it does not use the existing ASM RP in AS5373.

Community Comment Notes

The vote is C (100). Commenters state MSDP is the protocol to deliver multicast across different multicast domains (AS5373 and AS65773).

Community Votes

C
100%

100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 3 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 3

  1. PicoOstrava 👍 2 Answered C
    Given the network setup and the requirements, Multicast Source Discovery Protocol (MSDP) is the appropriate solution to deliver VoD content to clients across different multicast domains (AS5373 and AS65773)
  2. Seb82 👍 2
    shouldn't this be MSDP, considering there clients are in different mcast domains?
  3. Swiz005 👍 1
    I would expect the answer to be C , MSDP like Seb82 pointed out.

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