300-420 Question #373: Real Exam Question with Answer & Explanation

Question

A network engineer must design a multicast solution based on these requirements: - interactive communication - must not use source trees - users must register - 100 multicast sources Which solution must the company choose?

Options

• Aany-source multicast
• BMSDP
• CBIDIR-PIM
• DPIM-DM

Explanation

BIDIR-PIM is the ideal multicast solution because it supports interactive communication for a large number of sources and receivers by exclusively building bidirectional shared trees, fulfilling the requirement to avoid source trees.

Common mistakes.

• A. Any-Source Multicast (PIM-SM) typically switches from a shared tree to a shortest path tree (source tree) once data starts flowing, which violates the "must not use source trees" requirement.
• B. MSDP is a control plane protocol used with PIM-SM to allow RPs in different PIM-SM domains to discover active sources, and it does not define the tree-building mechanism itself.
• D. PIM-DM builds source trees by flooding traffic throughout the network and then pruning branches without receivers, which directly contradicts the requirement to avoid source trees.

Concept tested. Multicast PIM modes and characteristics

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_pim/configuration/xe-16/imc-pim-xe-16-book/imc-pim-bidir-pim.html

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