350-401 Question #890: Real Exam Question with Answer & Explanation

Question

A new multicast server is being added to an existing PIM Sparse mode network. Which device in this network must the new server register with before its multicast traffic can be dispersed throughout the network?

Options

• AIGMP Querier
• BLocal PIM router
• CLocal IGMP switch
• DRendezvous Point (RP)

Explanation

In a PIM Sparse Mode network, a multicast source must register its traffic with the Rendezvous Point (RP) via its directly connected PIM router to enable distribution throughout the network.

Common mistakes.

• A. An IGMP Querier is responsible for discovering multicast group members on a local LAN segment, not for registering multicast sources with the wider PIM network.
• B. The local PIM router (specifically the DR for the source's segment) is the first hop for the multicast source but forwards the registration information to the RP; it is not the ultimate registration point itself for the entire network.
• C. A local IGMP switch operates at Layer 2 to optimize multicast forwarding on a LAN by listening to IGMP messages from receivers, but it is not involved in multicast source registration for the PIM domain.

Concept tested. PIM Sparse Mode source registration

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-cfg-pim-sparse-mode.html

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