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350-401 · Question #567

Which statement about traffic management when PIM snooping is enabled is true?

The correct answer is D. Designated routers receive traffic only from groups through which a join message is received.. When PIM snooping is enabled, designated routers only receive multicast traffic for groups that have active join messages, preventing unnecessary flooding of traffic to all routers.

Submitted by olafpl· Mar 6, 2026Infrastructure

Question

Which statement about traffic management when PIM snooping is enabled is true?

Options

  • ATraffic is restricted to host ports.
  • BAll multicast traffic is flooded to the designated router.
  • CJoin message are flooded to all routers.
  • DDesignated routers receive traffic only from groups through which a join message is received.

How the community answered

(56 responses)
  • A
    2% (1)
  • B
    2% (1)
  • C
    7% (4)
  • D
    89% (50)

Why each option

When PIM snooping is enabled, designated routers only receive multicast traffic for groups that have active join messages, preventing unnecessary flooding of traffic to all routers.

ATraffic is restricted to host ports.

PIM snooping aims to restrict traffic to interested parties, but 'host ports' is too narrow; it applies to router ports as well, and often works in conjunction with IGMP snooping for host ports.

BAll multicast traffic is flooded to the designated router.

PIM snooping specifically aims to *prevent* all multicast traffic from being flooded to designated routers; instead, it intelligently forwards traffic based on membership.

CJoin message are flooded to all routers.

PIM Join messages are typically sent upstream towards the RP or source and are not flooded to all routers by PIM snooping; PIM snooping inspects these messages to build forwarding tables.

DDesignated routers receive traffic only from groups through which a join message is received.Correct

PIM snooping optimizes multicast forwarding by ensuring that multicast traffic is sent only to routers and end hosts that have explicitly requested it via IGMP or PIM join messages. Designated Routers, therefore, will only receive traffic from groups if they have an active PIM join message for those groups, preventing unsolicited multicast flooding.

Concept tested: PIM snooping traffic optimization

Source: https://www.cisco.com/c/en/us/td/docs/ios/ipmulticast/configuration/guide/imc_pmsg.html

Topics

#PIM snooping#Multicast traffic#Traffic management

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