352-001 · Question #653
Refer to the exhibit. Which two features can be used to make multicast work in this situation? (Choose two.)
The correct answer is C. Enable the IGMP querier feature on LAN switch A D. Configure a static MAC entry for the multicast server. Without a multicast router acting as an IGMP querier, enabling the querier on a switch and adding a static MAC entry for the multicast server restores proper Layer 2 multicast forwarding.
Question
Refer to the exhibit. Which two features can be used to make multicast work in this situation? (Choose two.)
Options
- ADisable IGMP snooping on both switches
- BDisable the IGMP query election process
- CEnable the IGMP querier feature on LAN switch A
- DConfigure a static MAC entry for the multicast server
- EDisable PIM snooping on both switches
How the community answered
(62 responses)- A6% (4)
- B13% (8)
- C76% (47)
- E5% (3)
Why each option
Without a multicast router acting as an IGMP querier, enabling the querier on a switch and adding a static MAC entry for the multicast server restores proper Layer 2 multicast forwarding.
Disabling IGMP snooping resolves the flooding problem by flooding multicast to all ports, but this wastes bandwidth and is not a targeted or best-practice solution for a missing querier.
Disabling the IGMP query election process does not solve the underlying problem - it still leaves no querier present, so group membership cannot be maintained by IGMP snooping.
Enabling the IGMP querier feature on LAN switch A allows the switch to originate IGMP General Query messages in the absence of a multicast router. This keeps IGMP snooping functional by prompting hosts to re-declare group membership, ensuring the switch correctly populates its forwarding table for multicast groups.
Configuring a static MAC entry for the multicast server group address guarantees that multicast frames are always forwarded to the server's port regardless of the IGMP snooping state, providing a reliable forwarding path even before dynamic group membership is established.
Disabling PIM snooping is unrelated to the Layer 2 IGMP querier absence issue and would not affect IGMP-based group membership tracking on the switches.
Concept tested: IGMP querier and static MAC for Layer 2 multicast forwarding
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_igmp/configuration/xe-16/imc-igmp-xe-16-book/imc-igmp-snooping.html
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