Which descriptions about IGMP Snooping are correct? (Multiple choice)

Question

Options

• AIGMP Snooping solves the problem of broadcasting multicast packets at Layer 3.
• BIGMP Snooping runs at the link layer and is a multicast restriction mechanism on Layer 2 Ethernet switches, used to manage and control multicast groups
• CIGMP Snooping forwards the multicast to all hosts of a device by listening to the IGMP text sent by the host
• DIGMP Snooping does not consume the CPU of the switch

• A
  9% (3)
• B
  71% (25)
• D
  20% (7)

Explanation

B is correct because IGMP Snooping is explicitly a Layer 2 (link layer) feature implemented on Ethernet switches - it intercepts IGMP messages to build a port-level multicast membership table, restricting multicast traffic to only interested receivers rather than flooding all ports.

C is correct (though the wording is awkward, likely due to translation) - the core mechanism is exactly this: the switch listens to (snoops) IGMP messages sent by hosts and uses that information to forward multicast streams only to the ports where interested hosts reside.

A is wrong because IGMP Snooping addresses Layer 2 flooding (multicast being treated like broadcast on a switch), not a Layer 3 problem. Layer 3 multicast routing is handled by protocols like PIM, not IGMP Snooping.

D is wrong because IGMP Snooping absolutely does consume switch CPU - the switch must process every IGMP Join/Leave/Query message to maintain its multicast forwarding table. This CPU overhead is actually a known trade-off of enabling the feature.

Memory tip: Think of the word "snooping" - a snooper listens at Layer 2 to figure out who wants the multicast, then delivers it only to those parties. If it didn't use CPU to listen, it couldn't snoop. And since it's snooping on a switch (Layer 2), it can't fix Layer 3 problems.

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