400-007 Question #22: Real Exam Question with Answer & Explanation

The correct answer is A: IGMP snooping. IGMP snooping (IPv4) and MLD snooping (IPv6) are the two Layer 2 mechanisms that selectively forward multicast traffic only to ports that have interested listeners, preventing flooding within a VLAN.

Question

Which two features control multicast traffic in a VLAN environment? (Choose two)

Options

AIGMP snooping
BMLD snooping
CRGMP
DPIM snooping
Epruning

Explanation

IGMP snooping (IPv4) and MLD snooping (IPv6) are the two Layer 2 mechanisms that selectively forward multicast traffic only to ports that have interested listeners, preventing flooding within a VLAN.

Common mistakes.

C. RGMP (Router-port Group Management Protocol) is used between multicast routers and switches to restrict multicast traffic on router-to-router links, not to control multicast within a VLAN at the host level.
D. PIM snooping is a Layer 3 protocol mechanism used to optimize multicast routing between PIM routers and is not a standard VLAN-level multicast control feature like IGMP/MLD snooping.
E. VTP pruning restricts unnecessary VLAN broadcast traffic across trunk links, but it does not specifically control or filter multicast group membership within a VLAN.

Concept tested. Layer 2 multicast control with IGMP and MLD snooping

Reference. https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17-9/configuration_guide/ip_mcast_rtng/b_179_ip_mcast_rtng_9300_cg/configuring_igmp_snooping.html

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