300-360 Question #92: Real Exam Question with Answer & Explanation

The correct answer is A: IGMP. IGMP (Internet Group Management Protocol) is the IPv4 protocol that hosts use to signal their membership in multicast groups to routers and network infrastructure. When IGMP snooping is enabled on a Wireless LAN Controller (WLC), the controller passively listens to IGMP Join and

Question

What protocol can be enabled to listen in on IPv4 multicast streams and maintain a map of what each client requests on a wireless LAN controller?

Options

AIGMP
BMLD
CPAP
DICMP
ESIP
FNTP

Explanation

IGMP (Internet Group Management Protocol) is the IPv4 protocol that hosts use to signal their membership in multicast groups to routers and network infrastructure. When IGMP snooping is enabled on a Wireless LAN Controller (WLC), the controller passively listens to IGMP Join and Leave messages exchanged between clients and the upstream router. This allows the WLC to build and maintain a precise map of which clients have subscribed to which multicast group addresses, enabling it to forward multicast traffic only to interested clients rather than flooding all wireless clients - a critical efficiency for wireless networks. MLD (Multicast Listener Discovery) is the IPv6 equivalent of IGMP and handles IPv6 multicast, not IPv4. PAP is an authentication protocol, ICMP is used for diagnostics like ping, SIP is a VoIP signaling protocol, and NTP handles time synchronization - none of these relate to multicast group membership tracking.

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