Which design solution reduces the amount of IGMP state in the network?

Using a single multicast group address throughout the network concentrates all traffic into one group, which creates scaling and management problems rather than reducing IGMP state.

Multiple multicast domains segment the network but do not inherently reduce the total IGMP state maintained within each domain or across the overall design.

IGMP filtering controls which multicast groups are permitted on specific interfaces but does not reduce the overall IGMP state maintained in the network.

IGMPv3 with PIM-SSM allows receivers to subscribe to traffic from a specific source using (S,G) channel pairs rather than (*,G) shared tree entries. This source-specific model eliminates the need for shared tree state and RP (Rendezvous Point) state throughout the network. The result is a significantly smaller amount of multicast state that must be maintained across all routers.