What command is used to enable the Auto-RP Listener on a router?

The command that enables the Auto-RP Listener on a router is "ip pim auto-rp listener." This command allows the router to receive Auto-RP advertisements, which are multicast routing information being sent by the Rendezvous Point (RP) to inform other routers about the availability of multicast sources and groups within the network. By enabling this feature, the router can dynamically learn about multicast group sources and their associated RPs without requiring manual configuration, enhancing the efficiency of multicast routing in the network.

The other options do serve important functions in the context of multicast routing, but they do not specifically enable the Auto-RP Listener feature. For instance, enabling multicast routing with "ip multicast-routing" is essential for overall multicast traffic handling, while "ip pim enable" is related to the broader scope of Protocol Independent Multicast (PIM) functionality. "Ip rp listener enable" simply does not exist as a recognized command in Cisco IOS. Therefore, the correct syntax and functionality of "ip pim auto-rp listener" stands out for its specific role in managing Auto-RP.