What command is used to enable multicast routing on a router?

The command used to enable multicast routing on a router is "ip multicast-routing." This command activates the multicast routing feature on a Cisco router, allowing it to forward multicast traffic. Enabling multicast routing is essential for facilitating the efficient distribution of data streams to multiple destinations without sending multiple copies of the same data.

Once multicast routing is enabled, the router can participate in multicast protocols like Protocol Independent Multicast (PIM), enabling it to manage multicast group memberships and efficiently route multicast packets throughout the network. This capability is crucial for applications such as streaming media, online gaming, and other services that rely on multicast traffic.

The other options provided do not represent valid commands for enabling multicast routing. They either do not exist or do not serve the purpose of enabling multicast routing on Cisco devices. By using the correct command, network engineers ensure that multicast traffic can be appropriately handled and routed as needed.