What configuration command is required to enable the EIGRP process on a router?

To enable the EIGRP (Enhanced Interior Gateway Routing Protocol) process on a router, the command "router eigrp" must be used, followed by the Autonomous System (AS) number. This command enters the router into EIGRP configuration mode, allowing the administrator to configure various parameters related to EIGRP such as network statements, timers, and interfaces to be included in the EIGRP routing process.

For example, the command would typically be followed by a designation of the AS number associated with the routing process, like so: "router eigrp 100". This tells the router to participate in EIGRP with the specified AS, facilitating the exchange of routing information with other routers that are also configured for EIGRP within the same AS.

The other options do not represent valid commands within the Cisco IOS for initiating the EIGRP routing process. Therefore, they would not lead to enabling EIGRP on the router, as only "router eigrp" is recognized to initiate the EIGRP process.