EIGRP for IPv6 Configuration

C

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To enable the EIGRP (Enhanced Interior Gateway Routing Protocol) for IPv6 on a device, you need to configure the router ID. The correct answer is option C: router ID.

The router ID is a unique identifier that is assigned to the router running EIGRP. It serves as a source identifier in EIGRP routing updates and helps in the selection of the best path to reach a destination. The router ID can be configured manually or can be automatically determined based on the highest IPv4 address assigned to any of the router's interfaces.

When EIGRP for IPv6 is enabled, the router ID is required to establish EIGRP neighbor adjacencies and exchange routing information with other routers running EIGRP for IPv6 in the network. The router ID is used to identify the router and ensure that each router has a unique identifier.

Option A, a public IP address, is not a prerequisite for enabling EIGRP for IPv6. EIGRP for IPv6 can run using both public and private IP addresses.

Option B, the loopback interface, is not specifically required for EIGRP to start running. However, the loopback interface can be used as a stable source for the router ID if no other suitable IPv4 address is available.

Option D, the process ID, is not relevant to EIGRP for IPv6. Process ID is used in other routing protocols like OSPF (Open Shortest Path First) for identification and configuration purposes.

Therefore, the correct value that must be configured on a device before EIGRP for IPv6 can start running is the router ID.