Final answer:
The Feasible Distance in EIGRP is the sum of the cost to reach a neighbor router plus the Advertised Distance from that neighbor to the destination network. It's a crucial metric in EIGRP for choosing the most efficient path.
Step-by-step explanation:
The Enhanced Interior Gateway Routing Protocol (EIGRP) uses a composite metric to determine the best path to a destination network. The component of this metric you are asking about is known as the Feasible Distance (FD). The Feasible Distance is calculated as the sum of a neighbor router's Advertised Distance (AD) to a destination network plus the cost of reaching that neighbor router. In other words, the FD represents the total cost of getting a packet from a router to a destination network through a particular neighbor. This metric is crucial in EIGRP's dual decision process for selecting the most efficient, loop-free path through a network.
In EIGRP, the Advertised Distance, as the name implies, is the distance (cost) that a neighbor router advertises for reaching a particular network. When a router receives this information, it adds its own cost to reach that neighbor, thereby calculating the FD. Keep in mind that the lowest FD to a destination is chosen as the best path, and that route is placed in the routing table. The route with the lowest FD is known as the successor route, and routes with higher FDs but still meeting certain feasibility conditions are called feasible successors and can be used for fast rerouting.