In EIGRP, what are a successor and a feasible successor?

• A. A successor is the best primary path; a feasible successor is a backup path that meets feasibility criteria for loop-free routing.
• B. A successor is a backup path; a feasible successor is the best path.
• C. A successor is a route with the lowest metric; a feasible successor is any other route.
• D. A successor is the path learned from BGP; a feasible successor is from OSPF.

Answer: (A)

In EIGRP, the path chosen to be used for forwarding traffic is called the successor—the best primary path to a destination, stored in the routing table as the route you actually take. The feasible successor is a backup path that can be used if the primary path fails, and it must meet a specific feasibility condition to guarantee loop-free routing.

The feasibility condition means the backup path’s reported distance from a neighbor must be less than the feasible distance to the destination as known by the router. When this condition is satisfied, the backup route is a feasible successor and can be promoted to the successor if the current primary path fails, enabling fast convergence without recalculating from scratch.

So the statement matches the correct concept: the successor is the best primary path, and the feasible successor is a loop-free backup path that meets the feasibility criteria.