Cisco Enterprise Network Core Technologies (ENCOR) Practice Exam

The concept of a feasible successor is specific to Enhanced Interior Gateway Routing Protocol (EIGRP). EIGRP utilizes a unique mechanism for determining the best route to a destination, which includes identifying backup routes known as feasible successors.

In EIGRP, when a primary path fails, the router can quickly switch to a feasible successor without needing to re-calculate the entire routing table, greatly enhancing convergence times. A feasible successor is defined as a backup route that meets specific criteria based on the feasibility condition, which assesses the metrics of the route to ensure it offers a viable alternative to the primary path.

This ability to maintain a list of feasible successors contributes to EIGRP's efficiency and reliability compared to other routing protocols, which may rely on different mechanisms for backup routes. In contrast, protocols like OSPF, RIP, and BGP do not have the same methodology for maintaining feasible successors, relying instead on different methods for route selection and redundancy.