Which of the following routing technologies uses a successor and a feasible successor?

IS-IS (Intermediate System to Intermediate System) is a link-state routing protocol that uses a shortest path first algorithm but does not use the terms successor and feasible successor.

OSPF (Open Shortest Path First) is also a link-state routing protocol that calculates shortest path trees but does not use the specific terminology of successor and feasible successor.

BGP (Border Gateway Protocol) is an exterior gateway protocol that uses path attributes and policies for routing, not successor/feasible successor terminology.

EIGRP (Enhanced Interior Gateway Routing Protocol) uses Diffusion Update Algorithm (DUAL) to calculate the best paths and backup paths. A "successor" is the primary route to a destination, while a "feasible successor" is a backup route that meets the feasibility condition, providing a loop-free path in case the successor fails.