Editing Enhanced Interior Gateway Routing Protocol (section)

===Feasible successor===
A feasible successor for a particular destination is a next hop router that is guaranteed not to be a part of a [[routing loop]]. This condition is verified by testing the [[#Feasibility condition|feasibility condition]].

Thus, every successor is also a feasible successor. However, in most references about EIGRP the term ''feasible successor'' is used to denote only those routes which provide a loop-free path but which are not successors (i.e. they do not provide the least distance). From this point of view, for a reachable destination, there is always at least one successor, however, there might not be any feasible successors.

A feasible successor provides a working route to the same destination, although with a higher distance. At any time, a router can send a packet to a destination marked "Passive" through any of its successors or feasible successors without alerting them in the first place, and this packet will be delivered properly. Feasible successors are also recorded in the topology table.

The feasible successor effectively provides a backup route in the case that existing successors become unavailable. Also, when performing unequal-cost load-balancing (balancing the network traffic in inverse proportion to the cost of the routes), the feasible successors are used as next hops in the routing table for the load-balanced destination.

By default, the total count of successors and feasible successors for a destination stored in the routing table is limited to four. This limit can be changed in the range from 1 to 6. In more recent versions of Cisco IOS (e.g. 12.4), this range is between 1 and 16.