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Routing & Switching · Intermediate

Feasible Successor (FS)

An EIGRP backup neighbor whose reported distance is lower than the current feasible distance, guaranteeing a loop-free path.

Definition

Feasible successors are precomputed and kept in the topology table, so EIGRP can fail over without queries when the successor is lost. They also form the candidate set for unequal-cost load balancing with variance.

Example

Successor FD 3072; neighbor B reports RD 2816 so B is a feasible successor.

Exam tip

Compare the neighbor's RD to the local FD, not the neighbor's total metric.

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