CCNP Routing and Switching ROUTE 300-101 Official Cert Guide

Fast Convergence to Feasible Successors

Earlier in this chapter, in the section “Calculating the Metrics: Feasible Distance and Reported Distance,” the text explains how a router, for each possible route, calculates two metric values. One value is the feasible distance (FD), which is the metric from that router’s perspective. The other metric is the reported distance (RD), which is the integer metric from the perspective of a next-hop router.

EIGRP routers use the RD value when determining whether a possible route can be considered to be a loop-free backup route called a feasible successor. This section explains the concepts and shows how to confirm the existence or nonexistence of such routes.

Successor and Feasible Successor Concepts

For each ...