3.5.d Implement and troubleshoot operations

http://tools.ietf.org/html/draft-savage-eigrp-00

3.5     Dual Finite State Machine (FSM)
The DUAL finite state machine embodies the decision process for all
route computations. It tracks all routes advertised by all neighbors.
The distance information, known as a metric, is used by DUAL to select
efficient loop free paths. DUAL selects routes to be inserted into a
routing table based on feasible successors. A successor is a
neighboring router used for packet forwarding that has least cost path
to a destination that is guaranteed not to be part of a routing loop.
When there are no feasible successors but there are neighbors
advertising the destination, a recalculation must occur to determine a
new successor.