Which statements are true about EIGRP successor routes? (Choose two.)

A.
Successor routes are saved in the topology table to be used if the primary route fails.

B.
A successor route is used by EIGRP to forward traffic to a destination.

C.
Successor routes are stored in the neighbor table following the discovery process.

D.
Successor routes are flagged as “active” in the routing table.

E.
A successor route may be backed up by a feasible successor route.

Explanation:
The following are some terms relating to EIGRP:
1. Feasible Distance : The lowest calculated metric to each destination
2. Feasibility Condition : A condition that is met if a neighbor’s advertised distance to a
destination is lower that the router’s Feasible Distance to that same destination.
3. Successor : The neighbor that has been selected as the next hop for a given destination

based on the Feasibility Condition.
Jeff Doyle, Routing TCP/IP, Volume I, Chapter 8: Enhanced Interior Gateway Routing
Protocol (EIGRP), p.336-337, Cisco Press, (ISBN 1-57870-041-8)
Additional info:
The Feasible Condition is met when the receiving router has a Feasible Distance (FD) to a
particular network and it receives an update from a neighbor with a lower advertised or Reported
Distance (RD) to that network. The neighbor then becomes a Feasible Successor (FS) for that
route because it is one hop closer to the destination network. There may be a number of Feasible
Successors in a meshed network environment.
The RD for a neighbor to reach a particular network must always be less than the FD for the local
router to reach that same network. In this way EIGRP avoids routing loops. This is why routes that
have RD larger than the FD are not entered into the Topology table.
Ravi Malhotra, IP Routing, Chapter 4: Enhanced Interior Gateway Routing Protocol
(EIGRP), O’Reilly Press, January 2002 (ISBN 0-596-00275-0)