Which statements are true about EIGRP successor routes? (Choose two.)
A.
A successor route is used by EIGRP to forward traffic to a destination.
B.
Successor routes are saved in the topology table to be used if the primary route fails.
C.
Successor routes are flagged as "active" in the routing table.
D.
A successor route may be backed up by a feasible successor route.
E.
Successor routes are stored in the neighbor table following the discovery process.
Explanation:
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 a 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 recomputation must occur. This is the process where a new successor is determined. The amount of time it takes to recompute the route affects the convergence time.
Even though the recomputation is not processor-intensive, it is advantageous to avoid recomputation if it is not necessary. When a topology change occurs, DUAL will test for feasible successors. If there are feasible successors, it will use any it finds in order to avoid any unnecessary recomputation. Feasible successors are defined in more detail later in this document.
Feasible SuccessorsA destination entry is moved from the topology table to the routing table when there is a feasible successor. All minimum cost paths to the destination form a set. From this set, the neighbors that have an advertised metric less than the current routing table metric are considered feasible successors.
Feasible successors are viewed by a router as neighbors that are downstream with respect to the destination. These neighbors and the associated metrics are placed in the forwarding table.
B is not correct because neighbor table only contains a list of directly connected EIGRP routers that have an adjacency with this router, it doesn’t contain successor routes.
C is not correct because successor routes are not flagged as “active”, they are always the best route to reach remote networks and are always used to send packets.
A and D are correct because successor route is the best and primary route to a remote network. It is stored in the routing table and topology table. If this route fails, a backup route (called feasible successor route) in the topology table will be used to route traffic to a destination.
You say “B is not correct because NEIGHBOR table only contains a list of directly connected EIGRP routers”, and thats true, but the answer B says “TOPOLOGY table”, and this is correct