Cisco CCNA mock exam questions sample test – Question 171

.Which of the following statements are TRUE regarding EIGRP operation? (Choose two.)

A. A successor is a backup route, and is installed in both the routing and topology tables.
B. A successor is a primary route, and is installed in both the routing and topology tables.
C. A successor is a primary route, and is installed only in the routing table.
D. A feasible successor is a backup route, and is installed in both the routing and topology tables.
E. A feasible successor is a primary route, and is only installed in the routing table.
F. A feasible successor is a backup route, and is only installed in the topology table.
G. If the successor route fails and no feasible successor route exists, the router will send an update with the route marked with an unreachable metric of 16.

Correct Answer: BF

Explanation:
In EIGRP operations, primary or active routes are known as successors. These routes are maintained in both the routing and topology tables. The routing table is the list of network
paths that are currently used by the router.
EIGRP also has the ability to maintain backup routes to destination networks. These backup routes are known as feasible successors. If a feasible successor is discovered by EIGRP,
it will be maintained only in the topology table, since it is not currently being used to route traffic. In the event of a successor failure, the backup feasible successor will become the
successor, and will be installed in the routing table automatically. If the successor route fails and no feasible successor route exists, the router will send queries to all neighbors until a
new successor is found.
EIGRP maintains three dynamic tables in RAM:
Neighbor table, which is a list of all neighboring EIGRP routers on shared subnets
Topology table, which contains all discovered network paths in the internetwork
Routing table, which contains the best path (based on lowest metric) to each destination network
A successor is not a backup route. A successor is a primary or active route, and it is stored in both the routing and topology tables.
A feasible successor is not a primary route. It is a backup route, and it is stored only in the topology table.
If the successor route fails and no feasible successor route exists, the router will not send an update with the route marked with an unreachable metric of 16. EIGRP does not send an
update with the route marked with an unreachable metric, and even if it did, 16 is not an unreachable metric in EIGRP as it is in RIP. Instead it sends a multicast query packet to all
adjacent neighbors requesting available routing paths to the destination network.
Objective:
Routing Fundamentals
Sub-Objective:
Configure, verify, and troubleshoot EIGRP for IPv4 (excluding authentication, filtering, manual summarization, redistribution, stub)
References:
Cisco > Support > IP > IP Routing > Technology Information > Technology White Paper > Enhanced Interior Gateway Routing Protocol > Document ID: 16406 > Feasible Distance,
Reported Distance, and Feasible Successor