EIGRP successor routes — properties and behavior Which statements about EIGRP successor routes are correct?

Introduction / Context:
EIGRP uses the Diffusing Update Algorithm (DUAL) to select loop-free paths. Understanding the distinction among successor routes, feasible successors, the topology table, and the neighbor table is key to interpreting outputs and convergence behavior.

Given Data / Assumptions:

• Successor = best next-hop path currently used for forwarding.
• Feasible successor = precomputed backup that satisfies the feasibility condition.
• Neighbor table = adjacency/transport stats, not routes.

Concept / Approach:
The successor route is installed in the routing table and also present in the topology table. If a feasible successor exists (reported distance < feasible distance), DUAL can switch to it immediately upon failure of the successor, avoiding queries. Neither successors nor feasible successors live in the neighbor table; neighbors are peers, not routes. Route states are typically passive in steady state; active indicates a recomputation is in progress.

Step-by-Step Solution:
Identify successor as the forwarding path in steady state.Confirm that feasible successors may back up the successor.Exclude neighbor table from route storage; it holds peer info (SRTT, RTO, Q count).Exclude “active in routing table”; passive is the steady state.

Verification / Alternative check:
Use show ip eigrp topology to see successors (via code P for passive) and feasible successors, and show ip route eigrp to verify installed successors used for forwarding.

Why Other Options Are Wrong:

• B: Successors are actively used for forwarding, not just backups.
• C: Successors are passive when healthy; active indicates reconvergence.
• D/E: Neighbor table is not a routing repository, and successors exist in steady state, not only during queries.

Common Pitfalls:
Confusing the meanings of passive/active, or assuming a neighbor entry implies a route. DUAL state applies to routes, not to peers.

Final Answer:
A successor route is used by EIGRP to forward traffic to a destination, and it may be backed up by a feasible successor route.