How Do OSPF and EIGRP Routing Protocols Compare?

350-401 By islever Editorial Last updated

Short answer

C EIGRP shows successor and feasible successor routes, and OSPF shows all known routes.

Question

How do OSPF and EIGRP compare?
  1. Both OSPF and EIGRP use the concept of areas.
  2. OSPF and EIGRP use the same administrative distance.
  3. EIGRP shows successor and feasible successor routes, and OSPF shows all known routes. Correct Answer
  4. EIGRP shows all known routes, and OSPF shows successor and feasible successor routes.

Key Takeaways

The exam tests protocol-specific route selection terminology; the common trap is confusing EIGRP's successor/feasible successor concept with OSPF's link-state database behavior.

This question tests the ability to differentiate OSPF and EIGRP route selection behaviors. Community consensus confirms that EIGRP maintains successor and feasible successor routes while OSPF retains all known routes in its topology and routing tables.

Common mistake: Option A is frequently chosen because both protocols use hierarchical structures, but OSPF uses areas while EIGRP uses Autonomous Systems, making the statement inaccurate.

Expert Analysis

Why the Answer Is Correct

EIGRP uses the DUAL algorithm to select a successor (best route) and feasible successor (loop-free backup route) for each destination. OSPF, as a link-state protocol, calculates all shortest-path routes using Dijkstra's algorithm and stores them in the link-state database. Therefore, EIGRP explicitly identifies successor and feasible successor routes, while OSPF shows all known routes within its area topology.

Why the Other Options Are Wrong

Option A is incorrect because EIGRP uses Autonomous Systems, not areas; only OSPF uses the area concept for hierarchical design. Option B is false because OSPF has an administrative distance of 110, while EIGRP's internal routes have an AD of 90. Option D reverses the correct relationship between the two protocols' route selection terminology.

Community Comment Notes

Comment [1] correctly identifies that EIGRP uses AS while OSPF uses areas, reinforcing why Option A is wrong. Comment [2] notes that while A might seem partially correct, C is the true comparison the question seeks. Comment [3] simply confirms C as the correct answer.

Exam Strategy

When comparing routing protocols, focus on their unique terminology and route selection mechanisms. EIGRP's successor/feasible successor concept is exclusive to that protocol, making it a reliable differentiator from OSPF.

Community Votes

C
100%

100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 3 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 3

  1. wamendoza 👍 1
    maybe you have a confusion here but A and C are correct but A is a characteristic of both C is a comparison? Be careful with questions like that from Cisco
  2. masrur 👍 1 Answered C
    EIGRP uses concept AS (Autonomous System), OSPF uses Area.
  3. yasmiine 👍 1 Answered C
    answer C

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