- A
The route is a feasible successor, but the successor route is not present.
Why wrong: Incorrect. A feasible successor must have a reported distance less than the feasible distance. Here, reported distance (120) is greater than feasible distance (100), so it is not a feasible successor.
- B
The route is not installed because the reported distance (80) from the neighbor is less than the feasible distance (100), but the router's computed distance (150) is higher.
Why wrong: Incorrect. The reported distance from the neighbor is 80, which is less than the feasible distance of 100, so it meets the feasibility condition. However, the router's computed distance is 150, which is higher than the feasible distance, but that does not prevent installation. The issue is that the route is not the best.
- C
The route is not installed because the feasible distance (100) is not the best metric; the router has another route with a lower metric.
Correct. The feasible distance is 100, but if there is another route with a lower metric (e.g., 90), that route would be the successor and installed. The route with FD 100 would not be installed. The scenario implies the route is not the best.
- D
The route is not installed because EIGRP is configured for stub routing, which prevents learning routes.
Why wrong: Incorrect. Stub routing only affects query propagation, not route learning. The route is in the topology table, so it is learned.
Quick Answer
The answer is that the route is not installed because the router already has a better successor route with a lower feasible distance of 100, making the computed distance of 150 a non-optimal path. In EIGRP route selection, the successor is the route with the best feasible distance (FD), which is the lowest metric from the router to the destination. Here, the topology table shows an FD of 100, which is lower than the router’s own computed distance of 150, so the router uses the FD 100 route as the successor and does not install the inferior path. On the ENCOR 350-401 exam, this tests your understanding of how EIGRP compares metrics and selects the successor—a common trap is confusing reported distance (the neighbor’s metric) with feasible distance (the router’s best metric). Remember: the successor is always the route with the lowest FD, not the lowest computed distance or advertised distance. A useful memory tip is “FD first: the smallest feasible distance wins the routing table.”
CCNP EIGRP Practice Question
This 350-401 practice question tests your understanding of eigrp. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An engineer is troubleshooting an EIGRP issue where a router is not learning a specific route from a neighbor. The engineer runs 'show ip eigrp topology all-links' and sees the route in the topology table with a feasible distance of 100 and a reported distance of 120. The neighbor's advertised distance is 80. The router's own computed distance to the network is 150. The route is not in the routing table. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The route is not installed because the feasible distance (100) is not the best metric; the router has another route with a lower metric.
Option C is correct because EIGRP installs the route with the best feasible distance (FD) into the routing table. The router's computed distance of 150 is lower than the feasible distance of 100, meaning the router has a better path (FD 100) already in the topology table. Since the route is not in the routing table, the router must have another route with a lower metric (FD 100) that is already installed, and the route with FD 150 is not selected as the successor.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The route is a feasible successor, but the successor route is not present.
Why it's wrong here
Incorrect. A feasible successor must have a reported distance less than the feasible distance. Here, reported distance (120) is greater than feasible distance (100), so it is not a feasible successor.
- ✗
The route is not installed because the reported distance (80) from the neighbor is less than the feasible distance (100), but the router's computed distance (150) is higher.
Why it's wrong here
Incorrect. The reported distance from the neighbor is 80, which is less than the feasible distance of 100, so it meets the feasibility condition. However, the router's computed distance is 150, which is higher than the feasible distance, but that does not prevent installation. The issue is that the route is not the best.
- ✓
The route is not installed because the feasible distance (100) is not the best metric; the router has another route with a lower metric.
Why this is correct
Correct. The feasible distance is 100, but if there is another route with a lower metric (e.g., 90), that route would be the successor and installed. The route with FD 100 would not be installed. The scenario implies the route is not the best.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The route is not installed because EIGRP is configured for stub routing, which prevents learning routes.
Why it's wrong here
Incorrect. Stub routing only affects query propagation, not route learning. The route is in the topology table, so it is learned.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the feasible distance (FD) and the computed distance (also called the metric) — candidates confuse the reported distance (RD) with the router's own computed distance, thinking that a lower RD automatically means the route is installed, but EIGRP installs only the route with the lowest FD, not the lowest RD.
Detailed technical explanation
How to think about this question
EIGRP uses the Diffusing Update Algorithm (DUAL) to select the successor route (best path) based on the lowest feasible distance (FD). The FD is the metric of the best path to a destination, and the reported distance (RD) is the neighbor's metric to that destination. The feasibility condition (RD < FD) ensures loop-free paths, but the route is only installed in the routing table if it is the successor (lowest FD). In this scenario, the router's computed distance of 150 is higher than the existing FD of 100, so the route is not the successor and is not installed, even though it is a feasible successor. This is a common scenario when a router has multiple paths and the best path is already in the routing table.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 350-401 question test?
EIGRP — This question tests EIGRP — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The route is not installed because the feasible distance (100) is not the best metric; the router has another route with a lower metric. — Option C is correct because EIGRP installs the route with the best feasible distance (FD) into the routing table. The router's computed distance of 150 is lower than the feasible distance of 100, meaning the router has a better path (FD 100) already in the topology table. Since the route is not in the routing table, the router must have another route with a lower metric (FD 100) that is already installed, and the route with FD 150 is not selected as the successor.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer is troubleshooting an EIGRP issue in a large enterprise network. Two routers, R1 and R2, are connected via a T1 link. R1 is learning a route to 10.0.0.0/8 from R2 with a metric of 28160, but the same route is also learned from another neighbor with a metric of 26880. The engineer notices that the route from R2 is not being installed in the routing table. What is the most likely cause?
medium- A.The route from R2 is a feasible successor, so it is not installed in the routing table.
- B.EIGRP is using unequal-cost load balancing, so the higher metric route is not used.
- ✓ C.The route with metric 28160 is not installed because EIGRP selects the route with the lowest metric.
- D.The route from R2 is a summary route, so it is not installed in the routing table.
Why C: C is correct because EIGRP installs only the route with the best (lowest) metric into the routing table. The route from R2 has a metric of 28160, while the other neighbor advertises the same route with a metric of 26880. Since 26880 is lower, R1 selects that route as the successor and does not install the higher-metric route from R2.
Last reviewed: Jun 24, 2026
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