JNCIA-JUNOS Routing Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. 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.
Your Juniper router is running OSPF with multiple neighbors. You have a prefix 10.10.10.0/24 that is being learned via OSPF from two different routers: Router A with metric 30 and Router B with metric 20. The OSPF route from Router B is active. You want to ensure that traffic to 10.10.10.0/24 uses the path through Router A instead, even though it has a higher metric. You cannot change the OSPF metric on Router A. Which action should you take?
Use a routing policy to increase the preference of the OSPF route from Router B.
Increasing preference makes it less preferred, so the route from Router A (with lower preference) becomes active.
B
Increase the metric on Router B for that prefix.
Why wrong: You cannot change Router B's metric if you don't have control.
C
Use a routing policy to reject the OSPF route from Router A.
Why wrong: Rejecting Router A's route would leave only Router B's route, opposite of desired.
D
Configure a static route to 10.10.10.0/24 pointing to Router A.
Why wrong: A static route would have a lower preference and become active, but that changes the path entirely, not just preferring Router A over Router B.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a routing policy to increase the preference of the OSPF route from Router B.
In JUNOS, route preference (administrative distance) determines which route is installed in the routing table when multiple protocols or sources provide the same prefix. By default, OSPF internal routes have a preference of 10. You can use a routing policy to increase the preference of the OSPF route from Router B (making it less preferred), which will cause the route from Router A (with its default preference of 10) to become active, even though its metric is higher. This approach does not require changing the OSPF metric or removing the route from Router A.
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.
✓
Use a routing policy to increase the preference of the OSPF route from Router B.
Why this is correct
Increasing preference makes it less preferred, so the route from Router A (with lower preference) becomes active.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the metric on Router B for that prefix.
Why it's wrong here
You cannot change Router B's metric if you don't have control.
✗
Use a routing policy to reject the OSPF route from Router A.
Why it's wrong here
Rejecting Router A's route would leave only Router B's route, opposite of desired.
✗
Configure a static route to 10.10.10.0/24 pointing to Router A.
Why it's wrong here
A static route would have a lower preference and become active, but that changes the path entirely, not just preferring Router A over Router B.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse metric (cost) with preference (administrative distance) and think they must change the metric or reject routes, when in fact JUNOS allows preference manipulation via routing policies to influence route selection without altering the OSPF metric.
Detailed technical explanation
How to think about this question
JUNOS uses a two-step route selection process: first, the route with the lowest preference is chosen from all sources (e.g., OSPF, static, BGP); then, among routes with the same preference, the lowest metric is used. By increasing the preference of the OSPF route from Router B (e.g., to 15), the router will prefer the OSPF route from Router A (preference 10) even though its metric is higher (30 vs 20). This is a common technique for traffic engineering without altering protocol metrics or adding static routes.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Routing Fundamentals — This question tests Routing Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a routing policy to increase the preference of the OSPF route from Router B. — In JUNOS, route preference (administrative distance) determines which route is installed in the routing table when multiple protocols or sources provide the same prefix. By default, OSPF internal routes have a preference of 10. You can use a routing policy to increase the preference of the OSPF route from Router B (making it less preferred), which will cause the route from Router A (with its default preference of 10) to become active, even though its metric is higher. This approach does not require changing the OSPF metric or removing the route from Router A.
What should I do if I get this JNCIA-JUNOS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This JNCIA-JUNOS practice question is part of Courseiva's free Juniper Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the JNCIA-JUNOS exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.