JNCIA-JUNOS Routing Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A route is present in the routing table but is not active. Which three conditions could explain this? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A route with a lower preference exists for the same destination.
A route with a lower preference (administrative distance) is preferred for the same destination prefix. In JUNOS, the route with the lowest preference value is installed as the active route in the forwarding table. If a route has a higher preference, it remains in the routing table as a backup but is not marked as active.
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.
✓
A route with a lower preference exists for the same destination.
Why this is correct
A route with lower preference (more preferred) will be active, making the other route inactive.
Related concept
Read the scenario before looking for a memorised answer.
✗
The route is hidden due to a firewall filter.
Why it's wrong here
Firewall filters affect forwarding decisions, not route visibility in the routing table.
✗
The route is an aggregate route.
Why it's wrong here
Aggregate routes can be active if configured correctly; being an aggregate does not automatically make it inactive.
✓
The next-hop is unreachable.
Why this is correct
If the next-hop is not in the routing table, the route is not active.
Related concept
Read the scenario before looking for a memorised answer.
✓
The route is a static route with a qualified-next-hop that is not satisfied.
Why this is correct
Qualified-next-hop conditions can prevent the static route from becoming active.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse firewall filters with routing policy or route filters, thinking they can hide routes, but firewall filters operate on packet forwarding, not on the routing table itself.
Detailed technical explanation
How to think about this question
Route preference in JUNOS is a numerical value (0–255) that determines which route is installed in the forwarding table when multiple protocols provide routes to the same destination. For example, direct routes have a preference of 0, static routes default to 5, OSPF internal routes to 10, and BGP to 170. A route with a higher preference is present in the routing table but is not active unless the lower-preference route is withdrawn. The 'active' flag in 'show route' indicates the route used for packet forwarding.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: A route with a lower preference exists for the same destination. — A route with a lower preference (administrative distance) is preferred for the same destination prefix. In JUNOS, the route with the lowest preference value is installed as the active route in the forwarding table. If a route has a higher preference, it remains in the routing table as a backup but is not marked as active.
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.
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Question Discussion
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