Quick Answer
The answer is the route with preference 10. In Junos, route preference—often called administrative distance—is the primary criterion for route selection, evaluated before any metric value. The router compares preferences first, and the lower preference wins, so the route with preference 10 is installed in the forwarding table regardless of the metric (5 vs. 3). This concept is a core topic on the JNCIA-Junos exam, frequently appearing in multiple-choice questions that test your understanding of Junos’s unique two-step selection process: preference first, then metric only as a tiebreaker. A common trap is assuming a lower metric always wins, but in Junos, preference overrides metric entirely. Memory tip: think of preference as the “boss” that decides first, while metric is the “assistant” that only steps in when preferences are equal.
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 router has two routes to the same destination: one with preference 10 and metric 5, and another with preference 15 and metric 3. Which route will be installed in the forwarding table?
The route with preference 10.
Preference is the primary selection criterion.
The route with metric 3.
Why wrong: Metric is secondary to preference.
Neither route is installed.
Why wrong: One route is installed.
Both routes are installed if ECMP is enabled.
Why wrong: ECMP requires equal preference and metric.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The route with preference 10.
In Junos, the route preference (administrative distance) is the primary criterion for selecting the best route to a destination. The route with preference 10 is preferred over the route with preference 15, regardless of metric values. The route with preference 10 is installed in the forwarding table.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The route with preference 10.
Why this is correct
Preference is the primary selection criterion.
Related concept
Read the scenario before looking for a memorised answer.
The route with metric 3.
Why it's wrong here
Metric is secondary to preference.
Neither route is installed.
Why it's wrong here
One route is installed.
Both routes are installed if ECMP is enabled.
Why it's wrong here
ECMP requires equal preference and metric.
Common exam traps
The trap here is that candidates often confuse metric with preference, assuming a lower metric always wins, but Junos prioritizes preference over metric in route selection.
Detailed technical explanation
Junos uses a two-step route selection process: first, the route with the lowest preference value is chosen; if preferences are equal, the metric (e.g., OSPF cost, BGP MED) is compared. Preference values are protocol-specific (e.g., 10 for OSPF internal, 15 for IS-IS Level 1, 170 for BGP). The selected route is placed in the routing table (inet.0) and then installed in the forwarding table (Kernel FIB) for packet forwarding.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Routing Fundamentals — This question tests Routing Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: The route with preference 10. — In Junos, the route preference (administrative distance) is the primary criterion for selecting the best route to a destination. The route with preference 10 is preferred over the route with preference 15, regardless of metric values. The route with preference 10 is installed in the forwarding table.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
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Same concept, more angles
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 administrator configures a default route using 'set routing-options static route 0.0.0.0/0 next-hop 10.0.0.1 preference 10' and later enables OSPF which also advertises a default route with default preference 150. Which route becomes active in the routing table?
easyWhy C: The static route with preference 10 is preferred over the OSPF route with preference 150 because JunOS selects the route with the lowest preference value. Option A is correct. Option B is incorrect because higher preference is less preferred. Option C is incorrect because ECMP requires equal cost routes, not different preference. Option D is incorrect because the static route is valid.
Last reviewed: Jun 11, 2026
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.
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