Route Preference vs Metric
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?
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.
⚠ Common exam trap
A common mix-up: candidates confuse metric with preference, assuming a lower metric always wins, but Junos prioritizes preference over metric in route selection.
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 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.
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 with preference 10.
Why this is correct
Preference is the primary selection criterion.
- ✗
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.
Go deeper
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Same concept, more angles
1 more way this is tested on JN0-106
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?
easy- A.Neither route becomes active due to conflicting protocols
- B.Both routes are active for ECMP load balancing
- ✓ C.Static route to 0.0.0.0/0 with next-hop 10.0.0.1
- D.OSPF route to 0.0.0.0/0
Why C: The static route has a preference of 10, which is lower than OSPF's default preference of 150. Junos uses the route with the lowest preference value as the active route in the routing table. Therefore, the static default route becomes active.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This JN0-106 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 JN0-106 exam.