- A
The external route because it is type 2
Why wrong: Route type influences metric calculation but not preference.
- B
The intra-area route because it has a lower preference
Preference 10 is lower than 150, so intra-area route is active.
- C
The external route because it has a higher metric
Why wrong: Higher metric does not make a route preferred; lower is better, but preference is decisive.
- D
The intra-area route because it has a lower metric
Why wrong: Metric is irrelevant when preferences differ; preference decides.
Question 145 of 514
OSPF Route Selection: Why Intra-Area Wins Over External | JNCIA-Junos
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 receives two OSPF routes for 10.10.10.0/24: one intra-area with preference 10 and metric 1, and one external type 2 with preference 150 and metric 20. Which route is selected as active?
Quick Answer
The intra-area route is the correct choice because it has a lower preference value of 10 compared to the external type 2 route’s preference of 150. In Junos, route preference is the primary tiebreaker, overriding any metric differences; the intra-area route wins here regardless of the external route’s lower metric. This question tests your understanding of OSPF route selection logic on the JNCIA-Junos exam, where a common trap is to assume metric decides the winner. Instead, remember that Junos always checks preference first—intra-area (10) beats external (150) every time. A useful memory tip: “Preference first, metric later—intra-area is the dictator.”
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 intra-area route because it has a lower preference
B is correct because Junos uses route preference (administrative distance) as the primary tiebreaker when selecting the active route for a destination. The intra-area OSPF route has a default preference of 10, which is lower than the external type 2 route's preference of 150, so the intra-area route is installed into the routing table regardless of metric values.
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 external route because it is type 2
Why it's wrong here
Route type influences metric calculation but not preference.
- ✓
The intra-area route because it has a lower preference
Why this is correct
Preference 10 is lower than 150, so intra-area route is active.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The external route because it has a higher metric
Why it's wrong here
Higher metric does not make a route preferred; lower is better, but preference is decisive.
- ✗
The intra-area route because it has a lower metric
Why it's wrong here
Metric is irrelevant when preferences differ; preference decides.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often focus on metric or route type (intra-area vs external) as the tiebreaker, but Junos strictly uses route preference first, and the large difference (10 vs 150) makes the intra-area route the clear winner regardless of metric values.
Detailed technical explanation
How to think about this question
In Junos, the route selection process first compares route preference (administrative distance), which is a per-protocol or per-route configurable value. OSPF intra-area routes default to preference 10, while OSPF external type 2 routes default to preference 150. Only if preferences are equal does Junos compare metric (cost), and for type 2 external routes, the metric is the external cost without adding internal path cost. This behavior is defined in RFC 2328 and Junos implementation follows the preference-first model, unlike Cisco's use of administrative distance.
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.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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 — study guide chapter
Learn the concepts, then practise the questions
- →
Routing Fundamentals practice questions
Targeted practice on this topic area only
- →
All JNCIA-JUNOS questions
514 questions across all exam domains
- →
Juniper Networks Certified Associate Junos JNCIA-Junos study guide
Full concept coverage aligned to exam objectives
- →
JNCIA-JUNOS practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related JNCIA-JUNOS practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
User Interfaces practice questions
Practise JNCIA-JUNOS questions linked to User Interfaces.
Junos Configuration Basics practice questions
Practise JNCIA-JUNOS questions linked to Junos Configuration Basics.
Operational Monitoring and Maintenance practice questions
Practise JNCIA-JUNOS questions linked to Operational Monitoring and Maintenance.
Routing Fundamentals practice questions
Practise JNCIA-JUNOS questions linked to Routing Fundamentals.
Networking Fundamentals practice questions
Practise JNCIA-JUNOS questions linked to Networking Fundamentals.
Junos OS Fundamentals practice questions
Practise JNCIA-JUNOS questions linked to Junos OS Fundamentals.
JNCIA-JUNOS fundamentals practice questions
Practise JNCIA-JUNOS questions linked to JNCIA-JUNOS fundamentals.
JNCIA-JUNOS scenario practice questions
Practise JNCIA-JUNOS questions linked to JNCIA-JUNOS scenario.
JNCIA-JUNOS troubleshooting practice questions
Practise JNCIA-JUNOS questions linked to JNCIA-JUNOS troubleshooting.
Practice this exam
Start a free JNCIA-JUNOS practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
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: The intra-area route because it has a lower preference — B is correct because Junos uses route preference (administrative distance) as the primary tiebreaker when selecting the active route for a destination. The intra-area OSPF route has a default preference of 10, which is lower than the external type 2 route's preference of 150, so the intra-area route is installed into the routing table regardless of metric values.
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 →
Keep practising
More JNCIA-JUNOS practice questions
- A junior engineer needs to collect a snapshot of the current system state, including routing tables, interfaces, and con…
- A network engineer is troubleshooting a connectivity issue and wants to see the active routes in the routing table. Whic…
- You are the network engineer for a mid-sized enterprise with a Juniper MX router running Junos. The router has two uplin…
- Which TWO attributes are used by Junos to select the active route among multiple routes to the same destination?
- What is the default preference of a direct route in Junos?
- A router has two routes to the same destination: one with preference 10 and metric 5, and another with preference 15 and…
Last reviewed: Jul 4, 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.
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.