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.”
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 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?
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
The correct answer is D. Junos selects routes based on preference first. Intra-area OSPF has preference 10, while external OSPF has preference 150. Since 10 < 150, the intra-area route is chosen regardless of metric. Options A, B, and C are incorrect because preference overrides metric and next-hop type.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
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: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related JNCIA-JUNOS OSPF questions on adjacency and route selection.
Routing Fundamentals — This question tests Routing Fundamentals — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The intra-area route because it has a lower preference — The correct answer is D. Junos selects routes based on preference first. Intra-area OSPF has preference 10, while external OSPF has preference 150. Since 10 < 150, the intra-area route is chosen regardless of metric. Options A, B, and C are incorrect because preference overrides metric and next-hop type.
What should I do if I get this JNCIA-JUNOS question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related JNCIA-JUNOS OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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