The answer is preference value and metric, as these two factors are directly used when comparing route preferences in JunOS. Preference value is applied first to select the best route when multiple routing protocols provide paths to the same destination, with a lower preference value indicating a more preferred route. If the preference values are equal, the metric—also called cost—is then compared within the same protocol to break the tie, with a lower metric being preferred. On the JNCIA-Junos exam, this concept tests your understanding of how JunOS selects the active route from the routing table, often appearing in multiple-choice questions that distinguish between route selection criteria and forwarding decisions. A common trap is confusing route preference with the longest prefix match, which is used for forwarding lookups, not for comparing route preferences. Remember the mnemonic: Prefer first, then measure—preference decides the protocol winner, metric decides the path within that protocol.
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.
Which TWO factors are directly used when comparing route preferences in JunOS? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Metric (or cost)
Route preference and metric (or cost) are used to compare routes from different protocols or within the same protocol. Options A and B are correct. Option C is a condition for route to be considered, not for comparison. Option D is used for longest prefix match, not preference. Option E is not a factor in JunOS route preference.
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.
✗
Next-hop reachability
Why it's wrong here
Reachability determines if a route is active, not its preference.
✗
Number of hops
Why it's wrong here
Hop count is not directly used; metric may represent hop count in some protocols.
✓
Metric (or cost)
Why this is correct
Within the same protocol, lower metric is preferred; across protocols, preference is compared first.
Related concept
Read the scenario before looking for a memorised answer.
✗
Prefix length
Why it's wrong here
Prefix length is used for route lookup, not preference comparison.
✓
Preference value
Why this is correct
Lower preference is more preferred, used across protocols.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the JNCIA-JUNOS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which JNCIA-JUNOS exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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: Metric (or cost) — Route preference and metric (or cost) are used to compare routes from different protocols or within the same protocol. Options A and B are correct. Option C is a condition for route to be considered, not for comparison. Option D is used for longest prefix match, not preference. Option E is not a factor in JunOS route preference.
What should I do if I get this JNCIA-JUNOS question wrong?
Identify which JNCIA-JUNOS exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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