JNCIA-JUNOS Junos OS Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos os fundamentals. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 statements correctly describe the function of the 'commit' command in Junos OS? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It validates the candidate configuration for syntax errors.
Option A is correct because the 'commit' command in Junos OS first validates the candidate configuration for syntax errors before applying it. If syntax errors are found, the commit fails and the candidate configuration is not applied, ensuring the device does not enter an inconsistent state. This validation step is a core part of Junos's transactional configuration model, where changes are staged in a candidate configuration and then committed atomically.
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.
✓
It validates the candidate configuration for syntax errors.
Why this is correct
Commit performs syntax validation before applying.
Related concept
Read the scenario before looking for a memorised answer.
✗
It schedules the configuration to be applied at a later time.
Why it's wrong here
Commit applies immediately; to schedule, use 'commit at'.
✗
It discards the candidate configuration after saving.
Why it's wrong here
The candidate becomes the active; it is not discarded.
✓
It saves the candidate configuration to the active configuration.
Why this is correct
Commit moves the candidate to the active configuration.
Related concept
Read the scenario before looking for a memorised answer.
✗
It automatically reboots the device to apply the changes.
Why it's wrong here
Commit does not reboot; changes are applied immediately.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates familiar with Cisco IOS may mistakenly think 'commit' requires a reboot (like 'write memory' followed by reload) or that it discards changes, whereas Junos applies changes dynamically and retains the candidate configuration for further editing.
Detailed technical explanation
How to think about this question
Under the hood, the 'commit' command triggers a series of checks including syntax validation, semantic checks (e.g., referencing interfaces that exist), and commit script execution. If successful, the candidate configuration is copied to the active configuration (stored in /config/juniper.conf.gz), and the change is applied to the running system. A subtle behavior is that if a commit fails due to a syntax error, the candidate configuration remains intact for correction, and no partial changes are applied—this atomicity is a key advantage of Junos's design.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Junos OS Fundamentals — This question tests Junos OS Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It validates the candidate configuration for syntax errors. — Option A is correct because the 'commit' command in Junos OS first validates the candidate configuration for syntax errors before applying it. If syntax errors are found, the commit fails and the candidate configuration is not applied, ensuring the device does not enter an inconsistent state. This validation step is a core part of Junos's transactional configuration model, where changes are staged in a candidate configuration and then committed atomically.
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.
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Question Discussion
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