The answer is that the candidate configuration was not committed. In Junos OS, all configuration changes are made to a candidate configuration, which is a temporary working copy that does not affect the device's operation until explicitly activated. The 'commit' operation is what saves those changes to the active configuration, making them persistent across reboots; without it, the device discards the candidate buffer upon restart and reverts to the last committed configuration. On the JNCIA-Junos exam, this concept tests your understanding of the Junos commit model, often appearing in questions about configuration persistence or troubleshooting unexpected resets. A common trap is assuming that changes are saved automatically, like in other operating systems, but Junos requires a deliberate commit. Remember the memory tip: "No commit, no keep—reboot will make your changes sleep."
JNCIA-JUNOS Junos OS Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos os fundamentals. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An engineer notices that a Juniper device is not saving configuration changes across reboots. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The candidate configuration was not committed.
In Junos OS, configuration changes are stored in a candidate configuration and only become active and persistent across reboots after a 'commit' operation. Without a commit, the changes remain in the candidate buffer and are discarded upon reboot, causing the device to revert to the last committed configuration.
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 rescue configuration is not set.
Why it's wrong here
Rescue configuration is for recovery, not for saving regular changes.
✗
The device is booting from factory-default configuration.
Why it's wrong here
This would require a specific action; normally the device uses the last committed configuration.
✓
The candidate configuration was not committed.
Why this is correct
Changes are only saved after a commit; otherwise they are lost on reboot.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The command 'request system reboot' was used instead of 'commit'.
Why it's wrong here
Rebooting without committing loses changes, but the direct cause is lack of commit.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates familiar with Cisco IOS may assume changes are saved automatically or with a 'copy running-config startup-config' equivalent, but Junos requires an explicit 'commit' to make changes persistent across reboots.
Detailed technical explanation
How to think about this question
Junos uses a two-phase commit model: changes are made in the candidate configuration (stored in /config/juniper.conf.gz) and only written to the active configuration after a 'commit'. The commit operation validates syntax, applies the configuration, and saves it to the permanent store (e.g., /config/juniper.conf.gz). If a reboot occurs without a commit, the device loads the last committed configuration from the permanent store, discarding any uncommitted candidate changes.
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: The candidate configuration was not committed. — In Junos OS, configuration changes are stored in a candidate configuration and only become active and persistent across reboots after a 'commit' operation. Without a commit, the changes remain in the candidate buffer and are discarded upon reboot, causing the device to revert to the last committed configuration.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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