JNCIA-JUNOS Rollback configuration 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. A key principle to apply: rollback configuration. 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.
Exhibit
Refer to the exhibit.
user@router> show system commit
0 2025-03-20 10:15:23 UTC by admin via cli
1 2025-03-20 09:45:10 UTC by root via cli (confirmed)
2 2025-03-19 14:30:00 UTC by admin via cli
Refer to the exhibit. The network administrator made a change that caused connectivity loss. They need to revert to the configuration before the most recent commit. Which command would accomplish this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Exhibit
Refer to the exhibit.
user@router> show system commit
0 2025-03-20 10:15:23 UTC by admin via cli
1 2025-03-20 09:45:10 UTC by root via cli (confirmed)
2 2025-03-19 14:30:00 UTC by admin via cli
A
rollback 0
Why wrong: Incorrect. rollback 0 loads the most recent committed configuration, which is the one that caused the connectivity loss.
B
rollback 3
Why wrong: Incorrect. rollback 3 loads the fourth most recent commit, which is too far back.
C
rollback 2
Why wrong: Incorrect. rollback 2 loads the third most recent commit, which is still too far back.
D
rollback 1
Correct. rollback 1 loads the configuration before the most recent commit, reverting the change that caused the issue.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
rollback 1
In Junos, rollback numbers are stored with 0 being the most recent committed configuration. To revert to the configuration before the most recent commit, you need to load the configuration that was active before that change. That is rollback 1, which represents the second most recent commit. Using rollback 0 would load the configuration that caused the issue, not fix it.
Key principle: Rollback configuration
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
rollback 0
Why it's wrong here
Incorrect. rollback 0 loads the most recent committed configuration, which is the one that caused the connectivity loss.
✗
rollback 3
Why it's wrong here
Incorrect. rollback 3 loads the fourth most recent commit, which is too far back.
✗
rollback 2
Why it's wrong here
Incorrect. rollback 2 loads the third most recent commit, which is still too far back.
✓
rollback 1
Why this is correct
Correct. rollback 1 loads the configuration before the most recent commit, reverting the change that caused the issue.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Rollback configuration
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many candidates mistakenly believe that rollback 0 undoes the last change. However, rollback 0 loads the most recent committed configuration—the one that caused the connectivity loss—so it would reload the problem, not fix it. To revert to the configuration before the last commit, you must use rollback 1.
Detailed technical explanation
How to think about this question
Junos maintains up to 50 previous committed configurations (rollback 0 through rollback 49) in the /config directory. Rollback 0 always points to the most recently committed configuration, while rollback 1 points to the configuration before that. When you issue 'rollback 0', you are loading the configuration that was active before the last commit, which is exactly what is needed to revert a change. This is different from Cisco IOS, where the 'reload' command is used to revert to a saved startup configuration.
KKey Concepts to Remember
Rollback configuration
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
Rollback configuration
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. Rollback configuration 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.
Review rollback configuration, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
Junos OS Fundamentals — This question tests Junos OS Fundamentals — Rollback configuration.
What is the correct answer to this question?
The correct answer is: rollback 1 — In Junos, rollback numbers are stored with 0 being the most recent committed configuration. To revert to the configuration before the most recent commit, you need to load the configuration that was active before that change. That is rollback 1, which represents the second most recent commit. Using rollback 0 would load the configuration that caused the issue, not fix it.
What should I do if I get this JNCIA-JUNOS question wrong?
Review rollback configuration, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Rollback configuration
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