Quick Answer
The answer is to use the rollback 1 command. This is correct because the Junos OS maintains a history of committed configurations, and rollback 1 specifically reverts the candidate configuration to the most recently committed configuration, which is the previous active state. Crucially, this command does not discard any uncommitted changes you have made since the last commit, allowing you to keep correct recent edits while discarding the accidental deletion. On the JNCIA-Junos exam, this question tests your understanding of configuration management and the rollback system, often appearing as a scenario where you must distinguish between rollback 0 (which reverts to the last committed config, discarding all uncommitted changes) and rollback 1. A common trap is confusing rollback 1 with a full revert; remember that rollback 1 is a surgical undo of the last commit, not a factory reset. For a quick memory tip: think of rollback 1 as "one step back" to the previous committed state, preserving your current work in progress.
This JNCIA-JUNOS practice question tests your understanding of user interfaces. 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.
A network administrator accidentally deleted a vital part of the configuration while in configuration mode. They need to revert to the previous configuration without losing recent changes that are correct. Which action should they take?
deactivate
Why wrong: Deactivates a configuration statement, does not revert.
rollback 1
Reverts to the configuration from the previous commit, discarding uncommitted changes.
delete
Why wrong: Deletes a configuration statement, does not revert.
rollback 0
Why wrong: Reverts to the current active configuration (same as candidate if no changes committed).
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
rollback 1
Option B is correct because the 'rollback 1' command reverts the candidate configuration to the most recently committed configuration (the previous active configuration), while preserving any uncommitted changes that were made after the rollback. This allows the administrator to discard the accidental deletion and then manually re-apply only the correct recent changes before committing.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
deactivate
Why it's wrong here
Deactivates a configuration statement, does not revert.
rollback 1
Why this is correct
Reverts to the configuration from the previous commit, discarding uncommitted changes.
Related concept
Read the scenario before looking for a memorised answer.
delete
Why it's wrong here
Deletes a configuration statement, does not revert.
rollback 0
Why it's wrong here
Reverts to the current active configuration (same as candidate if no changes committed).
Common exam traps
The trap here is that candidates often confuse 'rollback 0' (which reverts to the current active config, discarding all uncommitted changes) with 'rollback 1' (which reverts to the previous committed config, preserving uncommitted changes), leading them to choose option D instead of B.
Detailed technical explanation
Junos maintains a history of the last 50 committed configurations, accessible via 'rollback N' where N is the number of commits to go back (0 is the current active config, 1 is the previous commit, etc.). The rollback operation replaces the candidate configuration with the specified historical configuration, but does not automatically commit; the administrator can then merge or edit the candidate to retain desired changes before committing. This is distinct from a 'revert' in other systems, as Junos keeps the candidate separate from the active configuration until a commit is issued.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
User Interfaces — study guide chapter
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FAQ
User Interfaces — This question tests User Interfaces — Read the scenario before looking for a memorised answer..
The correct answer is: rollback 1 — Option B is correct because the 'rollback 1' command reverts the candidate configuration to the most recently committed configuration (the previous active configuration), while preserving any uncommitted changes that were made after the rollback. This allows the administrator to discard the accidental deletion and then manually re-apply only the correct recent changes before committing.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer needs to revert to the configuration that was active before the last commit. Which command accomplishes this?
mediumWhy A: The 'rollback 1' command reverts the active configuration to the configuration that was committed immediately before the most recent commit. Junos maintains up to 50 previous committed configurations (rollback 0 being the current active configuration, rollback 1 the previous, and so on). This command is the correct way to undo the last commit without manually editing the configuration.
Last reviewed: Jun 24, 2026
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