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.
A network administrator makes several changes to the configuration but decides to discard all uncommitted changes and start fresh. Which command should be used to revert the candidate configuration back to the current active configuration?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
rollback 0
The 'rollback 0' command reverts the candidate configuration to the currently active configuration, discarding all uncommitted changes. This is because Junos maintains a rollback database of the last 50 committed configurations, with index 0 always representing the active configuration. Using 'rollback 0' effectively resets the candidate configuration to match the active one, allowing the administrator to start fresh without affecting the running system.
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.
✗
load override
Why it's wrong here
load override loads a configuration from a file, completely replacing the candidate configuration.
✓
rollback 0
Why this is correct
rollback 0 discards uncommitted changes and sets the candidate configuration to match the current committed configuration.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
commit check
Why it's wrong here
commit check validates the configuration but does not roll back changes.
✗
rollback 1
Why it's wrong here
rollback 1 reverts to the previous commit, not the current active configuration.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'rollback 0' with 'rollback 1', mistakenly thinking that 'rollback 1' discards uncommitted changes, when in fact 'rollback 1' reverts to the previous committed configuration, which would undo the last commit and potentially cause service disruption.
Detailed technical explanation
How to think about this question
Junos stores committed configurations in a rollback database with indices 0 (current active) through 49 (oldest). The 'rollback' command copies the specified configuration from this database into the candidate configuration, overwriting any uncommitted changes. A common real-world scenario is when an administrator makes multiple uncommitted changes during troubleshooting and needs to quickly revert to the known-good active configuration without affecting the running system; 'rollback 0' achieves this instantly without requiring a reboot or reload.
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: rollback 0 — The 'rollback 0' command reverts the candidate configuration to the currently active configuration, discarding all uncommitted changes. This is because Junos maintains a rollback database of the last 50 committed configurations, with index 0 always representing the active configuration. Using 'rollback 0' effectively resets the candidate configuration to match the active one, allowing the administrator to start fresh without affecting the running system.
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: "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?
Read the scenario before looking for a memorised answer.
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