The answer is rollback 1. In Junos, the rollback number selection is based on a zero-indexed list where rollback 0 always represents the most recent commit, rollback 1 is the commit before that, and so on up to rollback 49. Since the exhibit shows the most recent commit occurred on January 15, reverting to the configuration from January 14 requires moving back one step, making rollback 1 the correct index. This concept is a core part of the JNCIA-Junos exam, testing your understanding of how Junos stores and retrieves previous configurations; a common trap is assuming rollback 1 is the oldest or that rollback 0 is the current active configuration rather than the most recent commit. To avoid confusion, remember the memory tip: "Zero is the hero of the now, one is the one just done."
JNCIA-JUNOS User Interfaces Practice Question
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.
Exhibit
user@router> show system commit
0 2023-01-15 12:34:56 UTC by admin via cli
1 2023-01-14 09:15:00 UTC by admin via cli
2 2023-01-13 16:45:23 UTC by admin via cli
Refer to the exhibit. An engineer wants to revert to the configuration from January 14. Which rollback number should they use?
user@router> show system commit
0 2023-01-15 12:34:56 UTC by admin via cli
1 2023-01-14 09:15:00 UTC by admin via cli
2 2023-01-13 16:45:23 UTC by admin via cli
A
load override 2
Why wrong: The correct command is rollback, not load override.
B
rollback 2
Why wrong: Rollback 2 is the third commit (Jan 13), not Jan 14.
C
rollback 0
Why wrong: Rollback 0 is the most recent commit (Jan 15), not Jan 14.
D
rollback 1
Rollback 1 corresponds to the second commit (Jan 14).
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
rollback 1
The rollback command in Junos reverts the candidate configuration to a previously committed configuration. The rollback numbers are indexed from 0 (the most recent commit) to 49 (the oldest). Since the engineer wants to revert to the configuration from January 14, and the most recent commit (rollback 0) is from January 15, rollback 1 corresponds to the January 14 configuration. Therefore, option D is correct.
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 2
Why it's wrong here
The correct command is rollback, not load override.
✗
rollback 2
Why it's wrong here
Rollback 2 is the third commit (Jan 13), not Jan 14.
✗
rollback 0
Why it's wrong here
Rollback 0 is the most recent commit (Jan 15), not Jan 14.
✓
rollback 1
Why this is correct
Rollback 1 corresponds to the second commit (Jan 14).
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse rollback 0 with the current active configuration, but rollback 0 is actually the most recent commit, not the running configuration; they may also mistakenly think rollback 1 is the oldest, when in fact rollback 49 is the oldest saved configuration.
Trap categories for this question
Command / output trap
The correct command is rollback, not load override.
Detailed technical explanation
How to think about this question
Junos maintains up to 50 previous committed configurations in the /config/ directory, indexed from 0 (most recent) to 49 (oldest). The 'rollback' command loads the candidate configuration from these saved files, and the configuration is not applied until a 'commit' is issued. In real-world scenarios, an engineer might use 'rollback 1' to quickly undo a recent commit that caused issues, but must remember that rollback numbers shift after each new commit.
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.
User Interfaces — This question tests User Interfaces — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: rollback 1 — The rollback command in Junos reverts the candidate configuration to a previously committed configuration. The rollback numbers are indexed from 0 (the most recent commit) to 49 (the oldest). Since the engineer wants to revert to the configuration from January 14, and the most recent commit (rollback 0) is from January 15, rollback 1 corresponds to the January 14 configuration. Therefore, option D is correct.
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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