- A
The 'commit confirmed' command immediately discards changes if not confirmed.
Why wrong: It schedules a rollback; changes are not immediately discarded.
- B
Multiple users can make configuration changes simultaneously, but only one can commit at a time.
Junos uses a lock to serialize commits.
- C
The 'commit check' command validates the configuration syntax without activating it.
'commit check' verifies syntax and semantics without committing.
- D
The 'commit confirmed' command allows a rollback to the previous configuration if not confirmed within the timeout period.
This is the purpose of 'commit confirmed'.
- E
The 'commit' command always requires 'commit synchronize' when using dual Routing Engines.
Why wrong: 'commit synchronize' is used only when you want to synchronize configurations; 'commit' alone commits only on the local RE.
Quick Answer
The correct answer is that the 'commit confirmed' command allows a rollback to the previous configuration if not confirmed within the timeout period. This is true because Junos OS serializes commit operations: while multiple users can enter configuration mode and make changes simultaneously, only one commit can be processed at a time, preventing conflicting updates from being applied concurrently. On the JNCIA-Junos exam, this concept tests your understanding of Junos commit operations advanced behavior, particularly how the system ensures configuration consistency in multi-user environments. A common trap is assuming that multiple users can commit at the same time, but the serialized commit model means each user must wait their turn. For the 'commit confirmed' command, remember that it automatically triggers a rollback if the timer expires, making it ideal for risky changes. Memory tip: think of "confirmed" as a safety net—if you don't confirm in time, the net catches you and pulls you back to the previous configuration.
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.
Which THREE statements are true about commit operations in Junos OS?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Multiple users can make configuration changes simultaneously, but only one can commit at a time.
Option B is correct because Junos OS allows multiple users to enter configuration mode and make changes simultaneously, but the commit operation is serialized: only one user can commit at a time. This prevents conflicting changes from being applied concurrently, ensuring configuration consistency.
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 'commit confirmed' command immediately discards changes if not confirmed.
Why it's wrong here
It schedules a rollback; changes are not immediately discarded.
- ✓
Multiple users can make configuration changes simultaneously, but only one can commit at a time.
Why this is correct
Junos uses a lock to serialize commits.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The 'commit check' command validates the configuration syntax without activating it.
Why this is correct
'commit check' verifies syntax and semantics without committing.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The 'commit confirmed' command allows a rollback to the previous configuration if not confirmed within the timeout period.
Why this is correct
This is the purpose of 'commit confirmed'.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The 'commit' command always requires 'commit synchronize' when using dual Routing Engines.
Why it's wrong here
'commit synchronize' is used only when you want to synchronize configurations; 'commit' alone commits only on the local RE.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing 'commit confirmed' with an immediate discard of changes, when in fact it temporarily activates the configuration and only rolls back if the confirmation is not received within the timeout period.
Detailed technical explanation
How to think about this question
Under the hood, Junos uses a candidate configuration model where changes are staged in a separate database. The 'commit confirmed' mechanism leverages a rollback timer that, upon expiry, triggers an automatic rollback to the last committed configuration. In a dual-RE chassis, each RE maintains its own candidate and active configuration; 'commit synchronize' uses a proprietary protocol to replicate the commit across REs, but a standard 'commit' only affects the local RE, which is critical for in-service software upgrades (ISSU) scenarios.
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 — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
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: Multiple users can make configuration changes simultaneously, but only one can commit at a time. — Option B is correct because Junos OS allows multiple users to enter configuration mode and make changes simultaneously, but the commit operation is serialized: only one user can commit at a time. This prevents conflicting changes from being applied concurrently, ensuring configuration consistency.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on JNCIA-JUNOS
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. Which TWO statements about the Junos commit model are true?
medium- ✓ A.A commit makes the candidate configuration the active configuration.
- B.The commit command is used to discard changes.
- ✓ C.The rollback command can be used to revert to a previous configuration.
- D.A commit validation is performed automatically before commit.
- E.Multiple candidates can be active simultaneously.
Why A: Option A is correct because the Junos commit model uses a two-phase process: changes are made to the candidate configuration, and the `commit` command activates that candidate configuration as the new active configuration. This ensures that changes are not applied until explicitly committed, providing a safe and predictable way to modify the device's operational state.
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Last reviewed: Jun 11, 2026
This JNCIA-JUNOS practice question is part of Courseiva's free Juniper Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the JNCIA-JUNOS exam.
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