Junos Commit Operations: commit confirmed, commit check, and rollback
Which THREE statements are true about commit operations in Junos OS?
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.
⚠ Common exam trap
Candidates often confuse '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.
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 uses a shared candidate configuration with per-user edit sessions, so multiple users can edit concurrently, but the commit operation itself is serialized through a lock so only one commit can activate changes at a time. Option C is correct because 'commit check' performs syntax and semantic validation of the candidate configuration against the schema without activating it, leaving the active configuration unchanged. Option D is correct because 'commit confirmed' activates the candidate configuration but automatically rolls back to the previously committed configuration unless the commit is confirmed within the timeout period (default 10 minutes). Option A is not correct because 'commit confirmed' does not immediately discard changes; it applies them and only rolls back if confirmation is not received before the timer expires. Option E is not correct because 'commit synchronize' is only needed to propagate a commit to both Routing Engines on a dual-RE system, and a plain 'commit' can still be used (it just commits to the local RE unless synchronize is specified).
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
'commit confirmed' activates the candidate configuration immediately and rolls back automatically only if no confirming commit arrives within the timeout (default 10 minutes); it does not discard changes at once. It is chosen precisely when you want a safety net against losing remote management access.
- ✓
Multiple users can make configuration changes simultaneously, but only one can commit at a time.
Why this is correct
Junos uses a shared candidate configuration, so several users may edit concurrently, but the commit operation itself is serialised: the commit lock permits only one user to activate changes at any moment, preventing conflicting commits.
- ✓
The 'commit check' command validates the configuration syntax without activating it.
Why this is correct
commit check parses and validates the candidate configuration against the schema and syntax rules without loading it into the running configuration, so errors are reported while the active configuration remains unchanged and traffic is unaffected.
- ✓
The 'commit confirmed' command allows a rollback to the previous configuration if not confirmed within the timeout period.
Why this is correct
commit confirmed activates the candidate configuration but starts a timer; unless the operator issues a confirming commit before it expires, Junos automatically reverts to the previously committed configuration, protecting against a change that severs management access.
- ✗
The 'commit' command always requires 'commit synchronize' when using dual Routing Engines.
Why it's wrong here
'commit synchronize' is required only when configuration changes must be replicated to both Routing Engines; a plain 'commit' applies to the local engine alone. Synchronised commits are the right choice when both engines must hold identical configuration, such as before a graceful switchover.
Visual reference
Go deeper
Related to this question
About these practice questions
This JN0-106 question is part of Courseiva's 326-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on JN0-106
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 in the Junos commit model, the commit command merges the candidate configuration into the active configuration (the running config used by the device), making the candidate the active configuration. Option C is correct because the rollback command reverts the active configuration to a previously committed configuration (e.g., rollback 1 restores the last committed config, rollback 0 restores the current active config), which is a core part of Junos configuration recovery. Option B is wrong because discarding changes is done with the 'rollback 0' or 'rollback' command (or 'discard' in some contexts), not commit; commit applies changes. Option D is wrong because commit validation is not automatic before every commit—validation is performed when you run 'commit check' or when using 'commit and-quit' with validation, but a standard commit does not automatically run a separate validation step. Option E is wrong because Junos supports only one candidate configuration at a time per routing instance; multiple candidates cannot be active simultaneously.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This JN0-106 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 JN0-106 exam.