JN0-106 Junos Configuration Basics Practice Question
An engineer issues the 'rollback 3' command in configuration mode. What is the effect?
⚠ Common exam trap
Watch out — candidates often confuse 'rollback' with 'commit' or 'save' operations, mistakenly thinking it saves the current candidate configuration rather than retrieving a previous one, or they assume it directly modifies the active configuration without requiring a subsequent commit.
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
✓
The candidate configuration is replaced with the configuration from three commits ago.
The 'rollback 3' command in Junos configuration mode replaces the current candidate configuration with the configuration from the third most recent commit. Junos maintains up to 50 rollback slots (numbered 0 through 49), where slot 0 is the most recent commit, slot 1 is the commit before that, and so on. Therefore, 'rollback 3' retrieves the configuration saved three commits ago, overwriting any uncommitted changes in the candidate configuration.
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 candidate configuration is saved as the third rollback slot.
Why it's wrong here
The rollback command is a retrieval operation, not a write operation: it copies a previously committed configuration from the rollback file system into the candidate configuration. No configuration is saved into a rollback slot when you issue rollback 3 because rollback slots are automatically populated on each commit, not by manual save commands. Thus the candidate is overwritten, not stored as the third slot.
- ✓
The candidate configuration is replaced with the configuration from three commits ago.
Why this is correct
When an engineer issues 'rollback 3' in Junos configuration mode, Junos loads the configuration snapshot that was active exactly three commits ago from the rollback store into the candidate configuration. Rollback identifies the desired version by its commit counter offset from the current committed configuration, not by a slot number in a list. The candidate now contains that older configuration, which must be reviewed and committed to make it active.
- ✗
The active configuration is replaced with the candidate configuration.
Why it's wrong here
Rollback works exclusively on the candidate configuration, which is a temporary working copy of the configuration held in the configuration database. The active configuration is the one currently used by the firewall/router for packet forwarding and routing; it remains untouched until you explicitly issue a 'commit' command. Therefore, 'rollback 3' does not swap active configuration directly; it only stages the older version in the candidate.
- ✗
The device reboots and loads configuration version 3.
Why it's wrong here
The 'rollback 3' command performs a quick configuration-level replacement in memory and does not trigger any device reboot or system reload. It is not analogous to loading a 'configuration version 3' of the OS image; it simply pulls the third-most-recent committed configuration from the persistent rollback store and copies it into the candidate. The device stays operational while the candidate is edited or committed.
About these practice questions
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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.