JN0-106 Junos OS Fundamentals Practice Question
Which TWO statements are correct regarding the Junos OS configuration hierarchy?
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 'show | compare' command displays differences between the candidate and active configurations.
Option C is correct because the 'show | compare' command in Junos displays the differences between the candidate configuration and the active (committed) configuration, allowing operators to review pending changes before committing. Option E is correct because the 'set' command is used in configuration mode to modify the candidate configuration, adding or changing statements in the hierarchy. Option A is incorrect because 'commit check' only validates the candidate configuration for syntax and semantic errors without applying it; the 'commit' command applies it to the active configuration. Option B is incorrect because 'load replace' replaces the entire candidate configuration with the contents of a file, whereas 'load merge' merges a file into the candidate configuration. Option D is incorrect because 'rollback 0' reverts the candidate configuration to the currently active configuration, discarding uncommitted changes; 'rollback 1' reverts to the previous committed 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 'commit check' command applies the candidate configuration to the active configuration.
Why it's wrong here
The 'commit check' command triggers a syntactic and semantic validation of the candidate configuration against the Junos schema and system constraints. However, it does not alter the active configuration; the candidate remains uncommitted, and the active configuration is untouched until an explicit 'commit' is issued.
- ✗
The 'load replace' command merges a configuration file into the candidate configuration.
Why it's wrong here
The 'load replace' directive replaces the entire candidate configuration with the contents of the specified file, overlaying only the statements that appear in that file onto a blank candidate. In contrast, 'load merge' is the command that combines the loaded file with the existing candidate configuration, preserving settings not present in the file.
- ✓
The 'show | compare' command displays differences between the candidate and active configurations.
Why this is correct
When you execute 'show | compare' in configuration mode, Junos displays the differences between the candidate configuration and the active configuration, prefixed with '+' for additions and '-' for deletions. This is a read-only diagnostic that helps you review pending changes before committing, and it does not modify either configuration.
- ✗
The 'rollback 0' command reverts the candidate configuration to the previous state.
Why it's wrong here
The 'rollback 0' command resets the candidate configuration to match the most recently committed active configuration, effectively discarding any uncommitted edits. It does not revert to a 'previous state' such as an earlier configuration version; to revert to an older commit, you must specify a non-zero rollback number (e.g., 'rollback 1').
- ✓
The 'set' command is used to modify the candidate configuration.
Why this is correct
The 'set' command is the primary CLI directive used to add, change, or remove configuration statements within the candidate configuration. It operates in configuration mode and can address hierarchy levels, such as 'set interfaces ge-0/0/0 unit 0 family inet address 192.0.2.1/24', modifying only the candidate until you commit.
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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.