JN0-106 Junos OS Fundamentals Practice Question
Which TWO statements about the Junos OS configuration hierarchy are correct? (Choose two.)
⚠ Common exam trap
It's easy for candidates to confuse Junos's hierarchical structure with Cisco IOS's flat or modular configuration approach, leading them to incorrectly assume that Junos uses multiple merged files or automatic root-level inheritance.
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
✓
Configuration is organized in a hierarchical structure with levels
Option C is correct because Junos OS stores its configuration in a hierarchical tree structure organized into levels (such as system, interfaces, protocols), which is the defining characteristic of the Junos configuration model. Option E is correct because within that hierarchy, each level can hold one or more statements or values, allowing multiple configuration elements to be nested under a given hierarchy node. Option A is incorrect because Junos does not store configuration as a flat file with line numbers; that describes a line-oriented format, not the Junos hierarchy. Option B is incorrect because the Junos configuration is not assembled by merging multiple configuration files at boot; it is maintained as a single hierarchical candidate/active configuration. Option D is incorrect because inheritance in Junos flows from parent levels down to child levels, not automatically from the root level to all statements.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
All configuration is stored in a flat file with line numbers
Why it's wrong here
The Junos OS configuration is structured as a hierarchy, not a flat file. After a commit, the active configuration is written to a single file named juniper.conf.gz on the device, which is compressed but not line-numbered or flat. The hierarchy is represented by indentation and statement levels, not line numbers.
- ✗
The hierarchy is stored in multiple configuration files that are merged at boot
Why it's wrong here
Junos maintains the active configuration in a single file (juniper.conf.gz) after each commit. While multiple files exist for rollback and rescue configurations, these are not merged at boot. The device loads the designated active configuration file, and the candidate config is held in memory and committed to that same single file.
- ✓
Configuration is organized in a hierarchical structure with levels
Why this is correct
Junos uses a tree-like hierarchy where configuration statements are nested under levels, such as protocols>bgp>group>neighbor. Each level is defined by the statement type and indentation in the CLI, allowing modular and structured configuration. This hierarchy is the foundation for editing, viewing, and applying configuration.
- ✗
Configuration values are inherited from the root level automatically
Why it's wrong here
Inheritance in Junos is not automatic from the root. Instead, you explicitly use configuration groups with apply-groups statements to apply a set of configurations to multiple places. Specific inheritance exists like from physical interfaces to logical units, but not from the root level universally.
- ✓
Each level can contain one or more statements or values
Why this is correct
Within the hierarchy, each level can contain multiple statements, each with its own values or sub-levels. For example, the interfaces level contains multiple interface statements, and each interface contains multiple unit statements. A statement like address under a unit can have a value, enabling complex, layered configurations.
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