JN0-106 Junos OS Fundamentals Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Configuration groups never override existing settings.

  Why it's wrong here

  This statement is false because Junos configuration groups are not limited to only filling in missing settings. When a configuration group is applied, its values can override existing configuration at the same hierarchy level, depending on the order in which the group is applied relative to other configuration or groups. Specifically, the last-applied group or explicitly configured statement wins, so a group can supersede a previously set value. Thus, the assertion that groups never override is incorrect.

• ✓

  Configuration groups are applied using the apply-groups statement.

  Why this is correct

  This is a true statement. In Junos, configuration groups are defined under the `groups` hierarchy, and to activate them, you must reference them via the `apply-groups` statement at the appropriate hierarchy level. For example, applying `apply-groups global` at the top-level ensures that the settings from the `global` group are merged into the active configuration. Without an explicit `apply-groups` statement, a configuration group has no effect on the running configuration.

• ✗

  Configuration groups are only useful for interface configuration.

  Why it's wrong here

  That statement is false because configuration groups are a general-purpose inheritance mechanism. They can be used for any configuration hierarchy, including protocols (like OSPF or BGP), system settings (such as NTP or SNMP), firewall filters, and more. While they are frequently used to consolidate interface settings, limiting their usefulness to interfaces ignores their broader capability to create reusable configuration templates across many parts of the Junos configuration. This flexibility is a key reason why they are a powerful scaling and automation tool.

• ✗

  Configuration groups are applied automatically to all hierarchies.

  Why it's wrong here

  This is incorrect because configuration groups do not automatically propagate to every hierarchy. A group must be explicitly activated with an `apply-groups` statement, and the statement's placement determines which parts of the hierarchy the group's settings affect. For instance, an `apply-groups` placed at the top level applies to the entire configuration, but placing it under an interface applies only to that interface subtree. Without such a statement, the group is defined but inert, and different groups can be applied selectively to different levels, providing granular control.

• ✓

  Configuration groups are applied in the order they are listed in apply-groups.

  Why this is correct

  This statement is true. When multiple groups are listed in a single `apply-groups` statement, Junos processes them from left to right, so the groups listed last take precedence over earlier groups. If two groups define the same parameter, the value from the last listed group wins. This ordering behavior is analogous to configuration inheritance where later files override earlier ones, and it gives operators predictable precedence when stacking reusable template groups.