JN0-106 Junos Configuration Basics 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.

• ✗

  prefix lists

  Why it's wrong here

  Prefix lists are a firewall-filter or routing-policy construct used to match route prefixes (e.g., in a route-filter or community list). They are not a mechanism for defining reusable blocks of configuration parameters, and they cannot be applied to inherit settings across multiple hierarchy levels. Unlike configuration groups, prefix lists do not have any 'apply' semantics for configuration inheritance; their sole purpose is packet or route matching.

• ✗

  set default

  Why it's wrong here

  There is no 'set default' command in Junos configuration mode. The Junos CLI uses 'set' for changing or adding configuration elements, but it does not have a 'default' keyword that triggers configuration inheritance. Inheritance is explicitly performed using 'apply-groups' and 'apply-groups-except' statements, not by any implicit default-setting command. If a 'set default' appears in documentation, it usually refers to resetting a system to factory defaults via 'load factory-default' or similar, which is unrelated to inheriting configuration blocks.

• ✓

  configuration groups with apply-groups

  Why this is correct

  Configuration groups are the correct Junos mechanism for defining reusable configuration blocks. You define named groups under the 'groups' hierarchy, then reference them with 'apply-groups' at any hierarchy level where you want the group's parameters to be inherited. When the configuration is evaluated, Junos merges the group's settings into the active configuration, and changes to the group automatically propagate to all points that apply it. This is distinct from one-time load operations or routing-policy filters, and it also supports 'apply-groups-except' to exclude specific groups below a certain level for granular control.

• ✗

  load merge

  Why it's wrong here

  'load merge' is a configuration management command that merges the contents of a file or terminal input into the candidate configuration. It is a one-time, manual operation—it does not create a persistent inheritance relationship between configuration blocks. Unlike configuration groups, which dynamically apply their contents wherever 'apply-groups' is placed, 'load merge' simply copies text into the candidate configuration; future changes to the original source file have no effect. It is a loading tool, not a grouping or inheritance construct.