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Configuration Groups Overview

This topic provides an overview of configuration groups and the inheritance model in the Junos OS CLI.

How Configuration Groups Work

Configuration groups enable you to create a group containing configuration statements and to direct the inheritance of that group’s statements in the rest of the configuration. The same group can be applied to different sections of the configuration. Different sections of one group’s configuration statements can be inherited in different places in the configuration.

Configuration groups enable you to create smaller, more logically constructed configuration files, making it easier to configure and maintain Juniper Networks devices. For example, you can group statements that are repeated in many places in the configuration, such as when configuring interfaces. By grouping statements, you can limit configuration updates to just the group.

You can also use wildcards in a configuration group. Any object that matches the wildcard expression inherits the group configuration data.

The configuration group mechanism is separate from the grouping mechanisms used elsewhere in the configuration, such as BGP groups. Configuration groups provide a generic mechanism that you can use throughout the configuration but that are known only to the CLI. The individual software processes that perform the actions directed by the configuration receive the expanded form of the configuration; they have no knowledge of configuration groups.

Inheritance Model

Configuration groups use true inheritance, which involves a dynamic, ongoing relationship between the source of the configuration data and the target of that data. The target automatically inherits data values that you change in the configuration group. The target does not need to contain the inherited information. However, the inherited values can be overridden in the target without affecting the source from which they were inherited.

This inheritance model enables you to see only the instance-specific information without seeing the inherited details. A command pipe in configuration mode enables you to display the inherited data.

Configure Configuration Groups

For areas of your configuration to inherit configuration statements, you must first put the statements into a configuration group. You then apply that group to the levels in the configuration hierarchy that require the statements.

For areas of your configuration to inherit configuration statements:

  1. Configure statements into a configuration group. To configure configuration groups and inheritance, you can include the groups statement at the [edit] hierarchy level:

  2. Apply the configuration group from step 1 to the levels in the configuration hierarchy that require the statements.

    Include the apply-groups [ group-names ] statement anywhere in the configuration where the configuration statements contained in a configuration group are needed.