Configuration groups allow 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, and different sections of one group’s configuration statements can be inherited in different places in the configuration.
Configuration groups allow you to create smaller, more logically constructed configuration files, making it easier to configure and maintain the JUNOS software. For example, you can group statements that are repeated in many places in the configuration, such as when configuring interfaces, and thereby limit updates to just the group.
You can also use wildcards in a configuration group to allow configuration data to be inherited by any object that matches a wildcard expression.
The configuration group mechanism is separate from the grouping mechanisms used elsewhere in the configuration, such as Border Gateway Protocol (BGP) groups. Configuration groups provide a generic mechanism that can be used throughout the configuration but that are known only to the JUNOS software command-line interface (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.
Configuration groups use true inheritance, which involves a dynamic, ongoing relationship between the source of the configuration data and the target of that data. Data values changed in the configuration group are automatically inherited by the target. The target need not contain the inherited information, although the inherited values can be overridden in the target without affecting the source from which they were inherited.
This inheritance model allows you to see only the instance-specific information without seeing the inherited details. A command pipe in configuration mode allows you to display the inherited data.