The JUNOS Internet software is configured through a hierarchy of configuration statements that define the desired software properties. All properties of the JUNOS Internet software, including interfaces, general routing information, routing protocols, and user access, as well as several system hardware properties, can be configured. First a candidate configuration is created, then it is committed, to be evaluated and activated by the JUNOS Internet software.
The software can be configured in one of two ways: by creating a configuration for the router interactively, working in the command-line interface (CLI) on the router, or by loading an ASCII file that contains a router configuration created earlier, either on this system or on another system. In the second case, the configuration can either be activated and run as is, or it can be edited using the CLI before being activated. When the router is initially booted , the system prompts for the minimal information needed to configure the router, including the router's name, domain name , and Internet address of at least one interface on the router. After the router finishes booting initially, the user booting the router logs in as the user "root" (with no password) and configures a password for the user "root." After this initial minimal configuration is completed, all other properties of the software can be configured. If the software is configured interactively using the CLI, configuration statements can be entered to create a candidate configuration that contains a hierarchy of statements. At any given hierarchy level, statements can generally be entered in any order. While configuring the software, all or portions of the candidate configuration can be displayed, and statements can be inserted or deleted. Any changes affect only the candidate configuration, not the active configuration that is running on the router. The configuration hierarchy logically groups related functions together, which results in configuration statements that have a regular, consistent syntax. For example, routing protocols, routing policies, interfaces, and Simple Network Management Protocol (SNMP) management are each configured in their own portion of the configuration hierarchy. At each level of the configuration hierarchy, a list of the statements available at that level, along with a short description of the statements' functions, can be displayed. The CLI features command completion, which allows typing a partial statement name followed by a space or tab to have the CLI complete the statement name if it is unambiguous or otherwise provide a list of possible completions. More than one user can edit a router configuration simultaneously . All changes made by all users are visible to everyone editing the configuration. A configuration is edited by working in a copy of the current configuration to create a candidate configuration. The changes made to the candidate configuration are visible in the CLI immediately, so if multiple users are editing the configuration at the same time, all users can see all changes. When the candidate configuration is committed, the changes take effect. At this point, the candidate file is checked for proper syntax, activated, and marked as the current operational software configuration file. If multiple users are editing the configuration and the candidate configuration is committed, all changes made by all the users take effect.
The CLI always maintains a copy of the previously committed version of the software configuration. A user can inactivate the current configuration and return to the previous configuration using the CLI. Candidate configurations can be saved to a file on the router. They are saved as plain text files. To initially configure the software:
The router is now connected to the network, but not fully configured. It must be completely configured before using the router to pass traffic. Information about configuring the software is presented in the following chapters. |