Whenever configuration changes are made, the modified configuration must be saved so the changes are not lost when the system is rebooted. The system uses the configuration and image files, as well as other operational parameters necessary for system initialization, according to the locations specified in the boot option file (BOF) parameters. For more information about boot option files, see Boot options.
Configuration files are saved by executing implicit or explicit command syntax.
An explicit save writes the configuration to the location specified in the save command syntax (the file-url option).
An implicit save writes the configuration to the file specified in the primary configuration location.
If the file-url option is not specified in the save command syntax, the system attempts to save the current configuration to the current BOF primary configuration source. If the primary configuration source (path and filename) changed after the last boot, the new configuration source is used.
The save command includes an option to save both default and non-default configuration parameters (the detail option).
The index option specifies that the system preserves system indexes when a save command is executed, regardless of the persistent status in the BOF file. During a subsequent boot, the index file is read along with the configuration file. As a result, a number of system indexes are preserved between reboots, including the interface index, LSP IDs, path IDs, and so on. This reduces resynchronizations of the Network Management System (NMS) with the affected network element.
If the save attempt fails at the destination, an error occurs and is logged. The system does not try to save the file to the secondary or tertiary configuration sources unless the path and filename are explicitly named with the save command.