To edit the candidate configuration, the user must first enter candidate edit mode with the candidate>edit command. The user can enter and quit candidate edit mode as many times as they need before committing the candidate configuration.
In candidate edit mode, the user builds a set of candidate configuration changes using the same CLI tree as the standard (line-by-line, non-transactional) configuration. Tab completion and keyword syntax checking is available.
Just as there is a single operational active configuration that can be modified simultaneously by multiple users, there is also a single global candidate configuration instance. All users make changes in the same global candidate configuration and any command that affects the candidate configuration (such as a save or commit) applies to the changes made by all users.
Users can enter an exclusive candidate edit mode by blocking other users, or sessions of the same user, from entering candidate edit mode.
When a candidate configuration is committed, the user can request an additional confirmation of the configuration. If the confirmation is not given with the confirm command within the specified time frame, the router automatically reverts to a configuration state before the candidate configuration changes were applied. If this automatic reversion occurs, the candidate configuration is not cleared and users can continue to edit it and try the commit later.
If the commit operation is successful and the confirm command is issued (if requested during the commit), all the candidate changes take operational effect and the candidate configuration is cleared. If there is an error processing the commit, the router returns to a configuration state before the candidate changes were applied. The candidate configuration is not cleared and users can continue to edit it and try the commit later.
A candidate commit may fail for various reasons, including:
misordering — the candidate configuration has changes that are not in the correct order; for example, an object is referred to before it is actually created
invalid options and combinations — although many syntax errors are eliminated during the candidate editing process, the candidate configuration may contain combinations of configurations and options that are not valid and are rejected when the 7705 SAR attempts to have them take operational effect
resource exhaustion — the application of the candidate configuration may exhaust various system resources, such as queue resources
If a commit fails, the system generates error messages to help the user correct the candidate configuration.
All commands in the candidate configuration must be in the correct order for a commit to be successful. Configuration that depends on other candidate objects must be placed after those objects in the candidate. A set of commands (such as copy, insert, and replace) are available to correct and reorder an existing candidate configuration.
Candidate edit mode is primarily intended for building a candidate configuration using commands from the configure branch of the CLI. Although many CLI commands in other branches are supported, access to some CLI commands and branches are blocked, including:
exec command
enable-admin command
admin branch
bof branch
debug branch
tools branch
The candidate configuration can be saved to a file and loaded into a new candidate configuration later. A saved candidate file is similar to, but not exactly the same as, a 7705 SAR configuration file generated with an admin save command. The saved candidate file cannot be used as a configuration file and may not execute without failures.
There is no SNMP access to the candidate configuration and no SNMP management of candidates. However, when a candidate configuration is committed, any changes to the active or operational configuration are reported via the standard 7705 SAR SNMP change traps. Basic candidate status information is also available via SNMP.
The active or operational configuration can still be modified with standard CLI or SNMP commands that take immediate effect while a candidate configuration is being created or edited or a candidate commit is being processed. While in candidate edit mode, users can view the current state of the operational configuration with the info operational command.