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Appendix A Working with the Cisco IOS File System, Configuration Files, and Software Images
Working with Configuration Files
Archiving a Configuration
The configuration archive provides a mechanism to store, organize, and manage an archive of
configuration files. The configure replace privileged EXEC command increases the configuration
rollback capability. As an alternative, you can save copies of the running configuration by using the copy
running-config destination-url privileged EXEC command, storing the replacement file either locally
or remotely. However, this method lacks any automated file management. The configuration replacement
and rollback feature can automatically save copies of the running configuration to the configurati on
archive.
You use the archive config privileged EXEC command to save configurations in the configuration
archive by using a standard location and filename prefix that is automatically appended with an
incremental version number (and optional timestamp) as each consecutive file is saved. You can specify
how many versions of the running configuration are kept in the archive. After the maximum number of
files are saved, the oldest file is automatically deleted when the next, most recent file is saved. The show
archive privileged EXEC command displays information for all the configuration files saved in the
configuration archive.
The Cisco IOS configuration archive, in which the configuration files are stored and available for use
with the configure replace command, is in any of these file systems: FTP, HTTP, RCP, TFTP.
Replacing a Configuration
The configure replace privileged EXEC command replaces the running configuration with any saved
configuration file. When you enter the configure replace command, the running configuration is
compared with the specified replacement configuration, and a set of configuration difference s is
generated. The resulting differences are used to replace the configuration. The configuration
replacement operation is usually completed in no more than three passes. To prevent looping behavior
no more than five passes are performed.
You can use the copy source-url running-config privileged EXEC command to copy a stored
configuration file to the running configuration. When using this command as an alternative to the
configure replace target-url privileged EXEC command, note these major differences:
• The copy source-url running-config command is a merge operation and preserves all the commands
from both the source file and the running configuration. This command does not remove commands
from the running configuration that are not present in the source file. In contrast, the configure
replace target-url command removes commands from the running configuration that are not pre sent
in the replacement file and adds commands to the running configuration that are not present.
• You can use a partial configuration file as the source file for the copy source-url running-config
command. You must use a complete configuration file as the replacement file for the configure
replace target-url command.
Rolling Back a Configuration
You can also use the configure replace command to roll back changes that were made since the previous
configuration was saved. Instead of basing the rollback oper ation on a specific set of changes that were
applied, the configuration rollback capability reverts to a specific configuration based on a saved
configuration file.
If you want the configuration rollback capability, you must first save the running configuration before
making any configuration changes. Then, after entering configurat ion changes, you can use that saved
configuration file to roll back the changes by using the configure replace target-url command.
You can specify any saved configuration file as the rollback configuration. You are not limited to a fixed
number of rollbacks, as is the case in some rollback model s.