Which statement best describes the ‘config rollback’ feature?
A.
Config rollback must be enabled by an administrator. Once enabled, it allows the administrator to re-apply a previously saved configuration file from Flash
B.
Config rollback is enabled by default; it allows the administrator to re-apply a previously saved configuration file from Flash without rebooting.
C.
Config rollback is enabled by default; it allows the administrator to re-apply a previously saved configuration file from Flash by rebooting and loading a "last known good" configuration.
D.
Config rollback allows the administrator to revert to the prior ScreenOS image in the event an upgrade operation aborts.
E.
Config rollback allows the administrator to revert to the prior ScreenOS image or configuration file in the event an upgrade operation aborts.
Explanation:
In the event that you load a configuration file that causes problems, such as the failure of the NetScreen device or remote users losing the ability to manage the device, you can perform a configuration rollback to revert to a
Last-Known-Good (LKG) configuration file that was saved in flash memory. Before performing a configuration rollback, make sure you have a LKG configuration file saved in flash memory so that the NetScreen device can revert to it if errors occur. To check for the LKG file, open the NetScreen CLI and then type the get config rollback command. The filename for a LKG configuration is $lkg$.cfg. If you do not see this file, then it does not exist so you must create it. To save a configuration file to flash as the LKG:
1. Ensure that the current configuration on the NetScreen device is good.
2. Save the current configuration to flash memory with the save config to last-known-good command. This
command overwrites the existing LKG configuration in flash memory with the current configuration file.
You can enable the NetScreen device to revert automatically to the LKG configuration or you can perform the
rollback manually. The automatic configuration rollback feature enables the NetScreen device to rollback to the LKG configuration if there is a problem with a newly loaded configuration. The automatic configuration rollback feature is disabled by default. Furthermore, it is disabled after every startup, regardless of whether it was enabled or disabled before starting up the device. To enable automatic configuration rollback, use the exec config rollback enable command. To disable the feature, use the exec config rollback disable command.
To perform a manual configuration rollback, use the exec config rollback command.