Some hardware or software changes can prevent operators from performing the rollback or can affect the operation of the node following the reversion.
If hardware is removed or changed after a rollback checkpoint file is saved, the node may not function as expected after the system reverts to that configuration. There is no effect if new hardware is added into previously empty slots.
A CLI rollback reversion is not supported if the rollback checkpoint file was saved in a previous major software load or if it was saved in a more recent major or minor software load. For example:
a node running Release 20.4.R1 cannot revert to a checkpoint file saved in Release 9.0.R4
a node running Release 9.0.R4 cannot revert to a checkpoint file saved in Release 20.4.R1
a node running Release 9.0.R4 cannot revert to a checkpoint file saved in Release 9.0.R6
CLI rollback reversion is supported if the checkpoint file was saved in a previous minor software release. For example, a node running Release 9.0.R6 can revert to a checkpoint file saved in Release 9.0.R4. It is also supported after an operator performs an admin reboot or changes the primary configuration and then performs an admin reboot. The reboot does not remove any previously saved rollback files.
If the system runs out of memory during a CLI rollback reversion, the process aborts and the node remains in an indeterminate configuration state. The CLI screen displays a warning message that the CLI reversion failed.
A CLI rollback reversion may also fail in rare cases if the node requires a long time to complete the configuration changes. If the CLI rollback reversion fails during execution, it should be attempted again. The second attempt typically completes the remaining configuration changes.
A high availability CSM switchover during a rollback reversion will cause the rollback process to abort, and the newly active CSM will have an indeterminate configuration. This may not be immediately obvious if the CLI rollback reversion was nearly complete when it was interrupted. To assist operators, a log event is created and the results of the last rollback reversion can be displayed with the show system rollback command. If a high availability switchover occurs during a rollback (or within a few seconds of a rollback completing), the Last Revert Result field will display Interrupted and the operator is advised to repeat the rollback revert operation to the same checkpoint.
Although the use of the <Ctrl-c> key combination is not recommended during a rollback revert, it is supported in the CLI and SNMP. Interrupting a rollback revert command may leave the router in an indeterminate state between the active and saved configuration.
If <Ctrl-c> is used during a CLI rollback reversion, the 7705 SAR displays a warning message to indicate that the operator must examine the configuration and potentially issue another rollback revert command to return to a known, complete configuration.