A Catalyst switch can allow a standby supervisor engine to take
over if the primary supervisor engine fails. This allows the switch to resume
operation quickly and efficiently in the event of a supervisor engine failure.
This capability is called supervisor engine redundancy. In software, this
capability is enabled by a feature called Route Processor Redundancy (RPR).
When RPR+ mode is used, the redundant Supervisor Engine is fully initialized
and configured, and the MSFC and the PFCs are fully operational. This
facilitates a faster failover time if than RPR in which the inactive Supervisor
Engine is only partially booted.
The active Supervisor Engine checks the
IOS version of the redundant Supervisor Engine when it boots. If the image on
the redundant Supervisor Engine does not match the image on the active
Supervisor Engine, RPR redundancy mode is used rather that RPR+.
The
differences between the two RPR modes are:
- RPR leaves the standby MSFC and PFC non operational until a failover
occurs.
- RPR + places the standby MSFC and PFC in an operational mode upon boot,
thereby providing faster failover.
- RPR+ maintains synchronization of the running-configuration file between
the two Supervisor Engines.
- Both RPR and RPR+ m maintain synchronization of the startup-configuration
file between the two Supervisor Engines.