Implementing Hardware and Software Redundancy on Modular Switches
What is Route Processor Redundancy Plus – RPR+?

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.