Cisco Systems 1000 Series User Manual

On the Cisco ASR 1000 Series Router, RPR can also be used to enable a second IOS process on a single 
RP for a Cisco ASR 1002 or 1004 Router. See the 

 for additional information on the second IOS process.

For the Cisco ASR 1000 Series Routers, RPR introduces the following functionality:

Startup configuration synchronization between the active and standby RP or IOS process. It is 
important to note, however, that changes in the running configuration are not synchronized using 
RPR.

Warm Reload—The Warm Reload feature allows users to reload their routers without reading 
images from storage; that is, the router reboots by restoring the read-write data from a previously 
saved copy in the RAM and by starting execution without either copying the software from flash to 
RAM or self-decompression of the image.

It is important to note that in most cases, Stateful Switchover (SSO) requires less downtime for 
switchover and upgrades than RPR. RPR should only be used when there is a compelling reason to not 
use SSO.

It is important to note RPR is supported on the Cisco ASR 1000 Series Routers while RPR+ is not.

The Stateful Switchover (SSO) feature takes advantage of processor redundancy by establishing one of 
the processors as the active processor while the other RP is designated as the standby processor, and then 
synchronizing critical state information between them. Following an initial synchronization between the 
two processors, SSO dynamically maintains RP state information between the dual processors. 

Stateful Switchover is particularly useful in conjunction with Nonstop Forwarding. SSO allows the dual 
processors to maintain state at all times, and Nonstop Forwarding lets a switchover happen seamlessly 
when a switchover occurs.

On the Cisco ASR 1000 Series Router, SSO can also be used to enable a second IOS process on a single 
RP for a Cisco ASR 1002 or 1004 Router. See the 

 for additional information on the second IOS process.

It is important to note that in most cases, SSO requires less downtime for switchover and upgrades than 
RPR. RPR should only be used when there is a compelling reason to not use SSO.

For additional information on NSF/SSO, see the 

document.

SSO-supported line protocols and applications must be SSO-aware. A feature or protocol is SSO-aware 
if it maintains, either partially or completely, undisturbed operation through an RP switchover. State 
information for SSO-aware protocols and applications is synchronized from active to standby to achieve 
stateful switchover for those protocols and applications. 

The dynamically created state of SSO-unaware protocols and applications is lost on switchover and must 
be reinitialized and restarted on switchover. 

To see which protocols are SSO-aware on your router, use the following commands show redundancy 
client or show redundancy history.