Cisco ASR1002-10G-VPN/K9 Software Guide - Page 207

Chapter 5 High Availability Overview Route Processor Redundancy Route Processor Redundancy Route Processor Redundancy (RPR) allows you to configure a standby RP. When you configure RPR, the standby RP loads the Cisco IOS software on bootup and initializes itself in standby mode. In the event of a fatal error on the active RP, the system switches to the standby RP, which reinitializes itself as the active RP. In this event, the entire system is rebooted, so the switchover with RPR is slower than with other High Availability switchover features such as Nonstop Forwarding/Stateful Switchover (NSF/SSO). 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 "Second IOS Process on a Cisco ASR 1002 or 1004 Router" section on page 5-4 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. Stateful Switchover 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 "Second IOS Process on a Cisco ASR 1002 or 1004 Router" section on page 5-4 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 Cisco Nonstop Forwarding document. OL-16506-10 Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide 5-5