Cisco Cisco IOS Software Release 12.2(20)S
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Stateful Switchover
First Published: July 22, 2002
Last Updated: August 21, 2007
Last Updated: August 21, 2007
Development of the Stateful Switchover (SSO) feature is an incremental step within an overall program
to improve the availability of networks constructed with Cisco IOS routers.
to improve the availability of networks constructed with Cisco IOS routers.
is particularly useful at the network edgeSSO provides protection for network edge devices with dual
Route Processors (RPs) that represent a single point of failure in the network design, and where an
outage might result in loss of service for customers.
Route Processors (RPs) that represent a single point of failure in the network design, and where an
outage might result in loss of service for customers.
SSO has many benefits. Because the SSO feature maintains stateful protocol and application
information, user session information is maintained during a switchover, and line cards continue to
forward network traffic with no loss of sessions, providing improved network availability. SSO provides
a faster switchover relative to HSA, RPR, and RPR+ by fully initializing and fully configuring the
standby RP, and by synchronizing state information, which can reduce the time required for routing
protocols to converge. Network stability may be improved with the reduction in the number of route flaps
had been created when routers in the network failed and lost their routing tables.
information, user session information is maintained during a switchover, and line cards continue to
forward network traffic with no loss of sessions, providing improved network availability. SSO provides
a faster switchover relative to HSA, RPR, and RPR+ by fully initializing and fully configuring the
standby RP, and by synchronizing state information, which can reduce the time required for routing
protocols to converge. Network stability may be improved with the reduction in the number of route flaps
had been created when routers in the network failed and lost their routing tables.
This document describes the Stateful Switchover (SSO) feature in Cisco IOS software.
Note
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. To reach
links to specific feature documentation in this module and to see a list of the releases in which each feature is
supported, use the
links to specific feature documentation in this module and to see a list of the releases in which each feature is
supported, use the
Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS
software image support. To access Cisco Feature Navigator, go to
software image support. To access Cisco Feature Navigator, go to
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