Table Of Contents
Stateful Switchover Between Redudancy Paired Intra or Inter-box Devices
Stateful switchover 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.
Cisco Unified Border Element (Enterprise)
•Cisco IOS XE Release 3.2 or a later release must be installed and running on your Cisco ASR 1000 Series Router.
•Transcoding calls are not check-pointed, when failover happens, these calls will not be persevered. The expected behavior is for the SPA card to reset the DSPs and start the firmware download.
Information About Stateful Switchover Between Redundancy Paired Intra or Inter-box Devices
In specific Cisco networking devices that support dual RPs, Stateful switchover takes advantage of Route Processors redundancy to increase network availability. The Stateful switchover (SSO) feature takes advantage of RP redundancy by establishing one of the RPs 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, Stateful switchover dynamically maintains RP state information between them.
A switchover from the active to the standby processor occurs when the active RP fails, is removed from the networking device, or is manually taken down for maintenance.
The following conditions and restrictions apply to the current implementation of SSO:
•Calls that are handled by non-default session application (TCL/VXML etc.) will not be checkpointed pre-bridge.
•Calls that require a DSP to be inserted (ex: Transcoded Calls) will not be checkpointed.
•Flow-through calls whose state has not been accurately check pointed will be cleared with media inactivity based clean up. This condition could occur if active failure happens when:
–Some check point data has not yet been sent to the standby
–The call leg was in the middle of a transaction.
–Flow around calls whose state has not been accurately check pointed (due to either of the reasons mentioned above) can be cleared with the clear call voice causecode command
For more information about the Stateful Switchover feature and for detailed procedures for enabling this feature, see the "Configuring Stateful Switchpover" chapter of the Cisco IOS High Availability Configuration Guide, Release 12.2SR.