Software Redundancy Overview
IOS runs as one of many processes within the operating system. This is different than on traditional Cisco IOS, where all processes are run within Cisco IOS. See the “IOS as a Process” section on page 2-7 for more information regarding IOS as a process.
This architecture allows for software redundancy opportunities that are not available on other platforms that run Cisco IOS software. Specifically, a standby IOS process can be available on the same Route Processor as the active IOS process. This standby IOS process can be switched to in the event of an IOS failure.
On the C84xx Series Platforms, the second IOS process can run only on the standby Route Processor.