Features configured on the active device CFM or CPM are also saved on the standby CFM or CPM. If the active device CFM or CPM fails, these features are brought up on the standby device that takes over the mastership and becomes the active CFM or CPM.
Even with modern modular and stable software, the failure of route processor hardware or software can cause the router to reboot or cause other service impacting events. In the best circumstances, failure leads to the initialization of a redundant route processor, which hosts the standby software configuration, to become the active processor. The following options are available:
warm standby
The router image and configuration is already loaded on the standby route processor. However, the standby could still take a few minutes to become effective because it must first reinitialize connections by bringing up Layer 2 connections and Layer 3 routing protocols, and then rebuild the routing tables.
hot standby
The router image, configuration, and network state are already loaded on the standby; it receives continual updates from the active route processor and the swap-over is immediate. Newer generation routers, like the 7210 SAS routers have extra processing built into the system so that router performance is not affected by frequent synchronization, which consumes increased system resources.