Features configured on the active device CPM are saved on the standby CPM as well. When the active device CPM fails, these features are brought up on the standby device CPM that takes over the mastership.
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 re-initialize connections by bringing up Layer 2 connections and Layer 3 routing protocols and then rebuild routing tables.
hot standby
The router image, configuration, and network state is already loaded on the standby and it receives continual updates from the active route processor and the swapover is immediate. However, hot standby affects conventional router performance as more frequent synchronization increases consumption of system resources. Nokia’s newer generation service routers address this issue because they already have extra processing built into the system.