Understanding Redundant Control Boards
Purpose
Inspect redundant Control Boards to ensure that router component functions are uninterrupted. Each Control Board works with an adjacent Routing Engine to provide control and monitoring functions for the router. These include determining Routing Engine mastership; controlling power, reset, and SONET clocking for the other router components; monitoring and controlling fan speed; and monitoring system status.
What Are Redundant Control Boards
Redundant Control Boards are two Control Boards installed in the M320 router, T320 router, or the T640 routing node.
The Control Board is a component of the host module. Each Control Board requires a Routing Engine to be installed in an adjacent slot. The Control Board in slot CB0 installs above the Routing Engine in slot RE0, and the Control Board in slot CB1 installs below the Routing Engine in slot RE1. Even if a Control Board is physically installed in the chassis, it does not function if there is no Routing Engine present in the adjacent slot.
If two Control Boards are installed, by default, CB0 acts as the master Control Board and CB1 acts as a backup. If the master Control Board (CB0) fails or is removed, the backup (CB1) restarts and becomes the master Control Board.
The Control Boards install into the midplane from the back of the chassis (see Figure 227). The Control Boards are hot-pluggable.
