T640 Host Subsystem Description
The host subsystem provides the routing and system management functions of the router. You can install one or two host subsystems on the router. To operate, each host subsystem functions as a unit; the Routing Engine requires the corresponding T–CB, and vice versa.
 | Note: We recommend that you install two host subsystems for redundant protection. If you install only one host subsystem, we recommend that you install it in slot RE0. |
Each host subsystem has three LEDs that display its status. The host subsystem LEDs are located on the upper right of the craft interface. For more information about the host subsystem LEDs, see T640 Craft Interface Host Subsystem LEDs.
