Control Board in a QFX3008-I Interconnect Device
The Control Board performs Routing Engine functions in a QFX3008 Interconnect device. See Figure 1.
The Control Boards install horizontally into the top rear of
the chassis in slots labeled CB 0
and CB 1
.

One Control Board functions as the master, and the other acts as the backup. If the master Control Board fails or is removed, the backup Control Board takes over as the master Control Board. When the Control Boards are configured for graceful switchover, the backup Control Board automatically synchronizes its configuration and state with those of the master Control Board. Any update to the master Control Board is replicated on the backup Control Board. If the master Control Board fails, or mastership is switched to the backup Control Board, packet forwarding stops on the QFXC08 chassis. When the backup Control Board assumes mastership, packet forwarding continues through the device.
If you need to replace the master Control Board, we recommend that you switch mastership to the backup Control Board. We recommend that you always take a Control Board offline before removing it. See Taking a Control Board Offline in a QFX3008-I Interconnect Device.
The Control Board provides these functions:
Powers the 16-port QSFP+ front cards on and off
Powers the rear cards on and off
Performs routing functions for the device
Controls system resets and the boot sequence for the device
Monitors and controls the speed of the fans in the fan trays
Monitors and controls the LCD panel and chassis status LEDs
Monitors the communication of the 16-port QSFP+ front cards with the rear cards
Monitors the status of the power supplies
The Control Board has these components:
Control Board LEDs—Indicate system status. See Control Board LEDs on a QFX3008-I Interconnect Device.
USB port—Provides an interface through which you can recover the device by reinstalling Junos OS software. See USB Port Specifications for the QFX Series ,Performing a Recovery Installation Using an Emergency Boot Device, and Performing a Recovery Installation.
Console port—Connects the Control Board to a management console through a serial connection using a cable with an RJ-45 connector. See Connecting a QFX Series Device to a Management Console.
Auxiliary port—This port is not enabled. It is reserved for future use.
Management port—This port is not enabled. It is reserved for future use.
Four Gigabit Ethernet SFP+ ports—Connect the Control Board to the QFX3000-G QFabric system control plane network. See Connecting a QFX3008-I Interconnect Device to a Copper-Based QFX3000-G QFabric System Control Plane Network.
Ejector levers—Used for installing and removing the Control Board.