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T4000 Control Board Description


The T4000 chassis supports up to two control boards. The Routing Engine requires an adjacent control board to provide control and monitoring functions for the router. These functions include determining Routing Engine mastership, controlling power and reset for the other router components, monitoring and controlling fan speed, and monitoring system status.

You can install up to two control boards in the chassis. Control boards install into the upper rear of the chassis in the slots labeled CB0 and CB1 (referred to as CB-0 and CB-1, top to bottom). If two control boards are installed, one functions as the master and the other as its backup. If the master fails or is removed, the backup restarts and becomes the master.

Each control board requires a Routing Engine to be installed in the adjacent slot. CB0 installs above RE0, and CB1 installs below RE1. Control boards cannot function if a Routing Engine is not present in the adjacent slot.

If the host system is redundant, the backup control board is hot-removable and hot-insertable, but the master control board is hot-pluggable. A control board that is not redundant is hot-pluggable.

The T4000 router supports the control board listed in Table 1

Table 1: T4000 Supported Control Board


Model Number

First Supported Junos OS Release

Line-card chassis control board (LCC-CB)