M120 Control Board (CB) Description

Each CB works with an installed Routing Engine to provide control and monitoring functions for the router (see Figure 1). These functions include determining Routing Engine mastership; controlling power and reset for the other router components; connecting the FEBs and FPCs; monitoring and controlling fan speed; and monitoring system status.

You can install one or two CBs in the router. The CBs install vertically into the rear of the chassis in the slots labeled CB0 and CB1. If two CBs are installed, one functions as the master CB and the other as its backup. If the master fails or is removed, the backup restarts and becomes the master.

With redundant CBs, the backup CB is hot-removable and hot-insertable, but the master CB is hot-pluggable. If a CB fails and switches mastership to the redundant CB, the Routing Engine mastership switches as well.

Figure 1: M120 CB

CB Components

Each CB consists of the following components:

• Switch fabric—Provides transit traffic through the Control Board.
• Control FPGA—Provides the PCI interface to the Routing Engine.
• 1000Base-T Ethernet controller—Provides a 1-Gbps Ethernet link between the Routing Engines.
• Ethernet switch—Provides Ethernet connectivity between the Routing Engine and the FPCs and FEBs; link speeds are 10 Gbps to the Routing Engine and FEBs and 100 Mpbs to the FPCs and CFPCs.
• SONET clocking module—Provides a Stratum 3 timing reference for all SONET interfaces installed in the system.
• LEDs—Three LEDs on the CB indicate the status of the CB and whether that CB is master. The LEDs, labeled OK, FAIL, and MSTR are located directly on the control board.
• Circuits for chassis management and control.
• Power circuits for the Routing Engine and CB.
• Offline button—Takes the CB offline when pressed.