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    PCG Overview

    You monitor the PCGs to ensure that they generate a clock signal to synchronize the modules and application-specific integrated circuits (ASICs) that make up the Packet Forwarding Engine.

    The PCG supplies a 125-MHz system clock to synchronize the modules and ASICs that make up the Packet Forwarding Engine (see Figure 1).

    Figure 1: PCG Component

    PCG Component

    A router has two PCGs. They are located at the rear of the chassis in the slots labeled PCG0 and PCG1, to the right of the Routing Engine slots.

    Both PCGs send clock signals to the Packet Forwarding Engine modules, along with a signal indicating which is the master clock source. The master Routing Engine controls which PCG is master and which is backup.

    The PCGs are field-replaceable and hot-pluggable. You can remove and replace them without powering down the router; however, the routing functions of the system are interrupted when a PCG is removed.

    Removing the backup PCG does not affect the functioning of the router. Taking the master PCG offline causes the Flexible PIC Concentrators (FPCs) and Switching and Forwarding Modules (SFMs) to power down and restart with the other PCG selected as master. The forwarding and routing functions are interrupted during this process.

    Figure 2 shows the location of the PCGs on the M40e and M160 router chassis.

    Figure 2: M40e and M160 Router PCG Location

    M40e and M160 Router
PCG Location

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    Published: 2012-08-20