Juniper Networks M160 manual Replacing a PCG, Removing a PCG

M160 Internet Router Hardware Guide

Figure 89: Connecting Fiber-Optic Cable to a PIC

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Replacing a PCG

During normal operation, both PCGs generate a 125-MHz clock signal, but only one is designated as the master. The modules and ASICs in the Packet Forwarding Engine that use the clock signal to gate packet processing use only the signal from the master PCG. For information about determining which PCG is the master, see “Maintaining the PCGs” on page 135.

PCGs are hot-pluggable, as described in Field-ReplaceableUnits (FRUs) on page

4.Removal or failure of the backup PCG does not affect router function. If the master PCG fails or is removed from the chassis, however, the Packet Forwarding Engine resets so that the components start using the signal from the other PCG (which becomes the master). Packet forwarding halts while there is no clock signal, because the Packet Forwarding Engine does not accept incoming packets.

To replace a PCG, perform the following procedures:

Removing a PCG on page 176

Installing a PCG on page 178

Removing a PCG

To remove a PCG, follow this procedure (see Figure 90):

1.Place an electrostatic bag or antistatic mat on a flat, stable surface.

2.Attach an electrostatic discharge (ESD) grounding strap to your bare wrist and connect the strap to one of the ESD points on the chassis. Make sure the router is attached to a proper earth ground. For more information about ESD, see

“Preventing Electrostatic Discharge Damage” on page 226.

176 Replacing Packet Forwarding Engine Components