M40 Router Redundant Cooling System Components - Juniper JUNOS - NETWORK OPERATION GUIDE REV1 Network Operation Manual

M40 Router Redundant Cooling System Components

The M40 router cooling system consists of three separate subsystems (see
Figure 214):
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Each cooling subsystem maintains a separate airflow, and each is monitored
independently for temperature control. Figure 214 shows the M40 router cooling
system airflow.
Temperature sensors on the backplane, the SCB, and the FPCs control the speed of
the impellers. Impeller failure triggers the red alarm LED on the craft interface. If
the temperature passes a certain threshold, the JUNOS software turns off the power
supplies.
The M40 router is designed to run normally with all three fans sharing the load
equally and running at half speed.
Figure 214: M40 Router Cooling System and Airflow
Exhaust for
Packet Forwarding
Engine cooling
Exhaust for Routing
Engine and backplane
cooling
Rear of Chassis
Exhaust for
power supply
Impellers—Two redundant pairs of impellers (top impeller and bottom impeller)
cool the Packet Forwarding Engine components (backplane, System Control
Board [SCB], FPCs, and Physical Interface Cards [PICs]). During normal
operation, both pairs of impellers function at less than full capacity.
Triple fan assemblies—Three load-sharing fans cool the backplane and the
Routing Engine (rear left fan, rear center fan, and rear right fan).
Power supply integrated fan—A built-in fan cools each power supply.
Upper impellers
Fan tray
Routing
Engine
Chapter 39: Monitoring Redundant Cooling System Components
Top impeller
Packet
Forwarding
Engine
Lower impellers
Power supply
and Fans
Bottom impeller
Understanding Redundant Cooling System Components
Front of Chassis
Air intake for
Packet Forwarding
Engine cooling
Air intake for
Routing Engine cooling
Air intake for
power supply cooling
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