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QFX5700 Cooling System Description and Airflow

The cooling system components work together to keep all router components within the acceptable temperature range.

When the router is operating normally, the fans function at lower than full speed. If a fan fails or the ambient temperature rises above a threshold, the speed of the remaining fans is automatically adjusted to keep the temperature within the acceptable range. If the maximum temperature specification is exceeded and the system cannot be adequately cooled, the Routing and Control Board (RCB) shuts down some or all of the hardware components.

The cooling system consists of the following components:

  • Airflow

  • Fan trays

  • Fan Status LEDs

The QFX5700 is cooled front to back with four fan modules. The QFX5700 offers Front to Back Air Cooling with two fan trays plugged in from the rear side. The fan modules pull air through the front panel around the gaps between the optical transceivers. Cooling for the power supplies is also front to back, utilizing fans inside the power supplies.


To know the power consumption of the fans, click the link. You'll need a valid Juniper account to access the power calculator.


Figure 1 shows the airflow through the switch.

Figure 1: Airflow Through the ChassisAirflow Through the Chassis

The cooling system contains the following fan trays: See Figure 2.

  • One upper front fan tray and one lower front fan tray that cool the components (the RCBs and FEBs).

    Figure 2: QFX5700 Cooling SystemQFX5700 Cooling System
  • Each fan tray contains four fans. See Figure 3.

    Figure 3: QFX5700 Fan Tray UnitQFX5700 Fan Tray Unit

The upper and lower front fan trays contain four fans each. Both fan trays are interchangeable with each other.

All fan trays are hot-insertable and hot-removable.


To maintain proper cooling, do not operate the routing node with the rear fan tray removed for more than one minute.

The QFX5700 switch supports the fan trays listed in Table 1.

Table 1: Supported Fan Trays


Model Number

First Supported Junos OS Release

Rear Fan Tray


21.2 R2

The following table describes the behavior of the fan and FEB LEDs.

Table 2: Fan Status and FEB Status LEDs
Label Color State Description

STATUS (Fan status)



Fan hardware initialization is complete. Software initialization is pending

On steadily

Software initialization is complete, and the fan is functioning normally


On steadily

Equipment is faulty and malfunctioning



Fan tray input power failure

FEB (FEB status)



The FEB is booting

On steadily

The FEB is online and functioning normally


On steadily

The FEB has failed



The FEB is offline