Cooling System and Airflow for a QFX3500 Device
The cooling system in a QFX3500 device consists of two field-replaceable unit (FRU) fan trays with two fan modules each (see Figure 1) and two fan modules on the management board FRU (see Figure 2). In addition, the power supplies have internal fans to cool themselves.
The QFX3500 device provides FRU-to-port or port-to-FRU airflow depending on the device model you purchase. Table 1 lists the different QFX3500 device models and their direction of airflow.
In QFX Series device model names, AFI, or airflow in, describes FRU-to-port airflow. AFO, or airflow out, describes port-to-FRU airflow.
The front panel of the device where the power supplies, fan trays, and management boards are located is the FRU side of the device.
Table 1: Airflow Direction in QFX3500 Device Models
Direction of Airflow
In the QFX3500 device models that have FRU-to-port airflow, the air intake to cool the chassis is located on the front panel of the chassis, where the FRUs are installed. Air is pulled into the chassis and pushed away from the fan trays and management board. Hot air exhausts from the rear of the chassis, where the ports are located. See Figure 3.
In the QFX3500 device models that have port-to-FRU airflow, the air intake to cool the chassis is located on the rear panel of the chassis, the side with access and uplink ports. Air is pulled into the chassis and pulled through the fan trays and management boards. Hot air exhausts from the front of the chassis, where the FRUs are installed. See Figure 4.
Each airflow type requires specific fan trays, management boards,
and power supplies, that have fan modules oriented in the proper direction.
The fan trays and management boards are designed so that they can
only be inserted into the QFX3500 device model that supports the same
airflow type. The power supplies have labels and arrows on the handles
that depict the direction of airflow (see Figure 5). The label
AFI denotes FRU-to-port airflow,
AFO denotes port-to-FRU
Verify that the direction of the arrow on the power supply handle matches the direction of airflow in the chassis. See Table 1 to determine your model’s airflow direction.
Table 2 lists the QFX3500 device FRUs and their direction of airflow.
Table 2: Airflow Direction in QFX3500 Device FRUs
Direction of Airflow
RJ-45 management board
SFP management board
AC power supply
DC power supply
The chassis includes a fan speed-control system. Under normal operating conditions, fans operate at reduced speed to reduce noise and power consumption.
Temperature sensors in the chassis monitor the temperature within the chassis. The system raises an alarm if a fan fails or if the temperature inside the chassis rises above permitted levels. If the temperature inside the chassis rises above the threshold, the device shuts down automatically. You can see the status of fans and the temperature remotely through the CLI by issuing the operational mode command show chassis environment.
You cannot replace a single fan module. If one or more fan modules fail, you must replace the entire fan tray or management board.