Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


EX9251 Cooling System

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

The cooling system in an EX9251 switch consists of three fan trays. Under normal operating conditions, the fans in the fan trays run at a moderate speed. Temperature sensors inside the chassis monitor the temperature of the switch components. If a fan fails or the ambient temperature rises above the acceptable range, the system raises an alarm and the speed of the remaining fans is automatically adjusted to keep the temperature within the acceptable range. If the ambient maximum temperature is exceeded and the switch cannot be cooled adequately, the Routing Engine shuts down the switch.

Fan Trays

The fan trays are hot-insertable and hot-removable field-replaceable units (FRUs). The fan trays are installed on the rear panel of the chassis. Each fan tray contains one counter rotating fan. See Figure 1 and Figure 2.

Figure 1: Fan Tray in an EX9251 SwitchFan Tray in an EX9251 Switch
Figure 2: Faceplate of a Fan Tray in an EX9251 SwitchFaceplate of a Fan Tray in an EX9251 Switch

Airflow Direction in the EX9251 Switch Chassis

The switch has front-to-back (AIR OUT) airflow. The air intake to cool the chassis is through the vents on the front of the chassis. Air is pulled through the chassis towards the fan tray and hot air exhausts through the rear of the chassis. See Figure 3.

Figure 3: Airflow Through the EX9251 Switch ChassisAirflow Through the EX9251 Switch Chassis

Cooling System in the Power Supplies

The power supplies are self-cooling units. Each power supply has its own built-in fan that cools the power supply. The power supplies are installed on the rear panel of the switch. The air exhaust for the power supplies are also located on the rear panel of the chassis.

Fan Tray Status LEDs

The LEDs indicating the state of the fan trays are located adjacent to the fan tray slots on the rear panel of the chassis (see Figure 4).

Figure 4: Fan Tray Status LEDsFan Tray Status LEDs
Fan tray status LEDs

The fan tray status LEDs are bicolor LEDs. Table 1 describes the behavior of the fan tray status LEDs.

Table 1: Fan Tray Status LEDs






Fan tray hardware initialization is complete and software initialization is pending.

On steadily

Software initialization is complete and the fan is functioning normally.


On steadily

Fan tray is faulty and not functioning normally.


Fan tray is not present.