The cooling system in an EX 4200 switch consists of a field-replaceable unit (FRU) fan tray with three fans (see Figure 17). The fan tray is located at the rear of the chassis and provides side-to-rear chassis cooling (see Figure 18).
Figure 17: Fan Tray Used in an EX 4200 Switch
Figure 18: Airflow Through the EX 4200 Switch Chassis
The fan tray used in an EX 4200 switch comes with load-sharing redundancy that can tolerate a single fan failure at room temperature (below 45° C/113° F) to still provide sufficient cooling.
Temperature sensors in the chassis monitor the temperature within the chassis. The system raises an alarm if the fan fails or if the temperature inside the chassis rises above permitted levels. If the temperature inside the chassis rises above the threshold, the system shuts down automatically and the temperature shutdown LED on the rear panel is lit. You can see the status of fans and the temperature from the Environmental Status menu on the LCD panel.