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ACX5048 and ACX5096 Cooling System


Cooling System and Airflow in an ACX5000 Router

The cooling system in ACX5000 routers consists of fan modules and a single fan in each power supply. The number of fan modules vary depending whether the size of the router is 1 U or 2 U high. All routers can be set up to work in the following airflow direction:

  • Airflow Out (AFO)—Air comes into the router through the vents in the front panel.

This topic describes:

Fan Modules

The fan modules in ACX5000 routers are hot-insertable and hot-removable field-replaceable units (FRUs). These fan modules are designed for air to enter from the ports to the FRU–Airflow Out. The fan modules are installed in the fan module slots on the management panel of the router next to the power supplies.

Both the 1 U and 2 U versions of ACX5000 fan modules have a similar design with different dimensions. The 1 U ACX5000 routers have 5 fan modules numbered 0 through 4 from left to right, where the 2 U, ACX5096 has 3 fan modules numbered 0 through 2. On all ACX5000 routers, each fan module slot has a fan icon next to it.

Figure 1 shows the 1 U fan module and Figure 2 shows the 2 U fan module.

Figure 1: 1 U Fan Module Used in ACX5048
1 U Fan Module Used in
Figure 2: 2 U Fan Module Used in ACX5096
2 U Fan Module Used
in ACX5096

You remove and replace a fan module from the FRU end of the chassis. The router continues to operate for a limited period of time (30 seconds) during the replacement of the fan module without thermal shutdown.


All fan modules must be installed for optimal operation of the router.

The fan module airflow direction (port-to-FRU, AFO) is indicated by either a gold color or the label AIR OUT . Table 1 lists the fan module product SKUs and the direction of airflow in them:

Table 1: Fan Module in ACX5000 Routers

Fan Module

ACX5000 Router Supported

Airflow Diagram

Label on the Fan Module

Color of Fan Module

Direction of Airflow in the Fan Module

Power Supplies



Figure 3


Juniper Gold

Port-to-FRU, that is, air comes in through vents on the end with ports; air exhausts out the end with the fans (also known as front-to-back airflow).

You must install only power supplies that have AIR OUT labels in routers in which the fan modules have AIR OUT labels.



Figure 4

In data center deployments, position the router in such a manner that the AIR OUT labels on router components are next to the hot aisle.

Figure 3: Air Out Airflow Through 1 U ACX5048 Chassis
Air Out Airflow Through 1 U
ACX5048 Chassis
Figure 4: Air Out Airflow Through 2 U ACX5096 Chassis
Air Out Airflow Through 2 U
ACX5096 Chassis

Fan Module Status

You can check the status of fan modules through the show system alarms command or by looking at the LEDs next to each fan module.

Each router has a Status LED (labeled ST) for each fan module on the left side of the corresponding fan module slot. It indicates the status of all the fan modules. Table 2 describes the Status LED on the fan module in an ACX5000 router.

Table 2: Fan Module LED

LED State


Solid Green

The individual fan module is present. After the hardware senses the fan module, software ensures the airflow is consistent with the other fan modules and that it is functioning correctly.

Blinking Amber

Indicates one of the following:

  • The fan module is not present.

  • The fan module is not functioning normally.

Under normal operating conditions, the fan modules operate at a moderate speed. Temperature sensors in the chassis monitor the temperature within the chassis.

The system raises an alarm if a fan module fails or if the ambient temperature inside the chassis rises above the acceptable range. If the temperature inside the chassis rises above the threshold temperature, the system shuts down automatically.

Fan Module LED on an ACX5000 Router

Figure 5 shows the location of the LED next to the fan module.

Figure 5: Fan Module LED in an ACX5000 Router
Fan Module LED in an
ACX5000 Router

Table 3 describes the function of the fan tray LED.

Table 3: Fan Tray LED in an ACX5000 Router







On steadily

The fan module is operating normally. The system has verified that the module is engaged, that the airflow is in the correct direction, and that the fan is operating correctly.



An error has been detected in the fan module. Replace the fan module as soon as possible. Either the fan has failed or it is seated incorrectly. To maintain proper airflow through the chassis, leave the fan module installed in the chassis until you are ready to replace it.