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MX304 Cooling System

MX304 Cooling System Description

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

The cooling system consists of the following components:

Fan Modules

The chassis monitors the temperature of the router components. When the router is operating normally, the fans function at a lower 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 ambient maximum temperature specification is exceeded and the system cannot be adequately cooled, the Routing Engine shuts down the router by disabling output power from each power supply.

The router has three fan modules that install at the rear of the router. Each fan tray uses two 80 mm x 80 mm counter rotating fans. The fan modules are hot-swappable and hot-removable field-replaceable units (FRUs) (see Figure 1 and Figure 2).


When the chassis is online, you can replace one fan at a time. See Table 1 for fan removal time. To avoid disturbing the air flow and cooling, don't operate the chassis when a fan module is removed.

Table 1: Fan Removal
Ambient Temperature Traffic Fan Removal Tray Time (Seconds)
25°C (77°F) 100% 115
40°C (104°F) 100% 40
Figure 1: Fan Module Fan Module
Figure 2: Fan Tray Fan Tray


The router has a front-to-back (AIR OUT) cooling system (see Figure 3). Cool air is pulled through the vents on the front the chassis and hot air exhausts through the vents on the rear of the chassis.

Figure 3: Airflow through the Router Airflow through the Router

Air Filter Unit

The air filter unit consists of three parts:the outer filter cover, the air filter, and the inner cage (see Figure 4). The air filter sits right inside the outer filter cover and the inner cage. The air filter unit is installed into the cable management brackets, and are held tightly by captive screws.

Figure 4: Air Filter Unit Air Filter Unit
Outer filter cover
Inner cage
Air filter
Table 2: Air Filter
Product Number Description Oderable
JNP-FLTRDR-2RU JNP304 Air filter assembly Spare
JNP-AIRFLTR-2RU Air Filter Spare

Power Supply Cooling System

The self-cooling power supplies and exhaust vents are in the rear of the router (to the left of the chassis).

MX304 Fan Module LED

Each fan module contains two bicolor LEDs. MX304 Cooling System Description shows the fan module LED.

Table 3 describes the behavior of the fan module LEDs.

Table 3: Fan Module LEDs








Fan module hardware initialization complete and software initialization pending

On steadily

Software initialization complete and the fan is functioning normally


On steadily

Faulty and not functioning normally


Fan locator beacon to identify a fan module
  Off Fan is off