When planning the installation site, you need to allow sufficient clearance around the rack (see Figure 1):
Airflow must always be from front to back with respect to the rack. If the device has side to rear airflow, then provisions must be made to ensure that fresh air from the front of the rack is supplied to the inlets, and exhaust exits the rear of the rack. The device must not interfere with the cooling of other systems in the rack. Fillers must be used as appropriate in the rack to ensure there is no recirculation of heated exhaust air back to the front of the rack. Care must also be taken around cables to ensure that no leakage of air in situations where recirculation may result.
Figure 1: Clearance Requirements for Airflow and Hardware Maintenance for an MX480 Router Chassis
