A high-performance network switch chassis has multiple network ports and air openings on the front end of the chassis, and multiple fan modules mounted on the back end of the chassis. The fan modules are hot-swap replaceable so that replacement of one of the fan modules does not require interruption of network switch operation. Air-blockers associated with each fan module prevent recirculation of air when fan modules are removed. Different types of fan modules may be used to provide either front-to-rear or rear-to-front airflow through the chassis. A fan speed controller determines fan speed based on temperature using one of two profiles. The two profiles correspond to the two different airflow directions.