The Cisco Catalyst 9500 Series Switches support dual 1+1 redundant power supplies. The switches ship with one power supply by default. The second power supply can be added at the time the switch is ordered or at a later time. If only one power supply is installed, it should always be in power supply bay 1. The switches also ship with five field-replaceable variable-speed fans. These have front-to-back airflow and can operate with up to one individual fan failure. The fan trays support fan-tray Online Insertion and Removal (OIR) for up to 120 seconds and can support a maximum fan speed of 2400 RPM.