Each Cisco Catalyst 9400 Series uses dual serviceable fan trays for cooling. Cisco Catalyst 9400 can optionally be accessed from the rear for flexible cable management. The chassis is enterprise closet-optimized with side-to-side airflow. All fan trays are composed of multiple independently controlled fans with N+1 redundancy. If any single fan fails, the system will continue to operate without a degradation in cooling. Speeds of fans change dynamically to compensate for fan failure. Catalyst 9400 Series fans have a barometric sensor, which allows slower fan speed curves at lower altitudes. Catalyst 9400 Series fans also have individual fan Pulse-Wide Modulation (PWM) fine-tuning to reduce variability in fan Revolutions Per Minute (RPM) under throttled conditions. This allows for optimal acoustic performance at 60dB when the system is operating at 50% load.
