On Nexus 3000 switch, following error messages can be seen
%PLATFORM-1-PFM_ALERT: OPPOSITE_FAN_DIR: Some fan-trays and/or power-supply fans are operating in opposite direction. PS(2) operating with Front-to-Back air flow. Fan-tray(1,2,3,4) and PS(1) operating with Back-to-Front air flow.
