查看電源和風扇配置：
1 <h3c-S5560>display power 2 Slot 1: 3 PowerID State Mode Current(A) Voltage(V) Power(W) 4 1 Normal AC -- -- -- 5 2 Absent -- -- -- --
6 7 8 [h3c-S5560]display fan 9 Slot 1: 10 Fan 1: 11 State : FanDirectionFault 12 Airflow Direction: Power-to-port 13 Prefer Airflow Direction: Port-to-power 14 Fan 2: 15 State : FanDirectionFault 16 Airflow Direction: Power-to-port 17 Prefer Airflow Direction: Port-to-power
檢查交換機風扇配置信息發現交換機風扇的實際氣流方向為：Airflow Direction: Power-to-port（風道風向是電源側進風、端口側出風）；而配置用戶下看到風扇模塊的優選氣流方向為：Prefer Airflow Direction: Port-to-power（端口側進風、電源側出風），兩者不一致（交換機風扇反轉），導致交換機風扇狀態為：FanDirectionFault（風扇方向錯誤），風扇信號燈告警，交換機SYS信號燈告警。
處理方法：
fan prefer-direction命令用來配置用戶期望的風扇模塊的風道風向。undo fan prefer-direction命令用來恢復缺省情況。當風扇模塊的風道風向和設備當前期望的風道風向不一致的時候，系統會打印Trap和Log信息提醒用戶。缺省情況下，設備的期望風道風向為電源側進風、端口側出風（power-to-port）。
或者更改用戶期望的風道風向為power-to-port， 保存配置，sys信號燈恢復綠色。
1 <h3c-S5560>system-view 2 System View: return to User View with Ctrl+Z. 3 [h3c-S5560]fan pre 4 [h3c-S5560]fan prefer-direction slot 5 [h3c-S5560]fan prefer-direction slot 1 6 [h3c-S5560]fan prefer-direction slot 1 ? 7 port-to-power From port to power 8 power-to-port From power to port 9 10 [h3c-S5560]fan prefer-direction slot 1 pow 11 [h3c-S5560]fan prefer-direction slot 1 power-to-port 12 [h3c-S5560]dis fan 13 Slot 1: 14 Fan 1: 15 State : Normal 16 Airflow Direction: Power-to-port 17 Prefer Airflow Direction: Power-to-port 18 Fan 2: 19 State : Normal 20 Airflow Direction: Power-to-port 21 Prefer Airflow Direction: Power-to-port 22 23 24 [h3c-S5560]save