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Maintaining the M120 Fan Trays



For optimum cooling, verify the condition of the fans.


  • Monitor the status of the fans. Each fan tray contains multiple fans that work in unison to cool the router components. If one fan fails, the host subsystem adjusts the speed of the remaining fans to maintain proper cooling. A red alarm is triggered when a fan fails, and a yellow alarm is triggered when a fan tray is removed.

  • To display the status of the cooling system, issue the show chassis environment command. The output is similar to the following:

    user@host> show chassis environment

The fan numbers are stamped into the fan tray sheet metal next to each fan.