Upgrading the Rear Fan Tray in a T640 Router Before Integrating the Router into a Routing Matrix

1. Attach an electrostatic discharge (ESD) grounding strap to your bare wrist, and connect the strap to one of the ESD points on the chassis.
2. Replace the rear fan tray with the model required for a converted T640 router. Use the standard replacement procedure described in the T640 Core Router Hardware Guide . To display the status of the fans in the router, issue the show chassis environment command. The output is similar to the following:
   user@host> show chassis environment

   ...
         Rear Tray Top fan      OK         Spinning at normal speed
         Rear Tray Second fan   OK         Spinning at normal speed
         Rear Tray Third fan    OK         Spinning at normal speed
         Rear Tray Fourth fan   OK         Spinning at normal speed
         Rear Tray Fifth fan    OK         Spinning at normal speed
         Rear Tray Sixth fan    OK         Spinning at normal speed
         Rear Tray Seventh fan  OK         Spinning at normal speed
         Rear Tray Bottom fan   OK         Spinning at normal speed
   ...
   

   Caution: To maintain proper cooling, do not operate the T640 router with the rear fan tray removed for more than 1 minute.