Reversing The Airflow of a Running Switch

Occasionally customers have a switch in production that they need to change the airflow direction of e.g. from a front-to-rear (-F) to a rear-to-front (-R), or vice-versa, without shutting down the switch. The following procedure outlines the steps to follow in order to accomplish this.

This procedure assumes that you already have the replacement fans and PSUs on hand and are ready to perform the swap.

  1. Start with the switch powered up, both power supplies powered and providing power to the switch. Gain access to the switch’s serial console to check status and run CLI commands as need be.
  2. Add the following to the switch’s configuration: “environment insufficient-fans action ignore“. This allows the admin to perform the swap without worrying about automated restart of the switch should it detect insufficient fans in the functional direction. Without the command, the switch will automatically shut itself down after 60 seconds should there not be sufficient fans and at least one PSU in the same direction. A warning is displayed upon entering the command.
  3. Line up the replacement power supplies and fans within easy reach.
  4. Start with one of the power supplies. Remove the old supply, replace with the new supply and power it up (plug it in). You do not need to wait for the supply to come online before proceeding with the remaining fans but you must ensure that the power supply is online before swapping the second PSU.
  5. One by one, go down the line and replace each of the 4 fans one at a time and with the new airflow type fan.
  6. By the time you get to the second power supply, the first power supply should be powered up and providing adequate power to the switch. You can verify this by checking the “STATUS” LED on the back of the power supply, or by reviewing “show environment power“. Remove the last power supply and replace with the new supply.
  7. Confirm the new fans/PSUs are all in place and functional via the command “show environment cooling”.
  8. Change the cooling check state back to normal with the configuration command: “environment insufficient-fans action shutdown“.

NOTE: The console will continue to print warnings regarding shutdown, but no action will be taken