• Troubleshooting a suspected defective fan

 
 
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Problem:

The “show environment cooling” command shows a fan as “NOT WORKING”.

Example:

M32-A2-06308-5>show env cooling

System Cooling Status: OK

Ambient temperature: 41C

Airflow: BACK-TO-FRONT (REV)

 

Fan  Status                      Speed

---- ------------------------ --------

1    OK                            51%

2    OK                            51%

3    NOT WORKING                    0%

4    OK                            50%

Solution:

A 7130 device uses two field replaceable fan modules with two fans each providing a total of four fans. The fans are numbered 1-4 from left to right as you look at the rear of the device. The fans should fit snuggly so that they snap into place. Fans are removed by pinching the tabs in and gently pulling or wriggling the module out.

Fan Images

Image 1: 1RU blue back-to-front fan

Image 2: 1RU red front-to-back fan

Image 3: 1RU blue back-to-front fan

Image 4: 2RU blue fan

Notes:

  1. You can remove and reinsert the modules while the device is running. However, you should immediately replace a module as soon as possible to avoid the device overheating.
  2. Fan sizes are either 1RU (double) or 2RU (single).

The fan modules either produce airflow from back-to-front (reverse) as shown on Image 2 or from front-to-back (forward) as shown on Image 3. Blue fans indicate that cold air is drawn in by the fan while red indicates that hot air is exhausted. The airflow direction must be the same between the fans and power supplies which also have fans otherwise the device may overheat. MOS provides a warning if the cooling is not operating correctly via the “show environment cooling” command. The airflow is regulated by firmware that monitors the temperature within the case and adjusts the fan speed accordingly.

Do the following steps below to confirm that the fan is indeed defective.

  1. Execute the “show environment cooling” commandExample:
    M32-A2-06308-5>show env cooling
    
    System Cooling Status: OK
    
    Ambient temperature: 41C
    
    Airflow: BACK-TO-FRONT (REV)
    
     
    
    Fan  Status                      Speed
    
    ---- ------------------------ --------
    
    1    OK                            51%
    
    2    OK                            51%
    
    3    OK                            51%
    
    4    OK                            50%
    
    

    If one of the fans is not working it will show like below:

    Fan  Status                      Speed
    
    ---- ------------------------ --------
    
    1    OK                            51%
    
    2    OK                            51%
    
    3    NOT WORKING       0%
    
    4    OK                            50%
    
  2. Swap the fan module with a known working module. In the example above, swap the suspected fan with a known working module. Ensure that the fans are properly seated (snaps into place and fit snuggly). Execute “show environment cooling” command again and check the status of the fan.
  3. If after swapping it still reports that the fan is not working, then please contact Arista Support at support@arista.com so that we can help you further.

 

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