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Nexus 5548UP running hot?

Perhaps I've never noticed before and they are always like this, but do the 5548UP switches run hot (50+C) and with fans at full speed by design (seems extraordinarily power inefficient), or is there some performance tweaking that needs to be done to them during initial installation? I started installing one the other day, with an ASA above it and an HP server below it (both running quiet and cool), and within 5 minutes the other two were hot to the touch, so I had to turn it off. Google hasn't been any help. This is a Dev/Test environment.

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Re: Nexus 5548UP running hot?

Hello George,


I'd say that is not the right operating temperature. What's the airflow where you installed the device? Where does it get the cool air? What colors are the fans in the back? Red or Blue?



Re: Nexus 5548UP running hot?

Airflow is front to back for other devices in the rack, while it is back to "front top". The air flows in the two fans in the back, and blows out the top front that sticks out from the rack a couple of inches. That's why its not in the rack with the airflow the same as others - because it would be blowing directly up into the bottom of the ASA and the top of the rack. Cooling is in front of the rack (to provide cool intake air for the other devices), while warm intake is in the back.

The fans are black. You mean the fans themselves, right? Not the fan modules? Those are silver. If you mean the LEDs on them, they are both Green, as are the status lights on the console module and the front panel of the switch.

The part that I'm confused about is why the thing runs with the fans at full blast and the CPU (apparently) at full usage and extremely hot, instead of being throttled back during idle operation before it is processing anything. I could understand it being hot like that when our UCS and NetApp are hooked up and pumping storage data through it, but there was nothing connected to it except the console cable while configuring it. According to the show env (attached), it is using 726 watts while idling!

Re: Nexus 5548UP running hot?

Typical operating power consumption is 390 watts, and that's to be expected when it is actually doing something, while 680 is its expected maximum consumption. This one is not yet doing anything and it is puling 700+ watts. I have backup hardware, but the diagnostic LED's are showing everything is green.


The operating environment temperature and humidity are both right in the middle of their respective ranges - 32 to 104F range, currently around 70F, and 45% humidity (5 to 95% is okay).


Also, I've shutdown all the ports on it and there was no change in power consumption.


Re: Nexus 5548UP running hot?



Thank you for the additional information

The fan modules normally should have the hooks colored blue or red. Blue means that they are taking the air from the back and spitting it out from the front(interfaces side). Red means that hot air is getting spitted out from the back.

If the 5548 is racked with the interfaces side on the back of the rack you should have the blue fans.

You are saying that CPU is 100%, can you show us the following commands:


show processes cpu sorted
show processes cpu history
show environment fan
show version

 Many thanks,


Re: Nexus 5548UP running hot?

Thank you for you assistance, very much.


Attached is a picture of one of the two fans. The "show env fan" result is part of my previous message when I ran "show env".


I'll have to run the show proc & ver commands later when I can power it up again, but in the meantime, can you verify whether the switch running hot and LOUD under no load is normal or not?





Re: Nexus 5548UP running hot?

Hello George,


Apologies for 2 reasons, the first I have missed the attachment you put on your previous comment, second I have confused Nexus 3K fans with N5K fans. 3K have them colored. 

We have a bunch of Nexus 5K all running code 7.1.4.N1.1.bin and we do not match the same behaviour of yours. If you are running an older version of code you might need to upgrade it to a more recent one.




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