topic Re: Catalyst 9800-L-F Fan Noise in Wireless

Catalyst 9800-L-F Fan Noise

bbocjcp — Sat, 26 Feb 2022 00:16:15 GMT

I've been asked to configure a 9800-L-F WLC, and even though the rommon has been updated to the 16.12-3r version, I am astonished at how noisy the fans are. They seem so much noiser than other models of 3504 or 9800 WLCs. Are there any cli commands to reduce the fan speed or fan noise ?

Re: Catalyst 9800-L-F Fan Noise

Scott Fella — Sat, 26 Feb 2022 00:32:55 GMT

Maybe you need to RMA the unit. I don't think there is any command to reduce the fan speed like other appliances through the CIMC. Open a ticket and see if TAC has any workaround, or else they will just issue an RMA for you.

Re: Catalyst 9800-L-F Fan Noise

Mark Elsen — Sat, 26 Feb 2022 06:58:52 GMT

- You may want to connect (SSH) to the device with : https://cway.cisco.com/cli , at the top left press or run System Diagnostics.

Re: Catalyst 9800-L-F Fan Noise

Leo Laohoo — Sat, 26 Feb 2022 23:25:45 GMT

@bbocjcp wrote:

and even though the rommon has been updated to the 16.12-3r version

What firmware is the WLC running on?

Re: Catalyst 9800-L-F Fan Noise

bbocjcp — Sun, 27 Feb 2022 02:40:51 GMT

I did a bit more investigation, I removed the cover to look at the fans. There is a pair of Delta BFB0512VHD fans in place. Fairly basic 12v fans, but the fan speed is controlled by a Pulse Width Modulator (PWM) which means this is software controlled. I have access to a 9800-L-C WLC too, and its fans are running at a much lower speed.

I disconnected one of the fans, to see if the chassis heats up, but it sat at 43C overnight with only one fan running so I don't get the impression that this chassis needs high speed fans. I suspect this is a software bug, but I'll do some more research with different IOx versions to try and confirm it.

Re: Catalyst 9800-L-F Fan Noise

Scott Fella — Sun, 27 Feb 2022 06:35:18 GMT

The F and the C models run the same software. It never hurts trying different versions, that is what I typically do.

Re: Catalyst 9800-L-F Fan Noise

Tristan G — Fri, 12 May 2023 01:13:33 GMT

Interesting observations! Would be interested to know if the -c and -f models you have encountered use different fan models or not. It's not uncommon for vendors to use different fan vendors etc in different hardware revisions.

Is there any difference with hardware version eg v01 v02 etc between the units you looked at? I also note that the power consumption of the -C is slightly higher, so I wouldn't expect the fans in the -F to run at a higher speed vs the C. I can't find any "show env" command to tell me how fast the fans are spinning.

Re: Catalyst 9800-L-F Fan Noise

Tristan G — Fri, 12 May 2023 02:28:13 GMT

A follow-up observation - I find that if I reload the box, the fans speed up and stay high, but if I power cycle, the fans remain low.

Try power cycling and allow the unit to boot up again and then observe if there's any difference between that, and then perform a reload and observe.