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3750X idle CPU usage?


I just started setting up some 3750X I received for an event. and after setting them up ive been just programming access points with just one. No real traffic going on just a 10G link to my core and adopting APs.. about 24 at a time. Ive noticed that the CPU has been at around 54 and 58%. Is that normal. ?


Switch Ports Model                     SW Version            SW Image                 
------ ----- -----                     ----------            ----------               
*    1 54    WS-C3750X-48P             15.2(4)E8             C3750E-UNIVERSALK9-M     

Configuration register is 0xF

Screen Shot 2022-07-01 at 6.35.49 PM.png


I did remove the http server and checked again

BigRedSw102(config)#do show proc cpu | e 0.0
CPU utilization for five seconds: 36%/0%; one minute: 39%; five minutes: 43%
 PID Runtime(ms)     Invoked      uSecs   5Sec   1Min   5Min TTY Process 
   4      487218       21036      23161  0.95%  2.37%  2.23%   0 Check heaps      
  87      446311      264642       1686  2.39%  2.13%  2.14%   0 RedEarth I2C dri 
  88      989100      170225       5810  4.63%  4.61%  4.61%   0 RedEarth Tx Mana 
 109        5039        1703       2958  0.15%  0.38%  0.74%   1 SSH Process      
 134       79018       21197       3727  0.79%  0.72%  0.62%   0 hpm counter proc 
 182     4337306      510139       8502 19.67% 19.97% 19.70%   0 Hulc LED Process 
 198       89731        4263      21048  0.47%  0.44%  0.42%   0 HQM Stack Proces 
 248      538380      203437       2646  1.75%  1.74%  2.39%   0 Spanning Tree   
17 Replies 17

Georg Pauwen
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in addition to the other posts, I think administratively shutting down (shut) all unused ports can help reducing CPU usage as well...

Rising star
Rising star

I wouldn't recommend just upgrading the .bin file.  Get the .tar image and use the 'archive' commands to do the upgrade as this will clean the flash of old images and install the HTML files as well.

As everyone has said the switch is attempting to do a microcode upgrade/downgrade during the initial boot.  This takes an AGE and it will reboot twice, and you don't want to interrupt it as you'll likely brick it and need to recover via the OoB Ethernet interface on the back.

archive download-sw /overwrite

Good luck.



These couple of DOCs will help to better understand the CPU outputs and usage on your C3750 Switch. If you follow both documents it will help you to determine if there is actually a problem on your CPU usage and to establish a baseline of CPU usage on your environment.

Troubleshooting High CPU Utilization (2016)

"Under normal operating conditions, on a non-stackable switch at a minimum, the CPU will have a certain baseline utilization. Depending on the model and the type being used this can range from 5 to 40% If the switch is stacked then, at a minimum, the CPU will operate normally a few percent higher. The number of members in the stack makes a difference on overall CPU utilization. In the stacked switch, the CPU utilization is measured on the master switch only. If the CPU is busy 5% of the time then the CPU is idle the other 95% of the time. The switch will never report CPU utilization at 0%. There are multiple background IOS processes running on timers that execute multiple times a second. This is why even in the simplest of deployments, the switch never reports 0% CPU utilization."

Catalyst 3750 Series Switches High CPU Utilization Troubleshooting (2009)

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