I have a cisco 2960 PoE 24 port switch. Adding 12 pcs cisco Aironet 1142 AP is running ok but when i try to add more....... that time switch Fan speed going high......& also disconnect additional AP , its some time runing up or down.
## sh processes memory sorted
Processor Pool Total: 33872160 Used: 9969056 Free: 23903104
I/O Pool Total: 4194304 Used: 1652372 Free: 2541932
Driver te Pool Total: 1048576 Used: 40 Free: 1048536
#sh processes cpu
CPU utilization for five seconds: 5%/0%; one minute: 5%; five minutes: 5%
24 APs will bring your Power-Supply of the switch to its maximum limit.
The 2960-24PC-S is able to deliver 370Watts of PoE Power which is 15.4 Watts per Port (full 802.3af-Power)
In the Docu for AP1140-Series you can find:
Note: When deployed using PoE, the power drawn from the power sourcing equipment will be higher by some amount dependent on the length of the interconnecting cable. This additional power may be as high as 2.45W, bringing the total system power draw (access point + cabling) to 15.4W.
Check if the environmental temperature is Ok... Check if all Fans are running - especially if the switch runs in dusty environment.
What is sh env all telling you?
You can also see how much power is available/used/remaining with show power inline.
I think your problem is related on power/temperature....
At normal fan speed, the 24PC can easily support up to 10 (or so) powered device of 15.4w. The same model can support up to 24 powered device (of 15.4 w) and you'll hear the fan strain (like a vacuum cleaner) because of the extra heat the components have to generate.
It will get even worst if the place where your switch is installed doesn't have adequate ventilation/cooling and/or when it's dusty.
CPU utilization will depend entirely on the IOS version.