"The Catalyst 3750-X switches have a CPU utilization level that is higher than the previous models of the
Catalyst 3750 switches. This is normal behavior. One can expect that the
overall CPU utilization will be between 25 - 35%. Plugging PoE devices into all ports on a 3750-X switch will cause the CPU utilization to increase however it will remain in the normal 25 - 35% range. Since almost all of the
packet forwarding is done in hardware and not by the CPU a CPU utilization of 25 - 35% should not be cause for concern. " This issue has been observed in 3560X/3750X with PoE, running 12.2(53)SE1 release and higher."
On the 3750X switch the normal CPU utilization without connections should not be more than 5% however on image
12.2(53)SE and later the CPU could be 15%-30% due to HULC LED process.
The details are mentioned in the bug CSCtn42790.
It is an expected behavior and it does not affect the traffic flow.