I have 200mb live traffic running on Cisco 3845 router. But from past few days CPU utilization is going very high(80%).
Normal cpu utilization was upto 20% earlier.
I am not able to find out why utilization is going this high.
Well, if shifting traffic away from the router has brought the CPU down, then the high CPU was likely due to the traffic itself.
As a personal rule, I try to avoid having a 3845 deal with more than 100 Mbps. Normally, I would expect 200 Mbps to peg the CPU of a 3845.
The real question was whether your high CPU was almost all interrupt usage, normally indicating optimal performance, or whether there was another process driving the high CPU, like IP Input. The latter can sometimes be corrected allowing a higher forwarding rate.