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Yes, it might be some traffic directed to the switch, rather than traffic through the switch, that causes the switch's CPU to jump. This because the switch usually has special hardware for dealing with transit traffic.
However, there are internal processing events that can cause the CPU to jump. There's also situations where, for some reason, the special hardware that normally handles transit traffic sends that traffic to the CPU for processing.
As Mark has noted, CPU process usage stats often provide insight into the cause of CPU usage.
