How can I be sure that the CPU high usage is due to heavy traffic loading?

Zyxel_Charlie

How can I be sure that the CPU high usage is due to heavy traffic loading?

Use the command line "debug system show cpu status" to see the CPU usage details. Refer to the screenshot below wherein "softirq" means that the CPU is occupied with traffic load.

On the other hand if the CPU is occupied with a system item, users can type "debug system ps" to check the process status.

Once confirmed that it is "softirq", go to Monitor > Traffic statistics to see the traffic loading of each interface. The statistics show the amount and not real-time data. When CPU high usage is encountered, users can flush data first then switch to every interface to see which IPs have heavy loads. 

In this case, the IP 10.10.10.2 has uploaded a lot of packets. Set the BWM on this IP to restrict the traffic and decrease the loading of the device.