High CPU utilization

 High CPU utilization means a device's processor is spending most of its time working instead of being idle.

In networking (CCNA context), this can happen on routers, switches, firewalls, or servers.

What does it mean?

CPU utilization is the percentage of CPU resources being used.

Example:

CPU Usage

Meaning

10–30%

Normal / Healthy

30–60%

Moderate load

60–80%

High load

80–100%

Very high / Potential problem

If a router shows 95% CPU usage, the CPU is busy 95% of the time.

Symptoms of High CPU Utilization

You may notice:

  • Slow response to pings

  • CLI becomes sluggish

  • Routing protocol instability

  • Packet drops

  • High latency

  • Interface queues filling up

  • Users complaining that the network is slow

  • Device reboots or crashes (in severe cases)

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