Which option is the best for protecting CPU utilization on a device?

Fragmentation is the process of breaking packets into smaller units and is a standard network function that can increase, not decrease, CPU load due to reassembly overhead.

CoPP (Control Plane Policing) allows administrators to define QoS policies to classify, rate-limit, and drop traffic that is destined for the router's control plane CPU. This protects the router's core functions from being overwhelmed by denial-of-service attacks, routing protocol floods, or excessive management traffic, ensuring the device remains stable and operational.

ICMP redirects are diagnostic messages used by routers to inform hosts about a better path to a destination, not a mechanism to protect CPU utilization.

ICMP unreachable messages are sent to indicate that a destination is inaccessible and are a symptom of network issues, not a preventative measure for CPU overload.