350-401 Network Assurance Practice Question
A network technician is troubleshooting a switch that is experiencing high CPU utilization. The technician runs the command 'show processes cpu sorted' and notices that the process 'ARP Input' is consuming a large percentage of CPU. Which action should the technician take to mitigate this issue?
⚠ Common exam trap
The trap here is thinking that security features like Dynamic ARP Inspection reduce CPU load, but they actually add processing overhead.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Implement ARP rate limiting or ARP policing on the affected interfaces.
High CPU utilization from the ARP Input process is typically caused by a large number of ARP packets being sent to the switch's CPU. Implementing ARP rate limiting or policing on interfaces can control the rate at which ARP packets are processed, preventing the CPU from being overwhelmed. Other options like static ARP entries or increasing cache timeout do not address the volume of ARP traffic. Enabling DAI can worsen the CPU load. Therefore, ARP rate limiting is the most effective mitigation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Implement ARP rate limiting or ARP policing on the affected interfaces.
Why this is correct
ARP rate limiting or policing limits the number of ARP packets processed by the switch's CPU, preventing excessive ARP traffic from overwhelming the control plane. This directly reduces the load on the ARP Input process. It is an effective mitigation for high CPU caused by ARP storms or ARP-based attacks. Configuring this on interfaces facing untrusted hosts can protect the switch.
- ✗
Enable Dynamic ARP Inspection (DAI) on all VLANs.
Why it's wrong here
Dynamic ARP Inspection validates ARP packets in a network, but it does not reduce the CPU load caused by ARP Input process. In fact, enabling DAI can increase CPU utilization because it requires additional processing of ARP packets. DAI is a security feature to prevent ARP spoofing, not a performance optimization tool. Therefore, it would not mitigate high CPU from ARP Input.
- ✗
Configure a static ARP entry for the affected hosts.
Why it's wrong here
Static ARP entries can reduce ARP requests for specific hosts, but they do not address the root cause if the high CPU is due to excessive ARP traffic from many hosts or a malicious source. Static entries are not scalable and would not significantly reduce the ARP Input process load in a large network. Thus, this is not a practical mitigation for the scenario.
- ✗
Increase the ARP cache timeout to reduce ARP requests.
Why it's wrong here
Increasing the ARP cache timeout reduces the frequency of ARP requests for existing entries, but it does not prevent a flood of ARP requests from new or malicious hosts. If the high CPU is due to a large volume of ARP traffic, a longer timeout may not help and could even delay updates. This is not a robust solution for mitigating ARP Input CPU spikes.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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