ARP Spoofing Attacks and Dynamic ARP Inspection (DAI) Mitigation
A security analyst receives an alert that an internal user's workstation is sending a high volume of ARP requests for multiple IP addresses on the local subnet. The analyst suspects a man-in-the-middle attack. Which security mechanism is most effective at mitigating this type of attack on a switched network?
Quick Answer
Dynamic ARP Inspection (DAI) is the correct choice because it actively validates ARP packets against a trusted binding table built by DHCP snooping, dropping any spoofed replies that attempt to associate an attacker’s MAC address with a legitimate host’s IP. This directly prevents man-in-the-middle attacks on a switched network by ensuring only authorized ARP responses are forwarded. On the CompTIA Network+ N10-009 exam, this scenario often appears as a high-volume ARP request alert, testing your ability to distinguish DAI from other mitigations like port security or MAC filtering—both of which fail to inspect ARP content. A common trap is choosing "static ARP entries," but DAI dynamically enforces trust. Memory tip: DAI = "Drop ARP Imposters" by checking the DHCP snooping database.
⚠ Common exam trap
The N10-009 exam often tests the distinction between DHCP snooping and DAI, where candidates mistakenly choose DHCP snooping because it builds the binding table, but DAI is the actual mechanism that validates ARP packets to prevent man-in-the-middle attacks.
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
✓
Dynamic ARP Inspection
Dynamic ARP Inspection (DAI) is the correct answer because it validates ARP packets on a switched network, ensuring that only legitimate ARP replies are forwarded. In a man-in-the-middle attack, an attacker sends spoofed ARP replies to associate their MAC address with the IP address of a legitimate host. DAI intercepts all ARP packets and compares them against a trusted binding table (built by DHCP snooping), dropping any that are invalid, thus preventing ARP spoofing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Port security
Why it's wrong here
Port security restricts the number of MAC addresses per port but does not inspect ARP packets.
When this WOULD be correct
Port security would be correct in a question about preventing unauthorized devices from connecting to a switch port by limiting MAC addresses, such as 'Which feature restricts the number of MAC addresses learned on a port to prevent MAC flooding?'
- ✗
DHCP snooping
Why it's wrong here
DHCP snooping filters rogue DHCP servers and builds a binding table, but does not directly validate ARP traffic.
When this WOULD be correct
DHCP snooping would be the correct answer if the question described a scenario where a rogue DHCP server is assigning malicious IP configurations to clients, enabling man-in-the-middle attacks via DHCP spoofing.
- ✓
Dynamic ARP Inspection
Why this is correct
DAI uses the DHCP snooping binding table to validate ARP packets and block spoofed ARP messages.
- ✗
MAC address filtering
Why it's wrong here
MAC filtering controls which MAC addresses are allowed, but does not prevent ARP spoofing.
When this WOULD be correct
MAC address filtering would be correct in a scenario where the question asks for a mechanism to prevent unauthorized devices from connecting to the network by limiting access based on MAC addresses, such as in a small office with a static device list.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Dynamic ARP InspectionCorrect answer▾
Why this is correct
DAI uses the DHCP snooping binding table to validate ARP packets and block spoofed ARP messages.
✗Port securityWrong answer — click to see why▾
Why this is wrong here
Port security limits the number of MAC addresses per port but does not inspect ARP packets, so it cannot prevent ARP spoofing or man-in-the-middle attacks.
★ When this WOULD be the correct answer
Port security would be correct in a question about preventing unauthorized devices from connecting to a switch port by limiting MAC addresses, such as 'Which feature restricts the number of MAC addresses learned on a port to prevent MAC flooding?'
Why candidates choose this
Candidates may think port security prevents all MAC-based attacks, confusing MAC address limiting with ARP inspection.
✗DHCP snoopingWrong answer — click to see why▾
Why this is wrong here
DHCP snooping filters DHCP messages to prevent rogue DHCP servers, but it does not inspect ARP traffic. The attack described involves ARP spoofing, which Dynamic ARP Inspection (DAI) directly mitigates by validating ARP packets against the DHCP snooping binding table.
★ When this WOULD be the correct answer
DHCP snooping would be the correct answer if the question described a scenario where a rogue DHCP server is assigning malicious IP configurations to clients, enabling man-in-the-middle attacks via DHCP spoofing.
Why candidates choose this
Candidates may confuse DHCP snooping with ARP inspection because both rely on the same binding table and are often implemented together, leading to the mistaken belief that DHCP snooping alone can prevent ARP-based attacks.
✗MAC address filteringWrong answer — click to see why▾
Why this is wrong here
MAC address filtering restricts which MAC addresses can communicate on a port, but it does not prevent ARP spoofing or man-in-the-middle attacks because an attacker can spoof a legitimate MAC address.
★ When this WOULD be the correct answer
MAC address filtering would be correct in a scenario where the question asks for a mechanism to prevent unauthorized devices from connecting to the network by limiting access based on MAC addresses, such as in a small office with a static device list.
Why candidates choose this
Candidates may confuse MAC address filtering with a security measure against ARP attacks, as both involve MAC addresses, but filtering does not validate ARP packets or prevent spoofing.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
Network Device Hardening
Key term
Dynamic ARP Inspection
Dynamic ARP Inspection is a security feature that validates ARP packets on a network to prevent man-in-the-middle attacks by ensuring that only legitimate ARP messages are forwarded.
Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
About these practice questions
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Same concept, more angles
1 more way this is tested on N10-009
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security analyst detects that an attacker is sending forged ARP replies to associate the attacker's MAC address with the IP address of the default gateway. What is this attack called?
hard- ✓ A.ARP poisoning
- B.MAC flooding
- C.DHCP snooping
- D.DNS spoofing
Why A: ARP poisoning (also known as ARP spoofing) is the correct answer because the attacker sends forged ARP replies to associate their MAC address with the IP address of the default gateway. This causes the victim's switch to update its ARP cache with the attacker's MAC for the gateway's IP, enabling man-in-the-middle attacks where the attacker intercepts traffic destined for the gateway.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the N10-009 exam.