- A
Port security
Why wrong: Port security limits the number of MAC addresses on a port but does not throttle DHCP requests or prevent DHCP starvation.
- B
DHCP snooping
DHCP snooping includes rate limiting and filters DHCP messages on untrusted ports, effectively preventing DHCP starvation and rogue DHCP servers.
- C
Dynamic ARP Inspection (DAI)
Why wrong: DAI validates ARP packets to prevent man-in-the-middle attacks but does not address DHCP starvation.
- D
802.1X
Why wrong: 802.1X provides network access control based on authentication, but it does not prevent DHCP starvation attacks.
Question 391 of 520
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An attacker is launching a DHCP starvation attack by sending a large number of DHCP discover messages with spoofed MAC addresses. This exhausts the DHCP pool and causes legitimate clients to fail to obtain IP addresses. Which security feature should be implemented on the switch to mitigate this attack?
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
✓
DHCP snooping
DHCP snooping is the correct mitigation because it filters untrusted DHCP messages on access ports. By default, it only allows DHCP server responses (OFFER, ACK, etc.) on trusted ports (typically uplinks to the legitimate DHCP server) and drops them on untrusted ports, preventing a rogue or spoofed server from replying. Additionally, DHCP snooping builds a DHCP snooping binding table that tracks valid MAC-to-IP address mappings, which can be used to rate-limit DHCP discover messages and detect starvation attacks.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 limits the number of MAC addresses on a port but does not throttle DHCP requests or prevent DHCP starvation.
When this WOULD be correct
Port security would be correct in a scenario where an attacker connects a rogue switch or device to flood the network with many MAC addresses to overflow the MAC address table (CAM table overflow attack).
- ✓
DHCP snooping
Why this is correct
DHCP snooping includes rate limiting and filters DHCP messages on untrusted ports, effectively preventing DHCP starvation and rogue DHCP servers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Dynamic ARP Inspection (DAI)
Why it's wrong here
DAI validates ARP packets to prevent man-in-the-middle attacks but does not address DHCP starvation.
When this WOULD be correct
DAI would be correct in a scenario where an attacker is sending forged ARP replies to associate their MAC address with the IP address of a legitimate device (e.g., default gateway) to intercept traffic.
- ✗
802.1X
Why it's wrong here
802.1X provides network access control based on authentication, but it does not prevent DHCP starvation attacks.
When this WOULD be correct
802.1X would be the correct answer for a question asking which feature prevents unauthorized devices from connecting to the network by requiring authentication before granting access, such as in a scenario where the goal is to block rogue devices from using the network.
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.
✓DHCP snoopingCorrect answer▾
Why this is correct
DHCP snooping includes rate limiting and filters DHCP messages on untrusted ports, effectively preventing DHCP starvation and rogue DHCP servers.
✗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 DHCP messages or prevent DHCP pool exhaustion from spoofed MAC addresses.
★ When this WOULD be the correct answer
Port security would be correct in a scenario where an attacker connects a rogue switch or device to flood the network with many MAC addresses to overflow the MAC address table (CAM table overflow attack).
Why candidates choose this
Candidates may confuse port security's MAC address limiting with DHCP snooping's ability to rate-limit DHCP messages, thinking both prevent spoofing without understanding the specific attack vector.
✗Dynamic ARP Inspection (DAI)Wrong answer — click to see why▾
Why this is wrong here
Dynamic ARP Inspection (DAI) validates ARP packets to prevent ARP spoofing and man-in-the-middle attacks, but it does not prevent DHCP starvation attacks, which target DHCP address exhaustion.
★ When this WOULD be the correct answer
DAI would be correct in a scenario where an attacker is sending forged ARP replies to associate their MAC address with the IP address of a legitimate device (e.g., default gateway) to intercept traffic.
Why candidates choose this
Candidates may confuse DAI with DHCP snooping because both are security features that inspect network traffic and are often implemented together on switches.
✗802.1XWrong answer — click to see why▾
Why this is wrong here
802.1X is an authentication protocol that controls network access at the port level, but it does not prevent DHCP starvation attacks because it does not monitor or rate-limit DHCP messages.
★ When this WOULD be the correct answer
802.1X would be the correct answer for a question asking which feature prevents unauthorized devices from connecting to the network by requiring authentication before granting access, such as in a scenario where the goal is to block rogue devices from using the network.
Why candidates choose this
Candidates may think 802.1X can mitigate DHCP starvation by blocking spoofed MAC addresses, but it only authenticates users, not DHCP message flooding.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests DHCP snooping as the answer for DHCP starvation attacks, but candidates confuse it with DAI because both rely on the DHCP snooping binding table, forgetting that DAI only validates ARP packets, not DHCP messages.
Detailed technical explanation
How to think about this question
DHCP snooping operates by classifying switch ports as trusted or untrusted; by default, all ports are untrusted. On untrusted ports, DHCP snooping drops all DHCP server messages (OFFER, ACK, NAK) and enforces a rate limit on DHCP client messages (DISCOVER, REQUEST, DECLINE, RELEASE) to prevent starvation. The DHCP snooping binding table also records the client MAC address, IP address, lease time, and port/VLAN, which can be used by DAI and IP Source Guard for additional security. In a real-world scenario, an attacker could use a tool like Yersinia to send thousands of DHCP discovers per second; without rate-limiting, the DHCP server's pool would be exhausted within seconds.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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 |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DHCP snooping — DHCP snooping is the correct mitigation because it filters untrusted DHCP messages on access ports. By default, it only allows DHCP server responses (OFFER, ACK, etc.) on trusted ports (typically uplinks to the legitimate DHCP server) and drops them on untrusted ports, preventing a rogue or spoofed server from replying. Additionally, DHCP snooping builds a DHCP snooping binding table that tracks valid MAC-to-IP address mappings, which can be used to rate-limit DHCP discover messages and detect starvation attacks.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 30, 2026
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