- A
MAC flooding; port security
Why wrong: MAC flooding overwhelms the switch MAC table but does not involve forging ARP replies.
- B
ARP poisoning; Dynamic ARP Inspection (DAI)
DAI trusts only ARP responses that match a valid IP-to-MAC binding, preventing ARP spoofing.
- C
DHCP starvation; DHCP snooping
Why wrong: DHCP starvation exhausts the DHCP server's address pool; DHCP snooping prevents rogue DHCP servers, not ARP attacks.
- D
DNS poisoning; DNSSEC
Why wrong: DNS poisoning targets the DNS cache, not ARP messages.
Question 408 of 520
ARP Poisoning Detection and Prevention
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.
A security analyst discovers that users on the network are receiving ARP replies that map the default gateway IP address to an unknown MAC address. This is causing intermittent connectivity issues. Which type of attack is occurring, and what security feature should be implemented to prevent it?
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
✓
ARP poisoning; Dynamic ARP Inspection (DAI)
This attack is ARP poisoning (also called ARP spoofing), where an attacker sends forged ARP replies to associate the default gateway's IP address with the attacker's MAC address. This allows the attacker to intercept, modify, or drop traffic intended for the gateway. Dynamic ARP Inspection (DAI) prevents this by validating ARP packets against a trusted DHCP snooping binding table, dropping any ARP reply that contains an IP-to-MAC mapping not present in the table.
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.
- ✗
MAC flooding; port security
Why it's wrong here
MAC flooding overwhelms the switch MAC table but does not involve forging ARP replies.
When this WOULD be correct
A question describing a switch receiving thousands of fake MAC addresses, causing it to fail open and flood traffic to all ports, where the solution is port security to limit MAC addresses per port.
- ✓
ARP poisoning; Dynamic ARP Inspection (DAI)
- ✗
DHCP starvation; DHCP snooping
Why it's wrong here
DHCP starvation exhausts the DHCP server's address pool; DHCP snooping prevents rogue DHCP servers, not ARP attacks.
When this WOULD be correct
A question describing users unable to obtain IP addresses due to a rogue DHCP server exhausting the address pool, asking which attack and which mitigation (e.g., DHCP snooping) would be correct.
- ✗
DNS poisoning; DNSSEC
When this WOULD be correct
This option would be correct if the question described users being redirected to malicious websites despite typing correct URLs, or if it mentioned DNS cache poisoning causing domain name resolution to point to a rogue server.
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.
✓ARP poisoning; Dynamic ARP Inspection (DAI)Correct answer▾
Why this is correct
DAI trusts only ARP responses that match a valid IP-to-MAC binding, preventing ARP spoofing.
✗MAC flooding; port securityWrong answer — click to see why▾
Why this is wrong here
The question describes ARP replies mapping the default gateway IP to an unknown MAC, which is ARP poisoning, not MAC flooding. MAC flooding overwhelms a switch's MAC table to force fail-open mode, causing frames to flood, but does not involve spoofing ARP replies.
★ When this WOULD be the correct answer
A question describing a switch receiving thousands of fake MAC addresses, causing it to fail open and flood traffic to all ports, where the solution is port security to limit MAC addresses per port.
Why candidates choose this
Candidates confuse ARP poisoning with MAC flooding because both involve MAC addresses and network attacks, and port security is a common security feature, leading to a mistaken association.
✗DHCP starvation; DHCP snoopingWrong answer — click to see why▾
Why this is wrong here
The question describes ARP replies mapping the default gateway IP to an unknown MAC, which is ARP poisoning, not DHCP starvation. DHCP starvation exhausts IP addresses, not ARP mappings.
★ When this WOULD be the correct answer
A question describing users unable to obtain IP addresses due to a rogue DHCP server exhausting the address pool, asking which attack and which mitigation (e.g., DHCP snooping) would be correct.
Why candidates choose this
Candidates may confuse network-layer attacks involving spoofing or exhaustion, and DHCP starvation is a common attack that also uses spoofed messages, leading to misidentification.
✗DNS poisoning; DNSSECWrong answer — click to see why▾
Why this is wrong here
DNS poisoning manipulates DNS records, not ARP tables. The question describes ARP replies mapping a gateway IP to a wrong MAC, which is ARP poisoning, not DNS poisoning.
★ When this WOULD be the correct answer
This option would be correct if the question described users being redirected to malicious websites despite typing correct URLs, or if it mentioned DNS cache poisoning causing domain name resolution to point to a rogue server.
Why candidates choose this
Candidates may confuse network-layer attacks (ARP) with application-layer attacks (DNS), both involving mapping IPs to wrong destinations, leading them to select DNS poisoning when the symptoms involve IP-to-MAC mapping.
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 the distinction between Layer 2 attacks (ARP poisoning, MAC flooding) and Layer 3/4 attacks (DHCP starvation, DNS poisoning), so candidates mistakenly choose DHCP starvation or DNS poisoning because they involve 'spoofing' or 'poisoning' without recognizing that the symptom—ARP replies mapping the gateway IP to an unknown MAC—is a direct indicator of ARP manipulation.
Detailed technical explanation
How to think about this question
ARP poisoning exploits the stateless nature of ARP—hosts accept unsolicited ARP replies (gratuitous ARPs) without verification. DAI relies on DHCP snooping to build a binding table of legitimate IP-MAC pairs; on untrusted ports, DAI intercepts all ARP packets and compares the sender MAC and IP against this table, dropping any mismatch. In a real-world scenario, an attacker on a guest VLAN could poison the default gateway ARP cache of all clients, performing a man-in-the-middle attack to capture credentials before forwarding traffic to the real gateway.
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
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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: ARP poisoning; Dynamic ARP Inspection (DAI) — This attack is ARP poisoning (also called ARP spoofing), where an attacker sends forged ARP replies to associate the default gateway's IP address with the attacker's MAC address. This allows the attacker to intercept, modify, or drop traffic intended for the gateway. Dynamic ARP Inspection (DAI) prevents this by validating ARP packets against a trusted DHCP snooping binding table, dropping any ARP reply that contains an IP-to-MAC mapping not present in the table.
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 →
Same concept, more angles
3 more ways 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 network security analyst notices high CPU utilization on the core switch and detects a large volume of ARP replies from a single IP address that claims to be the default gateway for all local subnets. Which type of attack is MOST likely occurring?
medium- ✓ A.ARP poisoning
- B.DHCP starvation
- C.MAC flooding
- D.DNS amplification
Why A: The attack described is ARP poisoning (also known as ARP spoofing), where an attacker sends forged ARP replies to associate their MAC address with the IP address of the default gateway. This causes all traffic destined for other subnets to be redirected to the attacker's machine, leading to high CPU utilization on the switch as it processes the flood of ARP packets and forwards the intercepted traffic.
Variation 2. A security analyst discovers that an unauthorized device is sending forged ARP replies to poison the ARP caches of other devices on the network. Which security feature should be implemented on the switches to prevent this?
medium- A.Port security
- B.DHCP snooping
- ✓ C.Dynamic ARP Inspection
- D.STP BPDU guard
Why C: Dynamic ARP Inspection (DAI) validates ARP packets on a per-interface basis by intercepting all ARP requests and replies and verifying that they match entries in the DHCP snooping binding table. If an ARP reply contains a forged IP-to-MAC mapping, DAI drops the packet, preventing ARP cache poisoning. This directly stops the described attack where an unauthorized device sends forged ARP replies.
Variation 3. A security analyst discovers that an unauthorized device is sending forged ARP replies, causing other devices to map the default gateway IP address to the attacker's MAC address. Which security feature should be implemented on the switches to prevent this attack?
medium- A.Port security
- B.DHCP snooping
- ✓ C.Dynamic ARP Inspection
- D.BPDU guard
Why C: Dynamic ARP Inspection (DAI) is the correct choice because it validates ARP packets on a per-port basis, ensuring that only legitimate ARP replies with correct IP-to-MAC bindings are forwarded. DAI uses a DHCP snooping binding table (or static ARP ACLs) to intercept and verify ARP packets, dropping forged replies that attempt to poison the ARP cache of other devices.
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Last reviewed: Jun 30, 2026
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