The answer is ARP spoofing, also known as ARP poisoning. This attack is correct because the workstation exploits the lack of authentication in the ARP protocol (RFC 826) by sending unsolicited ARP replies that map the default gateway IP to its own MAC address. These forged replies poison the ARP caches of other devices on the network, causing them to forward traffic destined for external networks to the attacker’s machine instead of the legitimate gateway. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how Layer 2 attacks disrupt traffic flow, often appearing as a classic “man-in-the-middle” setup. A common trap is confusing this with a MAC flooding attack, which overwhelms switch memory rather than corrupting ARP tables. Remember the key trigger: unsolicited ARP replies that change an IP-to-MAC mapping. For a memory tip, think “ARP Spoof = Spoof the Gateway’s MAC” to keep the core concept clear.
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 observes that a workstation on the network is sending unsolicited ARP replies stating that the workstation's MAC address corresponds to the default gateway IP for all subnets. This behavior is causing other devices to send traffic destined for external networks to the workstation instead of the legitimate gateway. Which type of attack is being performed?
ARP spoofing involves sending fake ARP messages to associate the attacker's MAC with another IP, typically the gateway.
B
B: DHCP starvation
Why wrong: DHCP starvation floods the DHCP server with requests to exhaust the IP pool, preventing legitimate clients from obtaining addresses, but does not involve ARP.
C
C: DNS poisoning
Why wrong: DNS poisoning corrupts DNS cache entries to redirect domain names to incorrect IPs, which operates at a higher layer.
D
D: MAC flooding
Why wrong: MAC flooding sends many frames with different MAC addresses to fill the switch's CAM table, causing it to flood traffic, but it doesn't involve ARP replies claiming the gateway.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A: ARP spoofing
The workstation is sending unsolicited ARP replies that map the default gateway IP to its own MAC address. This poisons the ARP caches of other devices on the network, causing them to forward traffic destined for external networks to the attacker's workstation instead of the legitimate gateway. This is the classic behavior of an ARP spoofing (or ARP poisoning) attack, which exploits the lack of authentication in the ARP protocol (RFC 826).
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.
✓
A: ARP spoofing
Why this is correct
ARP spoofing involves sending fake ARP messages to associate the attacker's MAC with another IP, typically the gateway.
Related concept
Read the scenario before looking for a memorised answer.
✗
B: DHCP starvation
Why it's wrong here
DHCP starvation floods the DHCP server with requests to exhaust the IP pool, preventing legitimate clients from obtaining addresses, but does not involve ARP.
✗
C: DNS poisoning
Why it's wrong here
DNS poisoning corrupts DNS cache entries to redirect domain names to incorrect IPs, which operates at a higher layer.
✗
D: MAC flooding
Why it's wrong here
MAC flooding sends many frames with different MAC addresses to fill the switch's CAM table, causing it to flood traffic, but it doesn't involve ARP replies claiming the gateway.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing ARP spoofing with MAC flooding, because both involve MAC addresses and network interception, but MAC flooding targets the switch's CAM table to capture traffic, while ARP spoofing targets host ARP caches to redirect traffic to a specific MAC address.
Detailed technical explanation
How to think about this question
ARP spoofing works by sending gratuitous ARP replies (or unsolicited ARP announcements) that update the ARP cache of target hosts without a prior request. In a real-world scenario, an attacker can use tools like `arpspoof` (from the dsniff suite) or `ettercap` to perform a man-in-the-middle attack, intercepting all traffic destined for the default gateway. This attack can be mitigated by using dynamic ARP inspection (DAI) on switches, which validates ARP packets against a trusted DHCP snooping binding database.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
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: A: ARP spoofing — The workstation is sending unsolicited ARP replies that map the default gateway IP to its own MAC address. This poisons the ARP caches of other devices on the network, causing them to forward traffic destined for external networks to the attacker's workstation instead of the legitimate gateway. This is the classic behavior of an ARP spoofing (or ARP poisoning) attack, which exploits the lack of authentication in the ARP protocol (RFC 826).
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.