- A
A: ARP spoofing
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.
Question 231 of 520
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?
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
✓
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
- ✗
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.
When this WOULD be correct
A DHCP starvation attack would be correct if the question described an attacker sending numerous DHCPDISCOVER messages to exhaust the DHCP server's address pool, preventing legitimate clients from obtaining IP addresses.
- ✗
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.
When this WOULD be correct
A question where users report being redirected to a phishing site when typing a legitimate domain name, and the attack is traced to a compromised DNS server or cache poisoning.
- ✗
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.
When this WOULD be correct
A security analyst notices that the switch's MAC address table is full and the switch begins flooding unicast traffic to all ports. Which attack is being performed?
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.
✓A: ARP spoofingCorrect answer▾
Why this is correct
ARP spoofing involves sending fake ARP messages to associate the attacker's MAC with another IP, typically the gateway.
✗B: DHCP starvationWrong answer — click to see why▾
Why this is wrong here
DHCP starvation floods a DHCP server with requests to exhaust its IP address pool, causing denial of service. The question describes unsolicited ARP replies mapping the attacker's MAC to the gateway IP, which is ARP spoofing, not DHCP-related.
★ When this WOULD be the correct answer
A DHCP starvation attack would be correct if the question described an attacker sending numerous DHCPDISCOVER messages to exhaust the DHCP server's address pool, preventing legitimate clients from obtaining IP addresses.
Why candidates choose this
Candidates may confuse DHCP starvation with ARP spoofing because both involve network-layer manipulation and can disrupt traffic flow, but they target different protocols (DHCP vs. ARP).
✗C: DNS poisoningWrong answer — click to see why▾
Why this is wrong here
DNS poisoning involves corrupting DNS resolver caches to redirect domain names to malicious IPs, not manipulating ARP tables with unsolicited replies for the default gateway IP.
★ When this WOULD be the correct answer
A question where users report being redirected to a phishing site when typing a legitimate domain name, and the attack is traced to a compromised DNS server or cache poisoning.
Why candidates choose this
Candidates may confuse 'poisoning' attacks (ARP vs. DNS) and think any redirection of traffic involves DNS, overlooking the Layer 2 ARP mechanism described.
✗D: MAC floodingWrong answer — click to see why▾
Why this is wrong here
MAC flooding involves sending many frames with different source MAC addresses to overflow the switch's MAC address table, causing it to fail open and broadcast traffic. The question describes unsolicited ARP replies, not MAC table overflow.
★ When this WOULD be the correct answer
A security analyst notices that the switch's MAC address table is full and the switch begins flooding unicast traffic to all ports. Which attack is being performed?
Why candidates choose this
Candidates may confuse MAC flooding with ARP spoofing because both involve manipulating network traffic, but MAC flooding targets the switch's forwarding table rather than ARP caches.
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
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.
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
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: 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
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Last reviewed: Jun 11, 2026
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