- A
Layer 3 – Network
Why wrong: Network layer handles routing and IP addressing; ARP is not at Layer 3.
- B
Layer 1 – Physical
Why wrong: Physical layer deals with raw bit transmission over physical media.
- C
Layer 4 – Transport
Why wrong: Transport layer manages end-to-end connections and data flow.
- D
Layer 2 – Data Link
ARP operates at Layer 2, and ARP spoofing manipulates MAC-to-IP mappings.
Question 660 of 1,000
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and 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 observes a network attack where an attacker sends forged ARP messages to associate the attacker's MAC address with the IP address of the default gateway. This attack occurs at which layer of the OSI model?
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
✓
Layer 2 – Data Link
ARP operates at Layer 2 (Data Link) because it maps IP addresses (Layer 3) to MAC addresses (Layer 2) and is encapsulated directly within an Ethernet frame, not an IP packet. The attack described—ARP spoofing—forges ARP replies to poison the target's ARP cache, which is a Layer 2 function. Therefore, the attack occurs at Layer 2 of the OSI model.
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.
- ✗
Layer 3 – Network
Why it's wrong here
Network layer handles routing and IP addressing; ARP is not at Layer 3.
- ✗
Layer 1 – Physical
Why it's wrong here
Physical layer deals with raw bit transmission over physical media.
- ✗
Layer 4 – Transport
Why it's wrong here
Transport layer manages end-to-end connections and data flow.
- ✓
Layer 2 – Data Link
Why this is correct
ARP operates at Layer 2, and ARP spoofing manipulates MAC-to-IP mappings.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates see 'IP address' in the question and incorrectly associate it with Layer 3 (Network), forgetting that ARP is a Layer 2 protocol that resolves Layer 3 addresses to Layer 2 addresses.
Detailed technical explanation
How to think about this question
ARP spoofing works by sending unsolicited ARP replies (gratuitous ARP) to poison the victim's ARP cache, causing frames destined for the gateway to be sent to the attacker's MAC address. This enables man-in-the-middle attacks at Layer 2, where the attacker can intercept, modify, or drop traffic without any IP-level detection. Tools like `arpspoof` (from the dsniff suite) or `ettercap` automate this by continuously sending forged ARP packets.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this CISSP question test?
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Layer 2 – Data Link — ARP operates at Layer 2 (Data Link) because it maps IP addresses (Layer 3) to MAC addresses (Layer 2) and is encapsulated directly within an Ethernet frame, not an IP packet. The attack described—ARP spoofing—forges ARP replies to poison the target's ARP cache, which is a Layer 2 function. Therefore, the attack occurs at Layer 2 of the OSI model.
What should I do if I get this CISSP 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.
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Last reviewed: Jul 4, 2026
This CISSP practice question is part of Courseiva's free ISC2 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 CISSP exam.
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