- A
They provide encryption of network traffic
Why wrong: VLANs do not encrypt traffic; they segregate it.
- B
They allow logical grouping of devices regardless of physical location
VLANs group devices based on configuration, not physical location.
- C
They can reduce broadcast traffic
Each VLAN is a separate broadcast domain, limiting broadcasts.
- D
They eliminate the need for firewalls
Why wrong: VLANs do not replace firewalls; they are a layer 2 segmentation tool.
- E
They provide inherent protection against ARP spoofing
Why wrong: VLANs do not prevent ARP spoofing within the same VLAN.
Question 645 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 team is reviewing network segmentation strategies. Which TWO of the following are benefits of using VLANs? (Select TWO.)
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
✓
They allow logical grouping of devices regardless of physical location
VLANs operate at Layer 2 (Data Link Layer) and allow network administrators to segment devices into distinct broadcast domains based on logical criteria such as department or function, regardless of their physical location on the network. This logical grouping reduces the scope of broadcast traffic because broadcasts are confined to the VLAN, not the entire physical network. By containing broadcasts, VLANs improve network performance and security by limiting unnecessary traffic and isolating potential threats.
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.
- ✗
They provide encryption of network traffic
Why it's wrong here
VLANs do not encrypt traffic; they segregate it.
- ✓
They allow logical grouping of devices regardless of physical location
Why this is correct
VLANs group devices based on configuration, not physical location.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
They can reduce broadcast traffic
Why this is correct
Each VLAN is a separate broadcast domain, limiting broadcasts.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
They eliminate the need for firewalls
Why it's wrong here
VLANs do not replace firewalls; they are a layer 2 segmentation tool.
- ✗
They provide inherent protection against ARP spoofing
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse VLANs with security mechanisms like encryption or firewalls, mistakenly believing VLANs provide confidentiality or replace perimeter defenses, when in fact VLANs only offer logical segmentation at Layer 2.
Detailed technical explanation
How to think about this question
VLANs use IEEE 802.1Q tagging to insert a 4-byte VLAN tag into Ethernet frames, allowing switches to identify and forward frames to the correct VLAN. A subtle behavior is that VLAN Trunking Protocol (VTP) can propagate VLAN configurations across switches, but misconfiguration can lead to VLAN hopping attacks if trunk ports are not properly secured. In a real-world scenario, a company with multiple floors can place all HR devices in VLAN 10 regardless of their physical switch ports, reducing broadcast traffic and simplifying access control policies.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Visual reference
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: They allow logical grouping of devices regardless of physical location — VLANs operate at Layer 2 (Data Link Layer) and allow network administrators to segment devices into distinct broadcast domains based on logical criteria such as department or function, regardless of their physical location on the network. This logical grouping reduces the scope of broadcast traffic because broadcasts are confined to the VLAN, not the entire physical network. By containing broadcasts, VLANs improve network performance and security by limiting unnecessary traffic and isolating potential threats.
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.
About these practice questions
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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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