CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Refer to the exhibit. A security team is reviewing switch configurations and notices that the native VLAN is set to VLAN 10. An attacker on an access port in VLAN 10 sends a frame with a VLAN tag of VLAN 20 inside another frame. Which type of attack does this configuration make possible?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
VLAN hopping via double tagging
The configuration with native VLAN 10 allows an attacker on an access port in VLAN 10 to craft a frame with an outer 802.1Q tag for VLAN 20 and an inner tag for VLAN 10. When the switch receives this frame on a trunk port, it strips the outer tag (native VLAN) and forwards the inner tag, causing the frame to hop into VLAN 20. This is the classic VLAN hopping via double tagging attack, exploiting the native VLAN behavior.
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.
✗
DHCP starvation
Why it's wrong here
DHCP starvation exhausts IP addresses; not related to VLAN hopping.
✓
VLAN hopping via double tagging
Why this is correct
Double tagging is possible when the native VLAN is used on trunk ports; the attacker can send frames with two tags to hop VLANs.
Related concept
Read the scenario before looking for a memorised answer.
✗
ARP spoofing
Why it's wrong here
ARP spoofing manipulates ARP tables; not related to VLAN tagging.
✗
MAC flooding
Why it's wrong here
MAC flooding attempts to overflow the CAM table, not related to native VLAN manipulation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that VLAN hopping only occurs via DTP (Dynamic Trunking Protocol) negotiation, but double tagging is a separate attack that exploits the native VLAN behavior on trunk ports.
Detailed technical explanation
How to think about this question
Double tagging works because switches on trunk ports strip only the outer 802.1Q tag when the frame arrives on the native VLAN (untagged by default), then forward the frame with the inner tag intact to the destination VLAN. This bypasses VLAN segmentation even if the trunk is configured to disallow the attacker's native VLAN; the attack succeeds because the first switch does not re-tag the native VLAN frame. In real-world scenarios, this attack is mitigated by setting the native VLAN to an unused VLAN and explicitly tagging it on all trunk ports.
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 team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
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: VLAN hopping via double tagging — The configuration with native VLAN 10 allows an attacker on an access port in VLAN 10 to craft a frame with an outer 802.1Q tag for VLAN 20 and an inner tag for VLAN 10. When the switch receives this frame on a trunk port, it strips the outer tag (native VLAN) and forwards the inner tag, causing the frame to hop into VLAN 20. This is the classic VLAN hopping via double tagging attack, exploiting the native VLAN behavior.
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
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 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.
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.