hardMultiple Choice
ISC2 CC Practice Question: A security auditor discovers that during a VLAN…
A security auditor discovers that during a VLAN hopping attack, a threat actor was able to send frames from a workstation on VLAN 10 to a target on VLAN 20. Which configuration flaw is most likely responsible?
⚠ Common exam trap
ISC2 often tests the distinction between VLAN hopping via DTP (trunk negotiation) and double-tagging attacks (native VLAN manipulation), so candidates may confuse the two and incorrectly choose the native VLAN option.
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
✓
Dynamic Trunking Protocol (DTP) is enabled on access ports
A VLAN hopping attack exploits the Dynamic Trunking Protocol (DTP) to negotiate a trunk link between the attacker's workstation and the switch. If DTP is enabled on an access port, the attacker can send DTP frames to form a trunk, allowing frames from VLAN 10 to be tagged and forwarded to VLAN 20. Disabling DTP on all access ports with the 'switchport nonegotiate' command prevents this attack.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Dynamic Trunking Protocol (DTP) is enabled on access ports
Why this is correct
DTP negotiates trunk links automatically; an access port left in dynamic auto or desirable mode can be persuaded to form a trunk, letting the attacker send 802.1Q-tagged frames that reach VLAN 20. Disabling DTP and hard-setting access mode prevents this VLAN hopping path.
- ✗
The trunk port is set to native VLAN 1
Why it's wrong here
A native VLAN 1 trunk lets untagged frames from VLAN 10 be placed into VLAN 1, but reaching VLAN 20 requires double-tagging or DTP negotiation, so this alone does not explain the crossing. It is tempting because native VLAN mismatches are a documented hopping vector, and setting the native VLAN to an unused ID is correct when that mismatch is the actual flaw.
- ✗
The switch is using default VLAN 1 for management
Why it's wrong here
Using VLAN 1 for management does not itself permit cross-VLAN frame delivery; hopping stems from 802.1Q double-tagging or trunk negotiation, not the management VLAN ID. It is tempting because VLAN 1 is the default and widely flagged as a hardening concern, and changing the native/management VLAN is correct when the flaw is native VLAN mismatch on a trunk.
- ✗
Port security is not configured
Why it's wrong here
Port security restricts MAC addresses on an access port but does not prevent 802.1Q double-tagging, which is the mechanism enabling frames to reach another VLAN. It is tempting because port security hardens switch access; however, disabling trunk negotiation or setting the native VLAN to an unused ID addresses the actual flaw.
Visual reference
Go deeper
Related to this question
Key term
Threat
A threat is any potential danger that could harm a computer system, network, or data, whether from a malicious hacker, a natural disaster, or an accidental mistake.
Key term
VLAN
A VLAN (Virtual Local Area Network) is a logical grouping of network devices that behave as if they are on the same physical network segment, regardless of their actual physical location.
About these practice questions
One of 989 original CC practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC 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 CC exam.