VCP-DCV vSphere Security Practice Question
A security administrator notices that a virtual machine (VM) running a legacy application is experiencing network connectivity issues after enabling Network I/O Control (NIOC) on the distributed switch. The VM is in a high-priority traffic class for management traffic. What is the most likely cause of the issue?
⚠ Common exam trap
The trap is assuming NIOC blocks traffic or conflicts with MTU/promiscuous settings — the real issue is traffic-class misclassification causing bandwidth throttling.
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
✓
The VM is assigned to the management traffic class, but its traffic should be in a different class, causing bandwidth throttling.
Network I/O Control (NIOC) on a vSphere Distributed Switch enforces bandwidth allocation based on traffic classes such as management, vMotion, iSCSI, and VM traffic. If a VM's traffic is incorrectly classified into the management traffic class, it is subject to that class's share, reservation, and limit, which can throttle the VM's bandwidth and cause connectivity issues. The most likely cause is misclassification of the VM's traffic into the wrong NIOC traffic class.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NIOC is blocking the VM's MAC address due to a security policy.
Why it's wrong here
NIOC shapes bandwidth allocation across traffic classes; it does not inspect or block MAC addresses, which is the role of port-level security policies such as MAC address changes or forged transmits. It is tempting because NIOC is a security-adjacent feature on the distributed switch.
- ✓
The VM is assigned to the management traffic class, but its traffic should be in a different class, causing bandwidth throttling.
Why this is correct
Misclassifying the legacy VM's traffic as management places it under Network I/O Control's management share allocation, which throttles bandwidth when the physical uplinks are saturated. NIOC enforces per-traffic-class shares, so traffic belonging in a virtual machine class instead competes against management reservations, producing the connectivity issues described.
- ✗
The VM is using jumbo frames, which are not supported with NIOC.
Why it's wrong here
NIOC supports jumbo frames; it only allocates bandwidth shares, limits and reservations per traffic class, leaving MTU handling to the vSwitch and physical uplinks. It is tempting because MTU mismatches do cause connectivity failures, but they are unrelated to enabling NIOC.
- ✗
The virtual switch has promiscuous mode enabled, which conflicts with NIOC.
Why it's wrong here
Promiscuous mode governs which frames a vNIC receives and operates independently of NIOC's bandwidth scheduling, so the two do not conflict. It is tempting because promiscuous mode is a security setting on the distributed switch, but it is used for monitoring and packet capture.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official VMware exam blueprint
This VCP-DCV practice question is part of Courseiva's free VMware 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 VCP-DCV exam.