ISC2 CC Network Security Practice Question
A small accounting firm has a flat network where all employee workstations and a guest Wi-Fi access point connect to the same switch. The owner asks a security consultant to keep guests from reaching the payroll server, which resides on the same subnet as employee devices. Which control should the consultant implement to meet this requirement with the least disruption?
⚠ Common exam trap
The trap here is assuming that a security appliance such as an IPS or a host firewall provides the same deterministic traffic separation as network segmentation with an ACL.
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
✓
Create a separate VLAN for guests and apply an access control list that denies guest subnet traffic to the payroll server.
Segmenting guest traffic into its own VLAN removes it from the employee broadcast domain, and an ACL on the Layer 3 device enforces the rule that guests cannot reach the payroll server. This addresses the requirement directly without redesigning the employee network. Host firewalls, key rotation, and intrusion prevention do not provide the same deterministic isolation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy an IPS between the guest access point and the switch to block attacks aimed at the payroll server.
Why it's wrong here
An IPS detects and blocks known malicious traffic patterns, but guest access to a payroll server on the same subnet is not inherently malicious and may not match a signature. The IPS also does not enforce a segmentation policy, so allowed but unwanted traffic can still pass. It adds cost and complexity without guaranteeing the required isolation.
- ✗
Enable a host-based firewall on the payroll server that permits only the payroll application's TCP port.
Why it's wrong here
A host-based firewall on the payroll server would restrict which ports reach the server, but it does not stop guests from sending traffic to the server or from probing it. It also fails to separate guest traffic from employee traffic, so it does not meet the goal of keeping guests off the payroll segment. The requirement is network isolation, not port filtering on one host.
- ✓
Create a separate VLAN for guests and apply an access control list that denies guest subnet traffic to the payroll server.
Why this is correct
Placing guests on a dedicated VLAN segments the guest broadcast domain from employee systems, and an ACL on the router or Layer 3 switch can explicitly deny guest-to-payroll traffic. This directly satisfies the requirement to keep guests from reaching the payroll server while preserving the existing flat employee network, resulting in minimal disruption to employee workflows.
- ✗
Change the guest Wi-Fi pre-shared key every 30 days and publish it only to visitors.
Why it's wrong here
Rotating the guest Wi-Fi pre-shared key only controls who can join the guest network; it does not prevent an authorized guest from reaching the payroll server once connected. This is an authentication control for network access, not a segmentation control. It leaves the flat network intact, so guests and payroll remain on the same Layer 2 domain and can communicate freely.
Visual reference
Go deeper
Related to this question
Learn chapter
Network Security Foundations
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
Key term
Isolation
Isolation is the process of separating a compromised or suspicious system from a network to prevent the spread of malware or unauthorized access.
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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 ISC2 exam blueprint
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.