easyMultiple ChoiceObjective-mapped
DMZ Architecture for Multi-Tier Web Applications: Three-Tier Segmentation
A security architect is designing a network segmentation strategy for a multi-tier web application. The web servers must be accessible from the internet, while the application and database servers must only be accessible from the web tier. Which architecture best meets these requirements?
Quick Answer
The correct answer is to deploy web servers in a DMZ, application servers in an internal network, and database servers in a separate restricted network with firewall rules allowing only necessary traffic. This classic three-tier DMZ architecture for multi-tier web application security enforces the principle of least privilege by segmenting each tier into its own security zone, where the DMZ absorbs direct internet traffic while the internal and backend networks remain isolated behind stateful firewall rules that permit only specific, required flows. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of layered network segmentation and how to prevent lateral movement—a common trap is placing the database in the same internal network as the application server, which would expose sensitive data if the app tier is compromised. Remember the memory tip: “Web in the DMZ, App in the middle, DB in the back—never let the internet touch the stack.”
⚠ Common exam trap
Test-takers frequently confuse network segmentation with simple access control lists or host-based firewalls, failing to recognize that true segmentation requires separate network zones (DMZ, internal, restricted) with firewall-enforced traffic flows between them.
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
✓
Deploy web servers in a DMZ, application servers in an internal network, and database servers in a separate restricted network with firewall rules allowing only necessary traffic.
It implements a classic three-tier DMZ architecture: web servers in a DMZ (publicly accessible), application servers in an internal network (accessible only from the DMZ), and database servers in a restricted backend network (accessible only from the application tier). This layered segmentation enforces the principle of least privilege and uses firewall rules to control traffic between each tier, ensuring that internet-facing components cannot directly reach sensitive data stores.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a single VLAN with access control lists to restrict traffic between servers.
Why it's wrong here
ACLs alone cannot replace proper network segmentation and may be complex to manage.
- ✗
Place all servers in the same subnet and use host-based firewalls for isolation.
Why it's wrong here
A flat network does not provide network-level segmentation, increasing risk.
- ✓
Deploy web servers in a DMZ, application servers in an internal network, and database servers in a separate restricted network with firewall rules allowing only necessary traffic.
Why this is correct
This provides defense in depth with proper segmentation and access controls.
- ✗
Use a VPN concentrator for all external access and place all servers in a private subnet.
Why it's wrong here
VPN-only access would hinder performance and does not address internal segmentation.
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Same concept, more angles
1 more way this is tested on CAS-005
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security architect is designing a new DMZ for an e-commerce platform. The DMZ must host a web server, an API gateway, and a database server. The architect needs to minimize the attack surface while ensuring the web server can communicate with the API gateway, and the API gateway can communicate with the database. Which network segmentation approach best meets these requirements?
medium- A.Place all three services in the same DMZ subnet and use host-based firewalls to restrict traffic.
- B.Create two DMZ subnets: one for the web server and API gateway, and another for the database server.
- C.Place the web server in a DMZ subnet, the API gateway in a separate DMZ subnet, and the database server on the internal network.
- ✓ D.Create three separate DMZ subnets: one for the web server, one for the API gateway, and one for the database server, with firewall rules allowing only required traffic.
Why D: It implements the principle of least privilege through network segmentation. By placing each service in its own DMZ subnet with firewall rules that allow only the required traffic (e.g., HTTP/HTTPS from web to API, SQL from API to database), the attack surface is minimized. This prevents lateral movement if one service is compromised, as an attacker cannot directly reach the database from the web server or the API gateway from the internet.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.