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ISC2 CC Practice Question: A network administrator is designing a DMZ to…
A network administrator is designing a DMZ to host a public-facing web server and a database server that should only be accessible from the web server. Which of the following firewall rule sets best achieves this design?
⚠ Common exam trap
ISC2 often tests the principle of least privilege by including options that allow overly broad access (like 'all traffic' from web to database) or reverse the direction of connections, so the trap here is assuming that any traffic between the web server and database is acceptable without specifying the exact protocol and port.
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
✓
Allow inbound HTTP/HTTPS to web server; allow web server to database on port 3306; deny all else
It implements the principle of least privilege for a DMZ: it allows inbound HTTP/HTTPS traffic (ports 80/443) to the public-facing web server, then permits only the web server to initiate outbound connections to the database server on port 3306 (MySQL/MariaDB default), and denies all other traffic. This ensures the database is not directly accessible from the internet, reducing the attack surface while still supporting the required application flow.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Allow inbound HTTP/HTTPS to web server; allow web server to database on port 3306; deny all else
Why this is correct
This rule set enforces least privilege: public traffic reaches only the web server, the database accepts connections solely from that web server on port 3306, and everything else is denied. The database therefore remains unreachable directly from the internet, satisfying the DMZ segmentation requirement.
- ✗
Allow web server to initiate outbound connections to internet; allow database to initiate connections to web server; deny all else
Why it's wrong here
This reverses the required direction: it lets the database initiate connections to the web server, whereas the design needs the web server to query the database. It is tempting because restricting outbound traffic is a valid DMZ hardening measure, but the stated requirement is inbound SQL access from the web server only.
- ✗
Allow inbound HTTP/HTTPS to web server; allow all traffic from web server to database; deny all else
Why it's wrong here
Allowing all traffic from the web server to the database permits any protocol or port, not just the database service, violating least privilege. It tempts because it is simple and functional, but a correct rule restricts the database to the specific database port from the web server only.
- ✗
Allow inbound HTTP/HTTPS to web server; allow inbound SQL from internet to database; deny all else
Why it's wrong here
Opening SQL from the internet to the database exposes it directly, defeating the DMZ's purpose since only the web server should reach it. It is tempting because public web access genuinely requires inbound HTTP/HTTPS, but that rule belongs to the web tier alone, not the database tier.
Go deeper
Related to this question
Learn chapter
Secure Network Architecture and Design
Key term
Access control
Access control is the security practice of determining who or what is allowed to view, use, or enter a resource, and under what conditions.
Key term
Least privilege
Least privilege is a security principle that means giving users, systems, or programs only the minimum permissions they need to do their job and nothing more.
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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.