This CC practice question tests your understanding of security operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Network Topology
Refer to the exhibit. An administrator notices that external access to the MySQL database (port 3306) is blocked, but internal access should be allowed. What change should be made?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a rule to allow traffic from internal IP range to port 3306
The correct answer is C because the exhibit shows a DROP rule for port 3306 in the INPUT chain, which blocks all incoming traffic to the MySQL database. To allow internal access while keeping external access blocked, a specific rule must be added to ACCEPT traffic from the internal IP range to port 3306, placed before the DROP rule. This ensures that internal packets are matched first and permitted, while external packets hit the DROP rule and are rejected. Simply modifying or removing the DROP rule would allow all traffic, violating the requirement to block external access.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Change the DROP rule to ACCEPT for port 3306
Why it's wrong here
This would allow all traffic to port 3306, which is not the goal (only internal).
✗
Allow port 3306 in the FORWARD chain
Why it's wrong here
The INPUT chain is for traffic to the local system; MySQL runs locally, so FORWARD is irrelevant.
✓
Create a rule to allow traffic from internal IP range to port 3306
Why this is correct
A specific allow rule for internal IPs overrides the default DROP, enabling internal access.
Related concept
Read the scenario before looking for a memorised answer.
✗
Remove the DROP rule for port 3306
Why it's wrong here
Since the policy is DROP, removing the DROP rule still leaves port 3306 implicitly blocked.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the distinction between INPUT and FORWARD chains, and the trap here is that candidates mistakenly think adding a rule to the FORWARD chain will fix the issue, not realizing that traffic to the local MySQL service is processed by the INPUT chain.
Detailed technical explanation
How to think about this question
In iptables, the INPUT chain handles packets destined for the local system, while the FORWARD chain handles packets routed through the system. The order of rules matters: iptables processes rules sequentially, so a specific ACCEPT rule for internal IPs must be placed before a general DROP rule to take effect. A common real-world scenario is when a database server must be accessible only from a private subnet (e.g., 10.0.0.0/24) but not from the internet, requiring a whitelist approach with a default DROP at the end of the chain.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC question in full detail.
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a rule to allow traffic from internal IP range to port 3306 — The correct answer is C because the exhibit shows a DROP rule for port 3306 in the INPUT chain, which blocks all incoming traffic to the MySQL database. To allow internal access while keeping external access blocked, a specific rule must be added to ACCEPT traffic from the internal IP range to port 3306, placed before the DROP rule. This ensures that internal packets are matched first and permitted, while external packets hit the DROP rule and are rejected. Simply modifying or removing the DROP rule would allow all traffic, violating the requirement to block external access.
What should I do if I get this CC question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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