mediumMultiple ChoiceObjective-mapped
ISC2 CC Practice Question: Refer to the exhibit
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?
⚠ Common exam trap
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.
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 rule to allow traffic from internal IP range to port 3306
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.
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.
- ✗
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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