- A
Attach an Elastic IP to the instance.
Why wrong: Even with an Elastic IP, the instance cannot reach the internet without a route to IGW.
- B
Update the private subnet's route table to point 0.0.0.0/0 to the Internet Gateway.
Why wrong: This would make the subnet public, not private.
- C
Remove the public IP address from the instance and ensure the private subnet has a route to the NAT gateway.
Private subnet instances should not have public IPs; they use NAT gateway for internet access.
- D
Allow outbound traffic in the instance's security group.
Why wrong: Security groups allow all outbound traffic by default.
Question 1,429 of 1,748
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A security engineer is setting up a new VPC with public and private subnets. The VPC has an Internet Gateway attached. The public subnet's route table has a default route (0.0.0.0/0) pointing to the Internet Gateway. The private subnet's route table has a default route pointing to a NAT gateway. The engineer launches an EC2 instance in the private subnet and assigns it a public IP address. However, the instance cannot access the internet. What should the engineer do to resolve this issue?
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
✓
Remove the public IP address from the instance and ensure the private subnet has a route to the NAT gateway.
Option C is correct because an EC2 instance in a private subnet cannot use a public IP address for internet access, as the private subnet's route table directs default traffic to a NAT gateway, not an internet gateway. The public IP is irrelevant because the instance's traffic must traverse the NAT gateway, which requires the instance to have no public IP and the private subnet route to point to the NAT gateway. Removing the public IP ensures the instance uses the NAT gateway's Elastic IP for outbound traffic, resolving the internet access issue.
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.
- ✗
Attach an Elastic IP to the instance.
Why it's wrong here
Even with an Elastic IP, the instance cannot reach the internet without a route to IGW.
- ✗
Update the private subnet's route table to point 0.0.0.0/0 to the Internet Gateway.
Why it's wrong here
This would make the subnet public, not private.
- ✓
Remove the public IP address from the instance and ensure the private subnet has a route to the NAT gateway.
- ✗
Allow outbound traffic in the instance's security group.
Why it's wrong here
Security groups allow all outbound traffic by default.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly think assigning a public IP or Elastic IP to an instance in a private subnet will grant internet access, overlooking that routing decisions are made at the subnet level, not the instance level.
Detailed technical explanation
How to think about this question
In AWS, a public IP assigned to an instance in a private subnet is not used for internet-bound traffic because the subnet's route table does not have a route to an internet gateway; instead, the NAT gateway performs source NAT (SNAT), replacing the instance's private IP with its own Elastic IP. The instance's public IP is only relevant if the subnet route table has a direct route to an internet gateway, which is not the case here. This design ensures that instances in private subnets cannot be directly reached from the internet, maintaining a security boundary.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Remove the public IP address from the instance and ensure the private subnet has a route to the NAT gateway. — Option C is correct because an EC2 instance in a private subnet cannot use a public IP address for internet access, as the private subnet's route table directs default traffic to a NAT gateway, not an internet gateway. The public IP is irrelevant because the instance's traffic must traverse the NAT gateway, which requires the instance to have no public IP and the private subnet route to point to the NAT gateway. Removing the public IP ensures the instance uses the NAT gateway's Elastic IP for outbound traffic, resolving the internet access issue.
What should I do if I get this SCS-C02 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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Last reviewed: Jul 4, 2026
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