- A
Allow outbound HTTPS (port 443) traffic from the application servers in the security group
Correct; security groups must allow outbound traffic.
- B
Modify the network ACL of the private subnet to allow all outbound traffic
Why wrong: Incorrect; while NACLs can be used, the question asks for two steps, and this is less specific.
- C
Add a route in the public subnet route table that points 0.0.0.0/0 to the NAT gateway
Why wrong: Incorrect; public subnet route should point to internet gateway.
- D
Add a route in the private subnet route table that points 0.0.0.0/0 to the NAT gateway
Correct; this routes outbound traffic through the NAT gateway.
- E
Associate an Elastic IP address with the NAT gateway
Why wrong: Incorrect; this is a configuration step but not directly needed for the application servers' access.
Quick Answer
The correct answer is to add a route in the private subnet route table that points 0.0.0.0/0 to the NAT gateway and to allow outbound HTTPS traffic in the security group associated with the application servers. This works because the NAT gateway, residing in a public subnet with an internet gateway, translates the private IPs of the application servers to its own elastic IP for outbound traffic, while the security group acts as a stateful firewall to permit only the necessary HTTPS connections for patch downloads. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of how to combine network address translation with security group egress rules to enable private subnet internet access via NAT gateway with security group and route table configurations, a common trap being that students forget to update the security group’s outbound rules or mistakenly point the route to an internet gateway. A helpful memory tip is “NAT for the path, SG for the pass”—the route table provides the path out, and the security group passes only the required traffic.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 company has a VPC with public and private subnets. The public subnet contains a NAT gateway and a bastion host. The private subnet contains application servers. The company wants to ensure that the application servers can download patches from the internet. Which TWO steps should be taken to allow this while maintaining security? (Choose two.)
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 outbound HTTPS (port 443) traffic from the application servers in the security group
Option A is correct because the application servers need to initiate outbound HTTPS connections (port 443) to download patches from the internet. By allowing outbound HTTPS traffic in the security group associated with the application servers, you permit the necessary traffic while maintaining stateful filtering and restricting other outbound traffic. This is a security best practice that follows the principle of least privilege.
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.
- ✓
Allow outbound HTTPS (port 443) traffic from the application servers in the security group
Why this is correct
Correct; security groups must allow outbound traffic.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Modify the network ACL of the private subnet to allow all outbound traffic
Why it's wrong here
Incorrect; while NACLs can be used, the question asks for two steps, and this is less specific.
- ✗
Add a route in the public subnet route table that points 0.0.0.0/0 to the NAT gateway
Why it's wrong here
Incorrect; public subnet route should point to internet gateway.
- ✓
Add a route in the private subnet route table that points 0.0.0.0/0 to the NAT gateway
- ✗
Associate an Elastic IP address with the NAT gateway
Why it's wrong here
Incorrect; this is a configuration step but not directly needed for the application servers' access.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the distinction between where routes are added (public vs. private subnet route tables) and the role of security groups versus network ACLs, leading candidates to incorrectly modify the public subnet's route table or use overly permissive network ACL rules.
Detailed technical explanation
How to think about this question
A NAT gateway enables instances in a private subnet to initiate outbound IPv4 traffic to the internet but prevents inbound traffic from the internet. The private subnet's route table must have a default route (0.0.0.0/0) pointing to the NAT gateway ID. Security groups are stateful, so if you allow outbound HTTPS (port 443), the return traffic is automatically permitted regardless of inbound rules. In contrast, network ACLs are stateless and require explicit inbound and outbound rules for return traffic.
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.
What to study next
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Allow outbound HTTPS (port 443) traffic from the application servers in the security group — Option A is correct because the application servers need to initiate outbound HTTPS connections (port 443) to download patches from the internet. By allowing outbound HTTPS traffic in the security group associated with the application servers, you permit the necessary traffic while maintaining stateful filtering and restricting other outbound traffic. This is a security best practice that follows the principle of least privilege.
What should I do if I get this ANS-C01 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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Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways this is tested on ANS-C01
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 company has a VPC with a public subnet containing a NAT gateway and a private subnet containing Amazon EC2 instances. The instances in the private subnet need to download patches from the internet. The NAT gateway is in the public subnet and has an Elastic IP address. The private subnet's route table has a default route pointing to the NAT gateway. However, the instances cannot reach the internet. What is the MOST likely cause?
medium- ✓ A.The public subnet's route table does not have a route to an internet gateway.
- B.The NAT gateway does not have a route back to the private subnet.
- C.The NAT gateway is not associated with a security group that allows inbound internet traffic.
- D.The security group attached to the EC2 instances does not allow outbound traffic to the internet.
Why A: Option D is correct. For a NAT gateway to work, it must be in a public subnet with a route to an internet gateway. If the public subnet does not have a route to the internet gateway, the NAT gateway cannot forward traffic to the internet. Option A is incorrect because security groups for instances in private subnets should allow outbound traffic, but that is not the most likely cause. Option B is incorrect because the NAT gateway automatically replies to traffic; no route back is needed for responses. Option C is incorrect because the NAT gateway does not need a security group; it uses network ACLs and route tables.
Variation 2. A company is deploying a VPC with public and private subnets. They need to provide internet access to instances in the private subnets for software updates. Which THREE components are required to achieve this?
easy- ✓ A.Route table in the private subnet with a default route pointing to the NAT Gateway
- B.AWS Site-to-Site VPN connection
- ✓ C.NAT Gateway in a public subnet
- ✓ D.Internet Gateway attached to the VPC
- E.AWS Direct Connect connection
Why A: Options B, C, and E are correct. A NAT Gateway (or NAT instance) in a public subnet, an Internet Gateway attached to the VPC, and a route table in the private subnet pointing to the NAT Gateway are required. Option A is wrong because a VPN connection is not needed. Option D is wrong because a Direct Connect connection is not needed.
Last reviewed: Jun 30, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services 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 ANS-C01 exam.
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