- A
Place all tiers in public subnets and use security group rules to restrict access to app and DB tiers
Why wrong: Public subnets have direct route to internet, so tiers are exposed.
- B
Place web tier in public subnets with Internet Gateway, app and DB tiers in private subnets with a NAT Gateway for outbound traffic
This design provides internet access to web tier while isolating app and DB tiers.
- C
Place web tier in a public subnet and app and DB tiers in the same public subnet but with restrictive Network ACLs
Why wrong: Network ACLs can limit inbound but cannot prevent outbound internet access if route exists.
- D
Place all tiers in private subnets and attach an Internet Gateway to the private subnets for the web tier
Why wrong: Internet Gateway requires a public subnet route table.
Designing a Multi-Tier Application with Public and Private Subnets
This ANS-C01 practice question tests your understanding of network implementation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 is designing a network for a multi-tier application that includes a web tier, application tier, and database tier. The web tier must be accessible from the internet, while the application and database tiers should have no direct internet access. All tiers are in the same VPC. Which configuration meets these requirements?
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
Place web tier in public subnets with Internet Gateway, app and DB tiers in private subnets with a NAT Gateway for outbound traffic
Option B is correct because it places the web tier in a public subnet with an Internet Gateway (IGW) for direct inbound internet traffic, while the application and database tiers reside in private subnets with no direct internet path. A NAT Gateway in a public subnet provides outbound-only internet access for the private tiers (e.g., for software updates) without allowing inbound connections, satisfying the requirement that only the web tier be internet-accessible.
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.
- ✗
Place all tiers in public subnets and use security group rules to restrict access to app and DB tiers
Why it's wrong here
Public subnets have direct route to internet, so tiers are exposed.
- ✓
Place web tier in public subnets with Internet Gateway, app and DB tiers in private subnets with a NAT Gateway for outbound traffic
Why this is correct
This design provides internet access to web tier while isolating app and DB tiers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Place web tier in a public subnet and app and DB tiers in the same public subnet but with restrictive Network ACLs
Why it's wrong here
Network ACLs can limit inbound but cannot prevent outbound internet access if route exists.
- ✗
Place all tiers in private subnets and attach an Internet Gateway to the private subnets for the web tier
Why it's wrong here
Internet Gateway requires a public subnet route table.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the misconception that security groups or NACLs alone can fully isolate tiers from the internet when placed in public subnets, ignoring that a public subnet’s route to an Internet Gateway inherently allows inbound traffic unless explicitly blocked by a firewall or stateful inspection.
Detailed technical explanation
How to think about this question
In AWS, a subnet is considered public only when its route table has a default route (0.0.0.0/0) pointing to an Internet Gateway. Private subnets route 0.0.0.0/0 to a NAT Gateway or NAT instance, which performs source NAT (SNAT) to translate private IPs to the NAT’s public IP for outbound traffic only. The NAT Gateway does not accept unsolicited inbound connections, ensuring the application and database tiers remain inaccessible from the internet even if they initiate outbound traffic. This architecture is commonly used for multi-tier applications requiring defense-in-depth, such as PCI-DSS or HIPAA workloads.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Place web tier in public subnets with Internet Gateway, app and DB tiers in private subnets with a NAT Gateway for outbound traffic — Option B is correct because it places the web tier in a public subnet with an Internet Gateway (IGW) for direct inbound internet traffic, while the application and database tiers reside in private subnets with no direct internet path. A NAT Gateway in a public subnet provides outbound-only internet access for the private tiers (e.g., for software updates) without allowing inbound connections, satisfying the requirement that only the web tier be internet-accessible.
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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Last reviewed: Jul 4, 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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