- A
Attach an Internet Gateway to the database subnets.
Why wrong: Wrong: This would expose them to the internet.
- B
Create a NAT Gateway in the database subnets.
Why wrong: Wrong: NAT Gateway is not needed for database isolation.
- C
Associate a security group that denies inbound traffic from 0.0.0.0/0.
Why wrong: Wrong: Security groups only support allow rules, not deny.
- D
Configure a network ACL on the database subnets to deny inbound traffic from 0.0.0.0/0.
Correct: Network ACLs can deny inbound traffic.
- E
Place the database subnets in private subnets.
Correct: Private subnets have no direct route to IGW.
Question 711 of 1,705
Isolating Database Subnets from Internet
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 is designing a network for a multi-tier application that must meet compliance requirements. The architecture includes a VPC with public, private, and database subnets. Which TWO actions should be taken to ensure the database subnets are not directly accessible from the internet? (Select 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
✓
Configure a network ACL on the database subnets to deny inbound traffic from 0.0.0.0/0.
Option D is correct because a network ACL (NACL) is a stateless firewall that operates at the subnet level. By configuring a NACL rule to deny inbound traffic from 0.0.0.0/0, you explicitly block all internet-originated traffic from reaching the database subnets, regardless of any security group rules. Option E is correct because placing the database subnets in private subnets means they have no direct route to an Internet Gateway, making them inherently inaccessible from the internet.
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 Internet Gateway to the database subnets.
Why it's wrong here
Wrong: This would expose them to the internet.
- ✗
Create a NAT Gateway in the database subnets.
- ✗
Associate a security group that denies inbound traffic from 0.0.0.0/0.
Why it's wrong here
Wrong: Security groups only support allow rules, not deny.
- ✓
Configure a network ACL on the database subnets to deny inbound traffic from 0.0.0.0/0.
Why this is correct
Correct: Network ACLs can deny inbound traffic.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Place the database subnets in private subnets.
Why this is correct
Correct: Private subnets have no direct route to IGW.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the misconception that a security group deny rule can block inbound traffic from 0.0.0.0/0, but security groups only support allow rules and are stateful, so the correct approach is to use a network ACL deny rule or place the subnets in a private subnet without an Internet Gateway route.
Detailed technical explanation
How to think about this question
Network ACLs are stateless, meaning you must explicitly define both inbound and outbound rules for traffic to flow; they are evaluated in order by rule number, and a deny rule for 0.0.0.0/0 at the subnet level ensures that even if a security group on an instance allows traffic, the NACL will block it. Private subnets lack a route to an Internet Gateway in their route table, so any traffic destined for 0.0.0.0/0 must go through a NAT device or VPN, effectively isolating the database subnets from direct internet access. In a real-world scenario, compliance frameworks like PCI DSS often require database subnets to be in private subnets with NACL restrictions to prevent any inadvertent exposure.
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
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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: Configure a network ACL on the database subnets to deny inbound traffic from 0.0.0.0/0. — Option D is correct because a network ACL (NACL) is a stateless firewall that operates at the subnet level. By configuring a NACL rule to deny inbound traffic from 0.0.0.0/0, you explicitly block all internet-originated traffic from reaching the database subnets, regardless of any security group rules. Option E is correct because placing the database subnets in private subnets means they have no direct route to an Internet Gateway, making them inherently inaccessible from the internet.
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
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