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Question 1,417 of 1,740

Security and Compliance →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is to use security groups alone, with inbound rules that chain access from the web tier to the application tier and then to the database tier. This works because security groups are stateful and default to deny all inbound traffic, so allowing 0.0.0.0/0 on ports 80 and 443 to the web tier, then referencing the web tier’s security group as the source for the app tier, and the app tier’s security group as the source for the database tier, creates a trusted, one-way flow of traffic that enforces strict multi-tier application access control without needing network ACLs. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of security group chaining versus stateless network ACLs, and a common trap is overcomplicating the answer by adding unnecessary ACL rules—remember that security groups alone provide the required isolation when properly configured. A helpful memory tip is “chain the groups, skip the ACLs,” reinforcing that stateful security groups can handle tier-to-tier access control without stateless ACLs.

DOP-C02 Security and Compliance Practice Question

This DOP-C02 practice question tests your understanding of security and compliance. 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 deploying a multi-tier application on AWS. The web tier must be publicly accessible, but the application tier must only be accessible from the web tier. The database tier should not be accessible from the internet at all. Which combination of security groups and network ACLs should be used?

Question 1hardmultiple choice

Study the full ACL explanation →

A
Use security groups: allow 0.0.0.0/0 on all ports to web tier, allow all traffic between all instances.
Why wrong: Too permissive, not secure.
B
Place all instances in the same security group with inbound rules allowing only ports 80/443 from 0.0.0.0/0.
Why wrong: This would allow all instances to be accessed from the internet, not secure.
C
Use security groups: allow 0.0.0.0/0 on port 80/443 to web tier, allow web tier security group to app tier, allow app tier security group to database tier.
This correctly restricts access between tiers.
D
Use network ACLs: allow 0.0.0.0/0 on port 80/443 to web subnet, allow web subnet to app subnet, allow app subnet to database subnet.
Why wrong: Network ACLs are stateless and more complex; security groups are simpler for this use case.

Full breakdown with real-world context →

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

✓

Use security groups: allow 0.0.0.0/0 on port 80/443 to web tier, allow web tier security group to app tier, allow app tier security group to database tier.

Security groups are stateful and default to deny all inbound. By allowing inbound on port 80/443 from 0.0.0.0/0 to the web tier, and allowing inbound from the web tier's security group to the app tier, and only allowing inbound from the app tier to the database tier, you achieve the required isolation. Network ACLs are stateless and not needed if security groups are properly configured.

Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Use security groups: allow 0.0.0.0/0 on all ports to web tier, allow all traffic between all instances.
Why it's wrong here
Too permissive, not secure.
✗
Place all instances in the same security group with inbound rules allowing only ports 80/443 from 0.0.0.0/0.
Why it's wrong here
This would allow all instances to be accessed from the internet, not secure.
✓
Use security groups: allow 0.0.0.0/0 on port 80/443 to web tier, allow web tier security group to app tier, allow app tier security group to database tier.
Why this is correct
This correctly restricts access between tiers.
Related concept
CIDR notation defines the prefix length.
✗
Use network ACLs: allow 0.0.0.0/0 on port 80/443 to web subnet, allow web subnet to app subnet, allow app subnet to database subnet.
Why it's wrong here
Network ACLs are stateless and more complex; security groups are simpler for this use case.

Common exam traps

Common exam trap: usable hosts are not the same as total addresses

Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.

Detailed technical explanation

How to think about this question

Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.

KKey Concepts to Remember

CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.

TExam Day Tips

Write the block size before choosing the subnet.
Check whether the question asks for hosts, subnets or a specific address range.
Do not confuse /24, /25, /26 and /27 host counts.

Key takeaway

Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

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.

What to study next

Got this wrong? Here's your next step.

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this DOP-C02 question test?

Security and Compliance — This question tests Security and Compliance — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: Use security groups: allow 0.0.0.0/0 on port 80/443 to web tier, allow web tier security group to app tier, allow app tier security group to database tier. — Security groups are stateful and default to deny all inbound. By allowing inbound on port 80/443 from 0.0.0.0/0 to the web tier, and allowing inbound from the web tier's security group to the app tier, and only allowing inbound from the app tier to the database tier, you achieve the required isolation. Network ACLs are stateless and not needed if security groups are properly configured.

What should I do if I get this DOP-C02 question wrong?

What is the key concept behind this question?

CIDR notation defines the prefix length.

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This DOP-C02 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 DOP-C02 exam.