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Question 798 of 1,705

Network Implementation →mediumMultiple ChoiceObjective-mapped

ANS-C01 Network Implementation Practice Question

This ANS-C01 practice question tests your understanding of network implementation. 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 company has deployed a web application behind an Application Load Balancer (ALB) in a VPC with public and private subnets. The ALB is in public subnets, and the web servers are in private subnets. Clients report intermittent connection errors. Investigation shows that the ALB is marking targets as unhealthy. What is the MOST likely cause?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

A
The network ACL for the private subnets is blocking inbound traffic from the ALB.
Why wrong: Network ACLs are stateless and must allow both inbound and outbound; but the more likely issue is health check configuration.
B
The security group for the web servers does not allow inbound traffic from the internet.
Why wrong: Traffic from the ALB originates from its private IPs within the VPC, not directly from the internet.
C
The ALB is deployed in private subnets and cannot reach the internet.
Why wrong: The scenario states ALB is in public subnets.
D
The health check is configured to use the public IP address of the targets, but the targets are in private subnets without public IPs.
Health checks must target the private IP of the instances; using public IPs will fail.

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

✓

The health check is configured to use the public IP address of the targets, but the targets are in private subnets without public IPs.

Option D is correct because when health checks are configured to use the public IP address of targets, the ALB attempts to reach the targets via the internet. Since the web servers are in private subnets without public IPs, the health check traffic cannot be routed to them, causing the ALB to mark them as unhealthy. Health checks must target private IP addresses within the VPC for instances in private subnets.

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.

✗
The network ACL for the private subnets is blocking inbound traffic from the ALB.
Why it's wrong here
Network ACLs are stateless and must allow both inbound and outbound; but the more likely issue is health check configuration.
✗
The security group for the web servers does not allow inbound traffic from the internet.
Why it's wrong here
Traffic from the ALB originates from its private IPs within the VPC, not directly from the internet.
✗
The ALB is deployed in private subnets and cannot reach the internet.
Why it's wrong here
The scenario states ALB is in public subnets.
✓
The health check is configured to use the public IP address of the targets, but the targets are in private subnets without public IPs.
Why this is correct
Health checks must target the private IP of the instances; using public IPs will fail.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often overlook that health checks must target private IPs within the VPC, not public IPs, and mistakenly focus on security group or ACL rules instead of the health check configuration.

Trap categories for this question

Scenario analysis trap
The scenario states ALB is in public subnets.

Detailed technical explanation

How to think about this question

Application Load Balancers perform health checks by sending HTTP/HTTPS requests to the target's private IP address on the configured port and path. If the health check is misconfigured to use the target's public IP (e.g., via the 'HealthCheck' target group attribute 'Matcher' or by specifying a public DNS name), the ALB will attempt to route traffic outside the VPC, which fails for private instances. Under the hood, the ALB uses its own private IPs within the VPC to communicate with targets, so health checks must target private IPs to succeed.

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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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: The health check is configured to use the public IP address of the targets, but the targets are in private subnets without public IPs. — Option D is correct because when health checks are configured to use the public IP address of targets, the ALB attempts to reach the targets via the internet. Since the web servers are in private subnets without public IPs, the health check traffic cannot be routed to them, causing the ALB to mark them as unhealthy. Health checks must target private IP addresses within the VPC for instances in private subnets.

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.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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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.