← ANS-C01·Amazon Web Services

Question 978 of 1,705

Network Security, Compliance and Governance →hardMultiple ChoiceObjective-mapped

ANS-C01 Network Security, Compliance and Governance Practice Question

This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 a VPC with public and private subnets. An EC2 instance in the private subnet needs to download patches from the internet. The company wants to use a proxy server running on an EC2 instance in the public subnet. The security group for the proxy server must allow inbound HTTP/HTTPS from the instance in the private subnet. The security group for the private instance must allow outbound HTTP/HTTPS to the proxy server. However, the private instance cannot connect to the proxy. 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.

Question 1hardmultiple choice

Read the full NAT/PAT explanation →

A
The security group for the private instance does not allow outbound traffic to the proxy server.
Why wrong: The question states that the security group allows outbound to the proxy.
B
The network ACL for the private subnet blocks inbound traffic from the proxy.
Why wrong: The network ACL must allow inbound traffic from the proxy for the return traffic, but the issue is outbound from the private instance.
C
The route table for the private subnet has a default route pointing to a NAT gateway instead of the proxy server.
If the default route points to a NAT gateway, traffic to the internet goes through the NAT gateway instead of the proxy.
D
The security group for the proxy server does not allow inbound traffic from the private instance's security group.
Why wrong: The question states that the security group is configured to allow inbound from the private instance.

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 route table for the private subnet has a default route pointing to a NAT gateway instead of the proxy server.

Option B is correct because the route table of the private subnet likely has a default route to a NAT gateway or internet gateway, causing traffic to bypass the proxy. The private instance's security group allows outbound HTTP/HTTPS to the proxy, but the subnet route may not point to the proxy. Option A is wrong because the network ACL must allow both inbound and outbound traffic; if it blocks inbound, the proxy cannot receive requests. Option C is wrong because the proxy's security group allows inbound from the private instance. Option D is wrong because the private instance's security group allows outbound to the proxy.

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.

✗
The security group for the private instance does not allow outbound traffic to the proxy server.
Why it's wrong here
The question states that the security group allows outbound to the proxy.
✗
The network ACL for the private subnet blocks inbound traffic from the proxy.
Why it's wrong here
The network ACL must allow inbound traffic from the proxy for the return traffic, but the issue is outbound from the private instance.
✓
The route table for the private subnet has a default route pointing to a NAT gateway instead of the proxy server.
Why this is correct
If the default route points to a NAT gateway, traffic to the internet goes through the NAT gateway instead of the proxy.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The security group for the proxy server does not allow inbound traffic from the private instance's security group.
Why it's wrong here
The question states that the security group is configured to allow inbound from the private instance.

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 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.

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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.

Related ANS-C01 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

Network Management and Operations practice questions

Practise ANS-C01 questions linked to Network Management and Operations.

Network Security, Compliance and Governance practice questions

Practise ANS-C01 questions linked to Network Security, Compliance and Governance.

Network Design practice questions

Practise ANS-C01 questions linked to Network Design.

Network Implementation practice questions

Practise ANS-C01 questions linked to Network Implementation.

ANS-C01 fundamentals practice questions

Practise ANS-C01 questions linked to ANS-C01 fundamentals.

ANS-C01 scenario practice questions

Practise ANS-C01 questions linked to ANS-C01 scenario.

ANS-C01 troubleshooting practice questions

Practise ANS-C01 questions linked to ANS-C01 troubleshooting.

Practice this exam

Start a free ANS-C01 practice session

Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.

10 questions 20 questions 30 questions 50 questions Timed 30

ANS-C01 practice-test guide →Study guide →Browse all practice tests

FAQ

Questions learners often ask

What does this ANS-C01 question test?

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

What is the correct answer to this question?

The correct answer is: The route table for the private subnet has a default route pointing to a NAT gateway instead of the proxy server. — Option B is correct because the route table of the private subnet likely has a default route to a NAT gateway or internet gateway, causing traffic to bypass the proxy. The private instance's security group allows outbound HTTP/HTTPS to the proxy, but the subnet route may not point to the proxy. Option A is wrong because the network ACL must allow both inbound and outbound traffic; if it blocks inbound, the proxy cannot receive requests. Option C is wrong because the proxy's security group allows inbound from the private instance. Option D is wrong because the private instance's security group allows outbound to the proxy.

What should I do if I get this ANS-C01 question wrong?

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?

CIDR notation defines the prefix length.

About these practice questions

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 →

How Courseiva writes practice questions · Editorial policy

Last reviewed: Jun 20, 2026

Question Discussion

Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.

Loading comments…

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.