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Network Security, Compliance and Governance →mediumMultiple 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. 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's security team is investigating a potential data exfiltration incident. They notice that an EC2 instance in a private subnet is making HTTPS connections to an unknown external IP address. The instance's security group only allows outbound HTTPS to a specific set of IPs. What is the MOST likely cause of the traffic?

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 instance is routing traffic through a NAT Gateway that has a route to the internet
The security group allows outbound HTTPS to certain IPs, but if the traffic goes through a NAT Gateway, the destination IP seen by the security group is the NAT Gateway's IP, not the final destination.
B
The instance is using a VPC Endpoint to connect to the external IP
Why wrong: VPC Endpoints only connect to AWS services, not external IPs.
C
The security group outbound rules are being overridden by a Network ACL
Why wrong: Network ACLs can override, but they are stateless and would affect both inbound/outbound; security groups are still evaluated.
D
The instance has a public IP address and is using an Internet Gateway directly
Why wrong: The instance is in a private subnet, so it cannot have a public IP.

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 instance is routing traffic through a NAT Gateway that has a route to the internet

Option A is correct because a NAT Gateway in a public subnet can allow outbound traffic to any destination, bypassing security group restrictions if the security group allows traffic to the NAT Gateway. Option B is wrong because security groups are stateful; outbound rules apply regardless. Option C is wrong because an Internet Gateway is not in a private subnet. Option D is wrong because a VPC Endpoint is for AWS services, not external IPs.

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 instance is routing traffic through a NAT Gateway that has a route to the internet
Why this is correct
The security group allows outbound HTTPS to certain IPs, but if the traffic goes through a NAT Gateway, the destination IP seen by the security group is the NAT Gateway's IP, not the final destination.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The instance is using a VPC Endpoint to connect to the external IP
Why it's wrong here
VPC Endpoints only connect to AWS services, not external IPs.
✗
The security group outbound rules are being overridden by a Network ACL
Why it's wrong here
Network ACLs can override, but they are stateless and would affect both inbound/outbound; security groups are still evaluated.
✗
The instance has a public IP address and is using an Internet Gateway directly
Why it's wrong here
The instance is in a private subnet, so it cannot have a public IP.

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.

Visual reference

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.

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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 instance is routing traffic through a NAT Gateway that has a route to the internet — Option A is correct because a NAT Gateway in a public subnet can allow outbound traffic to any destination, bypassing security group restrictions if the security group allows traffic to the NAT Gateway. Option B is wrong because security groups are stateful; outbound rules apply regardless. Option C is wrong because an Internet Gateway is not in a private subnet. Option D is wrong because a VPC Endpoint is for AWS services, not external IPs.

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.

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