Quick Answer
The answer is a network ACL. This is the correct choice because network ACLs are stateless, meaning they evaluate inbound and outbound traffic independently, and they explicitly support deny rules, allowing you to block specific IP address ranges at the subnet level. In contrast, security groups are stateful and can only allow traffic, not deny it, making them unsuitable for blocking a specific IP range. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding of the fundamental difference between stateful and stateless filtering, often appearing in scenario-based questions where you must choose the right component for IP-based blocking. A common trap is selecting a security group because it is more familiar, but remember that security groups lack a deny capability. For a quick memory tip: think of network ACLs as the “bouncer at the subnet door” that can explicitly say “no” to specific IPs, while security groups are like a “guest list” that can only say “yes.”
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 needs to block traffic from a specific IP address range in their VPC. Which component should be used?
Route table
Why wrong: Route tables define paths, not filtering.
Network ACL
NACLs can deny traffic from specific IP ranges.
Internet gateway
Why wrong: Internet gateway does not filter traffic.
Security group
Why wrong: Security groups only allow, not deny.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Network ACL
Option D is correct: Network ACLs are stateless and can block IP ranges at the subnet level. Option A is wrong because security groups are stateful and can't deny specific IPs (only allow). Option B is wrong because route tables control routing, not filtering. Option C is wrong because internet gateway is a gateway, not a filter.
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
For each option: why learners choose it and why it is or isn't the right answer here.
Route table
Why it's wrong here
Route tables define paths, not filtering.
Network ACL
Why this is correct
NACLs can deny traffic from specific IP ranges.
Related concept
CIDR notation defines the prefix length.
Internet gateway
Why it's wrong here
Internet gateway does not filter traffic.
Security group
Why it's wrong here
Security groups only allow, not deny.
Common exam traps
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
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.
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
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
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
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
The correct answer is: Network ACL — Option D is correct: Network ACLs are stateless and can block IP ranges at the subnet level. Option A is wrong because security groups are stateful and can't deny specific IPs (only allow). Option B is wrong because route tables control routing, not filtering. Option C is wrong because internet gateway is a gateway, not a filter.
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.
CIDR notation defines the prefix length.
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer needs to block traffic from a specific IP address to an EC2 instance. Which component should be modified?
easyWhy C: Option D is correct because a Network ACL can deny inbound traffic from a specific IP address at the subnet level. Option A is wrong because security groups allow rules only, not deny. Option B is wrong because route tables do not filter traffic. Option C is wrong because VPC Flow Logs only capture traffic, not filter.
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Last reviewed: Jun 20, 2026
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.
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