Quick Answer
The answer is subnets and security groups. Subnets provide network segmentation at the VPC subnet level by dividing the VPC’s IP address range into smaller segments, each tied to a specific Availability Zone and route table, enabling logical separation of resources like public and private tiers. Security groups act as stateful virtual firewalls at the instance (ENI) level, allowing you to isolate traffic between application tiers—such as web, app, and database—by assigning different groups to different instances. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this tests your understanding of both network-layer and instance-layer segmentation, a common trap being to overlook that security groups are a valid segmentation mechanism despite operating above the subnet layer. Remember: subnets split the network horizontally by IP range, while security groups split it vertically by traffic rules—think “subnets for location, security groups for permission.”
This ANS-C01 practice question tests your understanding of network implementation. 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.
Which TWO of the following are valid options for implementing network segmentation in a VPC?
Security Groups
Security groups act as virtual firewalls for instances.
Subnets
Subnets allow you to partition the VPC IP address space.
Route Tables
Why wrong: Route tables control traffic flow but are not a segmentation boundary.
NAT Gateway
Why wrong: NAT Gateway provides outbound internet access, not segmentation.
Internet Gateway
Why wrong: Internet Gateway provides internet connectivity, not segmentation.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Security Groups
Security Groups (A) are stateful virtual firewalls that operate at the instance level (ENI), allowing you to control inbound and outbound traffic based on rules. They are a valid mechanism for network segmentation because you can assign different Security Groups to different instances or groups of instances to isolate traffic between tiers (e.g., web, app, database). Subnets (B) provide network segmentation at the VPC subnet level by dividing the VPC's IP address range into smaller segments, each associated with a specific Availability Zone and route table, enabling logical separation of resources.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Security Groups
Why this is correct
Security groups act as virtual firewalls for instances.
Related concept
Read the scenario before looking for a memorised answer.
Subnets
Why this is correct
Subnets allow you to partition the VPC IP address space.
Related concept
Read the scenario before looking for a memorised answer.
Route Tables
Why it's wrong here
Route tables control traffic flow but are not a segmentation boundary.
NAT Gateway
Internet Gateway
Why it's wrong here
Internet Gateway provides internet connectivity, not segmentation.
Common exam traps
AWS often tests the misconception that Route Tables or NAT Gateways provide segmentation, but they are routing and translation services, not access control boundaries; the trap is confusing traffic direction with traffic filtering.
Detailed technical explanation
Security Groups operate as stateful firewalls at the hypervisor level, automatically allowing return traffic regardless of outbound rules, which differs from Network ACLs (stateless). Subnets are tied to a specific Availability Zone and use route tables to define traffic paths; segmentation is achieved by placing resources in different subnets with distinct route tables (e.g., public vs. private) and controlling inter-subnet traffic via Network ACLs or Security Groups. In real-world scenarios, a three-tier architecture uses separate subnets for web, app, and database layers, each with Security Groups that only allow specific traffic (e.g., web to app on port 8080, app to DB on port 3306).
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
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FAQ
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
The correct answer is: Security Groups — Security Groups (A) are stateful virtual firewalls that operate at the instance level (ENI), allowing you to control inbound and outbound traffic based on rules. They are a valid mechanism for network segmentation because you can assign different Security Groups to different instances or groups of instances to isolate traffic between tiers (e.g., web, app, database). Subnets (B) provide network segmentation at the VPC subnet level by dividing the VPC's IP address range into smaller segments, each associated with a specific Availability Zone and route table, enabling logical separation of resources.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 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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