- A
Configure the Direct Connect gateway to only advertise specific prefixes to the Transit Gateway.
Why wrong: Direct Connect gateway advertises routes but does not filter traffic; it only controls route propagation.
- B
Deploy AWS Network Firewall in the production VPC and configure stateful rule groups to allow only the on-premises IP ranges.
AWS Network Firewall can inspect and filter traffic between the Transit Gateway attachment and the production VPC.
- C
Use Transit Gateway route tables to blackhole traffic from other IP ranges.
Why wrong: Transit Gateway route tables cannot filter by source IP; they only determine next hops.
- D
Create a VPC peering connection between the on-premises network and the production VPC.
Why wrong: VPC peering is not used with on-premises networks and does not provide filtering.
Quick Answer
The correct approach is to deploy AWS Network Firewall in the production VPC and configure stateful rule groups to allow only the specific on-premises IP ranges. This works because AWS Transit Gateway connects multiple VPCs and on-premises networks via Direct Connect, but it does not perform packet-level filtering—it only handles routing through its route tables. By placing AWS Network Firewall as a centralized inspection point within the production VPC, you can enforce granular, stateful filtering on all traffic entering from the Transit Gateway attachment, ensuring only permitted on-premises IPs reach your workloads. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding that Transit Gateway route tables control path selection, not traffic filtering, and that native VPC security groups or network ACLs cannot inspect traffic traversing the Transit Gateway itself. A common trap is assuming Transit Gateway route tables can filter by IP address, but they only determine which attachment receives the traffic. Memory tip: Think of Transit Gateway as a highway interchange—it directs cars to the right exit, but you need a toll booth (Network Firewall) to check each car’s license plate.
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 uses AWS Transit Gateway to connect multiple VPCs and on-premises networks via AWS Direct Connect. They want to ensure that only traffic from specific on-premises IP ranges is allowed into the production VPC. Which approach should they use?
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
Deploy AWS Network Firewall in the production VPC and configure stateful rule groups to allow only the on-premises IP ranges.
AWS Transit Gateway supports route tables and can propagate routes from Direct Connect virtual interfaces. To filter traffic, you can use a network firewall appliance or AWS Network Firewall. However, the simplest approach is to use security groups and network ACLs within the VPC, but the question is about Transit Gateway. The best practice is to use AWS Network Firewall to inspect and filter traffic between attachments. Option C is correct. Option A (VPC peering) is not relevant. Option B (Direct Connect gateway) does not filter traffic. Option D (Transit Gateway route tables) does not filter by IP; they only determine routing.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the Direct Connect gateway to only advertise specific prefixes to the Transit Gateway.
Why it's wrong here
Direct Connect gateway advertises routes but does not filter traffic; it only controls route propagation.
- ✓
Deploy AWS Network Firewall in the production VPC and configure stateful rule groups to allow only the on-premises IP ranges.
- ✗
Use Transit Gateway route tables to blackhole traffic from other IP ranges.
Why it's wrong here
Transit Gateway route tables cannot filter by source IP; they only determine next hops.
- ✗
Create a VPC peering connection between the on-premises network and the production VPC.
Why it's wrong here
VPC peering is not used with on-premises networks and does not provide filtering.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related ANS-C01 ACL questions on filtering logic and placement.
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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 — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Deploy AWS Network Firewall in the production VPC and configure stateful rule groups to allow only the on-premises IP ranges. — AWS Transit Gateway supports route tables and can propagate routes from Direct Connect virtual interfaces. To filter traffic, you can use a network firewall appliance or AWS Network Firewall. However, the simplest approach is to use security groups and network ACLs within the VPC, but the question is about Transit Gateway. The best practice is to use AWS Network Firewall to inspect and filter traffic between attachments. Option C is correct. Option A (VPC peering) is not relevant. Option B (Direct Connect gateway) does not filter traffic. Option D (Transit Gateway route tables) does not filter by IP; they only determine routing.
What should I do if I get this ANS-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related ANS-C01 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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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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