- A
Enable route propagation for all VPC attachments in the Transit Gateway route table.
Why wrong: Propagation automatically adds routes, but doesn't force inspection.
- B
Create a blackhole route in the Transit Gateway route table for the VPC CIDR blocks that are destined for other VPCs.
Prevents direct routing between VPCs.
- C
Add a static route in the inspection VPC route tables pointing to the Transit Gateway for all other VPC CIDRs.
Sends traffic from inspection VPC to Transit Gateway for onward delivery.
- D
Configure a VPC Gateway Endpoint for the inspection VPC to attract traffic.
Why wrong: Gateway endpoints are for S3/DynamoDB, not inter-VPC routing.
- E
Deploy a NAT gateway in each VPC to route traffic through the inspection VPC.
Why wrong: NAT gateway is for outbound internet access.
Quick Answer
The correct answer involves adding a static route in the inspection VPC route tables pointing to the Transit Gateway for all other VPC CIDRs, combined with blackhole routes in the Transit Gateway route table to prevent direct VPC-to-VPC communication. This works because blackhole routes silently drop traffic that would otherwise bypass the inspection VPC, forcing all inter-VPC traffic to be routed through the centralized security appliance. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of Transit Gateway route tables and how to architect traffic inspection without using complex VPC peering. A common trap is assuming route propagation alone will steer traffic correctly, but propagation only learns routes—it does not force traffic through the inspection path. The key insight is that blackhole routes act as intentional dead-ends in the Transit Gateway, compelling traffic to follow the longer path via the inspection VPC’s advertised routes. Memory tip: think of blackhole routes as “traffic cops that block shortcuts” to enforce a mandatory inspection detour.
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 is implementing a hybrid network architecture with an AWS Transit Gateway connecting multiple VPCs and an on-premises data center via AWS Direct Connect. The company needs to ensure that traffic between VPCs is inspected by a centralized security appliance running on EC2 instances in a dedicated inspection VPC. To achieve this, traffic must be routed through the inspection VPC before reaching its destination. Which TWO configurations are required? (Choose two.)
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
Create a blackhole route in the Transit Gateway route table for the VPC CIDR blocks that are destined for other VPCs.
Option A is correct because blackhole routes in the Transit Gateway route table prevent direct VPC-to-VPC communication. Option C is correct because the inspection VPC must advertise specific routes to attract traffic. Option B is incorrect because enabling route propagation does not force traffic through inspection VPC. Option D is incorrect because NAT gateway is for outbound internet traffic. Option E is incorrect because VPC endpoints are not used for inter-VPC traffic inspection.
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.
- ✗
Enable route propagation for all VPC attachments in the Transit Gateway route table.
Why it's wrong here
Propagation automatically adds routes, but doesn't force inspection.
- ✓
Create a blackhole route in the Transit Gateway route table for the VPC CIDR blocks that are destined for other VPCs.
Why this is correct
Prevents direct routing between VPCs.
Related concept
CIDR notation defines the prefix length.
- ✓
Add a static route in the inspection VPC route tables pointing to the Transit Gateway for all other VPC CIDRs.
- ✗
Configure a VPC Gateway Endpoint for the inspection VPC to attract traffic.
Why it's wrong here
Gateway endpoints are for S3/DynamoDB, not inter-VPC routing.
- ✗
Deploy a NAT gateway in each VPC to route traffic through the inspection VPC.
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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Create a blackhole route in the Transit Gateway route table for the VPC CIDR blocks that are destined for other VPCs. — Option A is correct because blackhole routes in the Transit Gateway route table prevent direct VPC-to-VPC communication. Option C is correct because the inspection VPC must advertise specific routes to attract traffic. Option B is incorrect because enabling route propagation does not force traffic through inspection VPC. Option D is incorrect because NAT gateway is for outbound internet traffic. Option E is incorrect because VPC endpoints are not used for inter-VPC traffic inspection.
What should I do if I get this ANS-C01 question wrong?
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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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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