The answer is to subscribe to AWS Shield Advanced and deploy AWS WAF on the ALB. This combination provides defense-in-depth at the network edge: AWS Shield Advanced offers enhanced detection and mitigation against large-scale DDoS attacks, while AWS WAF allows you to create custom rules to filter out malicious application-layer traffic before it reaches the ALB. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of edge protection versus subnet-level controls—a common trap is confusing Network ACLs (which operate at the subnet level, not the edge) with true edge services. Remember that Shield Standard is free and automatic but lacks the advanced protections needed for a large-scale e-commerce platform, and Route 53 handles DNS, not traffic mitigation. A useful memory tip is “Edge, not Subnet”: for DDoS protection at the internet-facing boundary, always pair Shield Advanced with WAF on the ALB.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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 is designing a network for a large-scale e-commerce platform that must handle sudden traffic spikes. The architecture uses an Application Load Balancer (ALB) in front of an Auto Scaling group of EC2 instances across multiple Availability Zones. The ALB is internet-facing. To protect against DDoS attacks, which AWS services should be used at the network edge?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Subscribe to AWS Shield Advanced and deploy AWS WAF on the ALB.
Option D is correct. AWS Shield Advanced provides enhanced protection against DDoS attacks, and AWS WAF can be integrated with ALB to filter malicious traffic. Option A is wrong because Network ACLs are not at the edge; they are subnet-level. Option B is wrong because AWS Shield Standard is included automatically but does not provide advanced protection. Option C is wrong because Route 53 is for DNS, not DDoS mitigation at the network edge.
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.
✓
Subscribe to AWS Shield Advanced and deploy AWS WAF on the ALB.
Why this is correct
Shield Advanced provides DDoS protection at the edge, and WAF filters application-layer attacks.
Configure network ACLs to allow only known IP ranges.
Why it's wrong here
Network ACLs are not effective against DDoS at the edge; they are per-subnet and static.
✗
Enable AWS Shield Standard and configure security groups to block traffic from suspicious sources.
Why it's wrong here
Shield Standard is included, but security groups are not sufficient for DDoS.
✗
Use Amazon Route 53 with DNS-based failover to redirect traffic away from the ALB during an attack.
Why it's wrong here
Route 53 is not a DDoS mitigation service at the edge.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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.
Network Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Subscribe to AWS Shield Advanced and deploy AWS WAF on the ALB. — Option D is correct. AWS Shield Advanced provides enhanced protection against DDoS attacks, and AWS WAF can be integrated with ALB to filter malicious traffic. Option A is wrong because Network ACLs are not at the edge; they are subnet-level. Option B is wrong because AWS Shield Standard is included automatically but does not provide advanced protection. Option C is wrong because Route 53 is for DNS, not DDoS mitigation at the network edge.
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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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.
Question Discussion
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