The correct choice is to associate AWS WAF with the ALB and make the ALB internet-facing. This works because AWS WAF integrates directly with Application Load Balancers at the regional level, inspecting HTTP and HTTPS traffic against web access control lists before it reaches the backend EC2 instances. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of where WAF can be attached—specifically, it supports ALB, CloudFront, and API Gateway, but not Network Load Balancers or Security Groups. A common trap is assuming a Security Group can apply WAF-like rules, but Security Groups are stateful packet filters, not application-layer inspectors. Another pitfall is adding CloudFront unnecessarily; while CloudFront can host WAF, the requirement here is for a regional load balancer directly accessible from the internet. Memory tip: remember that WAF inspects the web layer (Layer 7), so it only pairs with Layer 7 services like ALB—think “WAF with ALB, not NLB.”
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 has a VPC with an Application Load Balancer (ALB) that distributes traffic to EC2 instances in private subnets. The ALB needs to be accessible from the internet. The security team requires that all traffic to the ALB be inspected by AWS WAF. Which configuration meets these requirements?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Associate AWS WAF with the ALB and make the ALB internet-facing
Option B is correct because AWS WAF can be integrated with an ALB to inspect HTTP/HTTPS traffic. Option A is incorrect because a Network Load Balancer does not support AWS WAF. Option C is incorrect because Security Groups are stateful firewalls but do not support WAF rules. Option D is incorrect because CloudFront can have WAF, but it is a CDN, not a regional load balancer.
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.
✓
Associate AWS WAF with the ALB and make the ALB internet-facing
Why this is correct
ALB supports AWS WAF integration for web traffic inspection.
NLB does not support AWS WAF; WAF works with ALB and CloudFront.
✗
Place the ALB behind a Security Group that inspects traffic
Why it's wrong here
Security Groups are for allow/deny rules, not WAF inspection.
✗
Use Amazon CloudFront in front of the ALB with AWS WAF
Why it's wrong here
While valid, it adds unnecessary complexity; WAF directly on ALB is sufficient.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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 Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Associate AWS WAF with the ALB and make the ALB internet-facing — Option B is correct because AWS WAF can be integrated with an ALB to inspect HTTP/HTTPS traffic. Option A is incorrect because a Network Load Balancer does not support AWS WAF. Option C is incorrect because Security Groups are stateful firewalls but do not support WAF rules. Option D is incorrect because CloudFront can have WAF, but it is a CDN, not a regional load balancer.
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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Question Discussion
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