The correct answer is to modify the security group attached to the ALB to allow only inbound traffic from 203.0.113.0/24 on port 443. Security groups act as a virtual firewall for your ALB, and by restricting the source IP to the corporate range, you directly block all other internet traffic while keeping the ALB in the public subnet. This approach is both stateful and simpler than using a WAF or NACL, which are unnecessary for basic IP filtering. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of security group behavior versus network ACLs and WAFs—a common trap is overcomplicating the fix by suggesting a WAF when a security group change is sufficient. Remember the memory tip: “SG for IP, WAF for app” — security groups handle IP-based access control, while WAFs inspect application-layer threats.
PAS-C01 Technology Practice Question
This PAS-C01 practice question tests your understanding of technology. 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 SAP BusinessObjects (BO) on AWS. The BO servers run on EC2 instances in a private subnet. Users access the BI Launch Pad through an Application Load Balancer (ALB) in a public subnet. The company recently received a security audit finding that the ALB is accessible from the internet on port 443, but the security group allows inbound traffic from 0.0.0.0/0. The audit requires that only the company's corporate IP range (203.0.113.0/24) should be allowed. Additionally, the company wants to reduce the attack surface by blocking traffic from other IPs. What should the company do to meet the security requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Modify the security group attached to the ALB to allow only inbound traffic from 203.0.113.0/24 on port 443.
Option A is correct because updating the ALB security group to restrict inbound traffic to the corporate IP range is the simplest and most effective solution. Option B is wrong because a WAF is not necessary for IP restriction; security groups can do it. Option C is wrong because a NACL can also restrict, but security groups are stateful and easier. Option D is wrong because moving the ALB to a private subnet would block all internet traffic.
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.
✗
Deploy AWS WAF on the ALB and create a rule to allow only the corporate IP range.
Why it's wrong here
WAF is overkill for simple IP restriction; security groups suffice.
✓
Modify the security group attached to the ALB to allow only inbound traffic from 203.0.113.0/24 on port 443.
Why this is correct
Security groups can restrict traffic by source IP.
Replace the security group with a network ACL on the ALB subnet to allow only the corporate IP range.
Why it's wrong here
NACLs are stateless and more complex; security groups are preferred.
✗
Move the ALB to a private subnet and use a VPN for user access.
Why it's wrong here
Would block all internet access, not just restrict IPs.
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 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.
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 PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Technology — This question tests Technology — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Modify the security group attached to the ALB to allow only inbound traffic from 203.0.113.0/24 on port 443. — Option A is correct because updating the ALB security group to restrict inbound traffic to the corporate IP range is the simplest and most effective solution. Option B is wrong because a WAF is not necessary for IP restriction; security groups can do it. Option C is wrong because a NACL can also restrict, but security groups are stateful and easier. Option D is wrong because moving the ALB to a private subnet would block all internet traffic.
What should I do if I get this PAS-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 PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This PAS-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 PAS-C01 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.