ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 public and private subnets. They launch an Application Load Balancer (ALB) in the public subnets and targets in private subnets. Security requirements dictate that the targets should only accept traffic from the ALB. Which security group configuration meets this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the target security group inbound rule to allow HTTP from the ALB security group ID.
Option D is correct because referencing the ALB security group by ID in the target security group rule allows traffic from that specific SG, which is the best practice. Option A is wrong because that would allow traffic from any resource in the VPC. Option B is wrong because that would allow traffic from any source, not just ALB. Option C is wrong because the ALB is not a source by its own IP; its traffic comes from its ENIs which belong to the ALB SG.
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.
✗
Set the target security group inbound rule to allow HTTP from 0.0.0.0/0.
Why it's wrong here
Allows traffic from any IP, not just the ALB.
✓
Set the target security group inbound rule to allow HTTP from the ALB security group ID.
Why this is correct
This allows traffic only from the ALB's elastic network interfaces.
Set the target security group inbound rule to allow HTTP from the ALB's public IP address.
Why it's wrong here
ALB IPs can change, and this does not scale; also does not restrict to ALB only.
✗
Set the target security group inbound rule to allow HTTP from the VPC CIDR.
Why it's wrong here
Allows traffic from any resource in the VPC, not just ALB.
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.
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Set the target security group inbound rule to allow HTTP from the ALB security group ID. — Option D is correct because referencing the ALB security group by ID in the target security group rule allows traffic from that specific SG, which is the best practice. Option A is wrong because that would allow traffic from any resource in the VPC. Option B is wrong because that would allow traffic from any source, not just ALB. Option C is wrong because the ALB is not a source by its own IP; its traffic comes from its ENIs which belong to the ALB SG.
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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