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Question 374 of 1,705
Network Security, Compliance and Governance →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct combination is an ALB security group with inbound rules allowing 0.0.0.0/0 on ports 80 and 443, and an outbound rule allowing traffic to the web server security group on the application port, paired with a web server security group that allows inbound traffic from the ALB security group on the application port and an outbound rule allowing 0.0.0.0/0 on ephemeral ports. This works because security groups are stateful for return traffic, so the web servers’ outbound rule to 0.0.0.0/0 on ephemeral ports permits responses from the internet for updates without needing a separate inbound rule. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of security group chaining and the distinction between stateful security groups and stateless NACLs—a common trap is confusing outbound ephemeral port ranges with inbound rules or using VPC CIDR instead of the ALB security group ID. Remember the memory tip: “ALB faces the world, web servers face the ALB, and ephemeral outbound keeps updates flowing.”

ANS-C01 Network Security, Compliance and Governance Practice Question

This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 deploying a multi-tier web application on EC2 instances behind an Application Load Balancer (ALB). The security team requires that the web servers only accept traffic from the ALB and that the ALB only accepts traffic from the internet on ports 80 and 443. Additionally, the web servers should be able to make outbound connections to the internet for updates. Which combination of security group rules meets these requirements?

Question 1hardmultiple choice
Read the full NAT/PAT explanation →

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

✓

ALB SG: inbound 0.0.0.0/0 on 80/443, outbound to web SG on app port; Web SG: inbound from ALB SG on app port, outbound to 0.0.0.0/0 on ephemeral

The ALB security group should allow inbound from 0.0.0.0/0 on 80 and 443, and outbound to web servers. The web server security group should allow inbound from ALB security group on application port, and outbound to 0.0.0.0/0 on ephemeral ports. Option D is correct. Option A is wrong because it uses VPC CIDR. Option B is wrong because it restricts outbound. Option C is wrong because NACLs are not the best fit.

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.

  • ✗

    Use network ACLs instead: public subnet NACL allow 80/443 inbound, private subnet NACL allow from ALB on app port

    Why it's wrong here

    NACLs are stateless and require explicit ephemeral port rules; security groups are simpler.

  • ✓

    ALB SG: inbound 0.0.0.0/0 on 80/443, outbound to web SG on app port; Web SG: inbound from ALB SG on app port, outbound to 0.0.0.0/0 on ephemeral

    Why this is correct

    Correct use of security group references.

    Related concept

    CIDR notation defines the prefix length.

  • ✗

    ALB SG: inbound 0.0.0.0/0 on 80/443, outbound deny all; Web SG: inbound from ALB SG on app port, outbound allow all

    Why it's wrong here

    ALB outbound deny all would block traffic to web servers.

  • ✗

    ALB SG: inbound 0.0.0.0/0 on 80/443, outbound to web SG on app port; Web SG: inbound from VPC CIDR on app port, outbound to 0.0.0.0/0 on ephemeral

    Why it's wrong here

    Web SG inbound from VPC CIDR is too broad; should be from ALB SG.

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 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 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: ALB SG: inbound 0.0.0.0/0 on 80/443, outbound to web SG on app port; Web SG: inbound from ALB SG on app port, outbound to 0.0.0.0/0 on ephemeral — The ALB security group should allow inbound from 0.0.0.0/0 on 80 and 443, and outbound to web servers. The web server security group should allow inbound from ALB security group on application port, and outbound to 0.0.0.0/0 on ephemeral ports. Option D is correct. Option A is wrong because it uses VPC CIDR. Option B is wrong because it restricts outbound. Option C is wrong because NACLs are not the best fit.

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

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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.