The correct answer is to allow inbound TCP 443 from 0.0.0.0/0 and outbound TCP 1024-65535 to 0.0.0.0/0. This is required because network ACLs are stateless, meaning they do not automatically permit return traffic; you must explicitly define both inbound and outbound rules. The inbound rule allows HTTPS requests from the internet to the web server, while the outbound rule covers the ephemeral ports (1024-65535) that the server uses to send response packets back to the client. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of stateless vs. stateful filtering, a common trap where candidates forget the outbound rule or mistakenly restrict it to port 443. Remember the memory tip: “Stateless means you must state both directions—inbound for the request, outbound for the reply on ephemeral ports.”
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 security engineer is designing a network ACL for a public subnet. The subnet hosts a web server on port 443. Which inbound and outbound rules should be configured to allow HTTPS traffic from the internet? (Assume default deny all rule.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Inbound: allow TCP 443 from 0.0.0.0/0; Outbound: allow TCP 1024-65535 to 0.0.0.0/0.
Option C is correct because NACLs are stateless; you need explicit rules for both inbound and outbound traffic. Inbound rule allows HTTPS from internet, outbound rule allows return traffic (ephemeral ports) to internet. Option A is wrong because it does not allow return traffic. Option B is wrong because outbound rule is too restrictive (only port 443). Option D is wrong because inbound rule is too restrictive (only port 443 from ephemeral ports).
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.
✓
Inbound: allow TCP 443 from 0.0.0.0/0; Outbound: allow TCP 1024-65535 to 0.0.0.0/0.
Why this is correct
This allows incoming HTTPS and outgoing return traffic on ephemeral ports.
Inbound: allow TCP 443 from 0.0.0.0/0; Outbound: allow TCP 443 to 0.0.0.0/0.
Why it's wrong here
Return traffic from the web server uses ephemeral ports, not port 443.
✗
Inbound: allow TCP 1024-65535 from 0.0.0.0/0; Outbound: allow TCP 443 to 0.0.0.0/0.
Why it's wrong here
This would allow incoming on ephemeral ports and outgoing on 443, which is incorrect.
✗
Inbound: allow TCP 443 from 0.0.0.0/0; Outbound: allow TCP 443 to 0.0.0.0/0 for responses.
Why it's wrong here
Return traffic uses high ports (1024-65535), not port 443.
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: Inbound: allow TCP 443 from 0.0.0.0/0; Outbound: allow TCP 1024-65535 to 0.0.0.0/0. — Option C is correct because NACLs are stateless; you need explicit rules for both inbound and outbound traffic. Inbound rule allows HTTPS from internet, outbound rule allows return traffic (ephemeral ports) to internet. Option A is wrong because it does not allow return traffic. Option B is wrong because outbound rule is too restrictive (only port 443). Option D is wrong because inbound rule is too restrictive (only port 443 from ephemeral ports).
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.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. A network engineer reviews the NACL entries for a subnet. What is the effect of this NACL on inbound traffic?
hard
✓ A.Only SSH from the internal network and HTTPS from any IP are allowed.
B.All inbound traffic is allowed.
C.Only HTTPS traffic is allowed from any IP.
D.All inbound traffic is denied.
Why A: Option B is correct. Inbound rules: Rule 100 allows SSH from 10.0.0.0/16. Rule 200 allows HTTPS from anywhere. Rule 300 denies all other traffic. So only SSH from 10.0.0.0/16 and HTTPS from anywhere are allowed. Option A is wrong because SSH is not allowed from anywhere. Option C is wrong because HTTPS is allowed. Option D is wrong because the NACL is not fully open.
Variation 2. Refer to the exhibit. A network engineer examines the network ACL for a subnet. Which statement best describes the effect of this network ACL?
medium
A.Both inbound and outbound TCP traffic are allowed
✓ B.Inbound TCP traffic is allowed, but all outbound traffic is denied
C.All inbound traffic is allowed
D.All outbound traffic is allowed
Why B: The inbound rule allows TCP traffic (protocol 6) from all sources, but the default deny rule blocks all other inbound traffic. Outbound traffic is all denied. The explicit allow rule for inbound TCP takes precedence over the default deny. Option A is wrong because it allows TCP inbound. Option B is wrong because it allows TCP inbound. Option C is wrong because outbound is denied.
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.
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