This SCS-C02 practice question tests your understanding of infrastructure security. 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 wants to block SSH access (port 22) to all EC2 instances from the internet, but allow SSH from a specific management VPN IP range (10.0.0.0/16). Which configuration should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure a security group to allow inbound SSH from 10.0.0.0/16 only.
Security groups are stateful and can be used to allow inbound SSH from the management IP range while denying all other traffic. Network ACLs are stateless and require separate inbound/outbound rules. IAM does not control network access.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Configure a security group to allow inbound SSH from 10.0.0.0/16 only.
Why this is correct
The default deny all rule will block other traffic.
Related concept
Standard ACLs match source addresses.
✗
Use an IAM policy to restrict SSH access to the management IP range.
Why it's wrong here
IAM does not control network traffic.
✗
Configure a network ACL to allow inbound SSH from 10.0.0.0/16 and deny from 0.0.0.0/0.
Why it's wrong here
Network ACLs are stateless; you must also configure outbound rules. Security groups are simpler.
✗
Configure a security group to allow inbound SSH from 0.0.0.0/0 and deny from 10.0.0.0/16.
Why it's wrong here
This would allow all except the management range, opposite of what is needed.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
Infrastructure Security — This question tests Infrastructure Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Configure a security group to allow inbound SSH from 10.0.0.0/16 only. — Security groups are stateful and can be used to allow inbound SSH from the management IP range while denying all other traffic. Network ACLs are stateless and require separate inbound/outbound rules. IAM does not control network access.
What should I do if I get this SCS-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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