ANS-C01 Network Management and Operations Practice Question
Network Topology
A network engineer is troubleshooting why an EC2 instance (with the above security group) is not responding to HTTP requests from the internet. The instance is in a public subnet with an Internet Gateway attached. The route table has a default route to the Internet Gateway. What is the most likely cause?
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
✓
The security group only allows traffic from the 10.0.0.0/8 range
The security group only allows inbound HTTP traffic from the 10.0.0.0/8 IP range, which is a private address space. Since the request originates from the internet (a public IP), it does not match the allowed source and is therefore denied. Option A correctly identifies this issue. Options B, C, and D are incorrect: ICMP is not required for HTTP, the route table does have a default route to the IGW, and there is no information about network ACLs blocking HTTP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The security group only allows traffic from the 10.0.0.0/8 range
Why this is correct
The security group rule only permits HTTP from the private 10.0.0.0/8 CIDR, not from the internet.
- ✗
The security group does not allow inbound ICMP traffic
Why it's wrong here
The issue is with HTTP, not ICMP.
- ✗
The route table does not have a route for the internet
Why it's wrong here
The route table has a default route to the Internet Gateway per the stem.
- ✗
The network ACL is blocking inbound HTTP
Why it's wrong here
No information about NACLs, and security groups are the first line of defense.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.