SAP-C02 Continuous Improvement for Existing Solutions Practice Question
Network Topology
A Solutions Architect runs the following command for an EC2 instance that is part of an Auto Scaling group. The instance is in a private subnet and should only receive traffic from an Application Load Balancer. However, the instance is accessible from the internet.
```
$ aws ec2 describe-instances --instance-id i-0abcd1234efgh5678
{
"Reservations": [
{
"Instances": [
{
"InstanceId": "i-0abcd1234efgh5678",
"SecurityGroups": [
{
"GroupName": "sg-web-app",
"GroupId": "sg-0123456789abcdef0"
}
],
"PublicIpAddress": null,
"SubnetId": "subnet-12345678",
"VpcId": "vpc-23456789"
}
]
}
]
}```
Based on the output, what is the most likely reason?
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 attached to the instance allows inbound traffic from 0.0.0.0/0.
The output shows the instance has a security group 'sg-web-app' attached to its network interface. If that security group allows inbound traffic from 0.0.0.0/0, the instance would be accessible from the internet regardless of the subnet being private. The subnet's route table (Option A) having a route to an internet gateway would not matter for inbound traffic because the instance is in a private subnet and lacks a public IP; the ALB would handle inbound traffic via its public IP and forward to the private instance. Option B is incorrect because an Elastic IP would make the instance directly reachable from the internet, but the output does not show an Elastic IP. Option C is incorrect because the instance is in a private subnet and would not have a public IP assigned automatically.
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 subnet's route table has a route to an internet gateway.
Why it's wrong here
The output does not show route tables; but if the instance is in a private subnet, the route table should not have a route to an IGW.
- ✗
The instance has an Elastic IP address attached.
Why it's wrong here
Elastic IP would appear in the output; it does not, and a private subnet instance typically does not have an EIP.
- ✗
The instance has a public IP address assigned.
Why it's wrong here
The output does not show a public IP; also, the instance is in a private subnet, so it should not have a public IP.
- ✓
The security group attached to the instance allows inbound traffic from 0.0.0.0/0.
Why this is correct
The security group 'sg-web-app' might have an inbound rule allowing all traffic, making the instance accessible even in a private subnet if there is a NAT gateway or if the instance has a public IP.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 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 SAP-C02 exam.