DBS-C01 Database Security Practice Question
Network Topology
A developer needs to connect to the RDS instance from an EC2 instance in the same VPC. The EC2 instance's security group allows outbound traffic to 0.0.0.0/0. The RDS security group inbound rules currently allow traffic from 0.0.0.0/0 on port 3306. After a security review, the company decides to restrict inbound traffic to the VPC only. Which inbound rule should be added to the RDS security group?
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
✓
An inbound rule allowing traffic from the EC2 instance's security group ID on port 3306.
Referencing the EC2 instance's security group ID in the RDS inbound rule is the most secure and specific method to restrict access to only that EC2 instance within the VPC. Option A is incorrect because the RDS endpoint is a DNS name for the database instance, not a source IP or security group. Option C is too broad, allowing any traffic from the 10.0.0.0/8 range, which may include subnets outside the VPC. Option D is less specific than using the security group ID and could permit access from any resource within the VPC CIDR, whereas the security group approach provides granular control.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
An inbound rule allowing traffic from the RDS endpoint address on port 3306.
Why it's wrong here
Endpoint address is a DNS name, not a source IP.
- ✓
An inbound rule allowing traffic from the EC2 instance's security group ID on port 3306.
Why this is correct
This restricts access to only the EC2 instances in that security group.
- ✗
An inbound rule allowing traffic from 10.0.0.0/8 on port 3306.
Why it's wrong here
Too broad, allows any IP in the 10.0.0.0/8 range.
- ✗
An inbound rule allowing traffic from the VPC CIDR (e.g., 10.0.0.0/16) on port 3306.
Why it's wrong here
Allows any resource in the VPC, not just the EC2 instance.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DBS-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 DBS-C01 exam.