DBS-C01 Management and Operations Practice Question
Network Topology
A DBA runs the above AWS CLI command. The DB instance is an Amazon RDS for MySQL instance. The DBA needs to connect to the database from an EC2 instance in the same VPC but cannot connect. Which action should be taken first?
⚠ Common exam trap
The trap here is that candidates often jump to checking DNS resolution (Option A) or instance status (Option D) first, overlooking that security group inbound rules are the most frequent cause of connectivity failures in same-VPC RDS scenarios.
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
✓
Check the inbound rules of the security group for port 3306.
The most common cause of connectivity failure from an EC2 instance to an RDS for MySQL instance in the same VPC is that the security group associated with the RDS instance does not allow inbound traffic on port 3306 from the EC2 instance's security group or IP address. Checking the inbound rules of the security group for port 3306 is the first logical troubleshooting step because it directly addresses the network access control that governs whether the EC2 instance can initiate a TCP connection to the database.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Verify that the DB instance endpoint resolves correctly from the EC2 instance.
Why it's wrong here
The endpoint appears correct.
- ✓
Check the inbound rules of the security group for port 3306.
Why this is correct
Security group inbound rules control access to the DB instance.
- ✗
Enable encryption on the DB instance.
Why it's wrong here
Encryption is not required for connectivity.
- ✗
Check the DB instance status in the output.
Why it's wrong here
The status is 'available'.
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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.