DBS-C01 Security Group Practice Question
A company is deploying a new Amazon RDS for Oracle database in a VPC. The database must be accessed by an application running on an EC2 instance in a different subnet. Which THREE steps are required to allow this access?
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
✓
Configure the network ACL for the RDS subnet to allow inbound traffic from the EC2 subnet.
The security group of the RDS instance must allow inbound traffic from the EC2 security group, which is option E. The VPC must have the 'Enable DNS hostnames' attribute set to true (option D) so that the RDS endpoint resolves correctly. Additionally, the network ACL for the RDS subnet must allow inbound traffic from the EC2 subnet (option C). Option A (VPC peering) is not needed because both resources are in the same VPC. Option B (Internet Gateway) is not needed because traffic is within the VPC and does not require internet access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a VPC peering connection between the subnets.
Why it's wrong here
Subnets are in same VPC, no peering needed.
- ✗
Attach an Internet Gateway to the VPC.
Why it's wrong here
Internet Gateway is for public access, not needed for private subnet.
- ✓
Configure the network ACL for the RDS subnet to allow inbound traffic from the EC2 subnet.
Why this is correct
NACLs provide stateless filtering.
- ✓
Ensure the VPC has the 'Enable DNS hostnames' attribute set to true.
Why this is correct
Required for DNS resolution.
- ✓
Add an inbound rule to the RDS security group that allows traffic from the EC2 security group.
Why this is correct
Required for inbound access.
Visual reference
Go deeper
Related to this question
About these practice questions
This DBS-C01 question is part of Courseiva's 1,663-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.