DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is deploying an Amazon RDS for MySQL database in a VPC. The database must be accessible only from a specific set of application servers in the same VPC. Which configuration provides the most secure access?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the security group inbound rule to reference the security group of the application servers
Using a security group that references the application servers' security group is the most secure because it allows traffic based on security group ID, not IP. Option A (publicly accessible) is insecure. Option B (all traffic from VPC CIDR) is too broad. Option D (database subnet group) does not control ingress traffic.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Set the security group inbound rule to allow all traffic from the VPC CIDR
Why it's wrong here
Allows traffic from all resources in VPC, not just the app servers.
✗
Place the RDS instance in a separate subnet group
Why it's wrong here
Subnet groups do not control security group rules.
✗
Set the RDS instance to publicly accessible
Why it's wrong here
Public accessibility exposes the database to the internet.
✓
Set the security group inbound rule to reference the security group of the application servers
Why this is correct
Restricts access to resources with that security group.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DBS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Deployment and Migration — This question tests Deployment and Migration — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Set the security group inbound rule to reference the security group of the application servers — Using a security group that references the application servers' security group is the most secure because it allows traffic based on security group ID, not IP. Option A (publicly accessible) is insecure. Option B (all traffic from VPC CIDR) is too broad. Option D (database subnet group) does not control ingress traffic.
What should I do if I get this DBS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DBS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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