DOP-C02 Resilient Cloud Solutions Practice Question
This DOP-C02 practice question tests your understanding of resilient cloud solutions. 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 startup runs a web application on EC2 instances behind an Application Load Balancer. They want to improve resilience by distributing instances across multiple Availability Zones. Currently, all instances are in us-east-1a. They create a launch template and an Auto Scaling group with a desired capacity of 2. They configure the Auto Scaling group to use two subnets: one in us-east-1a and one in us-east-1b. However, after updating, all instances remain in us-east-1a. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Auto Scaling group's subnet configuration was not updated to include the new subnet.
Auto Scaling group distributes instances across subnets specified. If only one subnet is used, it may be because the launch template specifies only one subnet or the Auto Scaling group's subnets were not updated. The most common cause is that the Auto Scaling group's subnet list still contains only the original subnet.
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.
✗
The instance type is not available in us-east-1b.
Why it's wrong here
If instance type unavailable, Auto Scaling would fail to launch, but would try other subnets.
✓
The Auto Scaling group's subnet configuration was not updated to include the new subnet.
Why this is correct
The group must have both subnets associated to distribute instances.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The new subnet in us-east-1b has no route to the internet.
Why it's wrong here
Lack of internet route would not prevent instance launch; instances would launch but be unreachable.
✗
The launch template specifies a single subnet in us-east-1a.
Why it's wrong here
Launch templates do not specify subnets; Auto Scaling group does.
Common exam traps
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The Auto Scaling group's subnet configuration was not updated to include the new subnet. — Auto Scaling group distributes instances across subnets specified. If only one subnet is used, it may be because the launch template specifies only one subnet or the Auto Scaling group's subnets were not updated. The most common cause is that the Auto Scaling group's subnet list still contains only the original subnet.
What should I do if I get this DOP-C02 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 DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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