The answer is that the IAM role attached to the EC2 instance lacks the cloudwatch:PutMetricData permission. This is the most likely cause because while standard EC2 metrics like CPU utilization are automatically sent to CloudWatch, custom or detailed metrics—often required for high-resolution alarms—must be published by the CloudWatch agent running on the instance. Without the correct IAM permissions, the agent cannot push metric data, so the alarm never receives the data points needed to evaluate the threshold and trigger. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of the difference between default EC2 metrics and agent-published metrics, and it’s a common trap to blame network connectivity or instance state instead. A key memory tip: if the alarm is silent, check the agent’s IAM permissions first—no PutMetricData means no data, no trigger.
DOP-C02 Monitoring and Logging Practice Question
This DOP-C02 practice question tests your understanding of monitoring and logging. 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 DevOps engineer notices that a CloudWatch alarm for high CPU utilization on an EC2 instance is not triggering despite the CPU consistently above the threshold. The instance is in a VPC with a public subnet and has internet access. What is the most likely cause?
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 IAM role attached to the instance does not have the cloudwatch:PutMetricData permission.
Option D is correct because CloudWatch requires the SSM Agent or the CloudWatch agent to send metrics; the standard EC2 metrics include CPU utilization, but if the instance is not sending detailed metrics, the alarm may not trigger if the threshold is based on a higher-resolution metric. However, the most common cause is that the CloudWatch agent is not installed or configured, or the IAM role lacks permissions. If the instance does not have the correct IAM role to publish custom metrics, CloudWatch alarms may not trigger. Option A is wrong because CloudWatch can collect metrics from instances without a public IP if they have a NATgateway or VPC endpoint. Option B is wrong because CloudWatch alarms are evaluated based on metric data, not instance state. Option C is wrong because standard monitoring collects metrics every 5 minutes, which should be sufficient for high CPU, though detailed monitoring (1-minute) is recommended.
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 EC2 instance does not have a public IP address.
Why it's wrong here
Instances can send metrics via NAT or VPC endpoints; public IP not required.
✗
The instance is using basic monitoring (5-minute intervals) which delays the alarm.
Why it's wrong here
Basic monitoring still sends data; alarm should trigger eventually if consistently high.
✓
The IAM role attached to the instance does not have the cloudwatch:PutMetricData permission.
Why this is correct
Without proper IAM permissions, the CloudWatch agent cannot publish metrics, causing the alarm not to trigger.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The CloudWatch alarm is in the 'INSUFFICIENT_DATA' state because the instance is stopped.
Why it's wrong here
The alarm would show INSUFFICIENT_DATA if no data, but the instance is running.
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.
Trap categories for this question
Command / output trap
The alarm would show INSUFFICIENT_DATA if no data, but the instance is running.
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 DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Monitoring and Logging — This question tests Monitoring and Logging — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The IAM role attached to the instance does not have the cloudwatch:PutMetricData permission. — Option D is correct because CloudWatch requires the SSM Agent or the CloudWatch agent to send metrics; the standard EC2 metrics include CPU utilization, but if the instance is not sending detailed metrics, the alarm may not trigger if the threshold is based on a higher-resolution metric. However, the most common cause is that the CloudWatch agent is not installed or configured, or the IAM role lacks permissions. If the instance does not have the correct IAM role to publish custom metrics, CloudWatch alarms may not trigger. Option A is wrong because CloudWatch can collect metrics from instances without a public IP if they have a NAT gateway or VPC endpoint. Option B is wrong because CloudWatch alarms are evaluated based on metric data, not instance state. Option C is wrong because standard monitoring collects metrics every 5 minutes, which should be sufficient for high CPU, though detailed monitoring (1-minute) is recommended.
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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