PAS-C01 Technology Practice Question
Network Topology
Refer to the exhibit. A CloudFormation stack creation failed with the message 'WaitCondition received failed signal'. What is the most likely cause?
⚠ Common exam trap
The most common pitfall is confusing a timeout (no signal received) with a failed signal (signal with non-zero exit code). Candidates often assume network issues like security groups blocking cfn-signal, but the error explicitly states a failed signal was received, indicating a script error on the instance.
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
✓
The script executed via cfn-signal failed to complete successfully
The `WaitCondition` resource in CloudFormation is designed to pause stack creation until it receives a success signal from a resource, typically an EC2 instance running a cfn-init script. The 'WaitCondition received failed signal' error indicates that the signal sent was explicitly a failure signal (e.g., via `cfn-signal --exit-code 1`), not that the signal was lost or blocked. This most commonly occurs when the script executed by cfn-init or a user-data script encounters an error and exits with a non-zero exit code, causing cfn-signal to send a failure signal to the WaitCondition.
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 security group rules are blocking the cfn-signal communication
Why it's wrong here
cfn-signal uses HTTPS to CloudFormation endpoint, not blocked by typical security groups.
- ✗
The stack creation timed out after 1 hour
Why it's wrong here
Timeout would show a different status reason.
- ✓
The script executed via cfn-signal failed to complete successfully
Why this is correct
The WaitCondition expects a success signal; failure indicates script error.
- ✗
The EC2 instance type is not supported in the region
Why it's wrong here
That would be a different error, not a signal failure.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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