ANS-C01 Network Design Practice Question
A company is designing a global application that will use Amazon CloudFront to serve content from an Application Load Balancer (ALB) in us-east-1. They want to restrict access to the ALB so that it only accepts traffic from CloudFront. Additionally, they want to ensure that if someone bypasses CloudFront and directly accesses the ALB, the request is denied. Which solution should they implement?
⚠ Common exam trap
AWS often tests the misconception that CloudFront Origin Access Control (OAC) or IP-based restrictions (security groups or WAF) are sufficient for ALB origins, but the trap is that OAC only works with S3 and IP lists are dynamic and spoofable, making the custom header method the only reliable solution for non-S3 origins.
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 CloudFront to add a custom HTTP header (e.g., X-Origin-Verify) to requests forwarded to the ALB. Configure the ALB to only forward requests that contain that specific header to the target group.
It uses a custom HTTP header (e.g., X-Origin-Verify) that CloudFront adds to requests forwarded to the ALB, and the ALB is configured to only forward requests containing that specific header to the target group. This ensures that any request not originating from CloudFront (i.e., direct access to the ALB) lacks the header and is denied, providing a secure and scalable method to restrict access without relying on static IP lists.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use CloudFront Origin Access Control (OAC) to restrict access to the ALB.
Why it's wrong here
OAC is designed for S3 bucket origins, not ALB.
- ✗
Configure the ALB security group to allow inbound traffic only from the CloudFront IP address ranges published in the AWS IP address ranges JSON file.
Why it's wrong here
CloudFront IP ranges change frequently, and maintaining security group updates is not scalable.
- ✗
Use AWS WAF on the ALB with a rule that allows traffic only from CloudFront IP ranges.
Why it's wrong here
CloudFront IP ranges are dynamic; WAF rules would need constant updates.
- ✓
Configure CloudFront to add a custom HTTP header (e.g., X-Origin-Verify) to requests forwarded to the ALB. Configure the ALB to only forward requests that contain that specific header to the target group.
Why this is correct
This ensures that only requests from CloudFront with the correct header are accepted, preventing direct access.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-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 ANS-C01 exam.