ANS-C01 Network Implementation Practice Question
A company is designing a highly available architecture for a web application using an Application Load Balancer (ALB) across multiple Availability Zones. The ALB is internet-facing and uses TLS termination. The application requires that client IP addresses be preserved in the backend logs. The backend instances are in private subnets behind the ALB. Which configuration will ensure client IP addresses are preserved without additional overhead?
⚠ Common exam trap
Many exam-takers confuse Proxy Protocol v2 (an NLB feature) with the ALB's X-Forwarded-For mechanism, or assume that preserving client IPs requires a complex solution like a VPC Endpoint or replacing the load balancer, when the ALB already handles it natively for HTTP traffic.
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 the ALB to pass the X-Forwarded-For header and ensure backend logs parse it
The ALB automatically adds the X-Forwarded-For header to HTTP requests, containing the original client IP address. Since the backend instances are in private subnets and receive traffic from the ALB's private IPs, parsing this header in the backend logs is the standard, zero-overhead method to preserve client IPs for HTTP/HTTPS traffic with TLS termination.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Attach a VPC Endpoint to the ALB to capture client IP
Why it's wrong here
Incorrect; VPC Endpoints are for private access to AWS services, not for client IP preservation.
- ✗
Enable Proxy Protocol v2 on the target group
Why it's wrong here
Incorrect; Proxy Protocol is needed for TCP traffic, but ALB already preserves IP via X-Forwarded-For for HTTP/HTTPS.
- ✗
Replace the ALB with a Network Load Balancer (NLB)
Why it's wrong here
Incorrect; NLB preserves client IP for TCP/UDP, but the application uses HTTP, and switching to NLB would lose TLS termination and HTTP features.
- ✓
Configure the ALB to pass the X-Forwarded-For header and ensure backend logs parse it
Why this is correct
Correct; ALB automatically adds X-Forwarded-For header, and backend can log that to capture client IP.
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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.