PAS-C01 Migration Practice Question
A company is migrating a legacy on-premises application to AWS. The application requires static IP addresses for its clients to whitelist. The migration strategy includes using an Application Load Balancer (ALB) to distribute traffic across multiple EC2 instances in an Auto Scaling group. The clients require a fixed set of IP addresses to whitelist. Which solution meets the requirement?
⚠ Common exam trap
Test-takers frequently assume an Application Load Balancer can be assigned Elastic IPs because they are familiar with assigning EIPs to EC2 instances, but ALBs do not support static IP assignment at all, making the NLB the only correct choice for fixed whitelist IPs.
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
✓
Use a Network Load Balancer with Elastic IP addresses.
A Network Load Balancer (NLB) supports static IP addresses via Elastic IP (EIP) assignment per Availability Zone, which allows clients to whitelist a fixed set of IPs. The ALB, by contrast, does not support static IP assignment; its DNS name resolves to dynamic IPs that can change. Using an NLB with EIPs meets the requirement for a fixed whitelist while still distributing traffic to the ALB or directly to EC2 instances.
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 AWS Global Accelerator with the Application Load Balancer as an endpoint.
Why it's wrong here
Global Accelerator provides static IPs but is overkill and more expensive for this simple requirement.
- ✗
Use an Application Load Balancer and assign Elastic IP addresses to it.
Why it's wrong here
ALB does not support Elastic IP assignment; it uses dynamic IP addresses.
- ✓
Use a Network Load Balancer with Elastic IP addresses.
Why this is correct
NLB supports static IP addresses via Elastic IPs, meeting the whitelisting requirement.
- ✗
Launch EC2 instances with Elastic IPs and place them behind a NAT Gateway.
Why it's wrong here
This does not provide load balancing and high availability; NAT Gateway is for outbound traffic.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PAS-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 PAS-C01 exam.