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Network ImplementationmediumMultiple ChoiceObjective-mapped

ANS-C01 Network Implementation Practice Question

A company is migrating a legacy application that requires static IP addresses for its clients' firewall whitelisting. The application will be hosted on EC2 instances behind a Network Load Balancer (NLB) in a private subnet. Which approach should the company use to provide static IP addresses for outbound traffic?

⚠ Common exam trap

Watch out — candidates often confuse inbound static IPs (NLB with Elastic IPs) with outbound static IPs, or mistakenly think Elastic IPs on instances work in private subnets without a NAT device.

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

Deploy a NAT Gateway in a public subnet with an Elastic IP

A NAT Gateway in a public subnet with an Elastic IP provides a static source IP address for outbound traffic from private subnets. Since the EC2 instances are in a private subnet behind an NLB, they cannot directly reach the internet; the NAT Gateway translates their private IPs to the Elastic IP, which clients can whitelist. This ensures consistent outbound IPs without exposing the instances to inbound traffic.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Assign Elastic IPs to the EC2 instances

    Why it's wrong here

    Elastic IPs are for inbound access, but instances in private subnets cannot be assigned EIPs directly.

  • Use an internet-facing NLB with Elastic IPs

    Why it's wrong here

    Internet-facing NLB is for inbound traffic, not outbound.

  • Use a VPC endpoint for the application

    Why it's wrong here

    VPC endpoints provide private connectivity to AWS services, not static IPs for outbound traffic.

  • Deploy a NAT Gateway in a public subnet with an Elastic IP

    Why this is correct

    NAT Gateway with an Elastic IP provides a static source IP for outbound traffic from private subnets.

Visual reference

Inside (Private) PC-A 10.0.0.1 PC-B 10.0.0.2 NAT Router Outside (Public) 203.0.113.1 Inside Global Server PAT: many private IPs share one public IP via unique port numbers

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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.