ANS-C01 Network Design Practice Question
A company is migrating a legacy application to AWS. The application requires a fixed IP address for outbound traffic to a partner's firewall. The application will run on Amazon EC2 instances in a private subnet. Which design meets the requirement without exposing the instances to inbound internet traffic?
⚠ Common exam trap
Many candidates confuse a NAT gateway with an Internet Gateway, thinking both provide outbound connectivity, but an Internet Gateway alone does not offer a fixed source IP for private instances and would expose them to inbound traffic if public IPs are assigned.
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 with an Elastic IP and route outbound traffic through it
A NAT gateway with an Elastic IP provides a fixed public IP address for outbound traffic from instances in a private subnet while preventing any unsolicited inbound connections from the internet. The NAT gateway translates the private source IPs of the instances to its own Elastic IP, meeting the partner firewall's requirement for a fixed source IP without exposing the EC2 instances directly.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Deploy a NAT gateway with an Elastic IP and route outbound traffic through it
Why this is correct
A NAT gateway with an Elastic IP provides a single fixed IP for all outbound traffic from private instances, and no inbound traffic is allowed.
- ✗
Attach an Internet Gateway to the VPC and assign public IPs to the instances
Why it's wrong here
Assigning public IPs would expose instances to inbound traffic and does not provide a fixed outbound IP because multiple instances would have different IPs.
- ✗
Place the instances behind an Application Load Balancer
Why it's wrong here
An ALB handles inbound traffic, but outbound traffic from instances would still use the instance's own IP, which is not fixed.
- ✗
Create a VPC Gateway Endpoint for the partner's service
Why it's wrong here
A Gateway Endpoint only supports AWS services like S3 and DynamoDB, not third-party partners.
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JA
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.