ANS-C01 Network Implementation Practice Question
A company has a VPC with multiple subnets across three Availability Zones. The company wants to deploy a Network Load Balancer (NLB) to distribute TCP traffic to a fleet of EC2 instances. The NLB must preserve the source IP address of the client. Which configuration is required?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that Proxy Protocol v2 must be enabled for source IP preservation on an NLB, when in fact NLBs preserve the source IP by default and Proxy Protocol is only needed for ALBs or when additional metadata is required.
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
✓
Create the NLB with a TCP listener and register the EC2 instances as targets in a target group.
Network Load Balancers (NLBs) preserve the source IP address of clients by default when using a TCP listener. No additional configuration is required to enable this behavior; the NLB forwards packets with the original source IP intact. Therefore, simply creating the NLB with a TCP listener and registering EC2 instances as targets is sufficient.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Proxy Protocol v2 on the NLB target group.
Why it's wrong here
Proxy Protocol adds a header but is not required for source IP preservation; NLB preserves IP by default.
- ✗
Enable cross-zone load balancing on the NLB.
Why it's wrong here
Cross-zone load balancing distributes traffic across AZs but does not affect source IP preservation.
- ✗
Attach a security group to the NLB that allows inbound traffic from the client IP range.
Why it's wrong here
NLBs do not use security groups; they are not stateful.
- ✓
Create the NLB with a TCP listener and register the EC2 instances as targets in a target group.
Why this is correct
NLB preserves source IP for TCP traffic when targets are instances.
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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.