ANS-C01 Network Design Practice Question
A company is migrating a legacy on-premises application to AWS. The application uses a large number of short-lived TCP connections and requires low latency. The network team is considering using either a Network Load Balancer (NLB) or a Gateway Load Balancer (GWLB). Which of the following is a key advantage of using NLB over GWLB for this use case?
⚠ Common exam trap
Candidates often confuse GWLB's transparent inline appliance support with NLB's source IP preservation, assuming that GWLB also preserves source IP by default, when in fact it uses GENEVE encapsulation that obscures the original client IP unless additional configuration is applied.
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
✓
NLB preserves the client source IP, while GWLB does not by default.
For an application using a large number of short-lived TCP connections requiring low latency, NLB is the optimal choice because it operates at Layer 4 and preserves the client source IP address by default, which is critical for applications that need to log or process the original client IP. GWLB, by design, uses GENEVE encapsulation (UDP port 6081) to tunnel traffic to backend appliances, which replaces the client source IP with the NLB's private IP unless explicit configuration (e.g., proxy protocol) is used. This makes NLB the better fit for preserving source IP without additional overhead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
NLB can forward traffic to third-party virtual appliances.
Why it's wrong here
GWLB is specifically designed for that purpose, not NLB.
- ✗
NLB can handle higher throughput than GWLB.
Why it's wrong here
Both can handle high throughput; NLB is not necessarily higher.
- ✓
NLB preserves the client source IP, while GWLB does not by default.
Why this is correct
NLB preserves source IP; GWLB uses GENEVE encapsulation and hides original source IP.
- ✗
NLB supports TLS termination, while GWLB does not.
Why it's wrong here
Both support TLS termination.
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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.