SOA-C02 Networking and Content Delivery Practice Question
A company has an application that requires UDP traffic to be distributed across multiple EC2 instances. Which AWS load balancer type should be used?
⚠ Common exam trap
Test-takers frequently confuse the Application Load Balancer's support for WebSockets (which start as HTTP) with UDP support, or assume the Classic Load Balancer can handle any Layer 4 protocol, but AWS specifically removed UDP support from CLB and ALB, reserving it for NLB.
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
✓
Network Load Balancer
A Network Load Balancer (NLB) operates at Layer 4 and can handle both TCP and UDP traffic, making it the correct choice for distributing UDP traffic across multiple EC2 instances. Unlike other load balancers, NLB preserves the source IP address and can forward UDP packets without inspecting application-layer headers, which is essential for UDP-based applications such as DNS, VoIP, or gaming servers.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Network Load Balancer
Why this is correct
Network Load Balancer (NLB) operates at Layer 4 of the OSI model and explicitly supports UDP traffic, along with TCP and TLS. It is designed to handle millions of requests per second with ultra-low latency, making it the only Elastic Load Balancer variant capable of routing connectionless UDP packets, such as DNS or NTP queries, to backend targets. For UDP workloads, NLB preserves the client source IP and can be allocated a static Elastic IP, which is often required for firewall allow-listing in front of your application.
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Classic Load Balancer
Why it's wrong here
Classic Load Balancer (CLB) is the legacy Elastic Load Balancer and lacks any native UDP support. It functions at both Layer 4 (TCP/SSL) and Layer 7 (HTTP/HTTPS), but its documentation and implementation fundamentally omit UDP as a supported protocol. Consequently, any attempt to configure a classic load balancer for UDP traffic will fail, because CLB simply has no listener option for the connectionless transport protocol.
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Amazon CloudFront
Why it's wrong here
Amazon CloudFront is a global content delivery network (CDN) that accelerates the delivery of web content, primarily over HTTP/HTTPS, by caching content at AWS edge locations. It is not a load balancer and does not forward or distribute raw UDP traffic to origin servers. Even if a distribution is configured with UDP-based origins, CloudFront only accepts standard web requests and cannot terminate or route connectionless UDP packets, making it entirely unsuitable for this requirement.
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Application Load Balancer
Why it's wrong here
Application Load Balancer (ALB) works exclusively at Layer 7, meaning it understands and routes traffic based on application-level protocols such as HTTP, HTTPS, and gRPC. It has no capability to inspect or forward UDP datagrams because its listener configuration only supports HTTP/HTTPS (and gRPC over HTTP/2). Since UDP is a connectionless Layer 4 protocol, the ALB cannot terminate or route it, so an ALB cannot satisfy the application's need for UDP traffic handling.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-C02 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 SOA-C02 exam.