📖 What is AWS Network Load Balancer (NLB)?
AWS Network Load Balancer (NLB) is a high-performance Layer 4 load balancer capable of handling millions of requests per second with ultra-low latency. It operates at the connection level, making it ideal for TCP, UDP, and TLS traffic where static IP addresses are required.
"If the exam question mentions "static IP" or "extreme performance" for non-HTTP traffic, NLB is almost always the correct answer."
📚 Certification: AWS Certified Solutions Architect - Associate (SAA-C03)
🔑 What are the Key Concepts of AWS Network Load Balancer (NLB)?
- ▸ Operates at the transport layer (Layer 4), routing traffic based on IP protocol data without inspecting the application-level payload, ensuring high efficiency and speed.
- ▸ Provides a static IP address per Availability Zone, which is essential for clients who must allow-list specific IPs in their corporate firewalls.
- ▸ Handles millions of requests per second with ultra-low latency and doesn't require 'pre-warming' to manage sudden, massive spikes in incoming traffic.
- ▸ Supports diverse target types, including instance IDs, IP addresses, and even Application Load Balancers, enabling complex architectural routing patterns.
- ▸ Optimized for TCP, UDP, and TLS traffic, making it the primary choice for non-HTTP applications such as gaming servers or VoIP services.
🎯 How does AWS Network Load Balancer (NLB) appear on the SAA-C03 Exam?
You may be asked to design a solution for a legacy application that requires a fixed entry point IP address so that external clients can configure their corporate firewall allow-lists.
A scenario might describe a high-performance application experiencing volatile traffic spikes that requires ultra-low latency for TCP connections, where the overhead of Layer 7 processing in an ALB is unacceptable.
Expect questions about routing traffic to an Application Load Balancer while maintaining a static IP address, which is achieved by placing an NLB in front of the ALB to provide the fixed IP.
❓ Frequently Asked Questions
When should I choose an NLB over an ALB?
Choose NLB for Layer 4 needs: TCP/UDP traffic, static IP requirements, or extreme performance. Choose ALB for Layer 7 needs: HTTP/HTTPS traffic, URL-based routing, or advanced request-level load balancing features.
How does NLB handle client IP addresses differently than ALB?
NLB preserves the client's source IP address when routing to instance targets. In contrast, ALB replaces the source IP with its own, requiring the use of X-Forwarded-For headers to identify the client.