Overview
Layer 4 (TCP/UDP) load balancer for extreme performance and static IPs.
Key Features
| Feature | Details |
|---|---|
| Layer | 4 (TCP, TLS, UDP) |
| Performance | Millions of requests/sec, ultra-low latency |
| Static IP | One static IP per AZ (can assign Elastic IP) |
| Security Groups | Supported (attach SG to NLB, similar to ALB) |
| Target Groups | EC2 instances, IP addresses, ALB |
| Health Checks | TCP, HTTP, or HTTPS |
| Free Tier | Not included |
See TCP, UDP, static IP, extreme performance, millions of requests → think NLB.
Elastic IP per AZ
When creating an NLB, for each AZ you enable:
- AWS assigns a fixed IPv4 address, OR
- You can assign your own Elastic IP per AZ
This means your application can be accessed via 1, 2, or 3 fixed IPs (one per AZ).
One static IP per AZ
Target Groups
| Target | Description |
|---|---|
| EC2 Instances | By instance ID |
| IP Addresses | Private IPs (EC2 or on-premises) |
| ALB | NLB in front of ALB (static IP + HTTP routing) |
NLB + ALB Combination
┌─────────┐ ┌─────────┐ ┌──────────┐
│ NLB │────▶│ ALB │────▶│ Target │
│ (Static │ │ (HTTP │ │ Groups │
│ IPs) │ │ routing)│ │ │
└─────────┘ └─────────┘ └──────────┘
Why? Get static IPs (NLB) + HTTP routing rules (ALB)
NLB in front of ALB
NLB vs ALB
| Feature | ALB | NLB |
|---|---|---|
| Layer | 7 (HTTP) | 4 (TCP/UDP) |
| Performance | High | Ultra-high (millions req/s) |
| IP | Fixed hostname | Static IP per AZ |
| Routing | Path, host, query | Port-based |
| Use case | Web apps | Gaming, IoT, financial |
Questions & Answers
Q1: What layer does NLB operate on?
Answer:
Layer 4 (TCP/UDP). It handles raw TCP, TLS, and UDP traffic without inspecting HTTP content.
Q2: When should you use NLB over ALB?
Answer:
When you need extreme performance (millions of req/s), static IPs/Elastic IPs, or TCP/UDP protocol support. ALB is for HTTP-level routing.
Q3: Can NLB provide static IP addresses?
Answer:
Yes. NLB has one static IP per AZ and you can assign Elastic IPs to each AZ. This is unique to NLB — ALB only provides a DNS hostname.
Q4: Can you put an NLB in front of an ALB?
Answer:
Yes. This gives you static IPs (NLB) combined with HTTP routing rules (ALB). It's a valid and common architecture.
Q5: What health check protocols does NLB support?
Answer:
TCP, HTTP, and HTTPS. Even though NLB operates at Layer 4, it can perform HTTP/HTTPS health checks on backend applications.
Q6: Is NLB included in the AWS free tier?
Answer:
No. NLB is not part of the free tier. You pay for NLB hours and data processed.
Q7: What are valid NLB target types?
Answer:
- EC2 instances (by instance ID)
- IP addresses (must be private IPs)
- Application Load Balancer (NLB → ALB)
Q8: What exam scenario points to NLB?
Answer:
"Application must be accessible via 1-3 static IPs" or "need to handle millions of requests per second" or "UDP traffic" → NLB.
Q9: How does NLB latency compare to ALB?
Answer:
NLB has ultra-low latency (100ms) compared to ALB (400ms). NLB passes traffic through without inspecting HTTP content.
Q10: Can NLB target on-premises servers?
Answer:
Yes. Register their private IP addresses as targets. This works via VPN or Direct Connect to your data center.
Check yourself
Quiz
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