3.1 Azure Load Balancer and Traffic Manager
📘Microsoft Azure Networking Solutions (AZ-700)
Overview
An Azure Load Balancer distributes network traffic across multiple servers (virtual machines, VM scale sets, or instances) to ensure high availability and reliability of applications. It operates at Layer 4 (Transport layer), which means it deals with TCP and UDP traffic.
When choosing a Load Balancer, the SKU and tier are the most important factors, because they define its features, scale, and pricing.
1. Load Balancer SKUs
Azure has two Load Balancer SKUs:
| SKU | Purpose | Features | Use Cases |
|---|---|---|---|
| Basic | Simple, small-scale workloads | • Supports up to 300 instances per backend pool • Single availability set or single virtual network • No zone redundancy • Free tier | Small apps, dev/test environments, single-region apps |
| Standard | Production-grade, larger-scale workloads | • Supports up to 1000 instances per backend pool • Works across availability zones • Provides higher security (needs NSG rules for inbound) • Metrics in Azure Monitor • SLA guaranteed | Enterprise apps, multi-region apps, apps needing higher security, high availability |
Key Differences Exam Candidates Must Know:
- Availability Zones: Only Standard supports zone redundancy.
- Scaling: Standard scales larger than Basic.
- SLA: Standard has guaranteed uptime SLA; Basic does not.
- Security: Standard requires explicit Network Security Group (NSG) rules; Basic allows open access by default.
💡 Exam Tip: If a question mentions production workload, high availability, or multi-zone deployment, the correct answer is almost always Standard.
2. Load Balancer Tiers
Azure Load Balancer supports two tiers:
| Tier | Scope | Connectivity | Use Cases |
|---|---|---|---|
| Regional | Within one Azure region | Only available within a single region | Most apps deployed in one region |
| Global (Premium/with Traffic Manager) | Across multiple regions | Works with Global Azure resources, supports cross-region failover | Multi-region disaster recovery, global apps |
Key Points for the Exam:
- Tier affects IP addressing:
- Regional uses standard public/private IPs in a region.
- Global requires Global Public IP.
- Tier affects scalability and high availability.
3. Choosing the Right SKU and Tier
When deciding which Load Balancer to deploy, consider these IT-focused questions:
- Workload Size & Scale
- If you have fewer than 300 VMs and only one availability set: Basic may be enough.
- If scaling beyond that or using multiple zones: Standard is required.
- Availability Requirements
- For apps needing high uptime and SLA: choose Standard.
- Security Requirements
- If you need strict NSG-based security: Standard is needed.
- Deployment Scope
- Single region: Regional tier.
- Multi-region/global failover: Global tier.
Example in an IT Environment:
- A small internal tool running in a single region with 5 VMs → Basic SKU, Regional tier.
- A global e-commerce application with 500 VMs across 3 zones → Standard SKU, Regional or Global tier depending on geo-distribution.
4. Exam Tips for AZ-700
- Remember SKU vs Tier:
- SKU = Features & Scale
- Tier = Scope & Geography
- Questions often describe:
- “High availability across zones” → Standard SKU
- “Enterprise SLA needed” → Standard SKU
- “Development/test, small app” → Basic SKU
- “Global access or disaster recovery” → Global tier
- Always read carefully if the question is asking SKU (features/scale) or tier (scope/region).
✅ Quick Summary Table for Exam
| Feature | Basic SKU | Standard SKU |
|---|---|---|
| Scale | ≤300 instances | ≤1000 instances |
| Zones | No | Yes |
| SLA | No | Yes |
| NSG Required? | No | Yes |
| Metrics in Monitor | Limited | Full |
| Best for | Small, dev/test | Production, enterprise |
| Tier | Regional | Global |
|---|---|---|
| Scope | Single region | Multi-region |
| IP Type | Regional IP | Global Public IP |
| Use Case | Most apps | Disaster recovery, geo-load balancing |
