What is Azure Load Balancer?
Azure Load Balancer is a Layer 4 load balancer that distributes incoming TCP and UDP traffic across multiple backend resources. The service enables high availability by distributing load and automatically removing failed instances from the pool based on health probes.
The former Basic Load Balancer SKU was retired by Microsoft on September 30, 2025, and is no longer supported; new deployments can only use the Standard Load Balancer. Compared to the retired Basic SKU, Standard provides a zone-redundant frontend, a secure-by-default network model (inbound traffic is blocked unless explicitly allowed via Network Security Groups), outbound rules, multi-dimensional metrics, and a 99.99% SLA.
Core Features
- Layer 4 load balancing for TCP and UDP traffic
- Health probes for automatic detection of failed backends
- Zone redundancy for high availability across Availability Zones
- Outbound rules for controlled outgoing connections
- Secure-by-default network model in combination with Network Security Groups
- Session persistence for sticky sessions
Typical Use Cases
Web Tier Load Balancing: Multiple web server VMs share incoming traffic for better performance and fault tolerance.
Internal Services: Internal load balancers distribute traffic between microservices within a Virtual Network without public IP exposure.
High Availability: Critical applications are distributed across VMs in multiple Availability Zones; Load Balancer routes traffic only to healthy instances.
Benefits
- Low latency through native Azure integration
- Scaling to a very large number of concurrent connections
- No management of dedicated load balancer infrastructure
- Integration with VM Scale Sets and AKS for automatic scaling
Frequently Asked Questions
What is Azure Load Balancer?
A managed Layer 4 load balancer that distributes TCP and UDP traffic across multiple backend instances and automatically removes unhealthy instances from rotation.
Is the Basic Load Balancer still available?
No. The Basic Load Balancer was retired on September 30, 2025. Existing Basic Load Balancer resources may continue to run in some cases but are considered unsupported and are not covered by an SLA. Only the Standard Load Balancer is available and recommended for new deployments.
When should I use Application Gateway instead of Load Balancer?
Application Gateway is a Layer 7 load balancer with SSL offloading, URL-based routing, and a Web Application Firewall. Use Application Gateway for HTTP/HTTPS workloads, and Load Balancer for other protocols or pure Layer 4 requirements.
How are costs calculated?
The Standard Load Balancer is billed at a fixed price per load-balancing rule plus charges for the processed data volume. Current rates are available on the official pricing page.
Can I use Load Balancer with AKS?
Yes, AKS automatically creates a Standard Load Balancer for Kubernetes Services of type LoadBalancer.
Integration with innFactory
As a Microsoft Solutions Partner, innFactory supports you in implementing scalable network architectures with Azure Load Balancer, including migrating from Basic to Standard load balancers. We help with design, migration, and optimization.
Contact us for a non-binding consultation on Azure Load Balancer.
Note: All product information on this page has been compiled with care, but is provided without guarantee and may be outdated or incomplete. Cloud services evolve rapidly — features, pricing, SLAs, and availability change frequently. Authoritative and up-to-date information can only be found on the official product page of Azure (official documentation). This page does not represent an offer by Azure.
