Azure Load Balancer Advanced Configuration

This article delves into the advanced configuration options for Azure Load Balancer, enabling you to fine-tune traffic distribution, enhance availability, and optimize performance for your applications.

High Availability and Resilience

Azure Load Balancer provides robust mechanisms to ensure your applications remain available even during component failures. Advanced configurations focus on leveraging these features effectively.

Availability Sets

Understand how to deploy virtual machines across multiple fault and update domains using Availability Sets in conjunction with Load Balancer to prevent single points of failure.

Availability Zones

Learn to configure Azure Load Balancer to span multiple Availability Zones within a region, offering the highest level of resilience against datacenter-level outages.

Customizing Health Probes

Health probes are crucial for determining the health of backend instances and directing traffic away from unhealthy ones. Advanced configuration allows for more granular control.

Probe Types

Explore different health probe types like TCP, HTTP, and HTTPS. Understand when to use each type and how to configure them based on your application's needs.

Probe Configuration Parameters

Dive into parameters such as protocol, port, request path (for HTTP/S probes), and interval and threshold for determining probe success.

Example: Advanced HTTP Health Probe

Configure an HTTP health probe to check a specific path on port 8080, with a probe interval of 15 seconds and requiring 3 successful probes before marking an instance as unhealthy.

                        
{
    "name": "myHttpProbe",
    "properties": {
        "protocol": "Http",
        "port": 8080,
        "requestPath": "/healthcheck",
        "intervalInSeconds": 15,
        "numberOfProbes": 3
    }
}
                        
                    

Load Balancing Rules and SNAT

Customizing load balancing rules and understanding Source Network Address Translation (SNAT) are key to managing outbound connections and traffic flow.

Session Persistence (Sticky Sessions)

Configure session persistence (client affinity) to ensure that requests from a particular client are consistently sent to the same backend server. This is vital for stateful applications.

SNAT Ports and IP Addresses

Learn how to manage SNAT ports for outbound connections. For scenarios with a very large number of outbound connections, you can configure SNAT IP addresses or use Azure Firewall for more advanced outbound control.

Load Balancing Rule Customization

Explore advanced options for load balancing rules, including floating IP (direct server return) and configuring different protocols and ports for frontend and backend.

Example: Load Balancing Rule with Session Persistence

Configure a TCP load balancing rule on frontend port 80 to distribute traffic to backend port 80, with session persistence enabled (ClientIP).

                        
{
    "name": "myTcpRule",
    "properties": {
        "frontendIPConfiguration": {
            "id": "/subscriptions/.../resourceGroups/.../providers/Microsoft.Network/loadBalancers/.../frontendIPConfigurations/frontend1"
        },
        "backendAddressPool": {
            "id": "/subscriptions/.../resourceGroups/.../providers/Microsoft.Network/loadBalancers/.../backendAddressPools/pool1"
        },
        "probe": {
            "id": "/subscriptions/.../resourceGroups/.../providers/Microsoft.Network/loadBalancers/.../probes/myTcpProbe"
        },
        "protocol": "Tcp",
        "loadDistribution": "Default",
        "frontendPort": 80,
        "backendPort": 80,
        "enableFloatingIP": false,
        "idleTimeoutInMinutes": 4,
        "disableOutboundSnat": false,
        "provisioningState": "Succeeded"
    }
}
                        
                    

Network Address Translation (NAT) Rules

For specific scenarios, you might need to configure inbound NAT rules to allow direct access to specific virtual machines behind the load balancer.

Direct Access to VMs

Understand how to create inbound NAT rules to map a specific public IP address and port to a specific virtual machine's private IP address and port.

Monitoring and Diagnostics

Effective monitoring is crucial for understanding load balancer behavior and diagnosing issues. Azure Load Balancer integrates with Azure Monitor and Diagnostic settings.

Diagnostic Settings

Configure diagnostic settings to collect logs and metrics for Load Balancer, enabling you to analyze traffic flow, health probe status, and identify performance bottlenecks.

Azure Monitor Integration

Leverage Azure Monitor to create alerts based on Load Balancer metrics, such as the number of healthy/unhealthy hosts or the count of received/sent packets.

Best Practices and Recommendations

Always use health probes to ensure traffic is only sent to healthy backend instances.
Configure appropriate session persistence based on application requirements.
For applications with very high outbound connection needs, consider using a Virtual Network NAT or Azure Firewall.
Leverage Availability Zones for maximum resilience.
Regularly review Load Balancer metrics and logs for performance insights.

MSDN Documentation

Azure Networking