Troubleshoot load balancing

Load balancing is an essential service for distributing traffic across multiple servers, ensuring high availability and reliability of applications. In Azure, the load balancing services include Azure Load Balancer, Azure Application Gateway, and Azure Traffic Manager, among others. When preparing for the AZ-104 Microsoft Azure Administrator exam, it’s important to understand how to troubleshoot issues that can arise with these services.

Load Balancer Troubleshooting

Azure Load Balancer distributes inbound traffic across multiple virtual machines. When troubleshooting, there are several common areas to consider:

• Health Probes

  Azure Load Balancer uses health probes to determine the health status of backend instances.

  • Check that health probes are correctly configured (appropriate protocol, port, and interval).
  • Ensure the health probe path is correct and that the application is responding appropriately.
  • Review the Load Balancer resource health to identify any issues reported by Azure.
• NSG and Firewall Rules

  Network Security Group (NSG) and firewall rules could prevent traffic from reaching your VMs.

  • Verify that NSG rules allow traffic on the Load Balancer probe and traffic ports.
  • Ensure firewall settings on your virtual machines permit the expected traffic.
• Backend Pool Configuration

  Incorrect configuration of backend pools can lead to traffic not being routed properly.

  • Confirm that the correct virtual machines are included in the backend pool.
  • Check each backend VM for any network interface (NIC) issues.
• Metrics and Logs

  Azure Monitor metrics and log files can provide insight into the Load Balancer’s performance.

  • Analyze Load Balancer metrics in Azure Monitor for anomalies.
  • Review Load Balancer logs for any error messages or unusual patterns.

Application Gateway Troubleshooting

Application Gateway provides application-level routing and load balancing services that allow you to manage traffic to your web apps.

• Backend Health

  Similar to Azure Load Balancer, Application Gateway uses health probes to monitor the status of backend resources.

  • Verify the health probe configuration, including correct protocol, port, and path.
  • Check the backend health status on the Application Gateway console.
• HTTP Settings and Listeners

  Incorrect settings could cause issues with traffic routing.

  • Check HTTP settings for correct timeout, protocol version, and authentication settings.
  • Inspect listeners to ensure they are correctly configured for the ports and hostnames you are serving.
• SSL/TLS Issues

  Misconfigured SSL certificates or encryption settings can cause communication errors.

  • Ensure SSL certificates are not expired and are correctly bound to the listeners.
  • Check that the cipher suites and TLS/SSL settings are compatible with the clients.

Traffic Manager Troubleshooting

Traffic Manager is a DNS-based load balancer that enables you to distribute traffic optimally to services across global Azure regions.

• DNS Configuration

  Incorrect DNS configurations can prevent Traffic Manager from working correctly.

  • Ensure that your domain’s NS records are pointing to Azure Traffic Manager.
  • Verify that the Traffic Manager profiles and endpoints are properly configured.
• Endpoint Monitoring

  Traffic Manager relies on endpoint monitoring to direct traffic.

  • Check that the monitoring settings are correct and the endpoints are accessible.
  • Monitor endpoint status to ensure they are online and responding as expected.
• Routing Method

  Different routing methods can affect how Traffic Manager distributes traffic.

  • Make sure you’re using the appropriate routing method for your scenario (Performance, Priority, Geographic, etc.).
  • Review the Traffic Manager configuration to ensure it matches your desired traffic distribution.

Common Troubleshooting Tools

Azure provides various tools and utilities for troubleshooting:

• Azure Portal: The primary interface for managing and diagnosing resources.
• Azure CLI or PowerShell: For scripting and automation of troubleshooting tasks.
• Network Watcher: A suite of tools to monitor, diagnose, view metrics, and enable or disable logs for resources in an Azure virtual network.

Conclusion

In conclusion, effectively troubleshooting load balancing in Azure requires a thorough understanding of how the different Azure load balancing services work and what tools are at your disposal. When preparing for the AZ-104 exam, ensure that you’re familiar with the configuration and troubleshooting of Azure Load Balancer, Application Gateway, and Traffic Manager. Understanding these concepts will not only help you in your role as an Azure Administrator but will also greatly assist you in passing the AZ-104 certification exam.