Training
Module
Troubleshoot inbound network connectivity for Azure Load Balancer - Training
Learn how to troubleshoot inbound network connectivity for Azure Load Balancer.
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Application Gateway health probes (default and custom) continuously monitor all the backend servers in a pool to ensure the incoming traffic is sent only to the servers that are up and running. These health checks enable a seamless data plane operation of a gateway. When a backend server can receive traffic, the probe is successful and considered healthy. Otherwise, it's considered unhealthy. The precise representation of the health probes report is also made available for your consumption through the Backend Health capability.
The possible statuses for a server's health report are:
For complete information on the cause and solution of the Unhealthy and Unknown states, visit the troubleshooting article.
Note
The Backend health report is updated based on the respective probe's refresh interval and doesn't depend on the moment of page refresh or Backend health API request.
The backend server health report can be generated through the Azure portal, REST API, PowerShell, and Azure CLI.
The Application Gateway portal provides an information-rich backend health report with visualizations and tools for faster troubleshooting. Each row shows the exact target server, the backend pool it belongs to, its backend setting association (including port and protocol), and the response received by the latest probe. Visit the Health Probes article to understand how this report is composed based on the number of Backend pools, servers, and Backend settings.
For Unhealthy and Unknown statuses, you will also find a Troubleshoot link presenting you with the following tools:
Azure Network Watcher's Connection troubleshoot - Visit the Connection Troubleshoot documentation article to learn how to use this tool.
Backend server certificate visualization - The Backend server certificate visualization makes it easy to understand the problem area, allowing you to act on the problem quickly. The three core components in the illustration provide you with a complete picture — The client, the Application Gateway, and the Backend Server. However, the problems explained in this troubleshooting section only focus on the TLS connection between the application gateway and the backend server.
Reading the illustration
The following PowerShell code shows how to view backend health by using the Get-AzApplicationGatewayBackendHealth
cmdlet:
Get-AzApplicationGatewayBackendHealth -Name ApplicationGateway1 -ResourceGroupName Contoso
az network application-gateway show-backend-health --resource-group AdatumAppGatewayRG --name AdatumAppGateway
The following snippet shows an example of the response:
{
"BackendAddressPool": {
"Id": "/subscriptions/00000000-0000-0000-000000000000/resourceGroups/ContosoRG/providers/Microsoft.Network/applicationGateways/applicationGateway1/backendAddressPools/appGatewayBackendPool"
},
"BackendHttpSettingsCollection": [
{
"BackendHttpSettings": {
"Id": "/00000000-0000-0000-000000000000/resourceGroups/ContosoRG/providers/Microsoft.Network/applicationGateways/applicationGateway1/backendHttpSettingsCollection/appGatewayBackendHttpSettings"
},
"Servers": [
{
"Address": "hostname.westus.cloudapp.azure.com",
"Health": "Healthy"
},
{
"Address": "hostname.westus.cloudapp.azure.com",
"Health": "Healthy"
}
]
}
]
}
Training
Module
Troubleshoot inbound network connectivity for Azure Load Balancer - Training
Learn how to troubleshoot inbound network connectivity for Azure Load Balancer.