Azure Public Load Balancer cannot access to backend pool VMs

Question

I'm facing the Azure Public Load Balancer issue, cannot access the load balancer public IP use by port 80 but I can access to backend pool VM's port 80.

My Azure Public Load Balancer setting all following the Microsoft Azure Documentation.

The Backend Pool VMs also can access port 80 by VMs public IP.

There any troubleshoot for this situation?

Thanks.

Answer 1

If you are unable to connect to your VMs via the load balancer front end IP / port, it is usually an issue with your LB configuration, backend health, or a firewall / NSG blocking the connection.

Please refer the below troubleshooting docs to go through your configuration: https://learn.microsoft.com/en-us/azure/load-balancer/load-balancer-troubleshoot-backend-traffic

Your LB configuration will be setup using the Load Balancing Rules of your load balancer.

Azure Load Balancer will not route traffic to backends that are not reporting healthy via the Health Probes, so make sure your backend is healthy.

A Firewall or NSG can also block the connection, so make sure there are no firewalls in your environment/OS firewalls that block the traffic, and check your Network Security Groups (NSGs) on your Subnet / NICs of the VM are not blocking the load balancing probes (AllowAzureLoadBalancerInBound rule).

You can also run the automated troubleshooter for specific issues on your load balancer from the "Diagnose and solve problems" tab of your load balancer resource in Azure portal as shown in the below picture: