Troubleshoot no inbound connectivity to Standard external load balancers

Summary

This article helps you troubleshoot why a Standard external load balancer isn't allowing inbound traffic to reach the backend virtual machines. Common causes include network security group (NSG) rules that block traffic, misconfigured load-balancing rules, or health probe failures that prevent the load balancer from routing traffic to the backend pool.

Cause

Standard load balancers and standard public IP addresses are closed to inbound connections unless network security groups open them. You use NSGs to explicitly permit allowed traffic. You must configure your NSGs to explicitly permit allowed traffic. If you don't have an NSG on a subnet or network interface card (NIC) of your virtual machine resource, traffic isn't allowed to reach the resource.

Solution

To allow ingress traffic, add a network security group to the subnet or interface for your virtual resource.