I'm exposing an application run on a GKE cluster using a LoadBalancer service. By default, the LoadBalancer creates a rule in the Google VPC firewall with IP range 0.0.0.0/0. With this configuration, I'm able to reach the service in all situations.
I'm using an OpenVPN server inside my default network to prevent outside access to GCE instances on a certain IP range. By modifying the service .yaml file loadBalancerSourceRanges value to match the IP range of my VPN server, I expected to be able to connect to the Kubernetes application while connected to the VPN, but not otherwise. This updated the Google VPN firewall rule with the range I entered in the .yaml file, but didn't allow me to connect to the service endpoint. The Kubernetes cluster is located in the same network as the OpenVPN server. Is there some additional configuration that needs to be used other than setting loadBalancerSourceRanges to the desired ingress IP range for the service?
You didn't mention the version of this GKE cluster; however, it might be helpful to know that, beginning with Kubernetes version 1.9.x, automatic firewall rules have changed such that workloads in your Google Kubernetes Engine cluster cannot communicate with other Compute Engine VMs that are on the same network, but outside the cluster. This change was made for security reasons. You can replicate the behavior of older clusters (1.8.x and earlier) by setting a new firewall rule on your cluster. You can see this notification on the Release Notes published in the official documentation