Use an internal load balancer with Azure Kubernetes Service (AKS)
To restrict access to your applications in Azure Kubernetes Service (AKS), you can create and use an internal load balancer. An internal load balancer makes a Kubernetes service accessible only to applications running in the same virtual network as the Kubernetes cluster. This article shows you how to create and use an internal load balancer with Azure Kubernetes Service (AKS).
Azure Load Balancer is available in two SKUs - Basic and Standard. By default, the Standard SKU is used when you create an AKS cluster. When creating a Service with type as LoadBalancer, you will get the same LB type as when you provision the cluster. For more information, see Azure load balancer SKU comparison.
Before you begin
You also need the Azure CLI version 2.0.59 or later installed and configured. Run
az --version to find the version. If you need to install or upgrade, see Install Azure CLI.
The AKS cluster service principal needs permission to manage network resources if you use an existing subnet or resource group. For information see Use kubenet networking with your own IP address ranges in Azure Kubernetes Service (AKS) or Configure Azure CNI networking in Azure Kubernetes Service (AKS). If you are configuring your load balancer to use an IP address in a different subnet, ensure the the AKS cluster service principal also has read access to that subnet.
Instead of a service principal, you can also use the system assigned managed identity for permissions. For more information, see Use managed identities. For more information on permissions, see Delegate AKS access to other Azure resources.
Create an internal load balancer
To create an internal load balancer, create a service manifest named
internal-lb.yaml with the service type LoadBalancer and the azure-load-balancer-internal annotation as shown in the following example:
apiVersion: v1 kind: Service metadata: name: internal-app annotations: service.beta.kubernetes.io/azure-load-balancer-internal: "true" spec: type: LoadBalancer ports: - port: 80 selector: app: internal-app
Deploy the internal load balancer using the kubectl apply and specify the name of your YAML manifest:
kubectl apply -f internal-lb.yaml
An Azure load balancer is created in the node resource group and connected to the same virtual network as the AKS cluster.
When you view the service details, the IP address of the internal load balancer is shown in the EXTERNAL-IP column. In this context, External is in relation to the external interface of the load balancer, not that it receives a public, external IP address. It may take a minute or two for the IP address to change from <pending> to an actual internal IP address, as shown in the following example:
$ kubectl get service internal-app NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE internal-app LoadBalancer 10.0.248.59 10.240.0.7 80:30555/TCP 2m
Specify an IP address
If you would like to use a specific IP address with the internal load balancer, add the loadBalancerIP property to the load balancer YAML manifest. In this scenario, the specified IP address must reside in the same subnet as the AKS cluster and must not already be assigned to a resource. For example, you shouldn't use an IP address in the range designated for the Kubernetes subnet.
apiVersion: v1 kind: Service metadata: name: internal-app annotations: service.beta.kubernetes.io/azure-load-balancer-internal: "true" spec: type: LoadBalancer loadBalancerIP: 10.240.0.25 ports: - port: 80 selector: app: internal-app
When deployed and you view the service details, the IP address in the EXTERNAL-IP column reflects your specified IP address:
$ kubectl get service internal-app NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE internal-app LoadBalancer 10.0.184.168 10.240.0.25 80:30225/TCP 4m
For more information on configuring your load balancer in a different subnet, see Specify a different subnet
Use private networks
When you create your AKS cluster, you can specify advanced networking settings. This approach lets you deploy the cluster into an existing Azure virtual network and subnets. One scenario is to deploy your AKS cluster into a private network connected to your on-premises environment and run services only accessible internally. For more information, see configure your own virtual network subnets with Kubenet or Azure CNI.
No changes to the previous steps are needed to deploy an internal load balancer in an AKS cluster that uses a private network. The load balancer is created in the same resource group as your AKS cluster but connected to your private virtual network and subnet, as shown in the following example:
$ kubectl get service internal-app NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE internal-app LoadBalancer 10.1.15.188 10.0.0.35 80:31669/TCP 1m
You may need to grant the service principal for your AKS cluster the Network Contributor role to the resource group where your Azure virtual network resources are deployed. View the service principal with az aks show, such as
az aks show --resource-group myResourceGroup --name myAKSCluster --query "servicePrincipalProfile.clientId". To create a role assignment, use the az role assignment create command.
Specify a different subnet
To specify a subnet for your load balancer, add the azure-load-balancer-internal-subnet annotation to your service. The subnet specified must be in the same virtual network as your AKS cluster. When deployed, the load balancer EXTERNAL-IP address is part of the specified subnet.
apiVersion: v1 kind: Service metadata: name: internal-app annotations: service.beta.kubernetes.io/azure-load-balancer-internal: "true" service.beta.kubernetes.io/azure-load-balancer-internal-subnet: "apps-subnet" spec: type: LoadBalancer ports: - port: 80 selector: app: internal-app
Delete the load balancer
When all services that use the internal load balancer are deleted, the load balancer itself is also deleted.
You can also directly delete a service as with any Kubernetes resource, such as
kubectl delete service internal-app, which also then deletes the underlying Azure load balancer.
Learn more about Kubernetes services at the Kubernetes services documentation.