Configure NGINX ingress controller to support Azure private DNS zone with application routing add-on

Article
02/27/2024

This article demonstrates how to configure an NGINX ingress controller to work with Azure internal load balancer and configure a private Azure DNS zone to enable DNS resolution for the private endpoints to resolve specific domains.

Before you begin

An AKS cluster with the application routing add-on.
To attach an Azure private DNS Zone, you need the Owner, Azure account administrator, or Azure co-administrator role on your Azure subscription.

Connect to your AKS cluster

To connect to the Kubernetes cluster from your local computer, you use kubectl, the Kubernetes command-line client. You can install it locally using the az aks install-cli command. If you use the Azure Cloud Shell, kubectl is already installed.

The following example configures connecting to your cluster named myAKSCluster in the myResourceGroup using the az aks get-credentials command.

az aks get-credentials --resource-group myResourceGroup --name myAKSCluster

Create a virtual network

To publish a private DNS zone to your virtual network, you need to specify a list of virtual networks that are allowed to resolve records within the zone. These are called virtual network links.

The following example creates a virtual network named myAzureVNet in the myResourceGroup resource group, and one subnet named mySubnet to create within the VNet with a specific address prefix.

az network vnet create \
  --name myAzureVNet \
  --resource-group myResourceGroup \
  --location eastus \
  --address-prefix 10.2.0.0/16 \
  --subnet-name mysubnet \
  --subnet-prefixes 10.2.0.0/24

Create an Azure private DNS zone

Note

You can configure the application routing add-on to automatically create records on one or more Azure global and private DNS zones for hosts defined on Ingress resources. All global Azure DNS zones and all private Azure DNS zones need to be in the same resource group.

You create a DNS zone using the az network private-dns zone create command, specifying the name of the zone and the resource group to create it in. The following example creates a DNS zone named private.contoso.com in the myResourceGroup resource group.

az network private-dns zone create --resource-group myResourceGoup -n private.contoso.com

You create a virtual network link to the DNS zone created earlier using the az network private-dns link vnet create command. The following example creates a link named myDNSLink to the zone private.contoso.com for the virtual network myAzureVNet. Include the --registration-enabled parameter to specify the link is not registration enabled.

az network private-dns link vnet create --resource-group myResourceGroup \
  --name myDNSLink \
  --zone-name private.contoso.com \
  --virtual-network myAzureVNet \
  --registration-enabled false

The Azure DNS private zone auto registration feature manages DNS records for virtual machines deployed in a virtual network. When you link a virtual network with a private DNS zone with this setting enabled, a DNS record gets created for each Azure virtual machine for your AKS node deployed in the virtual network.

Attach an Azure private DNS zone to the application routing add-on

Note

The az aks approuting zone add command uses the permissions of the user running the command to create the Azure DNS Zone role assignment. The Private DNS Zone Contributor role is a built-in role for managing private DNS resources and is assigned to the add-on's managed identity. For more information on AKS managed identities, see Summary of managed identities.

Retrieve the resource ID for the DNS zone using the az network dns zone show command and set the output to a variable named ZONEID. The following example queries the zone private.contoso.com in the resource group myResourceGroup.
```
ZONEID=$(az network private-dns zone show --resource-group myResourceGroup --name private.contoso.com --query "id" --output tsv)
```
Update the add-on to enable integration with Azure DNS using the az aks approuting zone command. You can pass a comma-separated list of DNS zone resource IDs. The following example updates the AKS cluster myAKSCluster in the resource group myResourceGroup.
```
az aks approuting zone add --resource-group myResourceGroup --name myAKSCluster --ids=${ZONEID} --attach-zones
```

Create an NGINX ingress controller with a private IP address and an internal load balancer

The application routing add-on uses a Kubernetes custom resource definition (CRD) called NginxIngressController to configure NGINX ingress controllers. You can create more ingress controllers or modify an existing configuration.

NginxIngressController CRD has a loadBalancerAnnotations field to control the behavior of the NGINX ingress controller's service by setting load balancer annotations.

Perform the following steps to create an NGINX ingress controller with an internal facing Azure Load Balancer with a private IP address.

Copy the following YAML manifest into a new file named nginx-internal-controller.yaml and save the file to your local computer.

apiVersion: approuting.kubernetes.azure.com/v1alpha1
kind: NginxIngressController
metadata:
  name: nginx-internal
spec:
  ingressClassName: nginx-internal
  controllerNamePrefix: nginx-internal
  loadBalancerAnnotations: 
    service.beta.kubernetes.io/azure-load-balancer-internal: "true"

Create the NGINX ingress controller resources using the kubectl apply command.
```
kubectl apply -f nginx-internal-controller.yaml
```
The following example output shows the created resource:
```
nginxingresscontroller.approuting.kubernetes.azure.com/nginx-internal created
```

Verify the ingress controller was created

You can verify the status of the NGINX ingress controller using the kubectl get nginxingresscontroller command.

kubectl get nginxingresscontroller

The following example output shows the created resource. It may take a few minutes for the controller to be available:

NAME             INGRESSCLASS                         CONTROLLERNAMEPREFIX   AVAILABLE
default          webapprouting.kubernetes.azure.com   nginx                  True
nginx-internal   nginx-internal                       nginx-internal         True

Deploy an application

The application routing add-on uses annotations on Kubernetes Ingress objects to create the appropriate resources.

Create an application namespace called hello-web-app-routing to run the example pods using the kubectl create namespace command.
```
kubectl create namespace hello-web-app-routing
```

Create the deployment by copying the following YAML manifest into a new file named deployment.yaml and save the file to your local computer.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: aks-helloworld  
  namespace: hello-web-app-routing
spec:
  replicas: 1
  selector:
    matchLabels:
      app: aks-helloworld
  template:
    metadata:
      labels:
        app: aks-helloworld
    spec:
      containers:
      - name: aks-helloworld
        image: mcr.microsoft.com/azuredocs/aks-helloworld:v1
        ports:
        - containerPort: 80
        env:
        - name: TITLE
          value: "Welcome to Azure Kubernetes Service (AKS)"

Create the service by copying the following YAML manifest into a new file named service.yaml and save the file to your local computer.

apiVersion: v1
kind: Service
metadata:
  name: aks-helloworld
  namespace: hello-web-app-routing
spec:
  type: ClusterIP
  ports:
  - port: 80
  selector:
    app: aks-helloworld

Create the cluster resources using the kubectl apply command.

kubectl apply -f deployment.yaml -n hello-web-app-routing

The following example output shows the created resource:

deployment.apps/aks-helloworld created created

kubectl apply -f service.yaml -n hello-web-app-routing

The following example output shows the created resource:

service/aks-helloworld created created

Create the Ingress resource that uses a host name on the Azure private DNS zone and a private IP address

Copy the following YAML manifest into a new file named ingress.yaml and save the file to your local computer.

Update <Hostname> with the name of your DNS host, for example, helloworld.private.contoso.com. Verify you're specifying nginx-internal for the ingressClassName.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: aks-helloworld
  namespace: hello-web-app-routing
spec:
  ingressClassName: nginx-internal
  rules:
  - host: <Hostname>
    http:
      paths:
      - backend:
          service:
            name: aks-helloworld
            port:
              number: 80
        path: /
        pathType: Prefix

Create the cluster resources using the kubectl apply command.
```
kubectl apply -f ingress.yaml -n hello-web-app-routing
```
The following example output shows the created resource:
```
ingress.networking.k8s.io/aks-helloworld created
```

Verify the managed Ingress was created

You can verify the managed Ingress was created using the kubectl get ingress command.

kubectl get ingress -n hello-web-app-routing

The following example output shows the created managed Ingress:

NAME             CLASS            HOSTS                            ADDRESS      PORTS   AGE
aks-helloworld   nginx-internal   helloworld.private.contoso.com   10.224.0.7   80      98s

Verify the Azure private DNS zone was updated

In a few minutes, run the az network private-dns record-set a list command to view the A records for your Azure private DNS zone. Specify the name of the resource group and the name of the DNS zone. In this example, the resource group is myResourceGroup and DNS zone is private.contoso.com.

az network private-dns record-set a list --resource-group myResourceGroup --zone-name private.contoso.com

The following example output shows the created record:

[
  {
    "aRecords": [
      {
        "ipv4Address": "10.224.0.7"
      }
    ],
    "etag": "188f0ce5-90e3-49e6-a479-9e4053f21965",
    "fqdn": "helloworld.private.contoso.com.",
    "id": "/subscriptions/xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxx/resourceGroups/foo/providers/Microsoft.Network/privateDnsZones/private.contoso.com/A/helloworld",
    "isAutoRegistered": false,
    "name": "helloworld",
    "resourceGroup": "foo",
    "ttl": 300,
    "type": "Microsoft.Network/privateDnsZones/A"
  }
]

Next steps

For other configuration information related to SSL encryption other advanced NGINX ingress controller and ingress resource configuration, review DNS and SSL configuration and application routing add-on configuration.