Use a static public IP address for egress traffic with a Basic SKU load balancer in Azure Kubernetes Service (AKS)

• 03/04/2019
• 4 minutes to read
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By default, the egress IP address from an Azure Kubernetes Service (AKS) cluster is randomly assigned. This configuration is not ideal when you need to identify an IP address for access to external services, for example. Instead, you may need to assign a static IP address to be added to an allow list for service access.

This article shows you how to create and use a static public IP address for use with egress traffic in an AKS cluster.

Before you begin

This article assumes you are using the Azure Basic Load Balancer. We recommend using the Azure Standard Load Balancer, and you can use more advanced features for controlling AKS egress traffic.

This article assumes that you have an existing AKS cluster. If you need an AKS cluster, see the AKS quickstart using the Azure CLI or using the Azure portal.

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.

Egress traffic overview

Outbound traffic from an AKS cluster follows Azure Load Balancer conventions. Before the first Kubernetes service of type LoadBalancer is created, the agent nodes in an AKS cluster are not part of any Azure Load Balancer pool. In this configuration, the nodes have no instance level Public IP address. Azure translates the outbound flow to a public source IP address that is not configurable or deterministic.

Once a Kubernetes service of type LoadBalancer is created, agent nodes are added to an Azure Load Balancer pool. For outbound flow, Azure translates it to the first public IP address configured on the load balancer. This public IP address is only valid for the lifespan of that resource. If you delete the Kubernetes LoadBalancer service, the associated load balancer and IP address are also deleted. If you want to assign a specific IP address or retain an IP address for redeployed Kubernetes services, you can create and use a static public IP address.

Create a static public IP

Get the resource group name with the az aks show command and add the --query nodeResourceGroup query parameter. The following example gets the node resource group for the AKS cluster name myAKSCluster in the resource group name myResourceGroup:

$ az aks show --resource-group myResourceGroup --name myAKSCluster --query nodeResourceGroup -o tsv

MC_myResourceGroup_myAKSCluster_eastus

Now create a static public IP address with the az network public ip create command. Specify the node resource group name obtained in the previous command, and then a name for the IP address resource, such as myAKSPublicIP:

az network public-ip create \
    --resource-group MC_myResourceGroup_myAKSCluster_eastus \
    --name myAKSPublicIP \
    --allocation-method static

The IP address is shown, as shown in the following condensed example output:

{
  "publicIp": {
    "dnsSettings": null,
    "etag": "W/\"6b6fb15c-5281-4f64-b332-8f68f46e1358\"",
    "id": "/subscriptions/<SubscriptionID>/resourceGroups/MC_myResourceGroup_myAKSCluster_eastus/providers/Microsoft.Network/publicIPAddresses/myAKSPublicIP",
    "idleTimeoutInMinutes": 4,
    "ipAddress": "40.121.183.52",
    [..]
  }

You can later get the public IP address using the az network public-ip list command. Specify the name of the node resource group, and then query for the ipAddress as shown in the following example:

$ az network public-ip list --resource-group MC_myResourceGroup_myAKSCluster_eastus --query [0].ipAddress --output tsv

40.121.183.52

Create a service with the static IP

To create a service with the static public IP address, add the loadBalancerIP property and the value of the static public IP address to the YAML manifest. Create a file named egress-service.yaml and copy in the following YAML. Provide your own public IP address created in the previous step.

apiVersion: v1
kind: Service
metadata:
  name: azure-egress
spec:
  loadBalancerIP: 40.121.183.52
  type: LoadBalancer
  ports:
  - port: 80

Create the service and deployment with the kubectl apply command.

kubectl apply -f egress-service.yaml

This service configures a new frontend IP on the Azure Load Balancer. If you do not have any other IPs configured, then all egress traffic should now use this address. When multiple addresses are configured on the Azure Load Balancer, any of these public IP addresses are a candidate for outbound flows, and one is selected at random.

Verify egress address

To verify that the static public IP address is being used, you can use DNS look-up service such as checkip.dyndns.org.

Start and attach to a basic Debian pod:

kubectl run -it --rm aks-ip --image=debian

To access a web site from within the container, use apt-get to install curl into the container.

apt-get update && apt-get install curl -y

Now use curl to access the checkip.dyndns.org site. The egress IP address is shown, as displayed in the following example output. This IP address matches the static public IP address created and defined for the loadBalancer service:

$ curl -s checkip.dyndns.org

<html><head><title>Current IP Check</title></head><body>Current IP Address: 40.121.183.52</body></html>

Next steps

To avoid maintaining multiple public IP addresses on the Azure Load Balancer, you can instead use an ingress controller. Ingress controllers provide additional benefits such as SSL/TLS termination, support for URI rewrites, and upstream SSL/TLS encryption. For more information, see Create a basic ingress controller in AKS.