Secure access to the API server using authorized IP address ranges in Azure Kubernetes Service (AKS)

Article
10/11/2024

This article shows you how to use API server authorized IP address ranges feature to limit which IP addresses and CIDRs can access control plane.

The Kubernetes API server is the core of the Kubernetes control plane and is the central way to interact with and manage your clusters. To improve the security of your clusters and minimize the risk of attacks, we recommend limiting the IP address ranges that can access the API server. To do this, you can use the API server authorized IP ranges feature.

Before you begin

You need the Azure CLI version 2.0.76 or later installed and configured. Run az --version to find the version. If you need to install or upgrade, see Install Azure CLI.
To learn what IP addresses to include when integrating your AKS cluster with Azure DevOps, see the Azure DevOps Allowed IP addresses and domain URLs article.

Limitations

The API server authorized IP ranges feature has the following limitations:

The API server authorized IP ranges feature was moved out of preview in October 2019. For clusters created after the feature was moved out of preview, this feature is only supported on the Standard SKU load balancer. Any existing clusters on the Basic SKU load balancer with the API server authorized IP ranges feature enabled will continue to work as is. However, these clusters cannot be migrated to a Standard SKU load balancer. Existing clusters will continue to work if the Kubernetes version and control plane are upgraded.
The API server authorized IP ranges feature isn't supported on private clusters.
When using this feature with clusters that use Node Public IP, the node pools using Node Public IP must use public IP prefixes. The public IP prefixes must be added as authorized ranges.

Overview of API server authorized IP ranges

The Kubernetes API server exposes underlying Kubernetes APIs and provides the interaction for management tools like kubectl and the Kubernetes dashboard. AKS provides a single-tenant cluster control plane with a dedicated API server. The API server is assigned a public IP address by default. You can control access using Kubernetes role-based access control (Kubernetes RBAC) or Azure RBAC.

To secure access to the otherwise publicly accessible AKS control plane / API server, you can enable and use authorized IP ranges. These authorized IP ranges only allow defined IP address ranges to communicate with the API server. Any requests made to the API server from an IP address that isn't part of these authorized IP ranges is blocked.

Create an AKS cluster with API server authorized IP ranges enabled

Important

By default, your cluster uses the Standard SKU load balancer which you can use to configure the outbound gateway. When you enable API server authorized IP ranges during cluster creation, the public IP for your cluster is allowed by default in addition to the ranges you specify. If you specify "" or no value for --api-server-authorized-ip-ranges, API server authorized IP ranges is disabled. Note that if you're using PowerShell, use --api-server-authorized-ip-ranges="" (with equals signs) to avoid any parsing issues.

Note

You should add these ranges to an allow list:

The cluster egress IP address (firewall, NAT gateway, or other address, depending on your outbound type).
Any range that represents networks that you'll administer the cluster from.

The upper limit for the number of IP ranges you can specify is 200.

The rules can take up to two minutes to propagate. Please allow up to that time when testing the connection.

When creating a cluster with API server authorized IP ranges enabled, you use the --api-server-authorized-ip-ranges parameter to provide a list of authorized public IP address ranges. When you specify a CIDR range, start with the first IP address in the range. For example, 137.117.106.90/29 is a valid range, but make sure you specify the first IP address in the range, such as 137.117.106.88/29.

Create an AKS cluster with API server authorized IP ranges enabled using the az aks create command with the --api-server-authorized-ip-ranges parameter. The following example creates a cluster named myAKSCluster in the resource group named myResourceGroup with API server authorized IP ranges enabled. The IP address ranges allowed are 73.140.245.0/24:
```
az aks create --resource-group myResourceGroup --name myAKSCluster --vm-set-type VirtualMachineScaleSets --load-balancer-sku standard --api-server-authorized-ip-ranges 73.140.245.0/24 --generate-ssh-keys
```

When creating a cluster with API server authorized IP ranges enabled, you use the -ApiServerAccessAuthorizedIpRange parameter to provide a list of authorized public IP address ranges. When you specify a CIDR range, start with the first IP address in the range. For example, 137.117.106.90/29 is a valid range, but make sure you specify the first IP address in the range, such as 137.117.106.88/29.

Create an AKS cluster with API server authorized IP ranges enabled using the New-AzAksCluster cmdlet with the -ApiServerAccessAuthorizedIpRange parameter. The following example creates a cluster named myAKSCluster in the resource group named myResourceGroup with API server authorized IP ranges enabled. The IP address ranges allowed are 73.140.245.0/24:
```
New-AzAksCluster -ResourceGroupName myResourceGroup -Name myAKSCluster -NodeVmSetType VirtualMachineScaleSets -LoadBalancerSku Standard -ApiServerAccessAuthorizedIpRange '73.140.245.0/24' -GenerateSshKey
```

Specify outbound IPs for a Standard SKU load balancer

When creating a cluster with API server authorized IP ranges enabled, you can also specify the outbound IP addresses or prefixes for the cluster using the --load-balancer-outbound-ips or --load-balancer-outbound-ip-prefixes parameters. All IPs provided in the parameters are allowed along with the IPs in the --api-server-authorized-ip-ranges parameter.

Create an AKS cluster with API server authorized IP ranges enabled and specify the outbound IP addresses for the Standard SKU load balancer using the --load-balancer-outbound-ips parameter. The following example creates a cluster named myAKSCluster in the resource group named myResourceGroup with API server authorized IP ranges enabled and the outbound IP addresses <public-ip-id-1> and <public-ip-id-2>:
```
az aks create --resource-group myResourceGroup --name myAKSCluster --vm-set-type VirtualMachineScaleSets --load-balancer-sku standard --api-server-authorized-ip-ranges 73.140.245.0/24 --load-balancer-outbound-ips <public-ip-id-1>,<public-ip-id-2> --generate-ssh-keys
```

Allow only the outbound public IP of the Standard SKU load balancer

When you enable API server authorized IP ranges during cluster creation, the outbound public IP for the Standard SKU load balancer for your cluster is also allowed by default in addition to the ranges you specify. To allow only the outbound public IP of the Standard SKU load balancer, you use 0.0.0.0/32 when specifying the --api-server-authorized-ip-ranges parameter.

Create an AKS cluster with API server authorized IP ranges enabled and allow only the outbound public IP of the Standard SKU load balancer using the --api-server-authorized-ip-ranges parameter. The following example creates a cluster named myAKSCluster in the resource group named myResourceGroup with API server authorized IP ranges enabled and allows only the outbound public IP of the Standard SKU load balancer:
```
az aks create --resource-group myResourceGroup --name myAKSCluster --vm-set-type VirtualMachineScaleSets --load-balancer-sku standard --api-server-authorized-ip-ranges 0.0.0.0/32 --generate-ssh-keys
```

Create an AKS cluster with API server authorized IP ranges enabled and allow only the outbound public IP of the Standard SKU load balancer using the -ApiServerAccessAuthorizedIpRange parameter. The following example creates a cluster named myAKSCluster in the resource group named myResourceGroup with API server authorized IP ranges enabled and allows only the outbound public IP of the Standard SKU load balancer:
```
New-AzAksCluster -ResourceGroupName myResourceGroup -Name myAKSCluster -NodeVmSetType VirtualMachineScaleSets -LoadBalancerSku Standard -ApiServerAccessAuthorizedIpRange '0.0.0.0/32' -GenerateSshKey
```

Update an existing cluster's API server authorized IP ranges

Update an existing cluster's API server authorized IP ranges using the az aks update command with the --api-server-authorized-ip-ranges parameter. The following example updates API server authorized IP ranges on the cluster named myAKSCluster in the resource group named myResourceGroup. The IP address range to authorize is 73.140.245.0/24:
```
az aks update --resource-group myResourceGroup --name myAKSCluster --api-server-authorized-ip-ranges 73.140.245.0/24
```
To allow multiple IP address ranges, you can list several IP addresses, separated by commas.
```
az aks update --resource-group myResourceGroup --name myAKSCluster --api-server-authorized-ip-ranges 73.140.245.0/24,193.168.1.0/24,194.168.1.0/24
```
You can also use 0.0.0.0/32 when specifying the --api-server-authorized-ip-ranges parameter to allow only the public IP of the Standard SKU load balancer.

Update an existing cluster's API server authorized IP ranges using the Set-AzAksCluster cmdlet with the -ApiServerAccessAuthorizedIpRange parameter. The following example updates API server authorized IP ranges on the cluster named myAKSCluster in the resource group named myResourceGroup. The IP address range to authorize is 73.140.245.0/24:
```
Set-AzAksCluster -ResourceGroupName myResourceGroup -Name myAKSCluster -ApiServerAccessAuthorizedIpRange '73.140.245.0/24'
```
You can also use 0.0.0.0/32 when specifying the -ApiServerAccessAuthorizedIpRange parameter to allow only the public IP of the Standard SKU load balancer.

Disable authorized IP ranges

Disable authorized IP ranges using the az aks update command and specify an empty range "" for the --api-server-authorized-ip-ranges parameter.
```
az aks update --resource-group myResourceGroup --name myAKSCluster --api-server-authorized-ip-ranges ""
```

Disable authorized IP ranges using the Set-AzAksCluster cmdlet and specify an empty range '' for the -ApiServerAccessAuthorizedIpRange parameter.
```
Set-AzAksCluster -ResourceGroupName myResourceGroup -Name myAKSCluster -ApiServerAccessAuthorizedIpRange ''
```

Find existing authorized IP ranges

Find existing authorized IP ranges using the az aks show command with the --query parameter set to apiServerAccessProfile.authorizedIpRanges.
```
az aks show --resource-group myResourceGroup --name myAKSCluster --query apiServerAccessProfile.authorizedIpRanges
```

Find existing authorized IP ranges using the Get-AzAksCluster cmdlet.

Get-AzAksCluster -ResourceGroupName myResourceGroup -Name myAKSCluster | Select-Object -ExpandProperty ApiServerAccessProfile

How to find my IP to include in `--api-server-authorized-ip-ranges`?

You must add your development machines, tooling, or automation IP addresses to the AKS cluster list of approved IP ranges to access the API server from there.

Another option is to configure a jumpbox with the necessary tooling inside a separate subnet in the firewall's virtual network. This assumes your environment has a firewall with the respective network, and you've added the firewall IPs to authorized ranges. Similarly, if you've forced tunneling from the AKS subnet to the firewall subnet, having the jumpbox in the cluster subnet is also okay.

Retrieve your IP address using the following command:

# Retrieve your IP address
CURRENT_IP=$(dig +short "myip.opendns.com" "@resolver1.opendns.com")

Add your IP address to the approved list using Azure CLI or Azure PowerShell:

# Add to AKS approved list using Azure CLI
az aks update --resource-group $RG --name $AKSNAME --api-server-authorized-ip-ranges $CURRENT_IP/24,73.140.245.0/24

# Add to AKS approved list using Azure PowerShell
Set-AzAksCluster -ResourceGroupName $RG -Name $AKSNAME -ApiServerAccessAuthorizedIpRange '$CURRENT_IP/24,73.140.245.0/24'

Note

The above example adds another IP address to the approved ranges. Note that it still includes the IP address from Update a cluster's API server authorized IP ranges. If you don't include your existing IP address, this command will replace it with the new one instead of adding it to the authorized ranges. To disable authorized IP ranges, use az aks update and specify an empty range "".

Another option is to use the following command on Windows systems to get the public IPv4 address, or you can follow the steps in Find your IP address.

Invoke-RestMethod http://ipinfo.io/json | Select -exp ip

You can also find this address by searching on what is my IP address in an internet browser.

Next steps

In this article, you enabled API server authorized IP ranges. This approach is one part of how you can securely run an AKS cluster. For more information, see Security concepts for applications and clusters in AKS and Best practices for cluster security and upgrades in AKS.