Last modified March 6, 2022

Setting an egress IP address on Azure

Giant Swarm’s workload clusters on Azure use NAT gateways to provide internet access to worker nodes.

By default, a new dedicated public IPv4 address is created during the workload cluster setup process to be used as the public IP address for the NAT gateway of worker nodes. This means there is no way to know in advance what public IP address a certain workload cluster will have for egress traffic until it is created.

Reuse of an existing public IP address

Starting from Giant Swarm release v15.1.0 for Azure it is possible to use an existing, externally created public IPv4 address for the NAT gateway of worker nodes.

In order to do so:

  1. Create a public IPv4 address in the same subscription the workload cluster will be created into. The IP address can be in any resource group, but it needs to use the Standard SKU and be in the same region as the workload cluster.
  2. Edit the workload cluster’s AzureCluster resource via the Management API and set the resource ID of the public IP address as a value for the giantswarm.io/workers-egress-external-public-ip annotation, as in the following example:
apiVersion: infrastructure.cluster.x-k8s.io/v1alpha3
kind: AzureCluster
metadata:
  name: ab123
  ...
  annotations:
    giantswarm.io/workers-egress-external-public-ip: "/subscriptions/<subscription ID>/resourceGroups/<resource group>/providers/Microsoft.Network/publicIPAddresses/<public ip name>"
spec:
  ...

You can set the annotation to either an existing workload cluster or a brand-new one.

To enable and disable the use of an external IP address for an existing workload cluster, just add or remove the annotation from the AzureCluster resource at any time. Reconciliation takes just a few minutes to switch between the two modes and there shouldn’t be any significant network packet loss while switching.

Caveats and limitations

  • You can’t use the same public IP address for more than one workload cluster at the same time. This is an Azure limitation.

  • This feature is only supported for node pools (worker nodes) and not for the control plane node.

  • If you enable the feature in an existing workload cluster, the previously used public IP will not be deleted. This can lead to some undesired increase in the Azure bill. If the external IP address feature is disabled again, the automatically generated public IP address will be reused.

  • There is no user interface support for enabling or disabling this setting.