kubernetes/kops · error

unexpected subnet type: for InstanceGroup %q; type was %s

Error message

unexpected subnet type: for InstanceGroup %q; type was %s

What it means

buildVMScaleSetTask switches on the resolved subnet's Type (Public/Utility, DualStack, Private) to configure whether the scale set requires a public IP. Any other subnet type reaches the default branch and aborts model building with this error.

Source

Thrown at pkg/model/azuremodel/vmscaleset.go:170

	if err != nil {
		return nil, err
	}
	if len(subnets) != 1 {
		return nil, fmt.Errorf("expected exactly one subnet for InstanceGroup %q; subnets was %s", ig.Name, ig.Spec.Subnets)
	}
	subnet := subnets[0]
	t.Subnet = b.LinkToAzureSubnet(subnet)

	switch subnet.Type {
	case kops.SubnetTypePublic, kops.SubnetTypeUtility:
		t.RequirePublicIP = new(true)
		if ig.Spec.AssociatePublicIP != nil {
			t.RequirePublicIP = ig.Spec.AssociatePublicIP
		}
	case kops.SubnetTypeDualStack, kops.SubnetTypePrivate:
		t.RequirePublicIP = new(false)
	default:
		return nil, fmt.Errorf("unexpected subnet type: for InstanceGroup %q; type was %s", ig.Name, subnet.Type)
	}

	if ig.Spec.Role.HasControlPlane() && b.Cluster.Spec.API.LoadBalancer != nil {
		t.LoadBalancer = &azuretasks.LoadBalancer{
			Name: to.Ptr(b.NameForLoadBalancer()),
		}
	}

	t.Tags = b.CloudTagsForInstanceGroup(ig)

	return t, nil
}

func getCapacity(spec *kops.InstanceGroupSpec) (*int64, error) {
	// Follow the convention that all other CSPs have.
	minSize := int32(1)
	maxSize := int32(1)
	if spec.MinSize != nil {

View on GitHub (pinned to 4c8573c808)

Solutions

1. Set spec.type of the referenced subnet to one of Public, Utility, DualStack, or Private in the cluster spec.
2. Upgrade kops to a version that recognizes the configured subnet type.
3. Re-run `kops get cluster -o yaml` and fix any manually edited subnet entries, then `kops update cluster`.

Example fix

// before (cluster spec subnet)
type: ""
// after
type: Private

valid := map[kops.SubnetType]bool{kops.SubnetTypePublic: true, kops.SubnetTypeUtility: true, kops.SubnetTypeDualStack: true, kops.SubnetTypePrivate: true}
for _, s := range cluster.Spec.Subnets {
  if !valid[s.Type] {
    return fmt.Errorf("subnet %q has unsupported type %q", s.Name, s.Type)
  }
}

When it happens

Trigger: An InstanceGroup on Azure references a subnet whose spec.type is an unrecognized/unset value (e.g. empty string, or a type only valid on other clouds).

Common situations: Subnet type omitted in cluster spec; hand-edited cluster.yaml introducing an invalid type; using a subnet type added by a newer kops version with an older binary (or vice versa).

Related errors

• expected exactly one subnet for InstanceGroup %q; subnets wa
• malformed format of image urn: %s
• creating VMSS VMs client: %w
• creating VMSSs client: %w
• found VMSS without IP config subnet

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/49d79551b8f62002. Report an issue: GitHub.