// as the clusterIP.
  // "ExternalName" aliases this service to the specified externalName.
  // Several other fields do not apply to ExternalName services.
  // More info: https://kubernetes.io/docs/concepts/services-networking/service/#publishing-services-service-types
  // +optional
  optional string type = 4;

  // externalIPs is a list of IP addresses for which nodes in the cluster

IPv4/IPv6 dual-stack has been reimplemented for 1.20 to support dual-stack Services, based on user and community feedback. If your cluster has dual-stack enabled, you can create Services which can use IPv4, IPv6, or both, and you can change this setting for existing Services. Details are available in updated [IPv4/IPv6 dual-stack docs](https://docs.k8s.io/concepts/services-networking/dual-stack/), which cover the nuanced array of options.

### Avoiding Collisions in IP allocation to Services

Kubernetes 1.24 introduced a new opt-in feature that allows you to
[soft-reserve a range for static IP address assignments](https://kubernetes.io/docs/concepts/services-networking/service/#service-ip-static-sub-range)
to Services.
With the manual enablement of this feature, the cluster will prefer automatic assignment from

* Properly manage security groups for loadbalancer services on OpenStack. ([#65373](https://github.com/kubernetes/kubernetes/pull/65373), [@multi-io](https://github.com/multi-io))

* Fix a scalability issue where high rates of event writes degraded etcd performance. ([#64539](https://github.com/kubernetes/kubernetes/pull/64539), [@ccding](https://github.com/ccding))
* Properly manage security groups for loadbalancer services on OpenStack. ([#65373](https://github.com/kubernetes/kubernetes/pull/65373), [@multi-io](https://github.com/multi-io))

- Added CEL expressions to `v1alpha1 AuthenticationConfiguration`. ([#121078](https://github.com/kubernetes/kubernetes/pull/121078), [@aramase](https://github.com/aramase))
- Added Windows support for InPlace Pod Vertical Scaling feature. ([#112599](https://github.com/kubernetes/kubernetes/pull/112599), [@fabi200123](https://github.com/fabi200123)) [SIG Autoscaling, Node, Scalability, Scheduling and Windows]

- The conformance tests:
  - Services should serve multiport endpoints from pods
  - Services should serve a basic endpoint from pods
  were only validating the API objects, not performing any validation on the actual Services implementation.

* Local volume source paths that are directories and not mount points fail to unmount.  A fix is in process ([#48331](https://github.com/kubernetes/kubernetes/issues/48331)).

* Services of type LoadBalancer (on GCE/GKE) that have static IP addresses will cause the Service Controller to panic and thereby causing the kube-controller-manager to crash loop.
([#48848](https://github.com/kubernetes/kubernetes/issues/48848))

* Fix issue of colliding nodePorts when the cluster has services with externalTrafficPolicy=Local ([#64468](https://github.com/kubernetes/kubernetes/pull/64468), [@nicksardo](https://github.com/nicksardo))

The use of dual-stack networking is not mandatory.
Although clusters are enabled to support dual-stack networking, Pods and Services continue to default to single-stack.
To use dual-stack networking: Kubernetes nodes have routable IPv4/IPv6 network interfaces, a dual-stack capable CNI network plugin is used, Pods are configured to be dual-stack and Services have their `.spec.ipFamilyPolicy` field set to either `PreferDualStack` or `RequireDualStack`.