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Docs update for enhancement 563, release 1.21. 

Signed-off-by: Bridget Kromhout <bridget@kromhout.org>
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Bridget Kromhout 2021-03-03 17:52:58 -06:00
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content/en/docs/concepts/services-networking/dual-stack.md
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@ -45,34 +45,30 @@ The following prerequisites are needed in order to utilize IPv4/IPv6 dual-stack
* Provider support for dual-stack networking (Cloud provider or otherwise must be able to provide Kubernetes nodes with routable IPv4/IPv6 network interfaces)
* A network plugin that supports dual-stack (such as Kubenet or Calico)
## Enable IPv4/IPv6 dual-stack
## Configure IPv4/IPv6 dual-stack
To enable IPv4/IPv6 dual-stack, enable the `IPv6DualStack` [feature gate](/docs/reference/command-line-tools-reference/feature-gates/) for the relevant components of your cluster, and set dual-stack cluster network assignments:
To configure IPv4/IPv6 dual-stack, set dual-stack cluster network assignments:
* kube-apiserver:
* `--feature-gates="IPv6DualStack=true"`
* `--service-cluster-ip-range=<IPv4 CIDR>,<IPv6 CIDR>`
* kube-controller-manager:
* `--feature-gates="IPv6DualStack=true"`
* `--cluster-cidr=<IPv4 CIDR>,<IPv6 CIDR>`
* `--service-cluster-ip-range=<IPv4 CIDR>,<IPv6 CIDR>`
* `--node-cidr-mask-size-ipv4|--node-cidr-mask-size-ipv6` defaults to /24 for IPv4 and /64 for IPv6
* kubelet:
* `--feature-gates="IPv6DualStack=true"`
* kube-proxy:
* `--cluster-cidr=<IPv4 CIDR>,<IPv6 CIDR>`
* `--feature-gates="IPv6DualStack=true"`
{{< note >}}
An example of an IPv4 CIDR: `10.244.0.0/16` (though you would supply your own address range)
An example of an IPv6 CIDR: `fdXY:IJKL:MNOP:15::/64` (this shows the format but is not a valid address - see [RFC 4193](https://tools.ietf.org/html/rfc4193))
Starting in 1.21, IPv4/IPv6 dual-stack defaults to true. Disable if necessary on kube-apiserver, kube-controller-manager, kubelet, and kube-proxy with `--feature-gates="IPv6DualStack=false"`.
{{< /note >}}
## Services
If your cluster has dual-stack enabled, you can create {{< glossary_tooltip text="Services" term_id="service" >}} which can use IPv4, IPv6, or both.
You can create {{< glossary_tooltip text="Services" term_id="service" >}} which can use IPv4, IPv6, or both.
The address family of a Service defaults to the address family of the first service cluster IP range (configured via the `--service-cluster-ip-range` flag to the kube-apiserver).
@ -81,11 +77,9 @@ set the `.spec.ipFamilyPolicy` field to one of the following values:
* `SingleStack`: Single-stack service. The control plane allocates a cluster IP for the Service, using the first configured service cluster IP range.
* `PreferDualStack`:
* Only used if the cluster has dual-stack enabled. Allocates IPv4 and IPv6 cluster IPs for the Service
* If the cluster does not have dual-stack enabled, this setting follows the same behavior as `SingleStack`.
* Allocates IPv4 and IPv6 cluster IPs for the Service. (If the cluster has `--feature-gates="IPv6DualStack=false"`, this setting follows the same behavior as `SingleStack`.)
* `RequireDualStack`: Allocates Service `.spec.ClusterIPs` from both IPv4 and IPv6 address ranges.
* Selects the `.spec.ClusterIP` from the list of `.spec.ClusterIPs` based on the address family of the first element in the `.spec.ipFamilies` array.
* The cluster must have dual-stack networking configured.
If you would like to define which IP family to use for single stack or define the order of IP families for dual-stack, you can choose the address families by setting an optional field, `.spec.ipFamilies`, on the Service.
@ -126,7 +120,7 @@ These examples demonstrate the behavior of various dual-stack Service configurat
#### Dual-stack defaults on existing Services
These examples demonstrate the default behavior when dual-stack is newly enabled on a cluster where Services already exist.
These examples demonstrate the default behavior when dual-stack is newly enabled on a cluster where Services already exist. (Upgrading an existing cluster to 1.21 will enable dual-stack unless `--feature-gates="IPv6DualStack=false"` is set.)
1. When dual-stack is enabled on a cluster, existing Services (whether `IPv4` or `IPv6`) are configured by the control plane to set `.spec.ipFamilyPolicy` to `SingleStack` and set `.spec.ipFamilies` to the address family of the existing Service. The existing Service cluster IP will be stored in `.spec.ClusterIPs`.