IPv4/IPv6 dual-stack enables the allocation of both IPv4 and IPv6 addresses to {{<glossary_tooltiptext="Pods"term_id="pod">}} and {{<glossary_tooltiptext="Services"term_id="service">}}.
If you enable IPv4/IPv6 dual-stack networking for your Kubernetes cluster, the cluster will support the simultaneous assignment of both IPv4 and IPv6 addresses.
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## Supported Features
Enabling IPv4/IPv6 dual-stack on your Kubernetes cluster provides the following features:
* Dual-stack Pod networking (a single IPv4 and IPv6 address assignment per Pod)
* IPv4 and IPv6 enabled Services (each Service must be for a single address family)
* Pod off-cluster egress routing (eg. the Internet) via both IPv4 and IPv6 interfaces
## Prerequisites
The following prerequisites are needed in order to utilize IPv4/IPv6 dual-stack Kubernetes clusters:
* Kubernetes 1.16 or later
* Provider support for dual-stack networking (Cloud provider or otherwise must be able to provide Kubernetes nodes with routable IPv4/IPv6 network interfaces)
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:
If your cluster has IPv4/IPv6 dual-stack networking enabled, you can create {{<glossary_tooltiptext="Services"term_id="service">}} with either an IPv4 or an IPv6 address. You can choose the address family for the Service's cluster IP by setting a field, `.spec.ipFamily`, on that Service.
You can only set this field when creating a new Service. Setting the `.spec.ipFamily` field is optional and should only be used if you plan to enable IPv4 and IPv6 {{<glossary_tooltiptext="Services"term_id="service">}} and {{<glossary_tooltiptext="Ingresses"term_id="ingress">}} on your cluster. The configuration of this field not a requirement for [egress](#egress-traffic) traffic.
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The default address family for your cluster is the address family of the first service cluster IP range configured via the `--service-cluster-ip-range` flag to the kube-controller-manager.
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You can set `.spec.ipFamily` to either:
*`IPv4`: The API server will assign an IP from a `service-cluster-ip-range` that is `ipv4`
*`IPv6`: The API server will assign an IP from a `service-cluster-ip-range` that is `ipv6`
The following Service specification does not include the `ipFamily` field. Kubernetes will assign an IP address (also known as a "cluster IP") from the first configured `service-cluster-ip-range` to this Service.
The following Service specification includes the `ipFamily` field. Kubernetes will assign an IPv6 address (also known as a "cluster IP") from the configured `service-cluster-ip-range` to this Service.
For comparison, the following Service specification will be assigned an IPv4 address (also known as a "cluster IP") from the configured `service-cluster-ip-range` to this Service.
On cloud providers which support IPv6 enabled external load balancers, setting the `type` field to `LoadBalancer` in additional to setting `ipFamily` field to `IPv6` provisions a cloud load balancer for your Service.
## Egress Traffic
The use of publicly routable and non-publicly routable IPv6 address blocks is acceptable provided the underlying {{<glossary_tooltiptext="CNI"term_id="cni">}} provider is able to implement the transport. If you have a Pod that uses non-publicly routable IPv6 and want that Pod to reach off-cluster destinations (eg. the public Internet), you must set up IP masquerading for the egress traffic and any replies. The [ip-masq-agent](https://github.com/kubernetes-incubator/ip-masq-agent) is dual-stack aware, so you can use ip-masq-agent for IP masquerading on dual-stack clusters.
## Known Issues
* Kubenet forces IPv4,IPv6 positional reporting of IPs (--cluster-cidr)
