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Edits to clarify.
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Signed-off-by: Bridget Kromhout <[email protected]>
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bridgetkromhout committed Nov 30, 2021
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6 changes: 4 additions & 2 deletions content/en/blog/_posts/2021-12-08-dual-stack-networking-ga.md
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Expand Up @@ -19,7 +19,9 @@ What does dual-stack networking mean for you? Let’s take a look…
The Service API now has new fields to support dual-stack, replacing the single ipFamily field.
* You can select your choice of IP family by setting `ipFamilyPolicy` to one of three options: SingleStack, PreferDualStack, or RequireDualStack. A service can be changed between single-stack and dual-stack (within some limits).
* Setting `ipFamilies` to a list of families assigned allows you to set the order of families used.
* `clusterIPs` is inclusive of the previous `clusterIP` but allows for multiple entries, so it’s no longer necessary to run duplicate services, one in each of the two IP families. Instead, you can assign cluster IP addresses in both IP families. Note that for a given pod, there is no possibility of setting multiple IP addresses in the same family.
* `clusterIPs` is inclusive of the previous `clusterIP` but allows for multiple entries, so it’s no longer necessary to run duplicate services, one in each of the two IP families. Instead, you can assign cluster IP addresses in both IP families.

Note that Pods are also dual-stack. For a given pod, there is no possibility of setting multiple IP addresses in the same family.


## Default behavior remains single-stack
Expand All @@ -29,7 +31,7 @@ Starting in 1.20 with the re-implementation of dual-stack services as alpha, the

Kubernetes 1.23 removed that feature flag as part of graduating the feature to stable. Dual-stack networking is always available if you want to configure it. You can set your cluster network to operate as single-stack IPv4, as single-stack IPv6, or as dual-stack IPv4/IPv6.

Pods and Services default to whatever the CNI plugin sets. If your CNI plugin assigns single-stack IPs, you will have single-stack unless `ipFamilyPolicy` specifies PreferDualStack or RequireDualStack. If your CNI plugin assigns dual-stack IPs, `pod.status.PodIPs` defaults to dual-stack.
While Services are set according to what you configure, Pods default to whatever the CNI plugin sets. If your CNI plugin assigns single-stack IPs, you will have single-stack unless `ipFamilyPolicy` specifies PreferDualStack or RequireDualStack. If your CNI plugin assigns dual-stack IPs, `pod.status.PodIPs` defaults to dual-stack.

Even though dual-stack is possible, it is not mandatory to use it. Examples in the documentation show the variety possible in [dual-stack service configuration](/docs/concepts/services-networking/dual-stack/#dual-stack-service-configuration-scenarios).

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