Add docs for dual-stack via kubeadm: examples
Signed-off-by: pacoxu <paco.xu@daocloud.io> Co-authored-by: Lubomir I. Ivanov <neolit123@gmail.com> Co-authored-by: Tim Bannister <tim@scalefactory.com>pull/26675/head
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@ -242,3 +242,5 @@ Ensure your {{< glossary_tooltip text="CNI" term_id="cni" >}} provider supports
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* [Validate IPv4/IPv6 dual-stack](/docs/tasks/network/validate-dual-stack) networking
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* [Enable dual-stack networking using kubeadm
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](/docs/setup/production-environment/tools/kubeadm/dual-stack-support/)
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@ -0,0 +1,154 @@
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---
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title: Dual-stack support with kubeadm
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feature:
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title: Dual-stack support with kubeadm
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content_type: task
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weight: 110
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min-kubernetes-server-version: 1.21
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---
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<!-- overview -->
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{{< feature-state for_k8s_version="v1.21" state="beta" >}}
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Your Kubernetes cluster can run in [dual-stack](/docs/concepts/services-networking/dual-stack/) networking mode, which means that cluster networking lets you use either address family. In a dual-stack cluster, the control plane can assign both an IPv4 address and an IPv6 address to a single {{< glossary_tooltip text="Pod" term_id="pod" >}} or a {{< glossary_tooltip text="Service" term_id="service" >}}.
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<!-- body -->
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## {{% heading "prerequisites" %}}
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You need to have installed the {{< glossary_tooltip text="kubeadm" term_id="kubeadm" >}} tool, following the steps from [Installing kubeadm](/docs/setup/production-environment/tools/kubeadm/install-kubeadm/).
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For each server that you want to use as a {{< glossary_tooltip text="node" term_id="node" >}}, make sure it allows IPv6 forwarding. On Linux, you can set this by running run `sysctl -w net.ipv6.conf.all.forwarding=1` as the root user on each server.
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You need to have an IPv4 and and IPv6 address range to use. Cluster operators typically
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use private address ranges for IPv4. For IPv6, a cluster operator typically chooses a global
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unicast address block from within `2000::/3`, using a range that is assigned to the operator.
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You don't have to route the cluster's IP address ranges to the public internet.
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The size of the IP address allocations should be suitable for the number of Pods and
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Services that you are planning to run.
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{{< note >}}
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If you are upgrading an existing cluster then, by default, the `kubeadm upgrade` command
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changes the [feature gate](/docs/reference/command-line-tools-reference/feature-gates/)
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`IPv6DualStack` to `true` if that is not already enabled.
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However, `kubeadm` does not support making modifications to the pod IP address range
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(“cluster CIDR”) nor to the cluster's Service address range (“Service CIDR”).
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{{< /note >}}
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### Create a dual-stack cluster
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To create a dual-stack cluster with `kubeadm init` you can pass command line arguments
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similar to the following example:
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```shell
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# These address ranges are examples
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kubeadm init --pod-network-cidr=10.244.0.0/16,2001:db8:42:0::/56 --service-cidr=10.96.0.0/16,2001:db8:42:1::/112
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```
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To make things clearer, here is an example kubeadm [configuration file](https://pkg.go.dev/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2) `kubeadm-config.yaml` for the primary dual-stack control plane node.
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```yaml
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---
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apiVersion: kubeadm.k8s.io/v1beta2
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kind: ClusterConfiguration
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featureGates:
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IPv6DualStack: true
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networking:
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podSubnet: 10.244.0.0/16,2001:db8:42:0::/56
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serviceSubnet: 10.96.0.0/16,2001:db8:42:1::/112
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---
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apiVersion: kubeadm.k8s.io/v1beta2
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kind: InitConfiguration
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localAPIEndpoint:
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advertiseAddress: "10.100.0.1"
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bindPort: 6443
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nodeRegistration:
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kubeletExtraArgs:
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node-ip: 10.100.0.2,fd00:1:2:3::2
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```
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`advertiseAddress` in InitConfiguration specifies the IP address that the API Server will advertise it is listening on. The value of `advertiseAddress` equals the `--apiserver-advertise-address` flag of `kubeadm init`
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Run kubeadm to initiate the dual-stack control plane node:
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```shell
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kubeadm init --config=kubeadm-config.yaml
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```
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Currently, the kube-controller-manager flags `--node-cidr-mask-size-ipv4|--node-cidr-mask-size-ipv6` are being left with default values. See [enable IPv4/IPv6 dual stack](/docs/concepts/services-networking/dual-stack#enable-ipv4ipv6-dual-stack).
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{{< note >}}
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The `--apiserver-advertise-address` flag does not support dual-stack.
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{{< /note >}}
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### Join a node to dual-stack cluster
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Before joining a node, make sure that the node has IPv6 routable network interface and allows IPv6 forwarding.
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Here is an example kubeadm [configuration file](https://pkg.go.dev/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2) `kubeadm-config.yaml` for joining a worker node to the cluster.
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta2
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kind: JoinConfiguration
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discovery:
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bootstrapToken:
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apiServerEndpoint: 10.100.0.1:6443
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nodeRegistration:
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kubeletExtraArgs:
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node-ip: 10.100.0.3,fd00:1:2:3::3
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```
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Also, here is an example kubeadm [configuration file](https://pkg.go.dev/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2) `kubeadm-config.yaml` for joining another control plane node to the cluster.
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta2
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kind: JoinConfiguration
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controlPlane:
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localAPIEndpoint:
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advertiseAddress: "10.100.0.2"
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bindPort: 6443
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discovery:
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bootstrapToken:
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apiServerEndpoint: 10.100.0.1:6443
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nodeRegistration:
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kubeletExtraArgs:
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node-ip: 10.100.0.4,fd00:1:2:3::4
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```
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`advertiseAddress` in JoinConfiguration.controlPlane specifies the IP address that the API Server will advertise it is listening on. The value of `advertiseAddress` equals the `--apiserver-advertise-address` flag of `kubeadm join`.
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```shell
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kubeadm join --config=kubeadm-config.yaml ...
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```
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### Create a single-stack cluster
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{{< note >}}
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Enabling the dual-stack feature doesn't mean that you need to use dual-stack addressing.
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You can deploy a single-stack cluster that has the dual-stack networking feature enabled.
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{{< /note >}}
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In 1.21 the `IPv6DualStack` feature is Beta and the feature gate is defaulted to `true`. To disable the feature you must configure the feature gate to `false`. Note that once the feature is GA, the feature gate will be removed.
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```shell
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kubeadm init --feature-gates IPv6DualStack=false
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```
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To make things more clear, here is an example kubeadm [configuration file](https://pkg.go.dev/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2) `kubeadm-config.yaml` for the single-stack control plane node.
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```yaml
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apiVersion: kubeadm.k8s.io/v1beta2
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kind: ClusterConfiguration
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featureGates:
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IPv6DualStack: false
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networking:
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podSubnet: 10.244.0.0/16
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serviceSubnet: 10.96.0.0/16
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```
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## {{% heading "whatsnext" %}}
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* [Validate IPv4/IPv6 dual-stack](/docs/tasks/network/validate-dual-stack) networking
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* Read about [Dual-stack](/docs/concepts/services-networking/dual-stack/) cluster networking
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