Add join examples and fix spelling errors

Co-authored-by: Lubomir I. Ivanov <neolit123@gmail.com>

content/en/docs/concepts/services-networking/dual-stack.md

@@ -74,35 +74,108 @@ An example of an IPv6 CIDR: `fdXY:IJKL:MNOP:15::/64` (this shows the format but
 
 Install kubeadm following the steps from the [Installing Kubeadm](/docs/setup/production-environment/tools/kubeadm/install-kubeadm/) documentation.
 
-Make sure that nodes allow ipv6 forwarding, if not, run `sudo sysctl -w net.ipv6.conf.all.forwarding=1` on every node in the cluster.
+Make sure that nodes allow IPv6 forwarding, if not, run `sudo sysctl -w net.ipv6.conf.all.forwarding=1` on every node in the cluster.
 
-* Notice that `kubeadm upgrade` will change IPv6DualStack to true by default if feature gate is not set in old cluster. However, cluster-cidr and service-cidr modification are not supported.
+{{< note >}}
+`kubeadm upgrade` will change `IPv6DualStack` to true by default if feature gate is not set in old cluster. However, cluster-cidr and service-cidr modification are not supported.
+{{< /note >}}
 
 #### Create a dual-stack cluster
 
-You must pass your `podCidr` and `serviceCidr` value to `kubeadm init`, like so:
+A simple command with `podCidr` and `serviceCidr` flags to create a dual-stack cluster via `kubeadm init`, it like below:
 
-```
+```shell
 kubeadm init --feature-gates IPv6DualStack=true --pod-network-cidr=172.30.0.0/16,fefe:ffff:0::/48 --service-cidr=172.31.0.0/16,fefe:ffff:1::/108
 ```
 
+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.yml` for the dual-stack control plane node.
+
+```yaml
+apiVersion: kubeadm.k8s.io/v1beta2
+kind: ClusterConfiguration
+featureGates:
+  IPv6DualStack: true
+networking:
+  podSubnet: 172.30.0.0/16,fefe:ffff:0::/48
+  serviceSubnet: 172.31.0.0/16,fefe:ffff:1::/108
+---
+apiVersion: kubeadm.k8s.io/v1beta2
+kind: InitConfiguration
+localAPIEndpoint:
+  advertiseAddress: "10.100.0.1"
+  bindPort: 6443
+```
+
+`advertiseAddress` in InitConfiguration specifies the IP address the API Server will advertise it's listening on. It equals to `--apiserver-advertise-address` flag of `kubeadm init`.
+
+Run kubeadm to initiate the dual-stack control plane node.
+
+```shell
+kubeadm init --config=kubeadm-config.yml
+```
+
 Currently, `kube-controller-manager` flags `--node-cidr-mask-size-ipv4|--node-cidr-mask-size-ipv6` are setting with the default value. See [enable IPv4/IPv6 dual stack](/docs/concepts/services-networking/dual-stack#enable-ipv4ipv6-dual-stack).
 
 There is a limitation here, `--apiserver-advertise-address` flag doesn't support dual-stack.
 
 #### Join a node to dual-stack cluster
 
-Before joining a node, make sure that the node has ipv6 routable network interface and allows ipv6 forwarding.
+Before joining a node, make sure that the node has IPv6 routable network interface and allows IPv6 forwarding.
 
 
-#### Create a single-stack cluster
+Here is an example kubeadm [configuration file](https://pkg.go.dev/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2) `kubeadm-config.yml` for joining a worker node to the cluster.
 
-As IPv6DualStack feature gate is beta and default to true after 1.21, you can run the command without `--feature-gates` flag.
+```yaml
+apiVersion: kubeadm.k8s.io/v1beta2
+kind: JoinConfiguration
+discovery:
+  bootstrapToken:
+    apiServerEndpoint: 10.100.0.1:6443
+    token: 0c0z4p.dnafh6vnmouus569
+    caCertHashes: ["sha256:fcb3e956a6880c05fc9d09714424b827f57a6fdc8afc44497180905946527adf"]
+```
+
+Besides, here is an example kubeadm [configuration file](https://pkg.go.dev/k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta2) `kubeadm-config.yml` for joining another control plane node to the cluster.
+```yaml
+apiVersion: kubeadm.k8s.io/v1beta2
+kind: JoinConfiguration
+controlPlane:
+  localAPIEndpoint:
+    advertiseAddress: "10.100.0.2"
+    bindPort: 6443
+discovery:
+  bootstrapToken:
+    apiServerEndpoint: 10.100.0.1:6443
+    token: 0c0z4p.dnafh6vnmouus569
+    caCertHashes: ["sha256:fcb3e956a6880c05fc9d09714424b827f57a6fdc8afc44497180905946527adf"]
+```
 
+`advertiseAddress` in JoinConfiguration.controlPlane specifies the IP address the API Server will advertise it's listening on. It equals to `--apiserver-advertise-address` flag of `kubeadm join`.
+
+```shell
+kubeadm join --config=kubeadm-config.yml ...
 ```
+
+#### Create a single-stack cluster
+
+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.
+
+```shell
 kubeadm init --feature-gates IPv6DualStack=false
 ```
 
+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.yml` for the single-stack control plane node.
+
+```yaml
+apiVersion: kubeadm.k8s.io/v1beta2
+kind: ClusterConfiguration
+featureGates:
+  IPv6DualStack: false
+networking:
+  podSubnet: 172.30.0.0/16
+  serviceSubnet: 172.31.0.0/16
+```
+
 ## 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.