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Merge pull request #31667 from mk46/remove_kubenet
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Removed kubenet reference from docs
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k8s-ci-robot committed Feb 22, 2022
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<!-- overview -->

Network plugins in Kubernetes come in a few flavors:
Kubernetes {{< skew currentVersion >}} supports [Container Network Interface](https://github.com/containernetworking/cni)
(CNI) plugins for cluster networking. You must use a CNI plugin that is compatible with your cluster and that suits your needs. Different plugins are available (both open- and closed- source) in the wider Kubernetes ecosystem.

* CNI plugins: adhere to the [Container Network Interface](https://github.com/containernetworking/cni) (CNI) specification, designed for interoperability.
* Kubernetes follows the [v0.4.0](https://github.com/containernetworking/cni/blob/spec-v0.4.0/SPEC.md) release of the CNI specification.
* Kubenet plugin: implements basic `cbr0` using the `bridge` and `host-local` CNI plugins
You must use a CNI plugin that is compatible with the
[v0.4.0](https://github.com/containernetworking/cni/blob/spec-v0.4.0/SPEC.md) release of the CNI specification.

<!-- body -->

## Installation

The kubelet has a single default network plugin, and a default network common to the entire cluster. It probes for plugins when it starts up, remembers what it finds, and executes the selected plugin at appropriate times in the pod lifecycle (this is only true for Docker, as CRI manages its own CNI plugins). There are two Kubelet command line parameters to keep in mind when using plugins:
The kubelet has a single default network plugin, and a default network common to the entire cluster.The CRI manages its own CNI plugins. There are two Kubelet command line parameters to keep in mind when using plugins:

* `cni-bin-dir`: Kubelet probes this directory for plugins on startup
* `network-plugin`: The network plugin to use from `cni-bin-dir`. It must match the name reported by a plugin probed from the plugin directory. For CNI plugins, this is `cni`.
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...
```

### kubenet

Kubenet is a very basic, simple network plugin, on Linux only. It does not, of itself, implement more advanced features like cross-node networking or network policy. It is typically used together with a cloud provider that sets up routing rules for communication between nodes, or in single-node environments.

Kubenet creates a Linux bridge named `cbr0` and creates a veth pair for each pod with the host end of each pair connected to `cbr0`. The pod end of the pair is assigned an IP address allocated from a range assigned to the node either through configuration or by the controller-manager. `cbr0` is assigned an MTU matching the smallest MTU of an enabled normal interface on the host.

The plugin requires a few things:

* The standard CNI `bridge`, `lo` and `host-local` plugins are required, at minimum version 0.2.0. Kubenet will first search for them in `/opt/cni/bin`. Specify `cni-bin-dir` to supply additional search path. The first found match will take effect.
* Kubelet must be run with the `--network-plugin=kubenet` argument to enable the plugin
* Kubelet should also be run with the `--non-masquerade-cidr=<clusterCidr>` argument to ensure traffic to IPs outside this range will use IP masquerade.
* The node must be assigned an IP subnet through either the `--pod-cidr` kubelet command-line option or the `--allocate-node-cidrs=true --cluster-cidr=<cidr>` controller-manager command-line options.

### Customizing the MTU (with kubenet)

The MTU should always be configured correctly to get the best networking performance. Network plugins will usually try
to infer a sensible MTU, but sometimes the logic will not result in an optimal MTU. For example, if the
Docker bridge or another interface has a small MTU, kubenet will currently select that MTU. Or if you are
using IPSEC encapsulation, the MTU must be reduced, and this calculation is out-of-scope for
most network plugins.

Where needed, you can specify the MTU explicitly with the `network-plugin-mtu` kubelet option. For example,
on AWS the `eth0` MTU is typically 9001, so you might specify `--network-plugin-mtu=9001`. If you're using IPSEC you
might reduce it to allow for encapsulation overhead; for example: `--network-plugin-mtu=8873`.

This option is provided to the network-plugin; currently **only kubenet supports `network-plugin-mtu`**.

## Usage Summary

* `--network-plugin=cni` specifies that we use the `cni` network plugin with actual CNI plugin binaries located in `--cni-bin-dir` (default `/opt/cni/bin`) and CNI plugin configuration located in `--cni-conf-dir` (default `/etc/cni/net.d`).
* `--network-plugin=kubenet` specifies that we use the `kubenet` network plugin with CNI `bridge`, `lo` and `host-local` plugins placed in `/opt/cni/bin` or `cni-bin-dir`.
* `--network-plugin-mtu=9001` specifies the MTU to use, currently only used by the `kubenet` network plugin.

## {{% heading "whatsnext" %}}
2 changes: 1 addition & 1 deletion content/en/docs/concepts/services-networking/dual-stack.md
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Kubernetes versions, refer to the documentation for that version
of Kubernetes.
* 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)
* A [network plugin](/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/) that supports dual-stack networking.

## Configure IPv4/IPv6 dual-stack

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4 changes: 2 additions & 2 deletions content/en/docs/setup/best-practices/node-conformance.md
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Expand Up @@ -30,8 +30,8 @@ To run the node conformance test, perform the following steps:
Because the test framework starts a local control plane to test the kubelet,
use `http://localhost:8080` as the URL of the API server.
There are some other kubelet command line parameters you may want to use:
* `--pod-cidr`: If you are using `kubenet`, you should specify an arbitrary CIDR
to Kubelet, for example `--pod-cidr=10.180.0.0/24`.
* `--pod-cidr`: The CIDR to use for pod IP addresses, only used in standalone mode.
In cluster mode, this is obtained from the master. For IPv6, the maximum number of IP's allocated is 65536. For example `--pod-cidr=10.180.0.0/24`.
* `--cloud-provider`: If you are using `--cloud-provider=gce`, you should
remove the flag to run the test.

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2 changes: 1 addition & 1 deletion content/en/docs/tasks/network/validate-dual-stack.md
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* 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](/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/) that supports dual-stack (such as Calico, Cilium or Kubenet)
* A [network plugin](/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/) that supports dual-stack networking.
* [Dual-stack enabled](/docs/concepts/services-networking/dual-stack/) cluster

{{< version-check >}}
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