Declare Network Policy [page]deterministic
This document helps you get started using the Kubernetes [NetworkPolicy API](/docs/concepts/services-networking/network-policies/) to declare network policies that govern how pods communicate with each other.
##
Make sure you've configured a network provider with network policy support. There are a number of network providers that support NetworkPolicy, including:
* [Antrea](/docs/tasks/administer-cluster/network-policy-provider/antrea-network-policy/) * [Calico](/docs/tasks/administer-cluster/network-policy-provider/calico-network-policy/) * [Cilium](/docs/tasks/administer-cluster/network-policy-provider/cilium-network-policy/) * [Kube-router](/docs/tasks/administer-cluster/network-policy-provider/kube-router-network-policy/) * [Romana](/docs/tasks/administer-cluster/network-policy-provider/romana-network-policy/) * [Weave Net](/docs/tasks/administer-cluster/network-policy-provider/weave-network-policy/)
## Create an `nginx` deployment and expose it via a service
To see how Kubernetes network policy works, start off by creating an `nginx` Deployment.
```console kubectl create deployment nginx --image=nginx ``` ```none deployment.apps/nginx created ```
Expose the Deployment through a Service called `nginx`.
```console kubectl expose deployment nginx --port=80 ```
```none service/nginx exposed ```
The above commands create a Deployment with an nginx Pod and expose the Deployment through a Service named `nginx`. The `nginx` Pod and Deployment are found in the `default` namespace.
```console kubectl get svc,pod ```
```none NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/kubernetes 10.100.0.1 <none> 443/TCP 46m service/nginx 10.100.0.16 <none> 80/TCP 33s
NAME READY STATUS RESTARTS AGE pod/nginx-701339712-e0qfq 1/1 Running 0 35s ```
## Test the service by accessing it from another Pod
You should be able to access the new `nginx` service from other Pods. To access the `nginx` Service from another Pod in the `default` namespace, start a busybox container:
```console kubectl run busybox --rm -ti --image=busybox -- /bin/sh ```
In your shell, run the following command:
```shell wget --spider --timeout=1 nginx ```
```none Connecting to nginx (10.100.0.16:80) remote file exists ```
## Limit access to the `nginx` service
To limit the access to the `nginx` service so that only Pods with the label `access: true` can query it, create a NetworkPolicy object as follows:
The name of a NetworkPolicy object must be a valid [DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names).
> Note: NetworkPolicy includes a `podSelector` which selects the grouping of Pods to which the policy applies. You can see this policy selects Pods with the label `app=nginx`. The label was automatically added to the Pod in the `nginx` Deployment. An empty `podSelector` selects all pods in the namespace.
## Assign the policy to the service
Use kubectl to create a NetworkPolicy from the above `nginx-policy.yaml` file:
```console kubectl apply -f https://k8s.io/examples/service/networking/nginx-policy.yaml ```
```none networkpolicy.networking.k8s.io/access-nginx created ```
## Test access to the service when access label is not defined When you attempt to access the `nginx` Service from a Pod without the correct labels, the request times out:
```console kubectl run busybox --rm -ti --image=busybox -- /bin/sh ```
In your shell, run the command:
```shell wget --spider --timeout=1 nginx ```
```none Connecting to nginx (10.100.0.16:80) wget: download timed out ```
## Define access label and test again
You can create a Pod with the correct labels to see that the request is allowed:
```console kubectl run busybox --rm -ti --labels="access=true" --image=busybox -- /bin/sh ```
In your shell, run the command:
```shell wget --spider --timeout=1 nginx …(trimmed)