# Declare Network Policy

Declare Network PolicyThis document helps you get started using the Kubernetes NetworkPolicy API to declare network policies that govern how pods communicate with each other.Note: This section links to third party projects that provide functionality required by Kubernetes. The Kubernetes project authors aren't responsible for these projects, which are listed alphabetically. To add a project to this list, read the content guide before submitting a change. More information.Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:iximiuz LabsKillercodaKodeKloudPlay with KubernetesYour Kubernetes server must be at or later than version v1.8.To check the version, enter kubectl version.Make sure you've configured a network provider with network policy support. There are a number of network providers that support NetworkPolicy, including:AntreaCalicoCiliumKube-routerRomanaWeave NetCreate an nginx deployment and expose it via a serviceTo see how Kubernetes network policy works, start off by creating an nginx Deployment.kubectl create deployment nginx --image=nginx deployment.apps/nginx created Expose the Deployment through a Service called nginx.kubectl expose deployment nginx --port=80 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.kubectl get svc,pod 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 PodYou 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:kubectl run busybox --rm -ti --image=busybox -- /bin/sh In your shell, run the following command:wget --spider --timeout=1 nginx Connecting to nginx (10.100.0.16:80) remote file exists Limit access to the nginx serviceTo 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:service/networking/nginx-policy.yaml apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: access-nginx spec: podSelector: matchLabels: app: nginx ingress: - from: - podSelector: matchLabels: access: "true" The name of a NetworkPolicy object must be a valid DNS subdomain name.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 serviceUse kubectl to create a NetworkPolicy from the above nginx-policy.yaml file:kubectl apply -f https://k8s.io/examples/service/networking/nginx-policy.yaml networkpolicy.networking.k8s.io/access-nginx created Test access to the service when access label is not definedWhen you attempt to access the nginx Service from a Pod without the correct labels, the request times out:kubectl run busybox --rm -ti --image=busybox -- /bin/sh In your shell, run the command:wget --spider --timeout=1 nginx Connecting to nginx (10.100.0.16:80) wget: download timed out Define access label and test againYou can create a Pod with the correct labels to see that the request is allowed:kubectl run busybox --rm -ti --labels="access=true" --image=busybox -- /bin/sh In your shell, run the command:wget --spider --timeout=1 nginx Connecting to nginx (10.100.0.16:80) remote file exists Items on this page refer to third party products or projects that provide functionality required by Kubernetes. The Kubernetes project authors aren't responsible for those third-party products or projects. See the CNCF website guidelines for more details.You should read the content guide before proposing a change that adds an extra third-party link.