Declare Network Policy
This document helps you get started using the Kubernetes NetworkPolicy API to declare network policies that govern how pods communicate with each other.
- Before you begin
- Create an
nginxdeployment and expose it via a service - Test the service by accessing it from another pod
- Limit access to the
nginxservice - Assign the policy to the service
- Test access to the service when access label is not defined
- Define access label and test again
Before you begin
You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using Minikube, or you can use one of these Kubernetes playgrounds:
To check the version, enter kubectl version.
Create an nginx deployment and expose it via a service
To see how Kubernetes network policy works, start off by creating an nginx deployment and exposing it via a service.
$ kubectl run nginx --image=nginx --replicas=2
deployment "nginx" created
$ kubectl expose deployment nginx --port=80
service "nginx" exposedThis runs two nginx pods in the default namespace, and exposes them through a service called nginx.
$ kubectl get svc,pod
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
svc/kubernetes 10.100.0.1 <none> 443/TCP 46m
svc/nginx 10.100.0.16 <none> 80/TCP 33s
NAME READY STATUS RESTARTS AGE
po/nginx-701339712-e0qfq 1/1 Running 0 35s
po/nginx-701339712-o00ef 1/1 Running 0 35sTest the service by accessing it from another pod
You should be able to access the new nginx service from other pods. To test, access the service from another pod in the default namespace. Make sure you haven’t enabled isolation on the namespace.
Start a busybox container, and use wget on the nginx service:
$ kubectl run busybox --rm -ti --image=busybox /bin/sh
Waiting for pod default/busybox-472357175-y0m47 to be running, status is Pending, pod ready: false
Hit enter for command prompt
/ # wget --spider --timeout=1 nginx
Connecting to nginx (10.100.0.16:80)
/ #Limit access to the nginx service
Let’s say you want to limit access to the nginx service so that only pods with the label access: true can query it. To do that, create a NetworkPolicy that allows connections only from those pods:
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
name: access-nginx
spec:
podSelector:
matchLabels:
run: nginx
ingress:
- from:
- podSelector:
matchLabels:
access: "true"Assign the policy to the service
Use kubectl to create a NetworkPolicy from the above nginx-policy.yaml file:
$ kubectl create -f nginx-policy.yaml
networkpolicy "access-nginx" createdTest access to the service when access label is not defined
If we attempt to access the nginx Service from a pod without the correct labels, the request will now time out:
$ kubectl run busybox --rm -ti --image=busybox /bin/sh
Waiting for pod default/busybox-472357175-y0m47 to be running, status is Pending, pod ready: false
Hit enter for command prompt
/ # wget --spider --timeout=1 nginx
Connecting to nginx (10.100.0.16:80)
wget: download timed out
/ #Define access label and test again
Create a pod with the correct labels, and you’ll see that the request is allowed:
$ kubectl run busybox --rm -ti --labels="access=true" --image=busybox /bin/sh
Waiting for pod default/busybox-472357175-y0m47 to be running, status is Pending, pod ready: false
Hit enter for command prompt
/ # wget --spider --timeout=1 nginx
Connecting to nginx (10.100.0.16:80)
/ #