134 lines
4.3 KiB
Markdown
134 lines
4.3 KiB
Markdown
---
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reviewers:
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- caseydavenport
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- danwinship
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title: Declare Network Policy
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content_template: templates/task
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---
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{{% capture overview %}}
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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.
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{{% /capture %}}
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{{% capture prerequisites %}}
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You'll need to have a Kubernetes cluster in place, with network policy support. There are a number of network providers that support NetworkPolicy, including:
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* [Calico](/docs/tasks/configure-pod-container/calico-network-policy/)
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* [Cilium](/docs/tasks/administer-cluster/cilium-network-policy/)
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* [Kube-router](/docs/tasks/administer-cluster/kube-router-network-policy/)
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* [Romana](/docs/tasks/configure-pod-container/romana-network-policy/)
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* [Weave Net](/docs/tasks/administer-cluster/weave-network-policy/)
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**Note**: The above list is sorted alphabetically by product name, not by recommendation or preference. This example is valid for a Kubernetes cluster using any of these providers.
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{{% /capture %}}
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{{% capture prerequisites %}}
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{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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{{% /capture %}}
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{{% capture steps %}}
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## Create an `nginx` deployment and expose it via a service
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To see how Kubernetes network policy works, start off by creating an `nginx` deployment and exposing it via a service.
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```console
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$ kubectl run nginx --image=nginx --replicas=2
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deployment "nginx" created
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$ kubectl expose deployment nginx --port=80
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service "nginx" exposed
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```
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This runs two `nginx` pods in the default namespace, and exposes them through a service called `nginx`.
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```console
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$ kubectl get svc,pod
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NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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svc/kubernetes 10.100.0.1 <none> 443/TCP 46m
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svc/nginx 10.100.0.16 <none> 80/TCP 33s
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NAME READY STATUS RESTARTS AGE
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po/nginx-701339712-e0qfq 1/1 Running 0 35s
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po/nginx-701339712-o00ef 1/1 Running 0 35s
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```
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## Test the service by accessing it from another pod
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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.
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Start a busybox container, and use `wget` on the `nginx` service:
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```console
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$ kubectl run busybox --rm -ti --image=busybox /bin/sh
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Waiting for pod default/busybox-472357175-y0m47 to be running, status is Pending, pod ready: false
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Hit enter for command prompt
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/ # wget --spider --timeout=1 nginx
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Connecting to nginx (10.100.0.16:80)
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/ #
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```
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## Limit access to the `nginx` service
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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:
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```yaml
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kind: NetworkPolicy
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apiVersion: networking.k8s.io/v1
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metadata:
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name: access-nginx
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spec:
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podSelector:
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matchLabels:
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run: nginx
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ingress:
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- from:
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- podSelector:
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matchLabels:
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access: "true"
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```
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## Assign the policy to the service
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Use kubectl to create a NetworkPolicy from the above nginx-policy.yaml file:
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```console
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$ kubectl create -f nginx-policy.yaml
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networkpolicy "access-nginx" created
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```
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## Test access to the service when access label is not defined
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If we attempt to access the nginx Service from a pod without the correct labels, the request will now time out:
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```console
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$ kubectl run busybox --rm -ti --image=busybox /bin/sh
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Waiting for pod default/busybox-472357175-y0m47 to be running, status is Pending, pod ready: false
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Hit enter for command prompt
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/ # wget --spider --timeout=1 nginx
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Connecting to nginx (10.100.0.16:80)
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wget: download timed out
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/ #
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```
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## Define access label and test again
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Create a pod with the correct labels, and you'll see that the request is allowed:
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```console
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$ kubectl run busybox --rm -ti --labels="access=true" --image=busybox /bin/sh
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Waiting for pod default/busybox-472357175-y0m47 to be running, status is Pending, pod ready: false
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Hit enter for command prompt
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/ # wget --spider --timeout=1 nginx
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Connecting to nginx (10.100.0.16:80)
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/ #
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```
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{{% /capture %}}
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