Apply concept template to extend-kubernetes and configuration dirs (#8995)

content/en/docs/concepts/services-networking/network-policies.md

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 - caseydavenport
 - danwinship
 title: Network Policies
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 A network policy is a specification of how groups of pods are allowed to communicate with each other and other network endpoints.
 
 `NetworkPolicy` resources use labels to select pods and define rules which specify what traffic is allowed to the selected pods.
 
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 ## Prerequisites
 
 Network policies are implemented by the network plugin, so you must be using a networking solution which supports `NetworkPolicy` - simply creating the resource without a controller to implement it will have no effect.
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 This ensures that even pods that aren't selected by any other NetworkPolicy will not be allowed ingress or egress traffic.
 
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 - See the [Declare Network Policy](/docs/tasks/administer-cluster/declare-network-policy/)
   walkthrough for further examples.
 - See more [Recipes](https://github.com/ahmetb/kubernetes-network-policy-recipes) for common scenarios enabled by the NetworkPolicy resource.
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