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In this guide, you’ll learn how to configure robust Pod-to-Pod encryption using a Cilium network policy. This policy ensures that outbound traffic (egress) for your application – for example, “myapp” – is encrypted and secure within your Kubernetes cluster.

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Cilium Network Policy Overview

The Cilium network policy is defined with key components to enforce encryption for your application’s traffic. Here’s a breakdown of the essential elements:
  1. API Version: The configuration uses "cilium.io/v2", specifying that this is a Cilium-specific network policy.
  2. Kind: The policy type is set as CiliumNetworkPolicy, indicating that Cilium will manage the enforcement.
  3. Metadata: The policy is named allow-encrypted-traffic.
  4. Endpoint Selector: It targets all pods with the label app: myapp, ensuring that the policy applies specifically to your application.
  5. Egress Rules: The rules allow outbound traffic directed to pods with the same label (app: myapp) over TCP port 80. This ensures encrypted traffic flows only to designated pods.

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Complete Cilium Network Policy

Below is the full YAML configuration for the Cilium network policy: 
apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
  name: allow-encrypted-traffic
spec:
  endpointSelector:
    matchLabels:
      app: myapp
  egress:
  - toEndpoints:
    - matchLabels:
        app: myapp
    toPorts:
    - ports:
      - port: "80"
        protocol: TCP
This policy is similar to standard Kubernetes network policies but includes additional settings to handle encrypted traffic effectively.

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Verify Encrypted Traffic Between Pods

To ensure that traffic between pods is properly encrypted, you can capture and inspect network packets using the tcpdump utility. Follow these steps:
  1. Launch a Pod Shell: Open a shell session in one of the pods.
  2. Install tcpdump: Update the package list and install tcpdump.
  3. Monitor Network Traffic: Use tcpdump to capture packets on the eth0 interface.
Run the following commands: 
kubectl exec -it <pod-name> -- /bin/bash
apt-get update && apt-get install -y tcpdump
tcpdump -i eth0 -nn
Ensure you replace <pod-name> with the actual name of your pod when executing the commands.
By monitoring the network interface using tcpdump, you can verify that no unencrypted packets are transmitted. When encryption is properly enabled, the captured traffic should appear encrypted and secure.

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Conclusion

By following the steps outlined in this tutorial, you can effectively control and secure Pod-to-Pod communication within your Kubernetes environment using Cilium network policies. This approach not only enhances the security of your applications but also ensures compliance with encryption best practices. For more information about Kubernetes network policies and advanced security configurations, refer to the following resources:

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