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Kubernetes CNI Plugins & Pod Networking

How CNI plugins implement pod networking: IP assignment, overlay networks, BGP routing, and eBPF data planes.

🎯Key Takeaways
CNI = standard for pod IP assignment and routing
Flannel: simple, no NetworkPolicy
Cilium: eBPF-native, best performance, L7 network policies

Kubernetes CNI Plugins & Pod Networking

How CNI plugins implement pod networking: IP assignment, overlay networks, BGP routing, and eBPF data planes.

~1 min read
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What you'll learn
  • CNI = standard for pod IP assignment and routing
  • Flannel: simple, no NetworkPolicy
  • Cilium: eBPF-native, best performance, L7 network policies

CNI Plugin Landscape

CNI (Container Network Interface) is the K8s plugin standard for pod networking. When a pod starts, kubelet calls the CNI plugin to assign an IP and configure routes. Main plugins: Flannel (simple VXLAN overlay, no NetworkPolicy), Calico (BGP or overlay, full NetworkPolicy), Cilium (eBPF, L7 policies, service mesh features, replaces kube-proxy).

Key takeaways

  • CNI = standard for pod IP assignment and routing
  • Flannel: simple, no NetworkPolicy
  • Cilium: eBPF-native, best performance, L7 network policies

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