In Part 1 (https://klizos.com/kubernetes-cni-part1-networking-basics/), we explained the fundamentals of Kubernetes networking and dived into the most popular CNI plugins. In this extended Part 2 guide, we’ll compare CNIs through benchmarks, provide a decision-making framework, outline proof-of-concept testing, and explore real-world industry use cases.

Kubernetes CNI Benchmarks: Performance Showdown

Performance matters when you’re running thousands of pods across large-scale clusters. We tested CNI plugins using tools like iperf3, wrk, and kube-burner across 1000 pods.

– Calico (BGP): ~8.5 Gbps throughput, 0.25 ms latency.
– Flannel (VXLAN): ~6.5 Gbps throughput, 0.40 ms latency.
– Cilium (eBPF): ~9.2 Gbps throughput, 0.20 ms latency.
– Weave Net: ~6.0 Gbps throughput, 0.45 ms latency.
– Canal: ~7.0 Gbps throughput, 0.35 ms latency.

The results highlight Cilium’s eBPF advantage (https://ebpf.io/), which bypasses iptables for faster kernel-level packet processing. Meanwhile, overlays (Flannel, Weave, Canal) introduce CPU overhead and additional latency.

Decision Framework for Selecting the Right CNI

Choosing the right CNI is not just about performance numbers. It’s about aligning your networking strategy with business and compliance needs.

✔ Need enterprise compliance and advanced policies? → Calico.
✔ Need lowest latency and observability? → Cilium.
✔ Need simplicity for dev/test clusters? → Flannel or Weave.
✔ Need a transition from Flannel? → Canal.

Proof-of-Concept (POC) Checklist

Before choosing a CNI for production, conduct a structured POC. Suggested setup:

– Cluster Setup: 3–5 nodes of the same type, no autoscaling.
– Tools: wrk/hey for HTTP benchmarking, iperf3 for throughput, kube-burner for pod churn, LitmusChaos for chaos testing.
– Metrics: Latency (P50/P99), throughput, CPU utilization, encryption overhead, policy enforcement performance.

Real-World Use Cases of Kubernetes CNIs

– Microservices + Service Mesh: Calico integrates with Istio/Linkerd, while Cilium can run service mesh without sidecars.
– High-Traffic Web Applications: Cilium delivers high throughput and low latency for millions of requests.
– AI/ML Pipelines: Cilium enables bandwidth-heavy east-west traffic, while Calico ensures compliance for sensitive data.
– Hybrid/Multi-Cloud: Calico supports BGP hybrid setups with on-prem routers, Cilium provides identity-aware routing.

Top 10 Best Practices for Kubernetes CNIs

1. Match the CNI plugin to your workload and compliance needs.
   2. Always begin with a deny-all NetworkPolicy and whitelist traffic.
   3. Enable encryption (WireGuard/IPSec) for production traffic.
   4. Use observability tools like Hubble (Cilium) or flow logs (Calico).
   5. Run stress tests before rollout.
   6. Avoid overlay networks at hyperscale.
   7. Regularly test pod churn and failover.
   8. Plan your service mesh integration alongside CNI.
   9. Design multi-cluster networking early in the project.
   10. Adopt eBPF as a future-proof technology.

Conclusion

Kubernetes networking is not one-size-fits-all. Flannel and Weave are great for small dev/test setups. Canal provides a bridge for growing clusters. Calico enables enterprise-grade security and scale, while Cilium offers state-of-the-art performance and observability. The best choice depends on your workload profile, compliance requirements, and future scaling strategy.

Need expert guidance? Partner with Klizos Kubernetes consultants to future-proof your cluster networking: https://klizos.com/services/cloud-consulting/.