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Posted on Originally published at blog.saaro.net

Cilium 2026: eBPF-based Networking as the New Kubernetes Standard

#kubernetes #networking #ebpf #cilium

In 2026, Cilium quietly but decisively evolved from a specialized CNI plugin to the central network backbone for Kubernetes. Google Cloud uses Cilium as the standard CNI in GKE Autopilot, Microsoft Azure offers it as the preferred advanced networking option in AKS, and Amazon EKS also recommends Cilium for demanding scenarios. What's behind this rise – and why should platform teams now pay special attention to eBPF-based networking?

eBPF: The Technical Foundation

Cilium is based on eBPF (Extended Berkeley Packet Filter), a technology that allows small programs to be loaded into the Linux kernel and executed there. Unlike classic CNIs that rely on iptables chains – which grow linearly with each additional service rule and lead to measurable latency spikes with thousands of rules – Cilium uses eBPF maps for constant lookup time (O(1)). This makes network performance independent of cluster size. Benchmarks from 2026 show: Cilium achieves up to 28.5 Gbit/s throughput in pod-to-service scenarios and a P99 latency of only 0.8 ms – at half the CPU consumption compared to iptables-based alternatives.

The catch: the kernel requirement is Linux 5.4+, with 5.15+ recommended for production environments. Anyone running older nodes will have to rely on Calico or Flannel for now.

L7 Policies Without Sidecar

The decisive advantage of Cilium over Calico or Flannel lies in native Layer 7 inspection. Where a classic Kubernetes NetworkPolicy can only allow "TCP port 8080", Cilium differentiates at the HTTP path level: GET /products is allowed, DELETE /admin is blocked – and it does so close to the kernel, without an Envoy sidecar running alongside each pod.

Configuration is done via CiliumNetworkPolicy resources in native Kubernetes manifest format:

apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
  name: api-http-policy
spec:
  endpointSelector:
    matchLabels:
      app: api-server
  ingress:
    - fromEndpoints:
        - matchLabels:
            app: frontend
      toPorts:
        - ports:
            - port: "8080"
          protocol: TCP
      rules:
        http:
          - method: GET
            path: "/api/v1/products"
          - method: POST
            path: "/api/v1/orders"
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For compliance requirements according to SOC 2 or ISO 27001, these rules can be verified as testable artifacts directly in the CI/CD pipeline – a massive improvement over retrospectively patched firewall rules.

Hubble: Observability from the Kernel

Hubble, Cilium's integrated observability layer, taps into the same eBPF hooks used for policy enforcement. The result: complete transparency across all network flows – without agents, without sidecars, without sampling. Every connection is logged with source and destination pod, protocol, verdict, and byte counters. For incident scenarios, that means: instead of digging through inconsistent application logs from twenty microservices, a hubble observe --verdict DROPPED directly filters out rejected connections.

Hubble integrations into Prometheus and Grafana are covered via the native OpenMetrics endpoint, allowing existing monitoring stacks to be extended.

Cilium vs. Calico vs. Istio: The Decision Matrix in 2026

As of 2026, the rule is: anyone setting up a new cluster should choose Cilium as the default CNI. Calico remains the right choice for environments with older kernels or BGP requirements in bare-metal operations. Istio, on the other hand, should only be used where genuinely complex traffic management (canary deployments, dynamic mirroring) is needed – many organizations today run Cilium for the base network layer and only layer Istio on top where the effort is justified.

Conclusion

In 2026, Cilium is more than a CNI plugin. It is a platform for networking, security, and observability in one piece – running at the kernel level, without sidecar overhead. Adoption by the major cloud providers (GKE, EKS, AKS) shows that eBPF-based networking is no longer a niche topic but is becoming the new standard. Platform teams still relying on Calico or even Flannel should develop a migration strategy – the switch to Cilium is well documented via the official Helm chart documentation and can be done through a node-by-node process without production downtime. The learning curve is real, but the gains in performance, security, and transparency clearly outweigh it.

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