How to Implement Micro-Segmentation in K8s Using Cilium Network Policies

The Challenge: Zero-Trust Networking in Kubernetes

Achieving Zero-Trust requires enforcing least-privilege communication. We must explicitly define which services can talk to each other, blocking all other traffic by default, without introducing unacceptable latency overhead.

The Solution: eBPF-Powered CiliumNetworkPolicy

We will define a CiliumNetworkPolicy (CNP) that isolates a PostgreSQL database, permitting ingress traffic only from authorized backend API pods over a specific port. Cilium implements this directly in the Linux kernel via eBPF maps.

apiVersion: "cilium.io/v2"kind: CiliumNetworkPolicymetadata: name: "db-micro-segmentation" namespace: "production"spec: endpointSelector: matchLabels: app: postgres-db tier: storage ingress: - fromEndpoints: - matchLabels: app: backend-api tier: application toPorts: - ports: - port: "5432" protocol: TCP

Policy Anatomy and eBPF Mechanics

Let's dissect this policy to understand how Cilium translates declarative YAML into robust kernel-level security:

• kind: CiliumNetworkPolicy: Unlike standard Kubernetes NetworkPolicy objects, CNPs offer advanced features like L7 filtering (HTTP/gRPC/Kafka) and DNS-based rules, though here we focus on stringent L4 isolation.
• endpointSelector:...

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