What Kubernetes Network Policies Do
Network Policies in Kubernetes control how pods communicate with each other and with external endpoints. They use label selectors to match pods and then specify allowed ingress and egress rules. Without them, all pods can talk to all other pods by default. With them, segmentation is explicit and enforced.
Segmentation at the Pod Level
Segmentation means splitting traffic paths into well-defined zones. In Kubernetes, you can isolate workloads by namespace, label, or IP block. Each policy becomes a firewall rule tailored to workloads, reducing blast radius and limiting lateral movement. Create separate policies for frontend pods, backend pods, and database pods so no component talks to another unless it must.
Key Configuration Patterns
- Default Deny – Start with a policy that drops all ingress and egress, then add specific allow rules.
- Namespace Isolation – Bound communication to specific namespaces.
- Service-Based Rules – Target labels that match specific services rather than broad ranges.
- Egress Control – Restrict outbound connections to only what is needed, e.g., specific CIDR blocks or external APIs.
Integrating with CNIs
Your CNI plugin must support Network Policies for enforcement. Popular options like Calico, Cilium, and Weave Net each have unique features. Choose one that matches your security requirements and operational tooling.
Why Network Policy Segmentation Matters
Kubernetes Network Policies segmentation stops noisy pods from flooding logs, contains compromised workloads, and enforces compliance boundaries. Each rule is declarative and version-controlled. When policies are part of your CI/CD pipeline, deviations are caught before they reach production.
Implementing at Scale
Automation makes large-scale segmentation possible. Use Helm charts or GitOps tools to apply consistent policies across clusters. Include testing pipelines that confirm expected blocking and allowing behaviors. Continuous monitoring ensures that changes in labels or namespaces do not break isolation.
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