What Is a Kubernetes Network Policy?

Kubernetes Network Policy is a Kubernetes resource that controls the flow of network traffic between pods at the IP address and port level. By default, all pods in a Kubernetes cluster can communicate with any other pod. Network Policies let you restrict this open communication by defining rules that specify which pods can send and receive traffic, acting as a built-in firewall for your cluster.

Why Network Policies Matter

The default allow-all networking in Kubernetes means that a compromised pod can freely communicate with any other pod in the cluster. This is a significant security risk, especially in multi-tenant environments. Network Policies implement the principle of least privilege at the network level, ensuring that pods can only communicate with the specific services they need, limiting the blast radius of any security breach.

For organizations pursuing zero trust architecture or meeting compliance requirements like PCI-DSS and SOC 2, network policies are a fundamental control. They provide verifiable, declarative network segmentation that can be audited, version-controlled, and enforced consistently across all namespaces and clusters.

How Network Policies Work

Network Policies use label selectors to identify which pods the policy applies to and which pods are allowed as traffic sources or destinations. You define ingress rules for incoming traffic and egress rules for outgoing traffic. Once a Network Policy selects a pod, all traffic not explicitly allowed is denied. A CNI plugin like Calico, Cilium, or Weave Net must be installed to enforce Network Policies, as the default kubenet does not support them.

Understanding how kubernetes network policy fits into the broader cloud-native ecosystem is important for making informed architecture decisions. It works alongside other tools and practices in the DevOps and platform engineering space, and choosing the right combination depends on your team's specific requirements, scale, and operational maturity.

Key Features

Label-Based Selection

Policies use Kubernetes label selectors to target pods and define allowed communication partners dynamically.

Ingress and Egress Rules

Control both incoming and outgoing traffic separately with granular rules based on pods, namespaces, and IP ranges.

Default Deny

Apply a default-deny policy to a namespace and then explicitly allow only the traffic paths that are required.

Namespace Isolation

Restrict cross-namespace traffic to prevent pods in one namespace from accessing services in another.

Common Use Cases

Isolating a database pod so that only the application pods in the same namespace can connect to it.

Implementing a default-deny ingress policy for all pods in a production namespace and explicitly whitelisting allowed traffic.

Preventing pods in the development namespace from communicating with production services.

Restricting egress traffic from pods to prevent unauthorized communication with external services.

How Obsium Helps

Obsium's Kubernetes consulting team helps organizations implement and optimize kubernetes network policy as part of production-grade infrastructure. Whether you are adopting kubernetes network policy for the first time or looking to improve an existing implementation, our engineers bring hands-on experience across cloud platforms and Kubernetes environments. Learn more about our Kubernetes consulting services →