Kubernetes Networking: Services, Ingress, and Network Policies

Kubernetes networking can be confusing. Here’s a concise guide to services, ingress, and network policy.

Services

• ClusterIP: Internal cluster DNS; default for in-cluster traffic.
• NodePort: Expose a port on every node; good for dev or legacy.
• LoadBalancer: Cloud LB per service; use when you need a dedicated external IP.

Ingress

• Ingress = HTTP(S) routing (host/path) to backend services. You need an Ingress controller (e.g. nginx, AWS ALB).
• TLS: Terminate at ingress; use cert-manager for certificates.

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp
spec:
  ingressClassName: nginx
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp
                port: { number: 80 }

Network Policies

• NetworkPolicy restricts pod-to-pod and pod-to-external traffic. Default-deny and allow only what’s needed.
• Start with a policy that allows DNS and ingress; then add app-specific rules.

Best practice: document your ingress and network policy approach so every new service follows the same pattern.