Kubernetes networking enables communication between pods, services, and external clients. It ensures connectivity, scalability, and security for applications running inside a cluster.
In this article, we will cover:
- Pod-to-Pod communication
- Services for exposing applications
- Ingress Controllers for managing external access
1. How Kubernetes Networking Works
Unlike traditional networks, Kubernetes follows a flat networking model, where:
- Every pod gets a unique IP address.
- Pods can communicate with each other without NAT (Network Address Translation).
- Services provide a stable endpoint to expose pods to internal or external users.
Kubernetes networking is designed to be highly scalable and works across different cloud providers and on-premise clusters.
2. Kubernetes Service Types
A Service is an abstraction that provides network access to a group of pods. Since pod IPs are dynamic, a Service ensures consistent connectivity.
Types of Services in Kubernetes
Service Type Description ClusterIP Default type, accessible only within the cluster. NodePort Exposes the service on a static port on each node. LoadBalancer Uses a cloud provider’s load balancer to expose the service. ExternalName Maps a service to an external DNS name.
3. Exposing an Application Using a Service
Example: Creating a ClusterIP Service
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
selector:
app: my-app
ports:
- protocol: TCP
port: 80
targetPort: 8080
Apply the Service:
kubectl apply -f service.yaml
Check the Service:
kubectl get services
Pods can now access this service using my-service:80.
Example: Exposing an Application Using a NodePort
apiVersion: v1
kind: Service
metadata:
name: my-nodeport-service
spec:
type: NodePort
selector:
app: my-app
ports:
- protocol: TCP
port: 80
targetPort: 8080
nodePort: 30080 # Exposes the service on <NodeIP>:30080
Apply the Service:
kubectl apply -f nodeport-service.yaml
Access the application:
http://<NodeIP>:30080
Find the Node IP:
kubectl get nodes -o wide
- Ingress Controller: Managing External Access
While NodePort and LoadBalancer expose services, Ingress Controllers offer a more flexible way to manage external traffic.
Ingress Controllers provide:
- Routing based on hostnames and paths.
- SSL/TLS termination for secure connections.
- Load balancing between multiple services.
- Deploying an Ingress Controller
Example: Installing Nginx Ingress Controller
For Minikube:
minikube addons enable ingress
For other clusters using Helm:
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm install my-ingress ingress-nginx/ingress-nginx
- Configuring an Ingress Resource
Example: Ingress YAML for Two Services
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: my-ingress
spec:
rules:
- host: myapp.local
http:
paths:
- path: /service1
pathType: Prefix
backend:
service:
name: service1
port:
number: 80
- path: /service2
pathType: Prefix
backend:
service:
name: service2
port:
number: 80
Apply the Ingress:
kubectl apply -f ingress.yaml
For local testing, add this to /etc/hosts:
127.0.0.1 myapp.local
Access the services:
http://myapp.local/service1
http://myapp.local/service2
- Best Practices for Kubernetes Networking
- Use Services to expose applications internally.
- Use Ingress Controllers for external access and routing.
- Secure Ingress with TLS certificates for HTTPS.
- Implement Network Policies to restrict traffic flow.
- Monitor networking performance using Kubernetes metrics and logs.
Kubernetes networking allows efficient communication between pods, services, and external users. Understanding Services, Ingress, and Networking Policies is essential for deploying production-ready applications.
