Services Introduction
A Service is used to connect applications together by exposing a network application (Pod) in the cluster.
The internal Pod network is in the range of 10.244.0.0.
Use kubectl describe pods/<pod-name> to get the pod IP address.
| Type | Description |
|---|
ClusterIP | Creates a virtual IP for enabling communication between different services within the cluster. |
NodePort | Exposes an application to external clients by opening a port on worker nodes. |
LoadBalancer | Supports external load balancers and distributes network traffic across multiple instances. |
Service Types
ClusterIP
NodePort
LoadBalancer
Each pod has its own IP address, but these IPs are not static — pods can restart at any time and get new IPs. With ClusterIP, each service is assigned a stable name and IP address inside the cluster. Other pods can use either the service name or cluster IP to access the service.This is the default service type.apiVersion: v1
kind: Service
metadata:
name: backend-service
spec:
selector:
app: backend
type: ClusterIP
ports:
- targetPort: 8080 # Port that the Pod exposes
port: 8000 # Service port
NodePort maps an internal port on the node to a port that the pod exposes via Service. The node port is used to access the application externally.NodePort (30121) → Service (8000) → Pod (8080)
apiVersion: v1
kind: Service
metadata:
name: backend-service
spec:
selector:
app: backend
type: NodePort
ports:
- targetPort: 8080 # Port that the Pod exposes
port: 8000 # Service port
nodePort: 30121 # Valid range: 30000-32767
If you don’t specify nodePort, the system will automatically assign one in the range 30000-32767.
# Get your cluster IP address
kubectl cluster-info
# Access via public node IP and node port
curl http://<public-node-ip>:<node-port>
curl http://192.168.1.5:30121
NodePort URLs (http://<public-node-ip>:<node-port>) are not user-friendly. The LoadBalancer type integrates with cloud providers (AWS, GCP, Azure) to provision a native load balancer automatically.Kubernetes sends a request to the cloud provider to create a load balancer, assign it a public IP address, and route traffic to the service and then to the pods.apiVersion: v1
kind: Service
metadata:
name: backend-service
spec:
selector:
app: backend
type: LoadBalancer
ports:
- targetPort: 8080
port: 8000
Using type: LoadBalancer has the same effect as NodePort for distributing traffic, but also provisions the cloud load balancer automatically.