What is the cluster IP in Kubernetes?

Question

I have created a cluster of three nodes: one master, two minions. How to check the cluster IP in Kubernetes? Is it the IP of the master node?

Answer 1

ClusterIP can mean 2 things: a type of service which is only accessible within a Kubernetes cluster, or the internal ("virtual") IP of components within a Kubernetes cluster. Assuming you're asking about finding the internal IP of a cluster, it can be accessed in 3 ways (using the simple-nginx example):

1. Via command line kubectl utility:

   $ kubectl describe service my-nginx Name:           my-nginx Namespace:      default Labels:         run=my-nginx Selector:       run=my-nginx Type:           LoadBalancer IP:         10.123.253.27 LoadBalancer Ingress:   104.197.129.240 Port:           <unnamed>   80/TCP NodePort:       <unnamed>   30723/TCP Endpoints:      10.120.0.6:80 Session Affinity:   None No events. 

2. Via the kubernetes API (here I've used kubectl proxy to route through localhost to my cluster):

   $ kubectl proxy & $ curl -G http://localhost:8001/api/v1/namespaces/default/services/my-nginx {   "kind": "Service",   "apiVersion": "v1",   "metadata": <omitted>,   "spec": {     "ports": [       {         "protocol": "TCP",         "port": 80,         "targetPort": 80,         "nodePort": 30723       }     ],     "selector": {       "run": "my-nginx"     },     "clusterIP": "10.123.253.27",     "type": "LoadBalancer",     "sessionAffinity": "None"   },   "status": {     "loadBalancer": {       "ingress": [         {           "ip": "104.197.129.240"         }       ]     }   } } 

3. Via the $<NAME>_SERVICE_HOST environment variable within a Kubernetes container (in this example my-nginx-yczg9 is the name of a pod in the cluster):

   $ kubectl exec my-nginx-yczg9 -- sh -c 'echo $MY_NGINX_SERVICE_HOST' 10.123.253.27 

More details on service IPs can be found in the Services in Kubernetes documentation, and the previously mentioned simple-nginx example is a good example of exposing a service outside your cluster with the LoadBalancer service type.

Answer 2

Run this

$ kubectl cluster-info 

It shows result like this where you can see the Kubernetes master IP