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17-Service-Networking.md

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Service Networking

In this section, we will take a look at Service Networking

Service Types

  • ClusterIP
clusterIP.yaml

apiVersion: v1
kind: Service
metadata:
  name: local-cluster
spec:
  ports:
  - port: 80
    targetPort: 80
  selector:
    app: nginx
  • NodePort
nodeportIP.yaml

apiVersion: v1
kind: Service
metadata:
  name: nodeport-wide
spec:
  type: NodePort
  ports:
  - port: 80
    targetPort: 80
  selector:
    app: nginx

To create the service

$ kubectl create -f clusterIP.yaml
service/local-cluster created

$ kubectl create -f nodeportIP.yaml
service/nodeport-wide created

To get the Additional Information

$ kubectl get pods -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP           NODE     NOMINATED NODE   READINESS GATES
nginx   1/1     Running   0          1m   10.244.1.3   node01   <none>           <no

To get the Service

$ kubectl get service
NAME            TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
kubernetes      ClusterIP   10.96.0.1       <none>        443/TCP        5m22s
local-cluster   ClusterIP   10.101.67.139   <none>        80/TCP         3m
nodeport-wide   NodePort    10.102.29.204   <none>        80:30016/TCP   2m

To check the Service Cluster IP Range

$ ps -aux | grep kube-apiserver
--secure-port=6443 --service-account-key-file=/etc/kubernetes/pki/sa.pub --
service-cluster-ip-range=10.96.0.0/12

To check the rules created by kube-proxy in the iptables

$ iptables -L -t nat | grep local-cluster
KUBE-MARK-MASQ  all  --  10.244.1.3           anywhere             /* default/local-cluster: */
DNAT       tcp  --  anywhere             anywhere             /* default/local-cluster: */ tcp to:10.244.1.3:80
KUBE-MARK-MASQ  tcp  -- !10.244.0.0/16        10.101.67.139        /* default/local-cluster: cluster IP */ tcp dpt:http
KUBE-SVC-SDGXHD6P3SINP7QJ  tcp  --  anywhere             10.101.67.139        /* default/local-cluster: cluster IP */ tcp dpt:http
KUBE-SEP-GEKJR4UBUI5ONAYW  all  --  anywhere             anywhere             /* default/local-cluster: */

To check the logs of kube-proxy

  • May this file location is vary depends on your installation process.
$ cat /var/log/kube-proxy.log

References Docs