How can I access the Kubernetes service through ClusterIP

From where are you trying to access clusterIP? The clusterIP (by default) only works from within the cluster. It is a virtual IP, not routed.

You do not have ClusterIP service. You do have a NodePort service. To access it, you connect to the NodePort on any of your nodes in the cluster, as you've already discovered. You do get load-balancing here. Even though you connect to a cluster node, the pod you get does not necessarily run on that particular node.

Read the relevant section in the documentation at https://kubernetes.io/docs/concepts/services-networking/service/#publishing-services---service-types to learn about additional service types. You probably do not want NodePort on GCP.

Talking about ClusterIP. To access a ClusterIP service for debugging purposes, you can run kubectl port-forward. You will not actually access the service, but you will directly connect to one of the pods.

For example

kubectl port-forward frontend-2b5us 80 8080

Now connect to localhost:8080

More sophisticated command, which discovers the port on its own, given namespace -n weave and a selector. Taken from https://www.weave.works/docs/scope/latest/installing/

kubectl port-forward -n weave \
    "$(kubectl get -n weave pod \
         --selector=weave-scope-component=app \
         -o jsonpath='{.items..metadata.name}')" \
    4040