For troubleshooting,
nicolaka/netshoot is useful.
kubectl run -it netshoot --image=nicolaka/netshoot --rm --restart=Never --command=true -- bash
Access any Service
curl http://<Service Name>.<Namespace>.svc.cluster.local:<Target Port>
Access the Kubernetes API
curl --cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt \
-H "Authorization: Bearer $(cat /var/run/secrets/kubernetes.io/serviceaccount/token)" \
https://kubernetes.default.svc.cluster.local