Users report that pods across the cluster cannot resolve any DNS names, both internal and external. You check the CoreDNS deployment and see two CoreDNS pods in Running state with 0 restarts, and the pods' logs show no errors. From a test pod, 'nslookup kubernetes.default' times out. You run 'kubectl get svc -n kube-system' and notice there is no service named 'kube-dns'. What is the most likely cause of the DNS failure?