<p>CoreDNS pod is not running. Please find below status.</p>

<pre><code>kubectl get po --all-namespaces -o wide | grep -i coredns
kube-system            coredns-6955765f44-8qhkr                    1/1     Running            0          24m     10.244.0.59      k8s-master          &lt;none&gt;           &lt;none&gt;
kube-system            coredns-6955765f44-lpmjk                    0/1     Running            0          24m     10.244.1.43      k8s-worker-node-1   &lt;none&gt;           &lt;none&gt;

</code></pre>

<p>Please find below logs of pod.</p>

<pre><code>kubectl logs coredns-6955765f44-lpmjk -n kube-system



E0420 03:43:03.855622       1 reflector.go:125] pkg/mod/k8s.io/client-go@v0.0.0-20190620085101-78d2af792bab/tools/cache/reflector.go:98: Failed to list *v1.Namespace: Get https://10.96.0.1:443/api/v1/namespaces?limit=500&amp;resourceVersion=0: dial tcp 10.96.0.1:443: connect: no route to host
E0420 03:43:03.855622       1 reflector.go:125] pkg/mod/k8s.io/client-go@v0.0.0-20190620085101-78d2af792bab/tools/cache/reflector.go:98: Failed to list *v1.Namespace: Get https://10.96.0.1:443/api/v1/namespaces?limit=500&amp;resourceVersion=0: dial tcp 10.96.0.1:443: connect: no route to host
E0420 03:43:03.855622       1 reflector.go:125] pkg/mod/k8s.io/client-go@v0.0.0-20190620085101-78d2af792bab/tools/cache/reflector.go:98: Failed to list *v1.Namespace: Get https://10.96.0.1:443/api/v1/namespaces?limit=500&amp;resourceVersion=0: dial tcp 10.96.0.1:443: connect: no route to host
E0420 03:43:03.855622       1 reflector.go:125] pkg/mod/k8s.io/client-go@v0.0.0-20190620085101-78d2af792bab/tools/cache/reflector.go:98: Failed to list *v1.Namespace: Get https://10.96.0.1:443/api/v1/namespaces?limit=500&amp;resourceVersion=0: dial tcp 10.96.0.1:443: connect: no route to host
E0420 03:43:05.859525       1 reflector.go:125] pkg/mod/k8s.io/client-go@v0.0.0-20190620085101-78d2af792bab/tools/cache/reflector.go:98: Failed to list *v1.Namespace: Get https://10.96.0.1:443/api/v1/namespaces?limit=500&amp;resourceVersion=0: dial tcp 10.96.0.1:443: connect: no route to host
E0420 03:43:05.859525       1 reflector.go:125] pkg/mod/k8s.io/client-go@v0.0.0-20190620085101-78d2af792bab/tools/cache/reflector.go:98: Failed to list *v1.Namespace: Get https://10.96.0.1:443/api/v1/namespaces?limit=500&amp;resourceVersion=0: dial tcp 10.96.0.1:443: connect: no route to host
</code></pre>

<p>To solve <code>no route to host</code> issue with CoreDNS pods you have to flush iptables by running:</p>

<pre><code>systemctl stop kubelet
systemctl stop docker
iptables --flush
iptables -tnat --flush
systemctl start kubelet
systemctl start docker
</code></pre>

<p>Also mind that flannel has been removed from the list of CNIs in the <a href="https://github.com/kubernetes/website/commit/f73647531dcdade2327412253a5f839781d57897/" rel="nofollow noreferrer">kubeadm documentation</a>:</p>

<blockquote>
  <p>The reason for that is that Cluster Lifecycle have been
  getting a number of issues related to flannel (either in kubeadm or
  kops tickets) and we don't have good answers for the users as the
  project is not actively maintained.
  - Add note that issues for CNI should be logged in the respective issue
  trackers and that Calico is the only CNI we e2e test kubeadm against.</p>
</blockquote>

<p>So recommended approach would be also move to Calico CNI.</p>
