title: Kubernetes: unreachable backend: read udp 10.200.0.9:46159->183.60.83.19:53: i/o timeout
body: <p><strong>I use kubernetes v12, my system is ubuntu 16.</strong></p>
  
  <p><strong>I use the followed command to create DNS resource.</strong></p>
  
  <pre><code>wget https://raw.githubusercontent.com/coredns/deployment/master/kubernetes/coredns.yaml.sed
  
  wget https://raw.githubusercontent.com/coredns/deployment/master/kubernetes/deploy.sh
  bash deploy.sh -i 10.32.0.10 -r "10.32.0.0/24" -s -t coredns.yaml.sed | kubectl apply -f -
  </code></pre>
  
  <p>After created coredns resource: I check the resources status.</p>
  
  <ol>
  <li>check coredns service</li>
  </ol>
  
  <pre><code>root@master:~# kubectl get svc -n kube-system
  NAME           TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)    AGE
  calico-typha   ClusterIP   10.32.0.10   &lt;none&gt;        5473/TCP   13h
  </code></pre>
  
  <ol start="2">
  <li>check code DNS pod endpoints</li>
  </ol>
  
  <pre><code>root@master:~# kubectl get ep -n kube-system
  NAME                      ENDPOINTS   AGE
  calico-typha              &lt;none&gt;      13h
  kube-controller-manager   &lt;none&gt;      18d
  kube-scheduler            &lt;none&gt;      18d
  </code></pre>
  
  <ol start="3">
  <li>My DNS config:</li>
  </ol>
  
  <pre><code>root@master:~# cat /etc/resolv.conf
  nameserver 183.60.83.19
  nameserver 183.60.82.98
  </code></pre>
  
  <ol start="4">
  <li>Check CoreDNS pod logs</li>
  </ol>
  
  <pre><code>root@master:~# kubectl get po -n kube-system | grep coredns-7bbd44c489-5thlj
  coredns-7bbd44c489-5thlj   1/1     Running   0          13h
  root@master:~#
  root@master:~# kubectl logs -n kube-system pod/coredns-7bbd44c489-5thlj
  .:53
  2019-03-16T01:37:14.661Z [INFO] CoreDNS-1.2.6
  2019-03-16T01:37:14.661Z [INFO] linux/amd64, go1.11.2, 756749c
  CoreDNS-1.2.6
  linux/amd64, go1.11.2, 756749c
   [INFO] plugin/reload: Running configuration MD5 = 2e2180a5eeb3ebf92a5100ab081a6381
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:45913-&gt;183.60.83.19:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:42500-&gt;183.60.82.98:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:48341-&gt;183.60.82.98:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:33007-&gt;183.60.83.19:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:52968-&gt;183.60.82.98:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:48992-&gt;183.60.82.98:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:35016-&gt;183.60.83.19:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:58058-&gt;183.60.82.98:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:51709-&gt;183.60.83.19:53: i/o timeout
   [ERROR] plugin/errors: 2 526217177044940556.1623766979909084596. HINFO: unreachable backend: read udp 10.200.0.93:53889-&gt;183.60.82.98:53: i/o timeout
  root@master:~#
  </code></pre>
  
  <p>I found <strong>CoreDNS pod ip</strong> cannot connected to <strong>node DNS server ip address</strong>.</p>