<p>The cni0 interface is missing altogether.
Any direction on how to get it back without tearing down the cluster will be greatly appreciated.
basically, the internal container networking is not working in trying to recover from that, I found this out
the IP's for coredns are docker0 interface instead of cni0, so may be if I get the cni0 back everything will start working</p>

<p>Below are the screenshots, please let me know if you need any additional command outputs</p>

<p>Master</p>

<pre><code>ip ro
default via 10.123.0.1 dev ens160 proto static metric 100
10.123.0.0/19 dev ens160 proto kernel scope link src 10.123.24.103 metric 100
10.244.0.0/24 dev cni0 proto kernel scope link src 10.244.0.1
10.244.1.0/24 via 10.244.1.0 dev flannel.1 onlink
10.244.2.0/24 via 10.244.2.0 dev flannel.1 onlink
10.244.3.0/24 via 10.244.3.0 dev flannel.1 onlink
172.17.77.0/24 dev docker0 proto kernel scope link src 172.17.77.1
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
</code></pre>

<p>Worker nodes</p>

<pre><code>default via 10.123.0.1 dev ens160 proto static metric 100
10.123.0.0/19 dev ens160 proto kernel scope link src 10.123.24.105 metric 100
10.244.0.0/24 via 10.244.0.0 dev flannel.1 onlink
10.244.2.0/24 via 10.244.2.0 dev flannel.1 onlink
10.244.3.0/24 via 10.244.3.0 dev flannel.1 onlink
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1


ifconfig -a
docker0: flags=4163&lt;UP,BROADCAST,RUNNING,MULTICAST&gt;  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        inet6 fe80::42:27ff:fe72:a287  prefixlen 64  scopeid 0x20&lt;link&gt;
        ether 02:42:27:72:a2:87  txqueuelen 0  (Ethernet)
        RX packets 3218  bytes 272206 (265.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 286  bytes 199673 (194.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

kubectl get pods -o wide --all-namespaces
NAMESPACE     NAME                                         READY     STATUS    RESTARTS   AGE       IP              NODE
kube-system   coredns-99b9bb8bd-j77zx                      1/1       Running   1          20m       172.17.0.2      abc-sjkubenode02
kube-system   coredns-99b9bb8bd-sjnhs                      1/1       Running   1          20m       172.17.0.3      abc-xxxxxxxxxxxx02
kube-system   elasticsearch-logging-0                      1/1       Running   6          2d        172.17.0.2      abc-xxxxxxxxxxxx02
kube-system   etcd-abc-xxxxxxxxxxxx01                      1/1       Running   3          26d       10.123.24.103   abc-xxxxxxxxxxxx01
kube-system   fluentd-es-v2.0.3-6flxh                      1/1       Running   5          2d        172.17.0.4      abc-xxxxxxxxxxxx02
kube-system   fluentd-es-v2.0.3-7qdxl                      1/1       Running   19         131d      172.17.0.2      abc-sjkubenode01
kube-system   fluentd-es-v2.0.3-l5thl                      1/1       Running   6          2d        172.17.0.3      abc-sjkubenode02
kube-system   heapster-66bf5bd78f-twwd2                    1/1       Running   4          2d        172.17.0.4      abc-sjkubenode01
kube-system   kibana-logging-8b9699f9c-nrcpb               1/1       Running   3          2d        172.17.0.3      abc-sjkubenode01
kube-system   kube-apiserver-abc-xxxxxxxxxxxx01            1/1       Running   2          2h        10.123.24.103   abc-xxxxxxxxxxxx01
kube-system   kube-controller-manager-abc-xxxxxxxxxxxx01   1/1       Running   3          2h        10.123.24.103   abc-xxxxxxxxxxxx01
kube-system   kube-flannel-ds-5lmmd                        1/1       Running   3          3h        10.123.24.106   abc-sjkubenode02
kube-system   kube-flannel-ds-92gd9                        1/1       Running   2          3h        10.123.24.104   abc-xxxxxxxxxxxx02
kube-system   kube-flannel-ds-nnxv6                        1/1       Running   3          3h        10.123.24.105   abc-sjkubenode01
kube-system   kube-flannel-ds-ns9ls                        1/1       Running   2          3h        10.123.24.103   abc-xxxxxxxxxxxx01
kube-system   kube-proxy-7h54h                             1/1       Running   3          3h        10.123.24.105   abc-sjkubenode01
kube-system   kube-proxy-7hrln                             1/1       Running   2          3h        10.123.24.104   abc-xxxxxxxxxxxx02
kube-system   kube-proxy-s4rt7                             1/1       Running   3          3h        10.123.24.103   abc-xxxxxxxxxxxx01
kube-system   kube-proxy-swmrc                             1/1       Running   2          3h        10.123.24.106   abc-sjkubenode02
kube-system   kube-scheduler-abc-xxxxxxxxxxxx01            1/1       Running   2          2h        10.123.24.103   abc-xxxxxxxxxxxx01
kube-system   kubernetes-dashboard-58c479587f-bkqgf        1/1       Running   30         116d      10.244.0.56     abc-xxxxxxxxxxxx01
kube-system   monitoring-influxdb-54bd58b4c9-4phxl         1/1       Running   3          2d        172.17.0.5      abc-sjkubenode01
kube-system   nginx-ingress-5565bdd5fc-nc962               1/1       Running   2          2d        10.123.24.103   abc-xxxxxxxxxxxx01


NAME                 STATUS    ROLES     AGE       VERSION   INTERNAL-IP     EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION              CONTAINER-RUNTIME
abc-sjkubemaster01   Ready     master    131d      v1.11.2   10.123.24.103   &lt;none&gt;        CentOS Linux 7 (Core)   3.10.0-862.2.3.el7.x86_64   docker://17.12.1-ce
abc-sjkubemaster02   Ready     &lt;none&gt;    131d      v1.11.2   10.123.24.104   &lt;none&gt;        CentOS Linux 7 (Core)   3.10.0-862.2.3.el7.x86_64   docker://17.12.1-ce
abc-sjkubenode01     Ready     &lt;none&gt;    131d      v1.11.2   10.123.24.105   &lt;none&gt;        CentOS Linux 7 (Core)   3.10.0-862.2.3.el7.x86_64   docker://17.12.1-ce
abc-sjkubenode02     Ready     &lt;none&gt;    131d      v1.11.2   10.123.24.106   &lt;none&gt;        CentOS Linux 7 (Core)   3.10.0-862.2.3.el7.x86_64   docker://17.12.1-ce
</code></pre>

<p>Edit:
Another thing I wanted to add is how to delete the pod coredns and recreate it? I don't have an yaml file for that it was created when I intalled the kubebernets cluster using kubeadm</p>

<pre><code>docker0: flags=4099&lt;UP,BROADCAST,MULTICAST&gt;  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        inet6 fe80::42:3fff:fe60:fea9  prefixlen 64  scopeid 0x20&lt;link&gt;
        ether 02:42:3f:60:fe:a9  txqueuelen 0  (Ethernet)
        RX packets 123051  bytes 8715267 (8.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 88559  bytes 33067497 (31.5 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ens160: flags=4163&lt;UP,BROADCAST,RUNNING,MULTICAST&gt;  mtu 1500
        inet 10.123.24.106  netmask 255.255.224.0  broadcast 10.123.31.255
        inet6 fd0f:f1c3:ba53:6c01:5de2:b5af:362e:a9b2  prefixlen 64  scopeid 0x0&lt;global&gt;
        inet6 fe80::ee61:b84b:bf18:93f2  prefixlen 64  scopeid 0x20&lt;link&gt;
        ether 00:50:56:91:75:d2  txqueuelen 1000  (Ethernet)
        RX packets 1580516  bytes 534188729 (509.4 MiB)
        RX errors 0  dropped 114794  overruns 0  frame 0
        TX packets 303093  bytes 28327667 (27.0 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

flannel.1: flags=4163&lt;UP,BROADCAST,RUNNING,MULTICAST&gt;  mtu 1450
        inet 10.244.1.0  netmask 255.255.255.255  broadcast 0.0.0.0
        inet6 fe80::4c0e:7dff:fe4b:12f2  prefixlen 64  scopeid 0x20&lt;link&gt;
        ether 4e:0e:7d:4b:12:f2  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 40 overruns 0  carrier 0  collisions 0

lo: flags=73&lt;UP,LOOPBACK,RUNNING&gt;  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10&lt;host&gt;
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 75  bytes 5864 (5.7 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 75  bytes 5864 (5.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099&lt;UP,BROADCAST,MULTICAST&gt;  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:54:00:fc:5b:de  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0-nic: flags=4098&lt;BROADCAST,MULTICAST&gt;  mtu 1500
        ether 52:54:00:fc:5b:de  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
</code></pre>

<p>First, check if your configs are present under <code>/etc/cni/net.d</code> on all your nodes.</p>

<p>Then I would try removing your flannel DaemonSet, killing all the pods and reinstall flannel altogether. </p>

<p>You may need to restart all your other pods except for the <code>kube-apiserver</code> and the <code>kube-controller-manager</code>.  It's ok if you want to restart those as well, but you don't have to.</p>

<p>Hope it helps!</p>
