<p>Problem:</p>

<pre><code>/ # ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes
ping: sendto: Network unreachable
</code></pre>

<p>Example container <code>ifconfig</code>: </p>

<pre><code>eth0      Link encap:Ethernet  HWaddr F2:3D:87:30:39:B8
      inet addr:10.2.8.64  Bcast:0.0.0.0  Mask:255.255.255.0
      inet6 addr: fe80::f03d:87ff:fe30:39b8%32750/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1
      RX packets:22 errors:0 dropped:0 overruns:0 frame:0
      TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0
      RX bytes:4088 (3.9 KiB)  TX bytes:648 (648.0 B)

eth1      Link encap:Ethernet  HWaddr 6E:1C:69:85:21:96
      inet addr:172.16.28.63  Bcast:0.0.0.0  Mask:255.255.255.0
      inet6 addr: fe80::6c1c:69ff:fe85:2196%32750/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:18 errors:0 dropped:0 overruns:0 frame:0
      TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0
      RX bytes:1418 (1.3 KiB)  TX bytes:648 (648.0 B)

lo        Link encap:Local Loopback
      inet addr:127.0.0.1  Mask:255.0.0.0
      inet6 addr: ::1%32750/128 Scope:Host
      UP LOOPBACK RUNNING  MTU:65536  Metric:1
      RX packets:0 errors:0 dropped:0 overruns:0 frame:0
      TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:0
      RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
</code></pre>

<p>Routing inside container:</p>

<pre><code>/ # ip route show
10.2.0.0/16 via 10.2.8.1 dev eth0
10.2.8.0/24 dev eth0  src 10.2.8.73
172.16.28.0/24 via 172.16.28.1 dev eth1  src 172.16.28.72
172.16.28.1 dev eth1  src 172.16.28.72
</code></pre>

<p>Host <code>iptables</code>: <a href="http://pastebin.com/raw/UcLQQa4J" rel="nofollow">http://pastebin.com/raw/UcLQQa4J</a></p>

<p>Host <code>ifconfig</code>: <a href="http://pastebin.com/raw/uxsM1bx6" rel="nofollow">http://pastebin.com/raw/uxsM1bx6</a></p>

<p>logs by <code>flannel</code>:</p>

<pre><code>main.go:275] Installing signal handlers
main.go:188] Using 104.238.xxx.xxx as external interface
main.go:189] Using 104.238.xxx.xxx as external endpoint
etcd.go:129] Found lease (10.2.8.0/24) for current IP (104.238.xxx.xxx), reusing
etcd.go:84] Subnet lease acquired: 10.2.8.0/24
ipmasq.go:50] Adding iptables rule: FLANNEL -d 10.2.0.0/16 -j ACCEPT
ipmasq.go:50] Adding iptables rule: FLANNEL ! -d 224.0.0.0/4 -j MASQUERADE
ipmasq.go:50] Adding iptables rule: POSTROUTING -s 10.2.0.0/16 -j FLANNEL
ipmasq.go:50] Adding iptables rule: POSTROUTING ! -s 10.2.0.0/16 -d 10.2.0.0/16 -j MASQUERADE
vxlan.go:153] Watching for L3 misses
vxlan.go:159] Watching for new subnet leases
vxlan.go:273] Handling initial subnet events
device.go:159] calling GetL2List() dev.link.Index: 3
vxlan.go:280] fdb already populated with: 104.238.xxx.xxx 82:83:be:17:3e:d6
vxlan.go:280] fdb already populated with: 104.238.xxx.xxx 82:dd:90:b2:42:87
vxlan.go:280] fdb already populated with: 104.238.xxx.xxx de:e8:be:28:cf:7a
systemd[1]: Started Network fabric for containers.
</code></pre>

<p>It is possible if you set a config map with upstreamNameServers.</p>

<p>Example:</p>

<pre><code>apiVersion: v1
kind: ConfigMap
metadata:
  name: kube-dns
  namespace: kube-system
data:
  upstreamNameservers: |
    ["8.8.8.8", "8.8.8.4"]
</code></pre>

<p>And in you Deployment definition add:</p>

<pre><code>dnsPolicy: "ClusterFirst"
</code></pre>

<p>More info here: </p>

<p><a href="https://kubernetes.io/docs/tasks/administer-cluster/dns-custom-nameservers" rel="nofollow noreferrer">https://kubernetes.io/docs/tasks/administer-cluster/dns-custom-nameservers</a></p>
