title: Docker Overlay Network, Port Connections not in netstat visible
body: <p>I'm playing with Docker Swarm, trying to understand the IPv6 problem for Docker Swarm and overlay Network, when i found a strange behaviour.</p>
  
  <p>netstat should show all the connections, but on a docker overlay network published port, then endpoint connection is not shown.</p>
  
  <p>Work to reproduce:</p>
  
  <ul>
  <li>Install two Server with Docker</li>
  <li>Install Docker and initialize Docker Swarm</li>
  <li>Create an Overlay Network</li>
  <li><p>Deploy nginx on the overlay network and publish port 80</p>
  
  <p>docker network create --driver overlay nginx
  docker service create --name my-nginx --publish target=80,published=80 --network nginx --replicas=2 nginx</p></li>
  </ul>
  
  <p>Then Connect from any Client to the webserver created with netcat:</p>
  
  <pre><code>nc 10.0.2.34 80
  </code></pre>
  
  <p>Check the netstat output on both sides:</p>
  
  <p>Client:</p>
  
  <pre><code>[root@docker1 centos]# netstat -ano | grep 80
  tcp        0      0 10.0.0.208:39924        10.0.2.34:80      ESTABLISHED off (0.00/0/0)
  </code></pre>
  
  <p>on Server:</p>
  
  <pre><code>[root@docker2 centos]# netstat -ano | grep 80
  tcp6       0      0 :::80                 :::*                    LISTEN      off (0.00/0/0)
  </code></pre>
  
  <p>You will not see the connection that has been established by the Client.
  But the connection is working, I can get the main page from nginx.</p>
  
  <p>Can anyone explain this?</p>