title: docker-compose internal DNS server 127.0.0.11 connection refused
body: <p>Suddenly when I deployed some new containers with docker-compose the internal hostname resolution didn't work.<br />
  When I tried to ping one container from the other using the service name from the docker-compose.yaml file I got <code>ping: bad address 'myhostname'</code>
  I checked that the <code>/etc/resolv.conf</code> was correct and it was using <code>127.0.0.11</code>
  When I tried to manually resolve my hostname with either <code>nslookup myhostname.</code> or <code>nslookup myhostname.docker.internal</code> I got error</p>
  <pre><code>nslookup: write to '127.0.0.11': Connection refused
  ;; connection timed out; no servers could be reached
  </code></pre>
  <p>Okay so the issue is that the docker DNS server has stopped working. All already started containers still function, but any new ones started has this issue.
  I am running <code>Docker version 19.03.6-ce, build 369ce74</code></p>
  <p>I could of course just restart docker to see if it solves it, but I am also keen on understanding why this issue happened and how to avoid it in the future.<br />
  I have a lot of containers started on the server and a total of 25 docker networks currently.
  Any ideas on what can be done to troubleshoot? Any known issues that could explain this?
  The <code>docker-compose.yaml</code> file I use has worked before and no changes has been done to it.</p>
  <p>Edit: No DNS names at all can be resolved. 127.0.0.11 refuses all connections. I can ping any external IP addresses, as well as the IP of other containers on the same docker network. It is only the 127.0.0.11 DNS server that is not working. 127.0.0.11 still replies to ping from within the container.</p>