title: Allow communication between two docker bridge networks using docker-compose
body: <p>I'm creating rather complex infrastructure of docker containers using docker compose. Those containers run in 4 different networks (similar to production environment that I'm mimicking).
  Docker Compose creates those four networks for me, and everything works as long, as containers don't try to communicate with other containers inside different networks. When they do, connection is dropped.
  I was able to find out why it is dropped, and it is because Docker adds iptables rules into DOCKER-ISOLATION chain.
  Example:</p>
  
  <pre><code>-A DOCKER-ISOLATION -i br-be010eaddd0e -o br-f788f16ed0dd -j DROP
  -A DOCKER-ISOLATION -i br-f788f16ed0dd -o br-be010eaddd0e -j DROP
  </code></pre>
  
  <p>I wrote a little script that removes rules I want to be removed (and allow communication between chosen bridges) and everything works like a charm, but somehow they are recreated by Docker at some point, even without recreating those networks, so it requires me to run that script again, which is very annoying.
  Is there any way to specifically tell Docker to allow communication between two bridges? Or maybe there's some trick to run specific shell script after starting containers with Docker-Compose?</p>