title: How to connect to local mariadb docker from another local docker container via server external IP address?
body: <p>Assume, I have server with external IP addr. 216.1.2.3.</p>
  <p>Also, I have my app docker container which fails to connect to another mariadb docker container hosted on the SAME machine by using --host=216.1.2.3. (it also fails for localhost, 127.0.0.1, host.docker.internal)</p>
  <p>But, that mariadb is perfectly reachable from server level, from remote machines, from anywhere except from inside that app docker. (from server level its also reachable for host=localhost, 127.0.0.1, all privileges granted to root@%, flushed). If db installed on another machine with own IP addr its perfectly reachable by app docker.</p>
  <p>What to check? Main goal is to connect via 216.1.2.3 as host.</p>