Inter-container communication with help of DNS

[Armin@netPI]

Docker automatically assigns IP adresses to all those containers started in default bridged network mode. A disadvantage is that each time netPI boots different IP addresses are assigned to these containers which makes a predicable inter-container communication impossible.
Instead is it recommended to create a local user-defined network on the system first where Docker is automatically operating a DNS service for. Then, in case a container is started, you can specify this user-defined network as network the container shall run with.
The embedded DNS server provides the discovery service for any container created with a valid name. Only then it maintains the mapping between the container name and its IP address on the network the container is connected to.
Example: Create two containers with names Container1 and Container2. For both containers specify your user-defined network to connect to. A DNS service will be provided automatically on this network. You can then address the containers over their names with a ping command for example like ping Container1 or ping Container2 instead of using their IP addresses.