All Docker installations represent the docker0 network with bridge; Docker connects to bridge by default. Run ifconfig on the Linux host to view the bridge network.
When you run the following command in your console, Docker returns a JSON object describing the bridge network (including information regarding which containers run on the network, the options set, and listing the subnet and gateway).
docker network inspect bridge
Docker automatically creates a subnet and gateway for the bridge network, and docker run automatically adds containers to it. If you have containers running on your network, docker network inspect displays networking information for your containers.
Any containers on the same network may communicate with one another via IP addresses. Docker does not support automatic service discovery on bridge. You must connect containers with the --link option in your docker run command.
The Docker bridge supports port mappings and docker run --link allowing communications between containers on the docker0 network. However, these error-prone techniques require unnecessary complexity. Just because you can use them, does not mean you should. It’s better to define your own networks instead.