Join network

docker run --network <network_name> <image>

docker run -d --name web-api --network app-net myapp:1.0
docker run -d --name db --network app-net postgres:16

Note Containers on the same user-defined network can reach each other by container name (e.g., web-api can connect to db:5432). The default bridge network does NOT provide this DNS — you must create a custom network.

docker network connect <network> <container>
docker network disconnect <network> <container>

docker network connect app-net web-api
docker network disconnect bridge web-api

Note A container can be connected to multiple networks simultaneously. This is useful for gateway containers that need to communicate with two isolated groups of services.