3.3: The Bridge network: Creating an insulator so that our containers can communicate with each other (Docker network)

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📚Docker for beginners: The Shipyard
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Creating a gateway so our containers can communicate with each other (docker network)

When you have multiple containers, the question quickly arises: How will my containers communicate with each other?

Docker provides a simple solution: networks, and in particular the bridge network.

The concept: an isolated network

A bridge network is like a small internal private network for your containers.

  • Containers connected to the same network can communicate directly.
  • By default,Docker creates a networkbridge called bridge, but it’s often better to create your own dedicated network for your projects.

Example of creating a network:

docker network create mon_reseau
  • mon_reseau will be an isolated network
  • Only containers connected to this network will be able to communicate with each other.

Launching containers on a network

docker run -d --name web --network mon_reseau nginx
docker run -d --name db --network mon_reseau mariadb
  • The containerweb can now contactdb via its service name: db:3306
  • No need to configure external ports for this internal communication.

This simplifies security and organization: only the necessary services are exposed to the outside.

Internal communication

  • Containers on the same network see each other’s names as internal DNS entries.
  • Example:
docker exec -it web ping db
  • Here,web can pingdb directly, without going through fixed IP addresses.
  • Docker handles internal name resolution automatically.

Multiple networks supported

You can connect a container to multiple networks if necessary:

docker network create reseau_front
docker network create reseau_backdocker run -d --name web --network reseau_front nginx
docker network connect reseau_back web
  • web can now communicate with containers on front_network and back_network.
  • Very useful for separating layers: front-end / back-end / database.

Other network types Docker

Docker offers several network types depending on your needs:

Network typeMain purpose
bridgeIsolated internal network, default for most projects
HostContainer shares the host’s network, no isolation
macvlanEach container has its own IP address on the physical network
overlayMulti-host networks, used withDockerSwarm

For most development scenarios and small stacks, the bridge network is more than sufficient.

Check networks and containers

To list networks:

docker network ls

To inspect a network and view the connected containers:

docker network inspect mon_reseau
  • You can then see the containers, their internal IPs, and the associated subnet.

Simplified visual diagram

      [ bridge network : mon_reseau ]
      ------------------------------
      |        |                     |
   web:80   db:3306                autre:5000
      |        |                     |
      ------------------------------
            Communication interne via noms
  • All containers connected to the same network can communicate directly with each other
  • External ports are not required for this internal communication.
  • The network is isolated from the outside world, unless a port is mapped.

Useful commands for managing networks Docker

Here are the most useful commands for creating, inspecting, and cleaning up your networks:

List all networks

docker network ls
  • DockerDisplays all existing networks on your machine.
  • Example output:
NETWORK ID     NAME         DRIVER    SCOPE
a1b2c3d4e5f6   bridge       bridge    local
b2c3d4e5f6g7   mon_reseau   bridge    local

Inspect a network

docker network inspect mon_reseau
  • Shows connected containers, their internal IPs, the subnet, etc.
  • Very useful for debugging internal communication.

Create a custom network

docker network create mon_reseau
  • Creates an isolated bridge network named mon_reseau.
  • You can connect existing containers to this network:
docker network connect mon_reseau mon_conteneur

Disconnect a container from a network

docker network disconnect mon_reseau mon_conteneur
  • Disconnects the container without stopping it.
  • Useful if you want to reorganize your networks dynamically.

Delete a network

docker network rm mon_reseau
  • Deletes the network (connected containers must be disconnected first).

Key takeaway

  • The bridge network allows your containers to communicate with each other without exposing ports.
  • Container names serve as an internal DNS for communication.
  • You can connect a container to multiple networks.
  • The commandsdocker network ls / inspect / create / connect / disconnect / rmare your tools for easily managing these networks.
  • For advanced configurations, other network types exist (macvlan, host, overlay), but bridge remains the simplest option for beginners.

🔹 Note

This section on networksDockerhas been briefly covered to give you the essential basics.

  • Some topics can be explored in greater depth through detailed tutorials on our website.
  • Other concepts, such as advanced networks (macvlan, overlay, multi-host), will be covered in an intermediate courseDocker.

The goal here is to understand the general operation of bridge networks and internal communication, so you can safely deploy your first stacks.