Networking allows containers to communicate with each other and with the host system. Containers run isolated from the host system and need a way to communicate with each other and with the host system.

By default, Docker provides two network drivers for you, the bridge and the overlay drivers.

docker network ls

NETWORK ID          NAME                DRIVER
xxxxxxxxxxxx        none                null
xxxxxxxxxxxx        host                host
xxxxxxxxxxxx        bridge              bridge

Bridge Networking

The default network mode in Docker. It creates a private network between the host and containers, allowing containers to communicate with each other and with the host system.

If you want to secure your containers and isolate them from the default bridge network you can also create your own bridge network.

docker network create -d bridge my_bridge

Now, if you list the docker networks, you will see a new network.

docker network ls

NETWORK ID          NAME                DRIVER
xxxxxxxxxxxx        bridge              bridge
xxxxxxxxxxxx        my_bridge           bridge
xxxxxxxxxxxx        none                null
xxxxxxxxxxxx        host                host

This new network can be attached to the containers, when you run these containers.

docker run -d --net=my_bridge --name db training/postgres

This way, you can run multiple containers on a single host platform where one container is attached to the default network and the other is attached to the my_bridge network.

These containers are completely isolated with their private networks and cannot talk to each other.

However, you can at any point of time, attach the first container to my_bridge network and enable communication

docker network connect my_bridge web

Host Networking

This mode allows containers to share the host system's network stack, providing direct access to the host system's network.

To attach a host network to a Docker container, you can use the --network="host" option when running a docker run command. When you use this option, the container has access to the host's network stack, and shares the host's network namespace. This means that the container will use the same IP address and network configuration as the host.

Here's an example of how to run a Docker container with the host network:

docker run --network="host" image_name command

Keep in mind that when you use the host network, the container is less isolated from the host system, and has access to all of the host's network resources. This can be a security risk, so use the host network with caution.

Additionally, not all Docker image and command combinations are compatible with the host network, so it's important to check the image documentation or run the image with the --network="bridge" option (the default network mode) first to see if there are any compatibility issues.

Overlay Networking

This mode enables communication between containers across multiple Docker host machines, allowing containers to be connected to a single network even when they are running on different hosts.

Macvlan Networking

This mode allows a container to appear on the network as a physical host rather than as a container.