Docker host network , also known as Docker network host, is a networking mode in which a Docker container shares its network namespace with the host machine.

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Let’s look at this in more detail.

Docker host network

The host in Docker is a machine that is responsible for running one or more containers. A port at the host’s IP address can be used to access the application inside the container (e.g., port 80).

To run a container in host networking mode, use the following Docker command:

docker run -it --name web2 --net=host bobcares/docker:webinstance2

Docker uses the host’s network stack for the container if the –net=host option is specified in the docker create or docker run commands. The container’s network configuration is identical to that of the host, and the container uses the same service ports as the host. A container’s network isolation is not provided by this configuration.

Use host networking

The network stack of a container that uses this driver is not isolated from the Docker host. For example, if we use host networking and run a container that binds to port 80, the container’s application will be available on port 80 on the host’s IP address.

We can use a host network for a swarm service and higher by passing –network host to the docker container create command. Control traffic (traffic related to managing the swarm and the service) is still sent over an overlay network in this case, but data is sent over the Docker daemon’s host network and ports by the individual swarm service containers. This imposes additional constraints. If a service container binds to port 80, for example, each swarm node can only run one service container. Host networking has no effect if our container or service does not publish any ports.

Use Cases

Over other Docker networking modes, such as “none” and “bridge,” the Docker network host can provide performance and optimizations. Furthermore, it does not require network address translation (NAT), making it easier to manage multiple ports at once. When working in this mode, users must be careful to avoid port conflicts.

Proceedure for Networking using the host network

1. As a detached process, create and start the container. When the container exits/stops, the --rm option is used to remove it. The -d flag tells the container to start detached (in the background).

   $ docker run --rm -d --network host --name name_nginx nginx
2. Then, go to http://localhost:80/ to access Nginx.
3. Examine all network interfaces to ensure no new ones have been created.

   $ ip addr show
4. Using the netstat command, determine which process is bound to port 80. We need to use sudo because the Docker daemon user owns the process, and we wouldn’t be able to see its name or PID otherwise.

   $ sudo netstat -tulpn | grep :80
5. Finally, turn off the container. It will be automatically removed because it was started with the --rm option.

   docker container stop my_nginx

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Conclusion

To sum up, our Support team went over the docker host network’s specifics.