Network

Network types

None

No network is attached to the containers, and they have no access to any external network or other containers. As they run in an isolated network, there is no IP configuration for the containers.

docker run --network=none ubuntu

Host (local)

The host network driver removes the network isolation between the Docker host and the Docker containers to use the host's networking directly. Therefore, the container won't get its own IP address.

For instance, if you run a container which binds to port 80, the container's application will be available on port 80 on the host's IP address (localhost, IP). Therefore, you no need to specify -p 80:80 for host networking, as that option is only for bridge network.

docker run --network=host apiapp

Bridge

By default, the bridge driver network is attached to all container.

docker run ubuntu # it uses Bridge network by default

Docker creates a private internal network called the bridge network on the host. The bridge network is attached to all containers by default and will get an internal IP address, normally in the 172.17 series range. Therefore, the containers can access each other using this internal IP.

Additional information;

• Containers connected to the same bridge network can communicate using a software bridge while remaining isolated from containers not connected to it.
• Containers can find each other by name in the same network instead of using an IP address.
• It provides better isolation and interoperability between containerized applications.
• Environment variables are shared between linked containers on the bridge network.

User-defined bridge network

You can create your own internal network.

docker network create --driver bridge --subnet 192.168.10.0/24 mynewinternalnetwork

With this setup, it will create a network with IP range of 192.168.10.0/24. (192.168.10.1-192.168.10.254)

List neworks

docker network ls

Inspect networks

docker network inspect <network-name>

Remove network

docker network rm <network-name>
docker network prune

Connect/Disconnect container to network

docker network connect <network-name> <container>
docker network disconnect <network-name> <container>

Container Communication

Container to host (local) communication

If you want your container to communicate with the host, you have to replace the container's localhost or IP address to host.docker.internal. This domain will translate to the IP address of your localhost machine as seen from inside the Docker container.

For example, now you have a Python API application that links to mongoDB. Here is the endpoint mongodb://localhost:27017/user. So, you have to change to mongodb://host.docker.internal:27017/user.

Container to container communication

There are two methods to let a container communicate with another container.

• Method 1 (not recommended)
  • Use docker inspect <container> to get the container IP address, then within your application code, put that specific IP address into it mongodb://172.17.0.3:27017/user
• Method 2
  • Use the container name as the input mongodb://mymongodb:27017/user
  • The container name refers to its IP address allocated by docker0.
  •