Connecting containers to multiple networks in Docker - Mini Project: Build & Apply

Connecting Containers to Multiple Networks

📖 Scenario: You are managing a small application that needs to communicate over two separate Docker networks. One network is for frontend communication and the other is for backend services. You will create these networks and connect a container to both networks.

🎯 Goal: Build a Docker setup where a container is connected to two different networks. This will help you understand how containers can communicate on multiple isolated networks.

📋 What You'll Learn

Create two Docker networks named frontend_net and backend_net

Run a container named my_app using the nginx image

Connect the my_app container to both frontend_net and backend_net

Verify the container is connected to both networks

💡 Why This Matters

🌍 Real World

In real projects, containers often need to communicate securely on different networks, such as separating frontend and backend traffic.

💼 Career

Understanding Docker networking is essential for DevOps roles to manage containerized applications and ensure proper network isolation and communication.

1

Create two Docker networks

Create two Docker networks named frontend_net and backend_net using the docker network create command.

Docker

# Create the frontend_net network
# Create the backend_net network

Need a hint?

Use docker network create followed by the network name.

2

Run a container named my_app using nginx image

Run a container named my_app using the nginx image and connect it to the frontend_net network using the docker run command with the --network option.

Docker

docker network create frontend_net
docker network create backend_net
# Run the my_app container connected to frontend_net

Need a hint?

Use docker run -d --name my_app --network frontend_net nginx to start the container.

3

Connect the my_app container to backend_net network

Use the docker network connect command to connect the running my_app container to the backend_net network.

Docker

docker network create frontend_net
docker network create backend_net
docker run -d --name my_app --network frontend_net nginx
# Connect my_app container to backend_net network

Need a hint?

Use docker network connect backend_net my_app to add the container to the second network.

4

Verify the container is connected to both networks

Use the docker inspect command on the my_app container and print the networks it is connected to by filtering the .NetworkSettings.Networks field.

Docker

docker network create frontend_net
docker network create backend_net
docker run -d --name my_app --network frontend_net nginx
docker network connect backend_net my_app
# Inspect my_app container networks and print the network names

Need a hint?

Use docker inspect -f '{{json .NetworkSettings.Networks}}' my_app to see connected networks.