Why custom networks matter in Docker - See It in Action

Why Custom Networks Matter in Docker

📖 Scenario: You are setting up a small Docker environment where two containers need to communicate securely and efficiently. Using Docker's default network can sometimes cause issues with container isolation and name resolution. To solve this, you will create a custom Docker network and connect containers to it.

🎯 Goal: Build a Docker setup where two containers run on a custom network, allowing them to communicate by container name. This will show why custom networks matter for container communication and isolation.

📋 What You'll Learn

Create a custom Docker bridge network named my_custom_net

Run two containers named webapp and database connected to my_custom_net

Verify that webapp can ping database by container name

Show the network details to confirm the custom network is used

💡 Why This Matters

🌍 Real World

Custom Docker networks are used in real projects to isolate services, improve security, and enable containers to find each other by name without exposing ports externally.

💼 Career

Understanding Docker networking is essential for DevOps roles to manage containerized applications efficiently and securely.

1

Create a custom Docker network

Create a Docker bridge network called my_custom_net using the command docker network create my_custom_net.

Docker

# Create the custom network
# Your code here

Need a hint?

Use the docker network create command with the network name my_custom_net.

2

Run two containers on the custom network

Run two containers named webapp and database using the alpine image. Connect both containers to the my_custom_net network using the --network my_custom_net option. Use the command docker run -dit --name webapp --network my_custom_net alpine sh for webapp and similarly for database.

Docker

docker network create my_custom_net
# Run the webapp container connected to my_custom_net
# Your code here

Need a hint?

Use docker run with --name and --network my_custom_net to start each container.

3

Test container communication by name

Use docker exec to run the ping -c 1 database command inside the webapp container to verify it can reach the database container by name.

Docker

docker network create my_custom_net
docker run -dit --name webapp --network my_custom_net alpine sh
docker run -dit --name database --network my_custom_net alpine sh
# Test ping from webapp to database
# Your code here

Need a hint?

Use docker exec to run ping inside the webapp container targeting database.

4

Show the custom network details

Use the command docker network inspect my_custom_net to display details of the custom network and confirm both containers are connected.

Docker

docker network create my_custom_net
docker run -dit --name webapp --network my_custom_net alpine sh
docker run -dit --name database --network my_custom_net alpine sh
docker exec webapp ping -c 1 database
# Inspect the custom network
# Your code here

Need a hint?

Use docker network inspect with the network name my_custom_net.