Networking

Docker networking is like the communication system for your containers, allowing them to talk to each other and the outside world.

It is used to communicate between multuple containers and also with the host machine.By default use bridge network which is a private internal network that allows containers to communicate with each other.

Bridge Network

When you run a Docker container, it uses a network called Bridge by default. This is like a private road inside Docker that lets containers talk to each other.

If you don’t tell Docker which network to use, it will automatically connect the container to this bridge network.

Docker also gives each container its own IP address inside this private network. These IPs are only for use inside Docker.

When a container needs to access the internet (like to download updates), it uses your computer’s internet connection through the bridge network.

Diagram

Ponts To Remember:

• Docker creates a private network (called bridge).
• Containers can talk to each other inside it.
• Each container gets its own IP address.
• For internet, they use your computer’s IP via the bridge network.

Custom Bridge Network

You can create your own bridge networks if you want more control over how containers communicate. It gives you more control than the default bridge network that Docker creates automatically.

You don’t need to Remember any command simply do docker network it list the all the usefull commands related to network.

Example

Imagine you're building a small web app with these components:

• web container → runs your front-end (React)
• api container → handles the back-end logic (Node.js)
• db container → stores your data (PostgreSQL)

Instead of putting all of these in the default Docker network. So you want these containers to talk to each other, so you create a custom bridge network called my_custom_network.

docker network create my_custom_network

Then you run your containers and attach them to this network:

PostgreSQL

docker run -d --name db --network my_custom_network postgres

Node.Js

docker run -d --name api --network my_custom_network my-api-image

React

docker run -d --name web --network my_custom_network my-web-image

Now:

• api can talk to db by just calling db:5432
• web can call api using api:3000
• All containers can communicate easily without worrying about IP addresses.
• But nothing outside this network can access these unless exposed.