Docker Networking

Docker networking allows containers to communicate with each other, the host system, and external networks. Understanding Docker networking is essential for deploying real-world applications.

1. Types of Docker Networks

Docker provides five types of networks:

Network Type	Default?	Description
Bridge	✅ Yes	Default network for standalone containers. Containers can communicate internally, but need port mapping to communicate externally.
Host	❌ No	Containers share the host’s networking stack (no isolation).
Overlay	❌ No	Used in Swarm mode to enable multi-host networking.
Macvlan	❌ No	Assigns a real MAC address to a container, making it look like a physical device.
None	❌ No	No network connectivity (fully isolated).

2. Checking Existing Networks

To list all available Docker networks, run:

docker network ls

Example output:

NETWORK ID          NAME                DRIVER         SCOPE
b7ef25d9a6d2        bridge              bridge         local
d1f49dc9f7cd        host                host           local
a12d9c5d84a8        none                null           local

🛠️ 3. Bridge Network (Default)

By default, when you run a container, it connects to the bridge network.

docker network inspect bridge

This shows details like IP ranges and connected containers.

🔹 Running a container in bridge mode:

docker run -d --name webserver nginx

This container won’t be accessible externally unless you map ports:

docker run -d -p 8080:80 --name webserver nginx

Now you can access the Nginx server at http://localhost:8080.

🛠️ 4. Creating a Custom Bridge Network

To create an isolated network for multiple containers:

docker network create mynetwork

To run a container in this network:

docker run -d --name app1 --network mynetwork nginx

Now, any container in mynetwork can communicate with app1 by using its name:

ping app1

🛠️ 5. Host Network

The host network mode removes network isolation, meaning:

The container shares the host’s IP address.
There is no need for port mapping.

🔹 Running a container in host mode:

docker run --network host -d nginx

Now, Nginx runs directly on the host’s network and can be accessed at http://localhost.

🔴 Security Risk: Containers can access all host services, making it less secure.

6. Connecting and Disconnecting Containers

Connect a running container to a network:

  docker network connect mynetwork container1

Disconnect a container from a network:

  docker network disconnect mynetwork container1

🛠️ 7. Inspecting a Network

To see detailed information about a network:

docker network inspect mynetwork

This will show:

Connected containers
Subnet & Gateway
IP Address assignment