How to Create and Manage Docker Networks

🔹 What Is a Docker Network?

A Docker network is a virtual layer that connects containers. By default, Docker provides some basic network types:

⚙️ Step 1: Check Existing Docker Networks

Before creating one, you can see what’s already available:

docker network ls

Example output:

NETWORK ID     NAME          DRIVER    SCOPE
a1b2c3d4e5f6   bridge        bridge    local
b2c3d4e5f6a7   host          host      local
c3d4e5f6a7b8   none          null      local

⚙️ Step 2: Create a Custom Network

You can create your own bridge network using the docker network create command.

Linux or macOS

docker network create frappe-net

Windows (PowerShell or CMD)

Same command works:

docker network create frappe-net

Output:

c9a2f3b8a7e9f48b1c3d0a57a9832d6c8e3d0b23b7b5f6a0d2a3f4c5a6e7b8c9

This creates a new user-defined bridge network named frappe-net.

⚙️ Step 3: Connect Containers to the Network

When you run a container, you can attach it to your network using --network.

Example:

docker run -d --name mariadb --network frappe-net -e MYSQL_ROOT_PASSWORD=frappe mariadb:10.6

Then run another container on the same network:

docker run -d --name frappe --network frappe-net -p 8080:8000 frappe/erpnext

Now, the frappe container can access the database container simply by its container name (mariadb) — no need for IP addresses.

⚙️ Step 4: Inspect a Docker Network

You can view detailed information (like connected containers, IP ranges, etc.) using:

docker network inspect frappe-net

Example output (simplified):

[
  {
    "Name": "frappe-net",
    "Driver": "bridge",
    "Containers": {
      "f1e2d3c4b5a6": {
        "Name": "mariadb",
        "IPv4Address": "172.18.0.2/16"
      },
      "a7b8c9d0e1f2": {
        "Name": "frappe",
        "IPv4Address": "172.18.0.3/16"
      }
    }
  }
]

⚙️ Step 5: Disconnect and Reconnect Containers

To disconnect a container from a network:

docker network disconnect frappe-net mariadb

To reconnect it:

docker network connect frappe-net mariadb

⚙️ Step 6: Remove Unused Networks

To remove a specific network:

docker network rm frappe-net

To prune (remove all unused networks):

docker network prune

(You’ll be asked for confirmation.)

🧠 Tips for Managing Docker Networks

• ✅ Use named networks (like frappe-net) for multi-container apps.
• ✅ Avoid exposing ports publicly when containers can talk over an internal network.
• ✅ Combine networks with Docker Compose for easier configuration.
• ✅ Always inspect your networks to debug connection issues.

⚙️ Optional: Use Docker Compose for Networks

Here’s a quick example of defining a custom network in docker-compose.yml:

version: "3.9"

services:
  mariadb:
    image: mariadb:10.6
    environment:
      MYSQL_ROOT_PASSWORD: frappe
      MYSQL_USER: frappe
      MYSQL_PASSWORD: frappe
      MYSQL_DATABASE: frappe
    volumes:
      - mariadb_data:/var/lib/mysql
    networks:
      - frappe-net

  frappe:
    image: frappe/erpnext
    ports:
      - "8080:8000"
    networks:
      - frappe-net

volumes:
  mariadb_data:

networks:
  frappe-net:
    driver: bridge

Then run:

docker-compose up -d

This automatically creates and manages your custom frappe-net network.

🧩 Summary