Here’s a complete tutorial on docker network, covering what it does, examples, and use cases.

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What is docker network?

docker network is a command used to manage Docker networks, enabling containers to communicate with each other and control how they connect internally and externally. Docker provides several types of networks (bridge, overlay, host, and macvlan), each suited for different use cases.

Key Features:

• Create, inspect, connect, and disconnect networks.
• Control how containers communicate within and across multiple hosts.
• Supports custom and isolated networks for security and scalability.

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Docker Network Types

1. Bridge Network (default)

• The most common type for standalone containers.
• Containers on the same bridge network can communicate with each other.

2. Host Network

• Removes network isolation; the container uses the host’s network stack directly.
• Suitable for high-performance network communication.

3. Overlay Network

• Used for multi-host networking in Docker Swarm.
• Allows containers on different hosts to communicate securely.

4. Macvlan Network

• Assigns a MAC address to containers, making them appear as physical devices on the network.
• Useful for integrating Docker with existing physical networks.

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Basic Syntax

docker network [COMMAND] [OPTIONS]

Common docker network Commands:

• create: Create a new network.
• ls: List all networks.
• inspect: Show detailed information about a network.
• connect: Connect a container to a network.
• disconnect: Disconnect a container from a network.
• rm: Remove a network.

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Examples of docker network Commands

1. List All Docker Networks

docker network ls

Example Output:

NETWORK ID     NAME      DRIVER    SCOPE
6e8d77eabc12   bridge    bridge    local
5aeb2c1234ab   host      host      local
9a8d12345def   none      null      local

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2. Create a New Bridge Network

docker network create my_custom_network

This creates a custom bridge network called my_custom_network.

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3. Create a Network with a Specific Subnet

docker network create \
  --subnet=192.168.1.0/24 \
  custom_subnet_network

This creates a network with the subnet 192.168.1.0/24.

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4. Inspect a Network

docker network inspect my_custom_network

This provides detailed information about the network, including connected containers and configuration.

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5. Connect a Container to a Network

docker network connect my_custom_network my_container

This connects my_container to my_custom_network.

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6. Disconnect a Container from a Network

docker network disconnect my_custom_network my_container

This disconnects my_container from my_custom_network.

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7. Create an Overlay Network

docker network create \
  --driver overlay \
  my_overlay_network

This creates an overlay network for multi-host communication (requires Docker Swarm).

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8. Create a Macvlan Network

docker network create \
  -d macvlan \
  --subnet=192.168.1.0/24 \
  --gateway=192.168.1.1 \
  -o parent=eth0 \
  my_macvlan_network

This creates a macvlan network where containers get their own IP addresses in the 192.168.1.0/24 subnet.

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9. Remove a Network

docker network rm my_custom_network

This removes the my_custom_network.

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10. Remove All Unused Networks

docker network prune

This removes all unused networks.

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11. Use a Custom Network When Running a Container

docker run --rm --network=my_custom_network nginx

This runs an nginx container attached to my_custom_network.

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12. List Connected Containers in a Network

docker network inspect my_custom_network | jq '.[0].Containers'

This lists all containers connected to my_custom_network (requires jq for JSON parsing).

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Use Cases for docker network

1. Container Communication in Isolated Environments

• Use custom bridge networks to group related containers for secure communication.
• Example: Create a network for a web app and database, ensuring they can communicate internally.

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2. High-Performance Networking with Host Mode

• Use the host network for low-latency and high-performance applications like monitoring tools or network proxies.
• Example: Run a Prometheus container in host mode to reduce network overhead.

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3. Multi-Host Networking (Docker Swarm)

• Use overlay networks for distributed applications across multiple Docker hosts.
• Example: Deploy a microservices application across a Docker Swarm cluster.

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4. Integrating Docker with Physical Networks (Macvlan)

• Use macvlan networks to assign unique IP addresses to containers on your physical network.
• Example: Deploy containers as part of your corporate network infrastructure.

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5. Secure and Private Networks

• Create isolated networks for sensitive applications to prevent external access.
• Example: Run an internal API service on a private network only accessible to specific containers.

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6. Simplified CI/CD Networking

• Create temporary networks in CI pipelines for testing container communication.
• Example: Set up an isolated network for integration tests in a CI/CD job.

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List of Common docker network Commands

Command	Description
docker network ls	List all networks
docker network create my_network	Create a new bridge network
docker network create --driver overlay my_overlay	Create an overlay network for multi-host setups
docker network inspect my_network	Inspect a network for detailed information
docker network connect my_network my_container	Connect a container to a network
docker network disconnect my_network my_container	Disconnect a container from a network
docker network rm my_network	Remove a network
docker network prune	Remove all unused networks

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Best Practices for Using Docker Networks:

1. Use custom networks for container communication to avoid exposing services to the default bridge network.
2. Isolate sensitive services on private networks for security.
3. Monitor and prune unused networks to avoid network clutter.
4. Use overlay networks for multi-host Docker Swarm deployments.
5. Plan subnets carefully to avoid conflicts with your physical network.

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Common Errors and Solutions

1. “Network not found”
   → Ensure the network exists by checking with docker network ls.
2. “Address already in use”
   → Choose a subnet that does not conflict with other networks on your host.
3. “Cannot connect to container”
   → Verify that the container is running and the network is properly configured.
4. “Permission denied”
   → Run the command with sudo or check user permissions.

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Combining docker network with Other Commands

Run a Web App with a Linked Database

docker network create web_net
docker run -d --network=web_net --name=web_app my_web_app
docker run -d --network=web_net --name=db my_database

Inspect and Check for IP Conflicts

docker network inspect my_network

Automate Network Cleanup

docker network prune -f

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