Configuring Docker Networks

1. Creating Networks

Option	Values	Description
docker network create	`network-name`	Create a new user-defined network
--driver	`bridge`, `overlay`, `null`	Network driver to use (default: bridge)
--subnet	`172.20.0.0/16`	Subnet for the network (CIDR notation)
--gateway	`172.20.0.1`	Gateway IP for the network
--ip-range	`172.20.1.0/24`	IP range for the network
--opt	`com.docker.network.bridge.name=br-abc123`	Driver-specific options

Example: Create a custom bridge network

docker network create --driver bridge --subnet 172.20.0.0/16 --gateway 172.20.0.1 my-network

Example: Create an overlay network for swarm mode

docker network create --driver overlay --subnet 10.0.9.0/24 my-overlay-network

Note: By default, Docker creates a bridge network named bridge when the daemon starts. This is used for containers not explicitly attached to a network.

2. Listing Networks

Command	Description	Options
docker network ls	List all networks	`--format` to customize output format
docker network ls --filter	Filter networks by criteria	`driver=bridge`, `name=network_name`

Example: List all networks with custom format

docker network ls --format "{{.ID}}\t{{.Name}}\t{{.Driver}}"

Example: Filter networks by driver

docker network ls --filter driver=bridge

3. Inspecting Networks

Command	Description	Example
docker network ls	List all networks	`docker network ls`
docker network inspect <network>	Inspect a specific network	`docker network inspect my-network`
docker network inspect --format	Inspect with custom JSON format	`docker network inspect --format '{{.Name}}' my-network`

Example: Inspecting a Network

docker network inspect bridge

Note: The inspect command provides detailed information about network configuration, including driver, options, and attached containers.

4. Connecting Containers to Networks

Option	Description	Default
--network	Connect container to a network	default
--network-alias	Alias for container on a specific network	None

Example: Connecting a Container to a Network

docker run --network my-network --network-alias web-server nginx

Example: Connecting to Default Bridge Network

docker run --network bridge nginx

Note: By default, containers connect to the bridge network if no --network is specified.

Warning: If a container is connected to multiple networks, it can communicate with containers on any of those networks.

5. Disconnecting Containers from Networks

Option	Values	Description
docker network disconnect	`network container`	Disconnects a running container from a network

Example: Disconnecting a Container from a Network

docker network disconnect my-network web-container

Note: The container must be running to disconnect it from a network.

Warning: Disconnecting a container from a network may affect its ability to communicate with other services.

Flag	Description	Usage
--force	Force disconnect even if the container is not connected to the network	`docker network disconnect --force my-network web-container`

6. Using Bridge Networks

Property	Description	Default	Notes
docker0	Default bridge network interface	Yes	Created automatically by Docker daemon
bridge	Network driver for bridge networks	No	Used to connect containers to each other or host
--network	Flag to specify network for container	default	Can be set to custom bridge or host network

Example: Creating a Custom Bridge Network

docker network create --driver bridge my-bridge-network

Example: Running Container on Custom Bridge Network

docker run --network my-bridge-network --name web-server nginx

Note: Bridge networks are isolated by default and do not allow direct communication between containers on different bridge networks.

7. Using Host Network

Option	Values	Notes
--network=host	`host`	Use the host's network stack inside the container

Example: Run container with host network

docker run --network=host nginx

Note: The host network mode shares the host's network namespace, which can lead to port conflicts and reduced security isolation.

Warning: Using --network=host disables the container's network isolation and can cause issues with port binding.

8. Using None Network

Option	Values	Notes
--network none	`none`	Disables networking for the container

Example: Run container with no network

docker run --network none alpine sh -c "echo 'No network access'"

Note: Containers with --network none cannot communicate with other containers or the host network.

9. Configuring Network Aliases

Property	Description	Usage
--network-alias	Assigns an alias to a container within a specific network	`docker run --network-alias=web-server --network=my-network nginx`
--network	Specifies the network to connect to	`docker run --network=my-network --network-alias=app-server alpine sh`

Example: Using Network Aliases in Docker Compose

version: '3.8'
services:
  web:
    image: nginx
    networks:
      app-network:
        aliases:
          - frontend
  api:
    image: node:18
    networks:
      app-network:
        aliases:
          - backend
networks:
  app-network:

Note: Aliases are only valid within the scope of a specific network and do not affect DNS resolution outside that network.

10. Setting Up DNS Configuration

Option	Values	Description
--add-host	`host:ip`	Add a custom host-to-IP mapping
--dns	`ip1,ip2`	Set custom DNS servers
--dns-search	`domain1,domain2`	Set DNS search domains
--dns-opt	`option1,option2`	Set DNS options (e.g., `timeout:1`)

Example: Custom DNS Servers

docker run --dns 8.8.8.8,8.8.4.4 nginx

Example: Adding Host Entry

docker run --add-host db:10.0.0.1 mysql

Note: DNS configuration can be overridden at the daemon level via /etc/docker/daemon.json.

11. Removing Networks

Option	Values	Notes
docker network rm	`<network-name>`	Remove a network by name
docker network rm	`<network-id>`	Remove a network by ID
docker network prune		Remove all unused networks

Example: Remove a network by name

docker network rm my-network

Example: Remove a network by ID

docker network rm 1234567890ab

Example: Remove all unused networks

docker network prune

Note: Networks that are in use by running containers cannot be removed. Stop the containers first using docker stop <container-id>.

12. Pruning Unused Networks

Use the docker network prune command to remove all unused networks that are not connected to any running containers.

Option	Values	Description
--force	`true`	Do not prompt for confirmation before pruning networks
--filter	`label=<key>[=<value>]`	Filter networks by label (e.g., `label=environment=production`)

Example: Prune unused networks with confirmation

docker network prune

Example: Prune networks without confirmation

docker network prune --force

Example: Prune networks with label filter

docker network prune --filter label=environment=staging