Docker Networks Part 3: Docker Compose Network Options

Network Design

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8th July 2024.

Updated 26th May 2025 - Added how to disable IPv4 in a docker compose file

Docker Compose is a tool used to define and run multi-container Docker applications. Instead of running multiple standalone containers and try to make them interact, you create a work directory with a YAML file that contains all the services, volumes and network parameters.

I will be writing some How-To’s on setting up some docker compose applications in the near future. This post will focus on the different network options available for Docker Compose.

Network Options

Source: https://docs.docker.com/compose/compose-file/06-networks/#examples

All drivers described in part 1 except overlay can be used in a docker compose project. In addition, some Docker compose specific options can be used as well.

Example Compose file

These options affects all containers attached to the same network.

services:
  nginx1:
    image: nginx
    networks:
      example_net: # optionally set IP addresses underneath:
        ipv4_address: 100.110.1.10
        ipv6_address: 2001:DB8:0:A01A::A

networks:
  example_net:
    external: false
    internal: false
    enable_ipv6: true
    attachable: true
    driver: bridge
    driver_opts:
      com.docker.network.enable_ipv4: "false"
    ipam:
      config:
        - subnet: 100.110.1.0/24
          gateway: 100.110.1.1
          aux_addresses: # exclude addresses already in use
            standalone_container: 100.110.1.2
            some_thing: 100.110.1.3
        - subnet: 2001:DB8:0:A01A::/80
          gateway: 2001:DB8:0:A01A::1
          aux_addresses:
            standalone_container: 2001:DB8:0:A01A::2
            some_thing: 2001:DB8:0:A01A::3

external:

• When set to true, it means that the network has been created outside of compose, meaning that you specify a network that was created with the docker network create command. Default is false.

• Setting external network means that all network settings are made outside docker compose. All other attributes apart from name are irrelevant. If you specify any other attribute, it rejects the compose file as invalid.

internal:

• When set to true, containers will not configure a default gateway, making them un-routable. Not even possible to expose ports. Default is false.

Note: Depending on which driver you use, the docker node will still assign itself an IP address meant for default GW. That seems quite unnecessary.

enable_ipv6:

• should be self-explanatory. Default is false.

attachable:

• When set to true, standalone containers and other compose projects should be able to attach to this network. Default is false.

driver:

• choose which network driver to use. default is bridge.

driver_opts:

com.docker.network.enable_ipv4: false turns off IPv4.

ipam:

• With ipam you can set your own subnets and gateways, instead of relying on the defaults.

• Setting IPv4 addresses when the above driver option is set to false will obviously create a conflict but I’m just trying to fit all parameters into one example.

Other Network Settings

There are two more things that can be set under docker compose networks.

name:

• Sets a custom name for the network. By default the name of a compose network will prepend the working directory or the COMPOSE_PROJECT_NAME variable set before the defined name inside the compose file.

• name: is the only parameter that can be configured with the external property. You can also specify the name from an environment variable:

networks:
  example_net:
    external: true
    name: "${NETWORK_ID}"

labels:

With labels you can set descriptions on the networks. It is recommended to use reverse-DNS notation to prevent labels from conflicting with those used by other software. Example:

networks:
  example_net:
    name: without-project-name
    labels:
      online.bastuklubben.description: "Test network"
      online.bastuklubben.location: "at home in the basement"

$ docker network inspect without-project-name
...
        "Labels": {
            "com.docker.compose.network": "vyos",
            "com.docker.compose.project": "vyos",
            "com.docker.compose.version": "2.27.1",
            "online.bastuklubben.description": "Test network",
            "online.bastuklubben.location": "at home in the basement"
        }
    }
]

Service Network Options

These options can be set under a specific service:

services:
  nginx1:
    image: nginx
    hostname: nginx1.bastuklubben.online
    networks:
      example_net:

  nginx2:
    image: nginx
    hostname: nginx2.bastuklubben.online
    network_mode: bridge

  nginx3:
    image: nginx
    hostname: nginx3.bastuklubben.online
    network_mode: host

Networks:

• Specifies which network to use as defined under networks:.

• If no network is specified, it will create a bridge network using the next available default scope with the name of the project directory.

• You can optionally assign addresses to containers. However, that require ipam: and subnet: configuration to be specified.

Network_Mode:

• Specifies an alternative driver. This means that you won’t be using a docker compose network.

  • When set to bridge, it will use the default bridge network.

  • When set to host, it will use the docker host addresses as explained in part 1.

• Be aware that the containers won’t receive any domain names when bridge or host network mode is set.

$ docker container inspect sauna-nginx1-1
...
            "Networks": {
                "bridge": {
...
                   "DNSNames": [
                        "sauna-nginx1-1",
                        "nginx1",
                        "fdeb486c4d87",
                        "nginx1.bastuklubben.online"
                    ]

$ docker container inspect sauna-nginx2-1
...
            "Networks": {
                "bridge": {
 ...
                    "DNSNames": null

Use-cases

In upcoming How-To’s i will demonstrate use-cases for many of these settings, including the driver options from Part 1. Stay tuned.