Compose: How does compose chooses subnet for default network?

[pedroxs]

I have my docker engine startup configured with:

{
  "bip": "172.80.0.1/16",
  "fixed-cidr": "172.80.0.0/16"
}

but if I start a compose without any network config it creates a bridge with subnet 172.17.0.0/16.

When the docker engine was running with default config it created docker0 with subnet 172.17.0.0/16 and when running compose the bridge network was created with subnet 172.18.0.0/16

Is this the expected behavior? How / where does compose gets the "default" network config from? Is there a way to change this globally to avoid spreading the following config on every compose.yaml?

networks:
  default:
    ipam:
      config:
        - subnet: 172.177.0.0/16

Thanks.

[shin-]

Unless specified, Compose will leave those details to the Engine at creation time.

[adenot]

I'm also seeing the same behaviour as described by OP.

Docker version 1.12.6, build 7392c3b/1.12.6

When running docker-compose up, it creates 2 bridge interfaces (other than docker0) with ip ranges 172.17.0.0/16 and 172.18.0.0/16, despite passing --bip=192.168.1.5/24 --fixed-cidr=192.168.1.5/24 to the main docker engine.

Is there any way to override the default bridge networks without modifying docker-composer.yml?

[shin-]

@adenot Like I said, this is not something docker-compose configures unless specified in the Compose file. If you witness some unexpected behavior, please create an issue on the Engine bug tracker: https://github.com/docker/docker/issues

[adamdrake]

I have observed the same behavior as OP. Docker engine is started with --bip argument, but it is ignored by docker-compose, which set up an additional bridge interface in addition to the docker0 interface. It is named br-f4a912f7750b and has the typical Docker 172.17.x.x format, which happens to conflict with the network I'm currently using. Confirmed with Docker version 1.12.6, build 78d1802 and docker-compose version 1.12.0, build b31ff33.

[pedroxs]

As stated by @shin this is handled by the docker engine. Currently there is no way to specify the default pool, there is a PR open here https://github.com/docker/docker/pull/29376

[sharksforarms]

Same issue on Fedora 26 (Works on centos 7 however...) any ideas?
Docker version 1.13.1
docker compose version 1.16.1

[miketwo]

Current status:
The PR with a possible fix is being held up because of issues with docker swarm. I suggest going to that PR and weighing in on the discussion.

[vogsphar]

simple workaround:
configure routing in your operating system for existing networks and docker will not use these networks.
e.g.

route add -net 172.17.0.0 netmask 255.255.0.0 gw 172.16.0.1
route add -net 172.18.0.0 netmask 255.255.0.0 gw 172.16.0.1

see your os manual for persisting these settings

[ripper2hl]

same issue on opensuse tumbleweed :(, why this is closed ?

[iznogoud06]

Nice workaround @vogsphar ! Works like a charm

[poursadeqi]

well actually you can first create that supposed network and then run docker-compose up -d

     docker-compose down
    docker network create --subnet=[your range] [the network name that would create if you run compose up -d]
    docker-compose up -d

[ripper2hl]

Hi for resolve this in your docker-compose need add a ip configuration

version : '3'

services:
  nginx:
    image: nginx
    networks:
          default:
            aliases:
              - aerogear.sistemasfamsaqa.com
networks:
  default:
    driver: bridge
    ipam:
      driver: default
      config:
      - subnet:  10.103.0.1/16

[pascencio]

@ripper2hl:

This it's tedious if you have many projects with compose. I use it because there is not solution for now.

[ripper2hl]

Yes i know :(

[SarahRiley]

I'm also running into this issue.

Another way around this is to set the default-address-pools in your docker daemon.json, which will put containers using both docker and docker-compose into your desired subnet.

[~]$ cat ~/.docker/daemon.json
{
  "debug" : true,
  "default-address-pools" : [
    {
      "base" : "172.31.0.0/16",
      "size" : 24
    }
  ]
}

[JorisVanEijden]

default-address-pools is only available in docker (18.09.1) for linux, not for windows or mac.

[ripper2hl]

nice !

[Lemon-le]

I'm also running into this issue.

Another way around this is to set the default-address-pools in your docker daemon.json, which will put containers using both docker and docker-compose into your desired subnet.

[~]$ cat ~/.docker/daemon.json
{
  "debug" : true,
  "default-address-pools" : [
    {
      "base" : "172.31.0.0/16",
      "size" : 24
    }
  ]
}

nice ! Thank you

[ilyaglow]

Docker for Mac Version 2.0.0.3 (31259) supports default-address-pools, but the setting doesn't affect containers inside docker-compose.

The workaround with networks doesn't work too.

[grit96]

@ilyaglow did you find a solution to this on Mac?

[fraserc12]

any further development with this?
looking for solution for Mac and Windows if possible

[s3bi77]

Hi, my docker is currently on Version 1.13.1 on Centos. Default-Address-Pools seem to be missing. It won't start with that option enabled in the daemon.json.

This is the error I get
dockerd-current[11625]: unable to configure the Docker daemon with file /etc/docker/daemon.json: the following directives don't match any configuration option: default-address-pools