Compose: Allow to specify subnet with docker-compose --x-networking

[ashatrov]

When i use docker-compose --x-networking up it create subnet for each containers group (for each folder with docker-compose.yml) with 172.18.0.0/16, 172.19.0.0/16 .... etc.

In our office network we already have 172.18.. and I can not connect to these machines from containers.

I want to specify subnet when I start containers group with docker-compose --x-networking

[dnephin]

This is not something that is controlled by compose. It's up to the docker engine to decide on the subnet.

[ashatrov-lazada]

how can i use specify subnet if i use docker-compose?
Or I should not use it?

[dnephin]

I think specifying a subnet might already be supported by docker network create.

It will be supported by compose with the changes in #2478 (#2564)

[SimplicityGuy]

@dnephin Can you provide examples on how to use this in docker-compose? When I try the following with docker-compose v2 files:

networks:
  front-tier:
    subnet: 192.170.0.0/16
    gateway: 192.170.0.1
  back-tier:
    subnet: 192.171.0.0/16
    gateway: 192.171.0.1

I get an error:

ERROR: Validation failed in file './docker-compose.yml', reason(s):
networks.back-tier value Additional properties are not allowed ('subnet', 'gateway' were unexpected)
networks.front-tier value Additional properties are not allowed ('subnet', 'gateway' were unexpected)

[dnephin]

It's under ipam config: https://docs.docker.com/compose/compose-file/#ipam

[SimplicityGuy]

Excellent, this works perfectly. Thank you for pointing that out!

[josefsabl]

Does not work in version 3.