Docker-compose - How to use second interface on a host with 2 NIC

Question

I have a cookiecutter django project inside a VM instance, a minimal one. Let's call VM_D. Here is the production.yml I am trying to run:

version: '2'

volumes:
  caddy: {}

services:
  django: &django
    build:
      context: .
      dockerfile: ./compose/production/django/Dockerfile
    depends_on:
      - redis
    env_file: .env
    command: /gunicorn.sh

  caddy:
    build:
      context: .
      dockerfile: ./compose/production/caddy/Dockerfile
    depends_on:
      - django
    volumes:
      - caddy:/root/.caddy
    env_file: .env
    ports:
      - "0.0.0.0:80:80"
      - "0.0.0.0:443:443"

  redis:
    image: redis:3.0

  celeryworker:
    <<: *django
    depends_on:
     - redis
    command: /start-celeryworker.sh

  celerybeat:
    <<: *django
    depends_on:
      - redis
    command: /start-celerybeat.sh

Besides, I have another VM instance with postgres running, but not inside a docker. Let's call it VM_P.

These two VMs are connected to each other (I can ping them from each other and even use psql remotely from VM_D) and the postgres one doesn't have access to Internet (for security reasons). So basically, the VM_D has two cards (en0 for external access to internet , and en1 for connection with VM_P) and VM_P has just one card (for connection with VM_D).

I want to be able to access VM_P from django container. I understand I have to connect the default "bridge" to the en1 card but I can't manage to do it yet without altering the connection to the en0.

Tries

• I tried to assign "bridge" and "host" networks to django in production.yml and just the "bridge" to others but it failed saying that only one "host" network is allowed.
• I tried to assign just "host" to django containers, the connection works to VM_P but other containers didn't have connection to django anymore.
• I checked Pipework solution but it is recommended to check a "native" way before using it.

Thanks for helping !