networks:
  net1:
  net2:
  net3:

services:
  nginx-proxy:
    networks:
      - net1

  web:
    image: web
    expose:
      - "81"
    environment:
      WEB_PORTS: "81"
      VIRTUAL_HOST: web1.nginx-proxy.example
    networks:
      - net1
      - net2
      - net3