Sample how to do multi-host overlay networking on swarm with docker compose

docker-compose.yml

version: '2'

services:
  db:
    image: mysql
    environment:
      - MYSQL_ROOT_PASSWORD=mypass
      - constraint:node==node01
    networks:
      - backend

  wp:
    image: wordpress
    environment:
      - WORDPRESS_DB_HOST=db
      - WORDPRESS_DB_PASSWORD=mypass
      - constraint:node==node02
    ports:
      - 80:80
    networks:
      - backend

networks:
  backend:
    driver: overlay
    ipam:
      config:
        - subnet: 192.168.18.0/24