https://stackoverflow.com/questions/58475127/docker-compose-service-name-conflict-with-external-network

other.docker-compose.yml

version: '3.4'

services:
  app:
    image: busybox
    # keep container running
    command: tail -f /dev/null
    networks:
      - paymentservice_default
      - default

networks:
  paymentservice_default:
    external: true

paymentservice.docker-compose.yml

version: '3.4'

services:
  app:
    image: busybox
    # keep container running
    command: tail -f /dev/null
  rabbit:
    image: rabbitmq

networks:
  default:
    driver: bridge

run.sh

#!/bin/sh
set -x
COMPOSE_PROJECT_NAME=paymentservice docker-compose -f paymentservice.docker-compose.yml up -d
COMPOSE_PROJECT_NAME=other docker-compose -f other.docker-compose.yml up -d

docker ps

# show Docker IPs
docker ps -q | xargs -n 1 docker inspect --format '{{ .Name }} {{range .NetworkSettings.Networks}} {{.IPAddress}}{{end}}' | sed 's#^/##';

docker exec -it other_app_1 ping -c 1 app.paymentservice_default
docker exec -it other_app_1 ping -c 1 app

# docker exec -it other_app_1 nslookup app
docker exec -it other_app_1 nslookup app.paymentservice_default
docker exec -it other_app_1 nslookup app

COMPOSE_PROJECT_NAME=other docker-compose -f other.docker-compose.yml down
COMPOSE_PROJECT_NAME=paymentservice docker-compose -f paymentservice.docker-compose.yml down