Traefik can access all network?

Traefik Traefik v2 (latest)
1

Hello,
I have created 2 differents docker-compose in 2 differents directories.
One for traefik and one for my ELK suite.
So my question is:
How Traefik can access to containers on an other network without link ?
Sorry for my bad english (French here) don't hesitate to correct it :stuck_out_tongue:

Traefik docker-compose (/opt/traefik):

version: "3.3"

services:
  traefik:
    image: "traefik:v2.1"
    container_name: "traefik"
    ports:
      - "80:80"
      - "443:443"
      - "8080:8080"
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock:ro"
      - "/opt/traefik/traefik.toml:/etc/traefik/traefik.toml:ro"

ELK Suite docker-compose (/opt/docker-elk):

version: '3.2'

services:
  elasticsearch:
    build:
      context: elasticsearch/
      args:
        ELK_VERSION: $ELK_VERSION
    volumes:
      - type: bind
        source: ./elasticsearch/config/elasticsearch.yml
        target: /usr/share/elasticsearch/config/elasticsearch.yml
        read_only: true
      - type: volume
        source: elasticsearch
        target: /usr/share/elasticsearch/data
    labels:
      - "traefik.enable=false"
    ports:
      - "9200:9200"
      - "9300:9300"
    environment:
      ES_JAVA_OPTS: "-Xmx4g -Xms4g"
      # Use single node discovery in order to disable production mode and avoid bootstrap checks
      # see https://www.elastic.co/guide/en/elasticsearch/reference/current/bootstrap-checks.html
      discovery.type: single-node

  logstash:
    build:
      context: logstash/
      args:
        ELK_VERSION: $ELK_VERSION
    volumes:
      - type: bind
        source: ./logstash/config/logstash.yml
        target: /usr/share/logstash/config/logstash.yml
        read_only: true
      - type: bind
        source: ./logstash/pipeline
        target: /usr/share/logstash/pipeline
        read_only: true
    labels:
      - "traefik.enable=false"
    ports:
      - "5000:5000/tcp"
      - "5000:5000/udp"
      - "9600:9600"
    environment:
      LS_JAVA_OPTS: "-Xmx256m -Xms256m"
    depends_on:
      - elasticsearch

  kibana:
    build:
      context: kibana/
      args:
        ELK_VERSION: $ELK_VERSION
    volumes:
      - type: bind
        source: ./kibana/config/kibana.yml
        target: /usr/share/kibana/config/kibana.yml
        read_only: true
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.kibana.entrypoints=http"
      - "traefik.http.routers.kibana.rule=Host(`kibana.site.io`)"
    depends_on:
      - elasticsearch

volumes:
  elasticsearch: