clarify automatic service creation/assignment with labels

docs/content/routing/providers/rancher.md

@@ -17,7 +17,7 @@ Attach labels to your services and let Traefik do the rest!
 !!! info "Labels"
     
     - Labels are case insensitive.
-    - The complete list of labels can be found [the reference page](../../reference/dynamic-configuration/rancher.md)
+    - The complete list of labels can be found in [the reference page](../../reference/dynamic-configuration/rancher.md).
 
 ### General
 
@@ -25,6 +25,32 @@ Traefik creates, for each rancher service, a corresponding [service](../services
 
 The Service automatically gets a server per container in this rancher service, and the router gets a default rule attached to it, based on the service name.
 
+#### Service definition
+
+--8<-- "content/routing/providers/service-by-label.md"
+
+??? example "Automatic service assignment with labels"
+
+    With labels in a compose file
+
+    ```yaml
+    labels:
+      - "traefik.http.routers.myproxy.rule=Host(`foo.com`)"
+      # service myservice gets automatically assigned to router myproxy
+      - "traefik.http.services.myservice.loadbalancer.server.port=80"
+    ```
+
+??? example "Automatic service creation and assignment with labels"
+
+    With labels in a compose file
+
+    ```yaml
+    labels:
+      # no service specified or defined and yet one gets automatically created
+      # and assigned to router myproxy.
+      - "traefik.http.routers.myproxy.rule=Host(`foo.com`)"
+    ```
+
 ### Routers
 
 To update the configuration of the Router automatically attached to the container, add labels starting with `traefik.routers.{name-of-your-choice}.` and followed by the option you want to change.