Add deploy default service with Interlock

_data/toc.yaml

@@ -1713,7 +1713,8 @@ manuals:
           section:
           - title: Simple swarm service
             path: /ee/ucp/interlock/usage/
-
+          - title: Set a default backend
+            path: /ee/ucp/interlock/usage/default-service/
 
 
         - sectiontitle: Introduction

ee/ucp/interlock/usage/default-service.md

@@ -0,0 +1,50 @@
+---
+title: Set a default service
+description: Learn about Interlock, an application routing and load balancing system
+  for Docker Swarm.
+keywords: ucp, interlock, load balancing
+ui_tabs:
+- version: ucp-3.0
+  orhigher: false
+- version: ucp-2.2
+---
+
+{% if include.version=="ucp-3.0" %}
+
+The default proxy service used by UCP to provide layer 7 routing is NGINX,
+so when users try to access a route that hasn't been configured, they will
+see the default NGINX 404 page.
+
+![Default NGINX page]()
+
+In this example we will publish a service to be a default host.  This service will respond
+whenever there is a request to a host that is not configured.
+
+First we will create an overlay network so that service traffic is isolated and secure:
+
+```bash
+$> docker network create -d overlay demo
+1se1glh749q1i4pw0kf26mfx5
+```
+
+Next we will create the initial service:
+
+```bash
+$> docker service create \
+    --name demo-default \
+    --network demo \
+    --detach=false \
+    --replicas=1 \
+    --label com.docker.lb.defaul_backend=true \
+    --label com.docker.lb.port=8080 \
+    ehazlett/interlock-default-app
+```
+
+Interlock will detect once the service is available and publish it.  Once the tasks are running
+and the proxy service has been updated the application should be available via any url that is not
+configured:
+
+
+![Default Backend](interlock_default_backend.png)
+
+{% endif %}