diff --git a/eg3/README.md b/eg3/README.md
index 84e845c..47a5306 100644
--- a/eg3/README.md
+++ b/eg3/README.md
@@ -14,4 +14,22 @@ How to test it:
 How to test it:
 1. Comment all other containers
 2. Run `docker compose build` & `docker compose up`
-3. Test by `curl localhost`, should return a html file (as `/eg3/frontend/index.html`)
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+3. Test by `curl localhost`, should return a html file (as `/eg3/frontend/index.html`)
+
+## Backend + Frontend
+
+In this section, we test frontend container can cross-communicate with backend container.
+
+Steps:
+1. Comment out proxy container
+2. frontend has port 80 exposed; backend has port 5000 exposed;
+3. Run `docker compose build` & `docker compose up`
+4. Create a network: `docker network create mynetwork`
+5. Add containers into network
+   1. `docker network connect mynetwork backend`
+   2. `docker network connect mynetwork frontend`
+6. Inspect `mynetwork` has containers `docker network inspect mynetwork`
+7. Test network:
+   1. Enter frontend container: `docker exec -it frontend /bin/sh`
+   2. Make a request to backend: `curl http://backend:5000`
+   3. Get response `{"version": "1.0.0"}`
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diff --git a/eg3/docker-compose.yaml b/eg3/docker-compose.yaml
index 9371d84..4da4dbe 100644
--- a/eg3/docker-compose.yaml
+++ b/eg3/docker-compose.yaml
@@ -20,10 +20,10 @@ services:
     ports:
       - "80:80" # Uncomment this line if you want to run the frontend container only
 
-  # backend:
-  #   container_name: backend
-  #   build:
-  #     context: ./backend
-  #     dockerfile: Dockerfile
-  #   ports:
-  #     - "5000:5000" # Uncomment this line if you want to run the backend container only
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+  backend:
+    container_name: backend
+    build:
+      context: ./backend
+      dockerfile: Dockerfile
+    ports:
+      - "5000:5000" # Uncomment this line if you want to run the backend container only
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