Tags

Architecture Description

1. VM Instances (Compute Engine) You created three individual VMs: www1, www2, www3 Each has Apache web server installed and serves a unique homepage (<h3>Web Server: wwwX</h3>). Tagged with network-lb-tag so firewall rules can target them. Purpose: Serve HTTP traffic. 2. Firewall Rules www-firewall-network-lb Allows incoming HTTP traffic (port 80) to VMs with tag network-lb-tag. fw-allow-health-check Allows incoming traffic from Google health check IP ranges to VMs tagged allow-health-check (so the load balancer knows which VMs are healthy). 3. Instance Template & Managed Instance Group (MIG) Template: lb-backend-template Defines configuration for new VMs (Apache, SSL enabled, metadata script serving hostname). Managed Instance Group: lb-backend-group 2 instances created from the template in us-west1-a. Ensures autoscaling, autohealing, and consistency. Purpose: Backend for the application load balancer. 4. Health Check http-basic-check Regularly pings the backend VMs on port 80. Only healthy instances get traffic from the load balancer. 5. Load Balancer (Application L7) Frontend Global static IP: lb-ipv4-1 HTTP traffic received via forwarding rule: http-content-rule HTTP Proxy http-lb-proxy routes traffic to URL map URL Map web-map-http sends requests to backend service: web-backend-service Backend Service web-backend-service connected to MIG lb-backend-group Only sends traffic to healthy instances (health-checked) Purpose: Distribute user traffic efficiently across backend VMs. 6. Traffic Flow User → Global IP (lb-ipv4-1) Forwarding rule → HTTP Proxy (http-lb-proxy) Proxy → URL Map (web-map-http) URL Map → Backend Service (web-backend-service) Backend Service → MIG VMs (lb-backend-group) → Apache serves web page Health check ensures only healthy VMs get traffic