Setting up a simple external HTTP load balancer

This setup guide shows you how to create a simple external HTTP load balancer with the following resources:

If this example doesn't match your use case, see one of the following pages:

For general concepts, see the External HTTP(S) Load Balancing overview.

HTTP load balancer topology

In this guide, you create the configuration that is illustrated in the following diagram.

Simple HTTP Load Balancing (click to enlarge)
Simple HTTP Load Balancing (click to enlarge)

The sequence of events in the diagram is as follows:

  1. A client sends a content request to the external IPv4 address defined in the forwarding rule.
  2. The forwarding rule directs the request to the target HTTP proxy.
  3. The target proxy uses the rule in the URL map to determine that the single backend service receives all requests.
  4. The load balancer determines that the backend service has only one instance group and directs the request to a virtual machine (VM) instance in that group.
  5. The VM serves the content requested by the user.

Set up permissions

To complete the steps in this guide, you must have permission to create Compute Engine instances, firewall rules, and reserved IP addresses in a project. You must have either a project owner or editor role, or you must have the following Compute Engine IAM roles.

Task Required role
Create instances Instance Admin
Add and remove firewall rules Security Admin
Create load balancer components Network Admin
Create a project (optional) Project Creator

For more information, see the following guides:

Creating a managed instance group

To set up a load balancer with a Compute Engine backend, your VMs need to be in an instance group. This guide describes how to create a managed instance group with Linux VMs that have Apache running, and then set up load balancing.

The managed instance group provides VMs running the backend servers of an external HTTP load balancer. For demonstration purposes, backends serve their own hostnames.


  1. In the Google Cloud Console, go to the Instance groups page.

    Go to the Instance groups page

  2. Click Create instance group.
  3. On the left, choose New managed instance group.
  4. For Name, enter lb-backend-example.
  5. Under Location, select Single zone.
  6. For Region, select your preferred region. This example uses us-east1.
  7. For Zone, select us-east1-b.
  8. Under Instance template, select Create a new instance template.
  9. For Name, enter lb-backend-template.
  10. Ensure that the Boot disk is set to a Debian image, such as Debian GNU/Linux 9 (stretch). These instructions use commands that are only available on Debian, such as apt-get.
  11. Do not configure the Firewall option.

    Because the external HTTP(S) load balancer is a proxy, you don't need to select Allow HTTP traffic under Firewall. In Configuring a firewall rule, you create the only necessary firewall rule for this load balancer.

  12. Under Management, security, disks, networking, sole tenancy, on the Management tab, insert the following script into the Startup script field.

    #! /bin/bash
    apt-get update
    apt-get install apache2 -y
    a2ensite default-ssl
    a2enmod ssl
    vm_hostname="$(curl -H "Metadata-Flavor:Google" \"
    echo "Page served from: $vm_hostname" | \
    tee /var/www/html/index.html
  13. On the Networking tab, add the network tags: allow-health-check

  14. Click Save and continue.

  15. Under Autoscaling mode, select Don't autoscale.

  16. Under Number of instances, enter 2.

  17. To create the new instance group, click Create.


  1. Create the template.

    gcloud compute instance-templates create lb-backend-template \
       --region=us-east1 \
       --network=default \
       --subnet=default \
       --tags=allow-health-check \
       --image-family=debian-9 \
       --image-project=debian-cloud \
       --metadata=startup-script='#! /bin/bash
         apt-get update
         apt-get install apache2 -y
         a2ensite default-ssl
         a2enmod ssl
         vm_hostname="$(curl -H "Metadata-Flavor:Google" \"
         echo "Page served from: $vm_hostname" | \
         tee /var/www/html/index.html
         systemctl restart apache2'
  2. Create the managed instance group based on the template.

    gcloud compute instance-groups managed create lb-backend-example \
       --template=lb-backend-template --size=2 --zone=us-east1-b

Adding a named port to the instance group

For your instance group, define an HTTP service and map a port name to the relevant port. Once configured, the load balancing service forwards traffic to the named port.


  1. In the Google Cloud Console, go to the Instance groups page.

    Go to the Instance groups page

  2. Click the name of your instance group (in this example lb-backend-example).
  3. On the instance group's Overview page, click Edit .
  4. Click Specify port name mapping.
  5. Click Add item.
  6. For the port name, enter http. For the port number, enter and 80.
  7. Click Save.


Use the gcloud compute instance-groups set-named-ports command.

gcloud compute instance-groups set-named-ports lb-backend-example \
    --named-ports http:80 \
    --zone us-east1-b

Configuring a firewall rule

In this example, you create the fw-allow-health-check firewall rule. This is an ingress rule that allows traffic from the Google Cloud health checking systems ( and This example uses the target tag allow-health-check to identify the VMs.


  1. In the Google Cloud Console, go to the Firewall page.

    Go to the Firewall page

  2. Click Create firewall rule to create the second firewall rule.
  3. For Name, enter fw-allow-health-check.
  4. Under Network, select Default.
  5. Under Targets, select Specified target tags.
  6. Populate the Target tags field with allow-health-check.
  7. Set Source filter to IP ranges.
  8. Set Source IP ranges to and
  9. Under Protocols and ports, select Specified protocols and ports.
  10. Select the tcp checkbox, and then type 80 for the port numbers.
  11. Click Create.


gcloud compute firewall-rules create fw-allow-health-check \
    --network=default \
    --action=allow \
    --direction=ingress \
    --source-ranges=, \
    --target-tags=allow-health-check \

Reserving an external IP address

Now that your instances are up and running, set up a global static external IP address that your customers use to reach your load balancer.


  1. In the Google Cloud Console, go to the External IP addresses page.

    Go to the External IP addresses page

  2. To reserve an IPv4 address, click Reserve static address.
  3. For Name, enter lb-ipv4-1.
  4. Set Network Service Tier to Premium.
  5. Set IP version to IPv4.
  6. Set Type to Global.
  7. Click Reserve.


gcloud compute addresses create lb-ipv4-1 \
    --ip-version=IPV4 \

Note the IPv4 address that was reserved:

gcloud compute addresses describe lb-ipv4-1 \
    --format="get(address)" \

Setting up the load balancer


  1. In the Google Cloud Console, go to the Load balancing page.

    Go to the Load balancing page

  2. Click Create load balancer.
  3. Under HTTP(S) Load Balancing, click Start configuration.
  4. Select From Internet to my VMs, and then click Continue.
  5. For the load balancer Name, enter web-map-http.
  6. Click Backend configuration.
    1. Under Create or select backend services & backend buckets, select Backend services > Create a backend service.
    2. Add a name for your backend service, such as web-backend-service.
    3. Under Protocol, select HTTP.
    4. For the Named Port, enter http.
    5. In Backends > New backend > Instance group, select your instance group, lb-backend-example.
    6. For the Port numbers, enter 80.
    7. Retain the other default settings.
    8. Under Health check, select Create a health check, and then add a name for your health check, such as http-basic-check.
    9. Set the protocol to HTTP, and then click Save and continue.
    10. Retain the other default settings.
    11. Click Create.
  7. In Host and path rules, retain the default settings.
  8. In Frontend configuration, use the following values:
    1. Set Protocol to HTTP.
    2. Set IP address to lb-ipv4-1, which you created earlier.
    3. Ensure that Port is set to 80 to allow HTTP traffic.
    4. Click Done.
  9. Click Review and finalize.
  10. When you finish configuring the load balancer, click Create.
  11. Wait for the load balancer to be created.
  12. Click the name of the load balancer.
  13. On the Load balancer details screen, note the IP:Port for your load balancer.


  1. Create a health check.
    gcloud compute health-checks create http http-basic-check \
        --port 80
  2. Create a backend service.
    gcloud compute backend-services create web-backend-service \
        --protocol=HTTP \
        --port-name=http \
        --health-checks=http-basic-check \
  3. Add your instance group as the backend to the backend service.
    gcloud compute backend-services add-backend web-backend-service \
        --instance-group=lb-backend-example \
        --instance-group-zone=us-east1-b \
  4. Create a URL map to route the incoming requests to the default backend service.
    gcloud compute url-maps create web-map-http \
        --default-service web-backend-service
  5. Create a target HTTP proxy to route requests to your URL map.
    gcloud compute target-http-proxies create http-lb-proxy \
        --url-map web-map-http
  6. Create a global forwarding rule to route incoming requests to the proxy.
    gcloud compute forwarding-rules create http-content-rule \
        --address=lb-ipv4-1 \
        --global \
        --target-http-proxy=http-lb-proxy \

Testing traffic sent to your instances

Now that the load balancing service is running, you can send traffic to the forwarding rule and watch the traffic be dispersed to different instances.


  1. In the Google Cloud Console, go to the Load balancing page.

    Go to the Load balancing page

  2. Click the load balancer that you just created.
  3. In the Backend section, confirm that the VMs are healthy. The Healthy column should be populated, indicating that both VMs are healthy (2/2). If you see otherwise, first try reloading the page. It can take a few moments for the Cloud Console to indicate that the VMs are healthy. If the backends do not appear healthy after a few minutes, review the firewall configuration and the network tag assigned to your backend VMs.
  4. After the Cloud Console shows that the backend instances are healthy, you can test your load balancer using a web browser by going to http://IP_ADDRESS. Replace IP_ADDRESS with the load balancer's IP address.
  5. Your browser should render a page with content showing the name of the instance that served the page, along with its zone (for example, Page served from: lb-backend-example-xxxx). If your browser doesn't render this page, review the configuration settings in this guide.

What's next