Set up a classic proxy Network Load Balancer (TCP proxy) with VM instance group backends

Google Cloud classic proxy Network Load Balancers let you use a single IP address for all users around the world. Classic proxy Network Load Balancers automatically route traffic to backend instances that are closest to the user.

This page contains instructions for setting up a classic proxy Network Load Balancer with a target TCP proxy and VM instance group backends. Before you start, read the External proxy Network Load Balancer overview for detailed information about how these load balancers work.

Setup overview

This example demonstrates how to set up an external proxy Network Load Balancer for a service that exists in two regions: Region A and Region B. For purposes of the example, the service is a set of Apache servers configured to respond on port 110. Many browsers don't allow port 110, so the testing section uses curl.

In this example, you configure the following:

  1. Four instances distributed between two regions
  2. Instance groups, which contain the instances
  3. A health check for verifying instance health
  4. A backend service, which monitors the instances and prevents them from exceeding configured usage
  5. The target TCP proxy
  6. An external static IPv4 address and forwarding rule that sends user traffic to the proxy
  7. An external static IPv6 address and forwarding rule that sends user traffic to the proxy
  8. A firewall rule that allows traffic from the load balancer and health checker to reach the instances

After the load balancer is configured, you test the configuration.

Permissions

To follow this guide, you must be able to create instances and modify a network in a project. You must be either a project owner or editor, or you must have all of the following Compute Engine IAM roles:

Task Required Role
Create networks, subnets, and load balancer components Network Admin
Add and remove firewall rules Security Admin
Create instances Compute Instance Admin

For more information, see the following guides:

Configure instance group backends

This section shows how to create basic instance groups, add instances to them, and then add those instances to a backend service with a health check. A production system would normally use managed instance groups based on instance templates, but this configuration is quicker for initial testing.

Configure instances

For testing purposes, install Apache on four instances, two in each of two instance groups. Typically, external proxy Network Load Balancers aren't used for HTTP traffic, but Apache software is commonly used for testing.

In this example, the instances are created with the tag tcp-lb. This tag is used later by the firewall rule.

Console

Create instances

  1. In the Google Cloud console, go to the VM instances page.

    Go to VM instances

  2. Click Create instance.

  3. Set Name to vm-a1.

  4. Set the Region to REGION_A.

  5. Set the Zone to ZONE_A.

  6. Click Advanced options.

  7. Click Networking and configure the following field:

    • For Network tags, enter tcp-lb,allow-health-check-ipv6.

  • Click Management. Enter the following script into the Startup script field.

    sudo apt-get update
sudo apt-get install apache2 -y
sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
sudo service apache2 restart
echo '<!doctype html><html><body><h1>vm-a1</h1></body></html>' | sudo tee /var/www/html/index.html

  • Click Create.

  • Create vm-a2 with the same settings, except with the following script in the Startup script field: 

    sudo apt-get update
sudo apt-get install apache2 -y
sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
sudo service apache2 restart
echo '<!doctype html><html><body><h1>vm-a2</h1></body></html>' | sudo tee /var/www/html/index.html

  • Create vm-b1 with the same settings, except with Region set to REGION_B and Zone set to ZONE_B. Enter the following script in the Startup script field: 

    sudo apt-get update
sudo apt-get install apache2 -y
sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
sudo service apache2 restart
echo '<!doctype html><html><body><h1>vm-b1</h1></body></html>' | sudo tee /var/www/html/index.html

  • Create vm-b2 with the same settings, except with Region set to REGION_B and Zone set to ZONE_B. Enter the following script in the Startup script field: 

    sudo apt-get update
sudo apt-get install apache2 -y
sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
sudo service apache2 restart
echo '<!doctype html><html><body><h1>vm-b2</h1></body></html>' | sudo tee /var/www/html/index.html

    • gcloud

    1. Create vm-a1 in zone ZONE_A

      gcloud compute instances create vm-a1 \
   --image-family debian-12 \
   --image-project debian-cloud \
   --tags tcp-lb \
   --zone ZONE_A \
   --metadata startup-script="#! /bin/bash
     sudo apt-get update
     sudo apt-get install apache2 -y
     sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
     sudo service apache2 restart
     echo '<!doctype html><html><body><h1>vm-a1</h1></body></html>' | tee /var/www/html/index.html
     EOF"

    2. Create vm-a2 in zone ZONE_A

      gcloud compute instances create vm-a2 \
   --image-family debian-12 \
   --image-project debian-cloud \
   --tags tcp-lb \
   --zone ZONE_A \
   --metadata startup-script="#! /bin/bash
     sudo apt-get update
     sudo apt-get install apache2 -y
     sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
     sudo service apache2 restart
     echo '<!doctype html><html><body><h1>vm-a2</h1></body></html>' | tee /var/www/html/index.html
     EOF"

    3. Create vm-b1 in zone ZONE_B

      gcloud compute instances create vm-b1 \
   --image-family debian-12 \
   --image-project debian-cloud \
   --tags tcp-lb \
   --zone ZONE_B \
   --metadata startup-script="#! /bin/bash
     sudo apt-get update
     sudo apt-get install apache2 -y
     sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
     sudo service apache2 restart
     echo '<!doctype html><html><body><h1>vm-b1</h1></body></html>' | tee /var/www/html/index.html
     EOF"

    4. Create vm-b2 in zone ZONE_B

      gcloud compute instances create vm-b2 \
   --image-family debian-12 \
   --image-project debian-cloud \
   --tags tcp-lb \
   --zone ZONE_B \
   --metadata startup-script="#! /bin/bash
     sudo apt-get update
     sudo apt-get install apache2 -y
     sudo sed -i '/Listen 80/c\Listen 110' /etc/apache2/ports.conf
     sudo service apache2 restart
     echo '<!doctype html><html><body><h1>vm-b2</h1></body></html>' | tee /var/www/html/index.html
     EOF"

    Create instance groups

    In this section you create an instance group in each zone and add the instances.

    Console

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

      Go to Instance groups

    2. Click Create instance group.

    3. Click New unmanaged instance group.

    4. Set the Name to instance-group-a.

    5. Set the Zone to ZONE_A.

    6. Under Port mapping, click Add port. A load balancer sends traffic to an instance group through a named port. Create a named port to map the incoming traffic to a specific port number.

      1. Set Port name to tcp110.
      2. Set Port numbers to 110.

    7. Under VM instances, select vm-a1 and vm-a2.

    8. Leave the other settings as they are.

    9. Click Create.

    10. Repeat the steps, but set the following values:

      • Name: instance-group-b
      • Region: REGION_B
      • Zone: ZONE_B
      • Port name: tcp110
      • Port numbers: 110
      • Instances: vm-b1 and vm-b2.

    gcloud

    1. Create the instance-group-a instance group.

      gcloud compute instance-groups unmanaged create instance-group-a \
   --zone ZONE_A

    2. Create a named port for the instance group.

      gcloud compute instance-groups set-named-ports instance-group-a \
   --named-ports tcp110:110 \
   --zone ZONE_A

    3. Add vm-a1 and vm-a2 to instance-group-a.

      gcloud compute instance-groups unmanaged add-instances instance-group-a \
   --instances vm-a1,vm-a2 \
   --zone ZONE_A

    4. Create the us-ig2 instance group.

      gcloud compute instance-groups unmanaged create instance-group-b \
   --zone ZONE_B

    5. Create a named port for the instance group.

      gcloud compute instance-groups set-named-ports instance-group-b \
   --named-ports tcp110:110 \
   --zone ZONE_B

    6. Add vm-b1 and vm-b2 to instance-group-b

      gcloud compute instance-groups unmanaged add-instances instance-group-b \
   --instances vm-b1,vm-b2 \
   --zone ZONE_B

    You now have one instance group per region. Each instance group has two VM instances.

    Create a firewall rule for the external proxy Network Load Balancer

    Configure the firewall to allow traffic from the load balancer and health checker to the instances. In this case, we will open TCP port 110. The health check will use the same port. Since the traffic between the load balancer and your instances uses IPv4, only IPv4 ranges need be opened.

    Console

    1. In the Google Cloud console, go to the Firewall policies page.

      Go to Firewall policies

    2. Click Create firewall rule.

    3. In the Name field, enter allow-tcp-lb-and-health.

    4. Select a network.

    5. Under Targets, select Specified target tags.

    6. Set Target tags to tcp-lb.

    7. Set Source filter to IPv4 ranges.

    8. Set Source IPv4 ranges to 130.211.0.0/22,35.191.0.0/16.

    9. Under Protocols and ports, set Specified protocols and ports to tcp:110.

    10. Click Create.

    gcloud 

    gcloud compute firewall-rules create allow-tcp-lb-and-health \
   --source-ranges 130.211.0.0/22,35.191.0.0/16 \
   --target-tags tcp-lb \
   --allow tcp:110

    Configure the load balancer

    Console

    Start your configuration

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

      Go to Load balancing

    2. Click Create load balancer.
    3. For Type of load balancer, select Network Load Balancer (TCP/UDP/SSL) and click Next.
    4. For Proxy or passthrough, select Proxy load balancer and click Next.
    5. For Public facing or internal, select Public facing (external) and click Next.
    6. For Global or single region deployment, select Best for global workloads and click Next.
    7. For Load balancer generation, select Classic proxy Network Load Balancer and click Next.
    8. Click Configure.

    Basic configuration

    Set the Name to my-tcp-lb.

    Backend configuration

    1. Click Backend configuration.
    2. Under Backend type, select Instance groups.
    3. Under Protocol, select TCP.
    4. Configure the first backend:
      1. Under New backend, select instance group instance-group-a.
      2. Retain the remaining default values.
    5. Configure the second backend:
      1. Click Add backend.
      2. Select instance group instance-group-b.
      3. Under Port numbers, delete 80 and add 110.
    6. Configure the health check:
      1. Under Health check, select Create health check.
      2. Set the health check Name to my-tcp-health-check.
      3. Under Protocol, select TCP.
      4. Set Port to 110.
      5. Retain the remaining default values.
      6. Click Save and continue.
    7. In the Google Cloud console, verify that there is a check mark next to Backend configuration. If not, double-check that you have completed all of the steps.

    Frontend configuration

    1. Click Frontend configuration.
    2. Add the first forwarding rule:
      1. Enter a Name of my-tcp-lb-forwarding-rule.
      2. Under Protocol, select TCP.
      3. Under IP address, select Create IP address:
        1. Enter a Name of tcp-lb-static-ip.
        2. Click Reserve.
      4. Set Port to 110.
      5. In this example, don't enable the Proxy Protocol because it doesn't work with the Apache HTTP Server software. For more information, see Proxy protocol.
      6. Click Done.
    3. Add the second forwarding rule:
      1. Click Add frontend IP and port.
      2. Enter a Name of my-tcp-lb-ipv6-forwarding-rule.
      3. Under Protocol, select TCP.
      4. Set IP version to IPv6.
      5. Under IP address, click Create IP address.
        1. Enter a name of tcp-lb-ipv6-static-ip.
        2. Click Reserve.
      6. Set Port to 110.
      7. In this example, don't enable the Proxy Protocol because it doesn't work with the Apache HTTP Server software. For more information, see Proxy protocol.
      8. Click Done.

    4. In the Google Cloud console, verify that there is a check mark next to Frontend configuration. If not, double-check that you have completed all the previous steps.

    Review and finalize

    1. Click Review and finalize.
    2. Review your load balancer configuration settings.
    3. Optional: Click Equivalent code to view the REST API request that will be used to create the load balancer.
    4. Click Create.

    gcloud

    1. Create a health check. 
          gcloud compute health-checks create tcp my-tcp-health-check --port 110
    2. Create a backend service. 
          gcloud compute backend-services create my-tcp-lb \
        --load-balancing-scheme EXTERNAL \
        --global-health-checks \
        --global \
        --protocol TCP \
        --health-checks my-tcp-health-check \
        --timeout 5m \
        --port-name tcp110
    3. Add instance groups to your backend service. 
          gcloud compute backend-services add-backend my-tcp-lb \
        --global \
        --instance-group instance-group-a \
        --instance-group-zone ZONE_A \
        --balancing-mode UTILIZATION \
        --max-utilization 0.8
    
          gcloud compute backend-services add-backend my-tcp-lb \
        --global \
        --instance-group instance-group-b \
        --instance-group-zone ZONE_B \
        --balancing-mode UTILIZATION \
        --max-utilization 0.8
    4. Configure a target TCP proxy. If you want to turn on the proxy header, set it to PROXY_V1 instead of NONE. 
          gcloud compute target-tcp-proxies create my-tcp-lb-target-proxy \
        --backend-service my-tcp-lb \
        --proxy-header NONE
    5. Reserve global static IPv4 and IPv6 addresses.

      Your customers can use these IP addresses to reach your load balanced service.

          gcloud compute addresses create tcp-lb-static-ipv4 \
        --ip-version=IPV4 \
        --global
    
          gcloud compute addresses create tcp-lb-static-ipv6 \
        --ip-version=IPV6 \
        --global
    6. Configure global forwarding rules for the two addresses. 
          gcloud compute forwarding-rules create my-tcp-lb-ipv4-forwarding-rule \
        --load-balancing-scheme EXTERNAL \
        --global \
        --target-tcp-proxy my-tcp-lb-target-proxy \
        --address tcp-lb-static-ipv4 \
        --ports 110
    
          gcloud compute forwarding-rules create my-tcp-lb-ipv6-forwarding-rule \
        --load-balancing-scheme EXTERNAL \
        --global \
        --target-tcp-proxy my-tcp-lb-target-proxy \
        --address tcp-lb-static-ipv6 \
        --ports 110

    Test the load balancer

    1. Get the load balancer's IP address.

      To get the IPv4 address, run the following command:

      gcloud compute addresses describe tcp-lb-static-ipv4

      To get the IPv6 address, run the following command:

      gcloud compute addresses describe tcp-lb-static-ipv6

    2. Send traffic to your load balancer by running the following command. Replace LB_IP_ADDRESS with your load balancer's IPv4 or IPv6 address.

      curl -m1 LB_IP_ADDRESS:110

      For example, if the assigned IPv6 address is [2001:db8:1:1:1:1:1:1/96]:110, the command should look like:

      curl -m1 http://[2001:db8:1:1:1:1:1:1]:110

    If you can't reach the load balancer, try the steps described under Troubleshooting your setup.

    Additional configuration options

    This section expands on the configuration example to provide alternative and additional configuration options. All of the tasks are optional. You can perform them in any order.

    PROXY protocol for retaining client connection information

    The proxy Network Load Balancer ends TCP connections from the client and creates new connections to the instances. By default, the original client IP and port information is not preserved.

    To preserve and send the original connection information to your instances, enable PROXY protocol version 1. This protocol sends an additional header that contains the source IP address, destination IP address, and port numbers to the instance as a part of the request.

    Make sure that the proxy Network Load Balancer's backend instances are running servers that support PROXY protocol headers. If the servers are not configured to support PROXY protocol headers, the backend instances return empty responses.

    If you set the PROXY protocol for user traffic, you can also set it for your health checks. If you are checking health and serving content on the same port, set the health check's --proxy-header to match your load balancer setting.

    The PROXY protocol header is typically a single line of user-readable text in the following format:

    PROXY TCP4 <client IP> <load balancing IP> <source port> <dest port>\r\n

    The following example shows a PROXY protocol:

    PROXY TCP4 192.0.2.1 198.51.100.1 15221 110\r\n

    In the preceding example, the client IP is 192.0.2.1, the load balancing IP is 198.51.100.1, the client port is 15221, and the destination port is 110.

    When the client IP is not known, the load balancer generates a PROXY protocol header in the following format:

    PROXY UNKNOWN\r\n

    Update PROXY protocol header for target proxy

    The example load balancer setup on this page shows you how to enable the PROXY protocol header while creating the proxy Network Load Balancer. Use these steps to change the PROXY protocol header for an existing target proxy.

    Console

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

      Go to Load balancing

    2. Click Edit for your load balancer.
    3. Click Frontend configuration.
    4. Change the value of the Proxy protocol field to On.
    5. Click Update to save your changes.

    gcloud

    In the following command, edit the --proxy-header field and set it to either NONE or PROXY_V1 depending on your requirement.

    gcloud compute target-tcp-proxies update TARGET_PROXY_NAME \
    --proxy-header=[NONE | PROXY_V1]

    Configure session affinity

    The example configuration creates a backend service without session affinity.

    These procedures show you how to update a backend service for the example load balancer so that the backend service uses client IP affinity or generated cookie affinity.

    When client IP affinity is enabled, the load balancer directs a particular client's requests to the same backend VM based on a hash created from the client's IP address and the load balancer's IP address (the external IP address of an external forwarding rule).

    Console

    To enable client IP session affinity:

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

      Go to Load balancing

    2. Click Backends.

    3. Click my-tcp-lb (the name of the backend service you created for this example) and click Edit.

    4. On the Backend service details page, click Advanced configuration.

    5. Under Session affinity, select Client IP from the menu.

    6. Click Update.

    gcloud

    Use the following Google Cloud CLI command to update the my-tcp-lb backend service, specifying client IP session affinity:

    gcloud compute backend-services update my-tcp-lb \
    --global \
    --session-affinity=CLIENT_IP

    API

    To set client IP session affinity, make a PATCH request to the backendServices/patch method.

    PATCH https://www.googleapis.com/compute/v1/projects/[PROJECT_ID]/global/us-west1/backendServices/my-tcp-lb
{
  "sessionAffinity": "CLIENT_IP"
}

    Enable connection draining

    You can enable connection draining on backend services to ensure minimal interruption to your users when an instance that is serving traffic is terminated, removed manually, or removed by an autoscaler. To learn more about connection draining, read the Enabling connection draining documentation.

    What's next