Set up an external passthrough Network Load Balancer with a backend service

Console

To support both IPv4 and IPv6 traffic, use the following steps:

1. In the Google Cloud console, go to the VPC networkspage.

   Go to VPC networks

2. Click Create VPC network.

3. Enter a Nameof lb-network .

4. In the Subnetssection:

   • Set the Subnet creation modeto Custom.
   • In the New subnetsection, configure the following fields and click Done:
     • Name: lb-subnet
     • Region: us-central1
     • IP stack type: IPv4 and IPv6 (dual-stack)
     • IPv4 range: 10.1.2.0/24
       Although you can configure an IPv4 range of addresses for the subnet, you cannot choose the range of the IPv6 addresses for the subnet. Google provides a fixed size (/64) IPv6 CIDR block.
     • IPv6 access type: External

5. Click Create.

To support IPv4 traffic only, use the following steps:

1. In the Google Cloud console, go to the VPC networkspage.

   Go to VPC networks

2. Click Create VPC network.

3. Enter a Nameof lb-network .

4. In the Subnetssection:

   • Set the Subnet creation modeto Custom.
   • In the New subnetsection, configure the following fields and click Done:
     • Name: lb-subnet
     • Region: us-central1
     • IP stack type: IPv4 (single-stack)
     • IPv4 range: 10.1.2.0/24

5. Click Create.

gcloud

1. Create the custom mode VPC network:

   gcloud compute networks create lb-network \
       --subnet-mode=custom

2. Within the lb-network network, create a subnet for backends in the us-central1 region.

   For both IPv4 and IPv6 traffic, use the following command to create a dual-stack subnet:

   gcloud compute networks subnets create lb-subnet \
     --stack-type=IPV4_IPv6 \
     --ipv6-access-type=EXTERNAL \
     --network=lb-network \
     --range=10.1.2.0/24 \
     --region=us-central1

   For IPv4 traffic only, use the following command:

   gcloud compute networks subnets create lb-subnet \
     --network=lb-network \
     --range=10.1.2.0/24 \
     --region=us-central1

Console

1. Create an instance template. In the Google Cloud console, go to the Instance templatespage.

   Go to Instance templates

   1. Click Create instance template.
   2. For Name, enter ig-us-template .
   3. In the Boot disksection, ensure that the Imageis set to a Debian image, such as Debian GNU/Linux 12 (bookworm). These instructions use commands that are only available on Debian, such as apt-get .
   4. Click Advanced options.
   5. Click Networking.
      1. For Network tags, enter lb-tag .
      2. For Network interfaces, click the defaultinterface and configure the following fields:
         • Network: lb-network
         • Subnetwork: lb-subnet
      3. Click Done.

   6. Click Managementand copy the following script into the Startup scriptfield.

      #! /bin/bash
      apt-get update
      apt-get install apache2 -y
      a2ensite default-ssl
      a2enmod ssl
      vm_hostname="$(curl -H "Metadata-Flavor:Google" \
      http://metadata.google.internal/computeMetadata/v1/instance/name)"
      echo "Page served from: $vm_hostname" | \
      tee /var/www/html/index.html
      systemctl restart apache2

   7. Click Create.

2. Create a managed instance group. In the Google Cloud console, go to the Instance groupspage.

   Go to Instance groups

   1. Click Create instance group.
   2. Select New managed instance group (stateless). For more information, see Stateless or stateful MIGs .
   3. For Name, enter ig-us-1 .
   4. For Instance template, select ig-us-template .
   5. For Location, select Single zone.
   6. For Region, select us-central1 .
   7. For Zone, select us-central1-a .

   8. Specify the number of instances that you want to create in the group.

      For this example, specify the following options in the Autoscalingsection:

      • For Autoscaling mode, select Off:do not autoscale .
      • For Maximum number of instances, enter 2 .

   9. Click Create.

3. Repeat the previous steps to create a second managed instance group in the us-central1-c zone with the following specifications:

   • Name: ig-us-2
   • Zone: us-central1-c
   • Instance template: Use the same ig-us-template template created in the previous section.

gcloud

The gcloud instructions in this guide assume that you are using Cloud Shell or another environment with bash installed.

1. Create a VM instance template with HTTP server with the gcloud compute instance-templates create command.

   To handle both IPv4 and IPv6 traffic, use the following command.

   gcloud compute instance-templates create ig-us-template \
   --region=us-central1 \
   --network=lb-network \
   --subnet=lb-subnet \ --ipv6-network-tier=PREMIUM \ 
    --stack-type=IPv4_IPv6 \ 
   --tags=lb-tag \
   --image-family=debian-12 \
   --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" \
     http://metadata.google.internal/computeMetadata/v1/instance/name)"
     echo "Page served from: $vm_hostname" | \
     tee /var/www/html/index.html
     systemctl restart apache2'

   To handle IPv4 traffic onlytraffic, use the following command.

   gcloud compute instance-templates create ig-us-template \
   --region=us-central1 \
   --network=lb-network \
   --subnet=lb-subnet \
   --tags=lb-tag \
   --image-family=debian-12 \
   --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" \
     http://metadata.google.internal/computeMetadata/v1/instance/name)"
     echo "Page served from: $vm_hostname" | \
     tee /var/www/html/index.html
     systemctl restart apache2'

2. Create a managed instance group in the zone with the gcloud compute instance-groups managed create command.

   gcloud compute instance-groups managed create ig-us-1 \
       --zone us-central1-a \
       --size 2 \
       --template ig-us-template

3. Create a second managed instance group in the us-central1-c zone:

   gcloud compute instance-groups managed create ig-us-2 \
       --zone us-central1-c \
       --size 2 \
       --template ig-us-template

Console

1. In the Google Cloud console, go to the Firewall policiespage.

   Go to Firewall policies

2. To allow IPv4 traffic, perform the following steps:

   1. Click Create firewall rule.
   2. For Name, enter allow-network-lb-ipv4 .
   3. In the Networklist, select lb-network .
   4. For Targets, select Specified target tags.
   5. In the Target tagsfield, enter lb-tag .
   6. For Source filter, select IPv4 ranges.
   7. Set the Source IPv4 rangesto 0.0.0.0/0 . This allows IPv4 traffic from any source. This also allows Google's health check probes to reach the backend instances.
   8. For Specified protocols and ports, select the TCPcheckbox and enter 80 .
   9. Click Create. It might take a moment for the Google Cloud console to display the new firewall rule, or you might have to click Refreshto see the rule.

3. To allow IPv6 traffic, perform the following steps:

   1. Click Create firewall ruleagain.
   2. For Name, enter allow-network-lb-ipv6 .
   3. In the Networklist, select lb-network .
   4. For Targets, select Specified target tags.
   5. In the Target tagsfield, enter lb-tag .
   6. For Source filter, select IPv6 ranges.
   7. Set the Source IPv6 rangesto ::/0 . This allows IPv6 traffic from any source. This also allows Google's health check probes to reach the backend instances.
   8. For Specified protocols and ports, select the TCPcheckbox and enter 80 .
   9. Click Create. It might take a moment for the Console to display the new firewall rule, or you might have to click Refreshto see the rule.

gcloud

1. To allow IPv4 traffic, run the following command:

   gcloud compute firewall-rules create allow-network-lb-ipv4 \
       --network=lb-network \
       --target-tags=lb-tag \
       --allow=tcp:80 \
       --source-ranges=0.0.0.0/0

2. To allow IPv6 traffic, run the following command:

   gcloud compute firewall-rules create allow-network-lb-ipv6 \
     --network=lb-network \
     --target-tags=lb-tag \
     --allow=tcp:80 \
     --source-ranges=::/0

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 Passthrough load balancer and click Next .
5. For Public facing or internal , select Public facing (external) and click Next .
6. Click Configure .

Backend configuration

1. On the Create external passthrough Network Load Balancerpage, enter the name tcp-network-lb for the new load balancer.
2. For Region, select us-central1 .
3. Click Backend configuration.
4. On the Backend configurationpage, make the following changes:
   1. For New Backend, select the IP stack type. If you created dual-stack backends to handle both IPv4 and IPv6 traffic, select IPv4 and IPv6 (dual-stack). To handle IPv4 traffic only, select IPv4(single-stack).
   2. In the Instance grouplist, select ig-us-1 , and then click Done.
   3. Click Add a backendand repeat this step to add ig-us-2 .
   4. For Health check, click Create a health checkor Create another health check, and then enter the following information:
      • Name: tcp-health-check
      • Protocol: TCP
      • Port: 80
   5. Click Save.
5. Verify that there is a blue checkmark next to Backend configurationbefore continuing.

Frontend configuration

1. Click Frontend configuration.
2. For Name, enter network-lb-forwarding-rule .
3. To handle IPv4 traffic, use the following steps:
   1. For IP version, select IPv4.
   2. In the Internal IP purposesection, in the IP addresslist, select Create IP address.
      1. On the Reserve a new static IP addresspage, for Name, enter network-lb-ipv4 .
      2. Click Reserve.
   3. For Ports, choose Single. For Port number, enter 80 .
   4. Click Done.

4. To handle IPv6 traffic, use the following steps:

   1. For IP version, select IPv6.
   2. For Subnetwork, select lb-subnet.
   3. In the IPv6 rangelist, select Create IP address.
      1. On the Reserve a new static IP addresspage, for Name, enter network-lb-ipv6 .
      2. Click Reserve.
   4. For Ports, select Single. For Port number, enter 80 .
   5. Click Done.

   A blue circle with a checkmark to the left of Frontend configurationindicates a successful setup.

Review the configuration

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

4. Click Create.

   On the load balancing page, under the Backend column for your new load balancer, you should see a green checkmark showing that the new load balancer is healthy.

gcloud

1. Reserve a static external IP address.

   For IPv4 traffic:Create a static external IPv4 address for your load balancer.

   gcloud compute addresses create network-lb-ipv4 \
       --region us-central1

   For IPv6 traffic:Create a static external IPv6 address range for your load balancer. The subnet used must be a dual-stack subnet with an external IPv6 range.

   gcloud compute addresses create network-lb-ipv6 \
       --region us-central1 \
       --subnet lb-subnet \
       --ip-version IPV6 \
       --endpoint-type NETLB

2. Create a TCP health check.

   gcloud compute health-checks create tcp tcp-health-check \
       --region us-central1 \
       --port 80

3. Create a backend service .

   gcloud compute backend-services create network-lb-backend-service \
       --protocol TCP \
       --health-checks tcp-health-check \
       --health-checks-region us-central1 \
       --region us-central1

4. Add the instance groups to the backend service.

   gcloud compute backend-services add-backend network-lb-backend-service \
   --instance-group ig-us-1 \
   --instance-group-zone us-central1-a \
   --region us-central1

   gcloud compute backend-services add-backend network-lb-backend-service \
   --instance-group ig-us-2 \
   --instance-group-zone us-central1-c \
   --region us-central1

5. Create the forwarding rules depending on whether you want to handle IPv4 traffic or IPv6 traffic. Create both forwarding rules to handle both types of traffic.

   1. For IPv4 traffic:Create a forwarding rule to route incoming TCP traffic to the backend service. Use the IPv4 address reserved in step 1 as the static external IP address of the load balancer.

      gcloud compute forwarding-rules create network-lb-forwarding-rule-ipv4 \
        --load-balancing-scheme EXTERNAL \
        --region us-central1 \
        --ports 80 \
        --address network-lb-ipv4 \
        --backend-service network-lb-backend-service

   2. For IPv6 traffic:Create a forwarding rule to handle IPv6 traffic. Use the IPv6 address range reserved in step 1 as the static external IP address of the load balancer. The subnet used must be a dual-stack subnet with an external IPv6 subnet range.

      gcloud compute forwarding-rules create network-lb-forwarding-rule-ipv6 \
          --load-balancing-scheme EXTERNAL \
          --region us-central1 \
          --network-tier PREMIUM \
          --ip-version IPV6 \
          --subnet lb-subnet \
          --address network-lb-ipv6 \
          --ports 80 \
          --backend-service network-lb-backend-service

Console

1. On the Load balancing componentspage, go to the Forwarding rulestab.

   Go to Forwarding rules

2. Locate the forwarding rule used by the load balancer.

3. In the External IP addresscolumn, note the external IP address listed.

gcloud: IPv4

Enter the following command to view the external IPv4 address of the network-lb-forwarding-rule forwarding rule used by the load balancer.

gcloud compute forwarding-rules describe network-lb-forwarding-rule-ipv4 \
    --region us-central1

gcloud: IPv6

Enter the following command to view the external IPv6 address of the network-lb-forwarding-rule forwarding rule used by the load balancer.

gcloud compute forwarding-rules describe network-lb-forwarding-rule-ipv6 \
    --region us-central1

Console

1. In the Google Cloud console, go to the Load balancingpage.

   Go to Load balancing

2. In the Load balancerstab, click the name of the backend service, and then click Edit.

3. On the Edit external passthrough Network Load Balancerpage, click Backend configuration.

4. Select an option from the Session affinitylist.

5. Click Update.

gcloud

Use the following gcloud command to update session affinity for the backend service:

gcloud compute backend-services update BACKEND_SERVICE 
\
    --region= REGION 
\
    --session-affinity= SESSION_AFFINITY_OPTION 

Replace the placeholders with valid values:

• BACKEND_SERVICE : the backend service that you're updating

• SESSION_AFFINITY_OPTION : the session affinity option that you want to set

  For the list of supported values for an external passthrough Network Load Balancer, see Session affinity options .

gcloud

Use the following gcloud compute backend-services command to update the connection tracking policy for the backend service:

gcloud compute backend-services update BACKEND_SERVICE 
\
    --region= REGION 
\
    --tracking-mode= TRACKING_MODE 
\
    --connection-persistence-on-unhealthy-backends= CONNECTION_PERSISTENCE_BEHAVIOR 

Replace the placeholders with valid values:

• BACKEND_SERVICE : the backend service that you're updating
• TRACKING_MODE : the connection tracking mode to be used for incoming packets. For the list of supported values, see Tracking mode .
• CONNECTION_PERSISTENCE_BEHAVIOR : the connection persistence behavior when backends are unhealthy. For the list of supported values, see Connection persistence on unhealthy backends .

gcloud

Use the following command to create a steering forwarding rule that points to a backend service:

gcloud compute forwarding-rules create STEERING_FORWARDING_RULE_BS 
\
    --load-balancing-scheme=EXTERNAL \
    --backend-service= BACKEND_SERVICE 
\
    --address= LOAD_BALANCER_VIP 
\
    --ip-protocol= IP_PROTOCOL 
\
    --ports= PORTS 
\
    --region= REGION 
\
    --source-ip-ranges= SOURCE_IP_ADDRESS_RANGES 

Use the following command to create a steering forwarding rule that points to a target instance:

gcloud compute forwarding-rules create STEERING_FORWARDING_RULE_TI 
\
    --load-balancing-scheme=EXTERNAL \
    --target-instance= TARGET_INSTANCE 
\
    --address= LOAD_BALANCER_VIP 
\
    --ip-protocol= IP_PROTOCOL 
\
    --ports= PORTS 
\
    --region= REGION 
\
    --source-ip-ranges= SOURCE_IP_ADDRESS_RANGES 

Replace the placeholders with valid values:

• FORWARDING_RULE : the name of the steering forwarding rule that you're creating.
• BACKEND_SERVICE or TARGET_INSTANCE : the name of the backend service or target instance to which this steering forwarding rule will send traffic. Even if the parent forwarding rule points to a backend service, you can create steering forwarding rules that point to target instances.
• LOAD_BALANCER_VIP , IP_PROTOCOL , PORTS : the IP address, IP protocol, and ports, respectively, for the steering forwarding rule that you're creating. These settings should match a pre-existing base forwarding rule.
• REGION : the region of the forwarding rule that you're creating.
• SOURCE_IP_ADDRESS_RANGES : comma-separated list of IP addresses or IP address ranges. This forwarding rule will only forward traffic when the source IP address of the incoming packet falls into one of the IP ranges set here.