# Ensure Managed Instance Group is Attached to a Load Balancer

- Source: https://support.icompaas.com/support/solutions/articles/a_1788888298683252-ensure-managed-instance-group-is-attached-to-a-load-balancer
- Section: [Solutions](https://support.icompaas.com/support/solutions) › [GCP Benchmarks](https://support.icompaas.com/support/solutions/62000112667) › [GCP Knowledge Bases](https://support.icompaas.com/support/solutions/folders/62000169178)
- Last updated: 2026-09-08
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**Description**

Ensure that Managed Instance Groups (MIGs) serving application traffic are attached to a backend service used by a load balancer, so that traffic is distributed across healthy instances and requests are not routed to a single instance directly.

**Rationale**

A Managed Instance Group that is not attached to a load balancer does not benefit from health-check-based traffic distribution, meaning traffic may continue to be directed at an unhealthy or overloaded instance, or clients may need to target instances individually. Attaching the group to a load balancer's backend service enables even traffic distribution, automatic exclusion of unhealthy instances from serving traffic, and supports scaling the group without reconfiguring clients.

**Impact**

-   Distributes incoming traffic evenly across healthy instances in the group
    
-   Automatically stops routing traffic to instances that fail load balancer health checks
    
-   Enables the group to scale without requiring changes to how clients connect
    

**Default Value**

By default, a newly created Managed Instance Group is not attached to any load balancer backend service; this must be configured explicitly.

**Pre-Requisites**

-   A configured load balancer (HTTP(S), TCP/SSL Proxy, or Network Load Balancer) with a backend service
    
-   A health check appropriate for the load balancer type
    
-   IAM permissions to edit load balancing and instance group configuration (e.g., Compute Load Balancer Admin, Compute Instance Admin)
    

**Test Plan**

1.  Sign in to the Google Cloud Console at [https://console.cloud.google.com](https://console.cloud.google.com/).
    
2.  Select the relevant project.
    
3.  Navigate to Network services > Load balancing and review the backend services configured.
    
4.  Confirm that the Managed Instance Group in question appears as a backend in the relevant backend service.
    
5.  Navigate to Compute Engine > Instance groups and confirm the group shows an associated load balancer usage indicator.
    
6.  If the group serving application traffic is not attached to a backend service, follow the implementation steps.
    

**Implementation Steps**

1.  Sign in to the Google Cloud Console at [https://console.cloud.google.com](https://console.cloud.google.com/).
    
2.  Navigate to Network services > Load balancing and create or edit the appropriate load balancer for the workload's traffic type.
    
3.  In the backend configuration, select Create/Add backend and choose the Managed Instance Group.
    
4.  Select the appropriate port name/number and attach a health check.
    
5.  Complete and save the load balancer / backend service configuration.
    
6.  Verify in Compute Engine > Instance groups that the group now shows as attached to the load balancer, and confirm instances are reporting healthy in the backend service.
    

**Backout Plan**

1.  Sign in to the Google Cloud Console at [https://console.cloud.google.com](https://console.cloud.google.com/).
    
2.  Navigate to Network services > Load balancing and select the relevant backend service.
    
3.  Remove the Managed Instance Group from the backend configuration.
    
4.  Save the change.
    

**Reference**

-   [https://cloud.google.com/load-balancing/docs/backend-service](https://cloud.google.com/load-balancing/docs/backend-service)

## Related compliance guidance

- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them.
- [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.