Basic Load Balancer Migration

Question

Hi,

I have two Windows 2022 VMs, running Exchange services in Azure, currently using two Basic Load Balancers—one internal and the other one external. As the Basic Load Balancer will be out of support starting September 30, 2025, and needs to be migrated to a Standard Load Balancer, could you please provide detailed steps and best practices for this migration? Specifically, I would like to know:

What steps should I take before the migration?

What is the expected impact on the Exchange VMs during the migration?

What are the best practices for creating a rollback plan in case the migration doesn't go as expected?

Which load balancer to migrate first (internal or external)?

Thank you

Answer 1

Hi @Ramona Istrate,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

I understand that you want to migrate Basic Load Balancer to Standard Load Balancer.

Refer this link to migrate Basic Load Balancer to Standard Load Balancer: https://learn.microsoft.com/en-us/azure/load-balancer/upgrade-basic-standard-with-powershell

To Answer your questions.

What steps should I take before the migration?

• Validate support for your scenario
• Plan for application downtime during migration
• Develop inbound and outbound connectivity tests for your traffic
• Plan for instance-level Public IP changes on Virtual Machine Scale Set instances (see note)
• [Recommended] Create Network Security Groups or add security rules to an existing Network Security Group for your backend pool members. Allow the traffic through the Load Balancer along with any other traffic to be explicitly allowed on public Standard SKU resources
• [Recommended] Prepare your outbound connectivity, taking one of the following approaches described in How should I configure outbound traffic for my Load Balancer?

What is the expected impact on the Exchange VMs during the migration?

There will be a short period of downtime for the services relying on the load balancer, typically lasting a few minutes. During this time, the VMs may experience a temporary loss of connectivity.

What are the best practices for creating a rollback plan in case the migration doesn't go as expected?

1. Address the cause of the migration failure. Check the log file Start-AzBasicLoadBalancerUpgrade.log for details
2. Remove the new Standard Load Balancer (if created). Depending on which stage of the migration failed, you can have to remove the Standard Load Balancer reference from the Virtual Machine Scale Set, Virtual Machine network interfaces (IP configurations), and/or Health Probes to remove the Standard Load Balancer.
3. Locate the Basic Load Balancer state backup file. This file is in the directory where the script was executed, or at the path specified with the -RecoveryBackupPath parameter during the failed execution. The file is named: State_<basicLBName>_<basicLBRGName>_<timestamp>.json
4. Rerun the migration script, specifying the -FailedMigrationRetryFilePathLB <BasicLoadBalancerbackupFilePath> and -FailedMigrationRetryFilePathVMSS <VMSSBackupFile> (for Virtual Machine Scale set backends) parameters instead of -BasicLoadBalancerName or passing the Basic Load Balancer over the pipeline

Which load balancer to migrate first (internal or external)?

I'd preferred you start with internal load balancer.

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Regards,

Rohith