Hi,
The error message you mentioned indicates that you need to upgrade all instances of your Virtual Machine Scale Set (VMSS) in order to apply the changes related to the addition of the backend pool to the load balancer.
In a VMSS, each instance is a replica of the same virtual machine, and changes to the configuration or setup of the instances usually require upgrading them. The upgrade process ensures that all instances have the same configuration and are in sync with the desired state.
Since you mentioned that you have created the VMSS with the flexible orchestration mode, which doesn't support the upgrade policy, you'll need to manually upgrade the instances to apply the changes.
Here are the steps to upgrade the instances in your VMSS:
Identify the name of your VMSS: In the error message, 'vmssname' refers to the name of your VMSS. Replace it with the actual name of your VMSS in the following steps.
Upgrade the instances: You can upgrade all the instances in the VMSS by running the following Azure CLI command:
az vmss update-instances --name vmssname --instance-ids '*' --resource-group yourResourceGroup
Monitor the upgrade progress: az vmss list-instances --name vmssname --resource-group yourResourceGroup --output table
Regards,
Karthik Srinivas