Machine creation fails with backend pool error in Azure

    Machine creation fails with with below error when trying to replace master nodes with a controlplanemachineset.

Original Error: Code="CannotMixIPBasedAddressesAndIPConfigurationsOnLoadBalancerBackendAddressPool" Message="Mixing backend ipconfigurations and IPAddresses in backend pool /subscriptions/<subscription_id>/resourceGroups/<resource_group_name>/providers/Microsoft.Network/loadBalancers/<infra_id_of_cluster>-internal/backendAddressPools/<backend_pool_name> is not allowed."

There are 3 backend pools for the internal load balancer in the customer environment and it seems that the machine is picking the backend pool which comes first alphabetically. The actual backend pool which should be used, has the cluster infra id in it's name.

4.13    

    Reproducible in customer environment

    1. Have multiple backend pools craeted for the internal load balancer.
    2. The backend pool created by the cluster installer should be lower alphabetically than the other backend pools.
    3. Create a controlplancemachineset and make some config change to recreate the master nodes.
    4. The machine creation fails with the said error.
    

    Machine creation fails

    Machine should be created using the backend pool which was created by the installer