We worked on a service request where our customer faced the following error message: Cannot perform creation/scaling of the managed instance as there are not enough available IP addresses in the subnet for performing the operation. For more details visit 'https://aka.ms/determine-subnet-size' and error code: ManagedInstanceIpAddressRangeLimit, deploying a managed instance.
As you know Azure SQL Managed Instance must be deployed within an Azure virtual network and the number of managed instances that can be deployed in the subnet of a virtual network depends on the size of the subnet (subnet range). Determine required subnet size & range - Azure SQL Managed Instance | Microsoft Learn
When you create a managed instance, Azure allocates a number of virtual machines that depend on the tier you selected during provisioning. Because these virtual machines are associated with your subnet, they require IP addresses. To ensure high availability during regular operations and service maintenance, Azure might allocate more virtual machines. The number of required IP addresses in a subnet then becomes larger than the number of managed instances in that subnet.
By design, a managed instance needs a minimum of 32 IP addresses in a subnet. As a result, you can use a minimum subnet mask of /27 when defining your subnet IP ranges. We recommend careful planning of subnet size for your managed instance deployments. Consider the following inputs during planning:
- Number of managed instances, including the following instance parameters:
- Service tier
- Number of vCores
- Hardware configuration
- Maintenance window
- Plans to scale up/down or change the service tier, hardware configuration, or maintenance window
As solution the Azure SQL Managed Instance was recreated to a different Subnet.
Enjoy!
