Explanation:
Box 1: /26
To minimize the number of IP addresses used by an Azure Bastion subnet, configure it with the smallest allowed subnet size, which is /26 (or larger, like /25 or /24). This provides the minimum necessary IP addresses while still allowing for Bastion's scaling requirements.
Box 2: AzureBastionSubnet
Creating the AzureBastionSubnet:
When creating the subnet for Azure Bastion, name it AzureBastionSubnet.
Assign it a CIDR block of /26 (or larger, like /25 or /24).
Ensure this subnet is within the virtual network's address space.
For example, if your VNet has the address space 10.1.0.0/16, you could assign AzureBastionSubnet as 10.1.1.0/26.
Reference:
https://learn.microsoft.com/en-us/azure/bastion/configuration-settings