This article explains communication in an Azure SQL Database managed instance. It also describes connectivity architecture and how the components direct traffic to the managed instance.
The SQL Database managed instance is placed inside the Azure virtual network and the subnet that's dedicated to managed instances. This deployment provides:
•A secure private IP address.
•The ability to connect an on-premises network to a managed instance.
•The ability to connect a managed instance to a linked server or another on-premises data store.
•The ability to connect a managed instance to Azure resources.