Which outbound connectivity must be allowed from Azure Virtual Desktop clients to establish connections to session hosts?

To establish connections from Azure Virtual Desktop clients to session hosts, allowing outbound connectivity on TCP 443 is essential. TCP 443 is primarily used for secure web traffic, employing HTTPS. Azure Virtual Desktop utilizes this protocol for various management and authentication tasks, ensuring that communication between clients and session hosts is secured and reliable.

When a user attempts to connect to an Azure Virtual Desktop session host, the initial connection and subsequent communications typically occur over HTTPS. This includes authentication processes, session establishment, and management functions. Therefore, it’s crucial for clients to have unrestricted outbound access to TCP port 443 to facilitate these operations smoothly and securely.

The other options relate to different protocols and ports that serve specific purposes. For example, while TCP 3389 is the default port for RDP (Remote Desktop Protocol) connections, it is primarily used for direct RDP connections rather than the initial management and authentication handshakes that occur over HTTPS. Similarly, while UDP can enhance performance for certain applications, especially in multimedia scenarios, it does not play the same role in secure management connections as TCP does in this context. Hence, TCP 443 is the definitive choice required for establishing a proper connection between clients and session hosts in Azure Virtual Desktop.