Hyper-V USB Passthrough to RDP Client in Enhanced Session Mode

It’s no secret for active Microsoft hypervisor users that setting up Hyper-V USB passthrough is a good alternative way of accessing local resources from the guest operating systems. Some even say that when it comes to redirecting USB over Ethernet, Hyper-V server is much easier to use than a VMware ESX one, largely due to its enhanced session mode.

What is Enhanced Session Mode in Hyper-V

Technically speaking, it’s a special mode created to link the VMConnect.exe application with the host machine's VMBus component. Simply put, when you turn on the Enhanced Session Mode, all local devices like USB dongle keys, SCSI controllers, etc., become instantly accessible from your guest OS through the console connection. The same thing is also true for USB redirection over Ethernet. You’ll be able to access not only the devices attached to the host but the ones connected to other PCs in your network too.

This feature of enhanced session mode can be instrumental in many various scenarios where a VM needs to interact with local resources but may not be able to achieve network connectivity.

Here are some examples:

• Printing: you can send files directly from a VM to local printers.
• Authentication: log into a VM with your smart card using a local USB card reader or a USB dongle.
• Debugging: fix any VM-related issues even with no network connection.

On top of that, Hyper-V USB passthrough is widely used by software and hardware developers, especially the ones focused on products for Windows users. The enhanced session mode makes testing and debugging USB applications from within a VM much faster and easier.

How to enable Enhanced Session Mode in Hyper-V

Much unlike a VMware workstation, a Windows Hyper-V won’t require you to download any additional libraries or components to enable the enhanced session mode. All you need to do is make some minor changes to your Hyper-V configuration. Here is a quick guide:

1. Open the Hyper-V Manager (typically found in C:\Windows\System32) and select the Hyper-V server you want to enable the enhanced session mode for.
   Then click Hyper-V Settings:
   
2. Tick the ‘Allow enhanced session mode’ checkbox to enable server settings in the Enhanced Session Mode Policy. Please note that these settings will be used for all VMs running under the Hyper-V host. Enabling the Allow enhanced session mode setting determines if the guest VMs will be able to use enhanced sessions.
   
3. When enabled, enhanced session mode connections will be allowed by Hyper-V but only on certain conditions.

If you need to set up a USB passthrough on a Linux machine, enable the enhanced session mode or use a specifically designed USB redirector, e.g., USB Network Gate. Unlike the native method, UNG has no limitations when it comes to the device type, brand, shape, or form. You won’t have to suffer through endless lags using redirected PnP devices and will be able to pass through a USB hub with a less fiddly set-up process compared to features embedded into MS Hyper-V.

The list of requirements to work in Enhanced Session mode

✓ The OS of the virtual machine supports enhanced session mode.

✓ The VM is running Remote Desktop Service.

✓ The Virtual Machine Connection tools requested an enhanced session mode connection.

Enhanced session mode is used to configure user settings. Enabling this setting allows the Virtual Machine Connection tool to use enhanced session mode if it is available in the guest VM. Hence, the user automatically gains access to local peripherals without any additional USB redirector tools.

To use the enhanced session mode, your set-up must meet these conditions:

• The OS of the guest VM supports enhanced session mode.
• Remote Desktop Service is running on the guest.
• Allow enhanced session mode is enabled on the Hyper-V host.

When you disable the enhanced session mode setting, it forces the Virtual Machine Connection tool to use the methods previously seen in pre-R2 Hyper-V releases.