Can a Hyper-V guest operating system access a USB device connected to the Hyper-V host?
If so, how can I set this up?
Hyper-V specifically does not allow this. At all. (At least as of Server 2012 R2). The best work-around I've seen is to look for third party software that supports sending usb datagrams over a network connection. There will be an app installed on the host to make the usb device available, and an app installed on the guest that connects to the host and creates a "virtual" usb device in the guest operating system.
I have had luck doing this specifically with a security dongle that a certain software package required be attached. The usb network software we used was from a company called Fabula Tech. Even better, this system can work with any set of machines on the network, so the usb host not need be located on the same machine as the virtual machine guest.
In researching this, I also found small embedded devices with a LAN connection and as many as 10 usb ports, in one case even designed to mount in a rack. The idea was that for shops running systems where a virtual machine may move around to different physical hosts, you weren't tied to keeping your guest on a specific physical box any more just because it needs access to a specific physical usb device, and your physical usb devices weren't tied to machine with a small upgrade cycle and service windows. Then the usb host device itself could be viewed more like an appliance or as part of the cable plant.
Hyper-V will not provide access to the host machine's USB ports. This may change in Windows 8, which, it is rumored, may use Hyper-V as a foundational technology even for client versions of the OS.
Instead of using the host machine's USB ports, a far better approach would be to buy a network-attached USB device, like an AnywhereUSB hub or something cheaper and then install special USB-over-IP drivers on the guest machine. One key advantage of this approach is that you can migrate the virtual machine to another Hyper-V server without worrying about where theUSB devices actually reside in the physical world.
Note that USB 2.0 speeds are not currently when emulating USB over an IP network, possibly due to latency issues. Basically, it works great for product licensing/security dongles and other low-bandwidth devices. Your results may be disappointing if you try to mount a hard drive or a printer. These are higher-bandwidth devices that should be shared from a physical computer using SMB (Windows File and Printer Sharing) instead.
Yes, you can, though only starting in Windows Server 2008 R2 SP1, with the Remote Desktop Virtualization roll applied. With this in place, and by setting Group Policy to allow it, you can remote USB over a "terminal services" or "remote desktop" connection to the VM. See the following link for configuration:
This will allow you to redirect the USB device (from the machine at which you sit) to the VM (which may be on the same machine) for as long as you have a remote desktop connection.