>>>Bit of a long shot but anyone know how to redirect a USB port from one OS to another with VFP? I guess the communication between them would probably be done via a named pipe.
>>>
>>>In this case what I actually want to do is USB passthrough from a Server 2012 R2 hyper-V host to a win XP virtual machine.
>>
>>Maybe: http://www.msserverpro.com/support-for-usb-access-in-windows-server-2012-r2-hyper-v-through-microsofts-new-virtual-machine-enhanced-session-mode/
>
>Thanks for the suggestion Al but I have investigated that and it only works via a RDP connection not a proper network connection. Also only supports use of Windows 8 and above. My problem is that the virtual machine needs to be XP (which this type of connection does not support) because we want to run NTBackup to backup to tape.

Just to be clear, you want to run NTBackup on the XP VM using an external device as the target. You say "tape" above but I assume you mean an external USB hard drive (?)

You might want to consider a couple of alternatives to getting direct host hardware access:

1. Windows Server Backup - I don't know about bare-metal Hyper-V, but if you're running Hyper-V as a role on a conventional Server 2012 R2 host, Server Backup is available. It can back up running VMs with the caveat it may take them off-line for a bit while doing so.

2. There are 3rd-party utilities available that run on the host and can back up running VMs. One client of mine is using Altaro. Its main selling points for us are that it can back up running VMs without taking them off-line, and that it uses reverse-delta incremental backup technology so that the most recent backup can be quickly restored. Pricing is reasonable: http://www.altaro.com/hyper-v-backup/pricing.php . It has been reliable and slick for us. We back up from the host to a NAS but you can definitely back up to a directly attached USB hard drive.

In general, the idea with VMMs like Hyper-V is to isolate the VMs from access to the host hardware. This is especially important with networking. If you set up a host that has only one physical Ethernet connection then by default the host and VMs are on the same subnet but that's bad from a security POV. Far better is to have 2 (or more) physical Ethernet adapters; the host on one subnet (so-called "out of band") and the VMs on a virtual switch connected to the other(s), on a different subnet. If you're currently using the latter, preferred configuration it's a bad idea to try to go back to a shared subnet configuration.

If you Google [hyper-v usb passthrough] there are some links to 3rd-party products and some hacks in earlier versions of Hyper-V. I haven't used any of them but in general, if you're looking for backup, I wouldn't go that route. Windows Server Backup or something like Altaro would be the way to go.