In the process of setting up a new Hyper-V 2008 R2 server, I accidentally disabled "Host Access" to both network cards, thus killing remote access to the server (which is in my basement). Since I'm running Hyper-V Server which has no full GUI like Server Core installs, I don't have access to the normal Network Connections GUI to unbind the virtual switch protocol from the network cards.
I did some searching around the web, and all the solutions I found involve downloading some scripts or tools, and since I'm too lazy to put one of these tools on a USB drive and walk downstairs to run them, I wanted a solution that I could run from the command line remotely (as I have access to the server via Intel AMT's VNC KVM). I finally found what I was looking for on this blog post at ENIAC KB.
So, the steps are simple:
Remove the virtual switch protocol from all network adapters:
netcfg -u vms\_pp
Re-install the virtual switch protocol (which will leave it disabled by default):
netcfg -l c:\\windows\\winsxs\\amd64\_wvms\_pp.inf\_31bf3856ad364e35\_6.1.7600.16385\_none\_beda85050b13680c\\wvms\_pp.inf -c p -i vms\_pp
So if you broke remote access to your Hyper-V server under server core, and you can still get access to the CLI either through a remote KVM or at the physical console, you can uninstall the Virtual switch protocol, reboot, re-install, and continue your network configuration from VMM or the Hyper-V Console remotely.