Sometimes with Windows 7 VDI desktops, the systems lose the IP address on the NIC when they are saved, and the NIC won't get a new one when it "wakes" back up.
Run this PowerShell on your hosts to see which VDI desktops have not been able to get an IP address when they unsaved (the IP addresses will all begin with 196.254.x.x):
Get-VM | Select -ExpandProperty NetworkAdapters | Select VMName, IPAddresses, Status
This was the question at work. Can we reboot certain servers without really effecting currently connected users? There are two roles you can do this with:
RD Connection Broker & RD Licensing Server
If you reboot the RD Gateway/RD Web Access Server (which are on the same system in our lab setup) it will disconnect any active sessions on the VDI environment.