I had a Hyper V host that wouldn't boot, but I had some backups of the VMs on another machine that I fired up. Two of the VMs are DCs, one is the DHCP server and the other the DFS root. Once the backup VMs booted, I was able to ping both of them. Things seemed normal until I realized that users were not getting DHCP. I tried clearing the arp cache on our switches, thinking that those machines couldn't find the DHCP server, but that didn't work. I even reset one workstation's NICs, but that didn't work either. Nothing I tried would cause the machine to get an IP assigned. Only after I assigned a manual IP did that workstation seem to be back to normal.
I also noticed that some of our DFS mapped drives didn't work either, even though the DFS root was up and running and I could ping it.
In the meantime, I was able to get the original Hyper V host up and running again, so I shut down the backup VMs and started up the original VMs. DHCP and DFS started working immediately! Can someone help me understand why this happened, why the backup VM wouldn't hand out DHCP requests? Or why the DFS root didn't seem to work either? It's kind of useless to have backup VMs if they won't do the jobs they're supposed to...
I am fully up and running with all the original Hyper V host and VMs once more, so the fire has been put out for now. But, I'm worried that the next time I actually need those backup VMs to work that I'll be in the same situation once more. Help?