How do you determine which DC is used in an isolated network and/or a virtualization lab where all DCs are not available?

I'm setting up a virtualization lab for disaster recovery testing, and I'm running into a problem by only having 1 of my 5 domain controllers available within this lab. This issue also seems like it would present itself if I lost one of my subnets that contains 3 out of my 5 domain controllers. Let me briefly describe my virtualization lab. I'm using a single VMware ESX server that runs 4 VMs which correspond to my 4 most important servers - SQL server, Backup Exec sever, IIS/web server, and domain controller. The core issue here is that with the exception of the domain controller, none of my other VM servers can see my domain. So when I try to log into the severs with a privileged domain user, I keep getting a message that the domain is not available. It appears that all of these servers are trying to authenticate with one of the 4 other DCs that I did not virtualize. I also realized that I did not virtualize a DNS server, but I've used the host file to create entries for basic name resolution and I can ping between all of the severs using computer names. What can I change so that all of my VMs can see my 1 domain controller and authenticate? I don't have the option of disjoining the domain or creating a new one because these VMs need to be able to run as my production servers in the event of a real disaster so they have to be a part of the same domain the rest of my organization uses. However, during my testing I need them to be able to operate with my single virtualized domain controller. This issue also makes me wonder whether I would experience similar authentication issues if my primary subnet/site is lost and I only have 2 out of 5 remaining DCs available at my secondary subnet/site. What happens to those workstations that need to authenticate on the 3 unanavailable DCs?