The environment is one single domain, four (4) Server 2008 domain controllers, two sites, DHCP everywhere!
Site 1 has the FSMO role holder DC in it and DHCP is running on that server issuing IPs on the high side of our subnet. It's an 80/20 split for the most part. The second DC in site one has DHCP running and it's issuing IPs on the low side of the subnet.
Site two is set up the same. One DC issuing IPs on the high range and one issuing IPs on the low range.
So, all four existing DCs run server 2008 STD and all four are DHCP servers. UGH! Who thinks this stuff up?
My job is to bring online four new 2012 R2 domain controllers to replace these four older servers. I would like to use DHCP failover, instead of this high/low thing they have going on. The problem is how to do that.
How is the best way to do this? THAT is my question.
Option 1 is to bring up one new DC at a time and do a one to one swap. Turn off DHCP on server 1, back it up and restore it to its replacement and start DHCP on the new server. That way I get my current leases, and stand the least likely chance of problems. Of course, when I'm done, I still have four DCs with DHCP and the whole high/low scope going on, but I could deal with that as a new problem.
Option 2 is to take my lease times down to five mins or something REALLY low. After I spin up my new DCs, I could install DHCP, set up failover and then activate the new servers moments after killing the service on the four old servers. For some reason, that seems problematic.
At any given moment, I have 600 + active users in play so I'm trying to mimimize down time, duplicate IPs, etc.
Thoughts, suggestions, recommendations on how best to migrate all of this?