I am running a 2008r2 domain with 2008r2 DHCP servers. When I migrate from one dhcp server to another, what I normally do is the following
1. Turn on Conflict detection attempts to "2" on both 2008r2 dhcp servers
2. Backup DHCP database on original dhcp server
3. Restore dhcp database on new dhcp server
4. Get network guys to add new dhcp server ip as an "additional" iphelper. My dhcp servers are always physically located next to each other so now the leases start breaking up to about 50% from the original and 50% from the new dhcp server. Conflict detection keeps them from handing out duplicate ip addresses
5. Wait several days and make sure no one reports any issues
6. Remove the iphelper for old dhcp server
I have never had any issues doing this, but I have traditionally done smaller scopes with lots of room in each scope. I am now doing scopes slightly larger(500 addresses) and about 50% utilized, with computers that do reboot nightly. I know there are a lot of ways to do this stuff and have read the best practices below, but this always felt like the safest way to make these changes because multiple people are involved with the change. Does anyone see any issues with this or think another migration method is smarter?
https://technet.microsoft.com/en-us/library/cc780311(v=ws.10).aspx
Thanks,