We have a problem of many workstations getting different IP addresses depending on which DHCP server responds first. Since our existing DHCP servers are not R2, they don't have the functionality to add a response delay to one server.
We are going to migrate to 2012 R2 and set up DHCP failover to get away from this issue.
What's the best way to get DHCP configuration including leases transferred from 2008 to 2012 R2 and also filter out any clients that managed to get leases on multiple DHCP servers (such as after a system reboot before the existing lease expired) so there is only one lease per machine imported into the new DHCP failover cluster?