Im in the process of migrating, DHCP from 2008 to 2012R2.
I create all the scope detail, reservations...
At first the scope overlaps with the 2008 scope, 172.16.2.1 - 200
I stop the 2008 DHCP service, perform an IP release/renew on a test machine and nothing.
Checking the event logs shows
The IP address lease 172.16.2.1 for the Network Card with network address xxxxxxxxx has been denied by the DHCP server xxxxxxxx (The DHCP Server sent a DHCPNACK message).
I have since deleted the Scope totally and placed it on a differnet range. 172.16.4.1 - 172.16.4.200
Now I just get a timeout that the DHCP server can not be contacted. The 2012 r2 server is authorised but im not sure why it wont give out addresses.