ISSUE: Windows 2008 R2 Enterprise (64bit) randomly deletes DHCP reservations after making the reserved IP active. Additionally when I try recreating the reservation, I get "The specified address is not available." I click "OK" and click "Add" again and get "The specified IP address or hardware address is being used by another client". I then click "Close" to close the window. Now bear in mind that the IP/MAC address combination did not appear in the "Reservations" folder or the "Address Leases" folder on either server ( see current configuration below) prior to me trying to recreate the reservation. After attempting the above recreation, and refreshing the "Address Leases" folder, the IP/MAC combination shows up but with no "Name" and the "Type" is Unknown. I can delete this "Unknown" entry and now go back and recreate the reservation without a problem. HISTORY: The original infrastructure consisted of 6 Windows 2003 R2 Enterprise (32bit) servers; 2 of which are DCs and 4 are member servers. The 2 DCs were running a DHCP server service. Both of which had identical reservations but different scopes. This solution worked fine for years. When moving to the Windows 2008 R2 Enterprise infrastructure, I created 2 new DCs; and started with a single DHCP server. I migrated the database according to Microsofts instructions and all seemingly went well. I needed to make changes to the scope to accomodate the changes made in the new DHCP architecture. I then noticed that random PCs and printers were unable to communicate to the new DHCP server (BTW, the other 2003 DHCP server services were stopped). I looked in Windows Event Viewer/System/ Properties on the local PC and find this error message: "The IP address lease 192.168.13.x for the Network Card with network address XXXXXXXXXXX has been denied by the DHCP server 0.0.0.0. {The DHCP Server sent a DHCPNACK message}." Preforming a ipconfig /release and /renew would not fix the issue. Sometimes physically disconnecting the computer from power and disconnecting the patch cable would fix the issue but I think this was more of a coincidence than an actual solution. I needed to statically assign an IP to the host to get it to come back online. After dealing with this for two weeks I decided to build another DHCP server on 2008. The hosts that were statically assigned immediately took to the new server after reseting them back to DHCP. I now have two DHCP servers each with their own unique distribution range which is what I wanted anyway for redundancy, and dynamically assigned IP's are populating OK but I still have the randomly deleting reservations - and both servers are deleting reservations. Current configuration is as follows: Server-1 (192.168.5.0) DHCP Scope = 192.168.0.0, Lease duration 14 day, assigning DHCP only. Address pool = 192.168.0.1 - 192.168.15.254 with exclusions of 192.168.0.1 to 192.168.12.255 and 192.168.14.0 to 192.168.15.254 This leaves onle the 192.168.13.x range as the distribution range Server-2 (192.168.5.5) DHCP Scope = 192.168.0.0, Lease duration 1 days, assigning DHCP only. Address pool = 192.168.0.1 - 192.168.15.254 with exclusions of 192.168.0.1 to 192.168.11.255 and 192.168.13.0 to 192.168.15.254 This leaves onle the 192.168.12.x range as the distribution range Has anyone run into this type of issue? Is there something I'm missing that may have changed in 2008 from 2003 that needs to be configured? I'm running out of options (and hair) and statically assigning 50 hosts is not an option. John

There is a bug fix for that issue. http://support.microsoft.com/kb/981776 Here is another blog posting going through the history of it. http://social.technet.microsoft.com/Forums/en-US/winserverNIS/thread/5f0872d9-ff50-4ce9-a001-d9f7ab8cc4c6 Happy Hunting!

Thanks Lurchmiester - That worked great. Was pulling my hair out on this. John