I'm preparing for a migration of my windows 2000 domain (native mode) to Windows 2008 R2. The current 2000 domain contains two windows 2000 DCs and two 2003 DCs. I'm planning on using the new 2008 DCs as DNS servers too. In addition, I would like to reuse the IP addresses from the old DCs on the new ones so that I won't have to reconfigure every device and client on the domain. At what time or stage is it best to switch the IP addresses from the old DCs (old DNS servers) to new DCs (new DNS servers)?