This is using a Windows 2003/2008 AD domain. There are 3 DCs, 2 located at siteA, and 1 located at siteB. At site A, DC1 is W2K8 32-bit, and DC2 is W2K3 64-bit Enterprise edition. At site B, DC3 is W2K3 server.
According to the planning, we have to decomm DC2 as its hardware too old. I have moved all 5 fsmo to DC1. I open AD sites and services, and found that there are 2 AD sites - Site A (with DC1 & DC2), and Site B (with DC3). And then I check the each DC's NTDS settings as follows:
DC1 - only 1 connection object with DC2
DC2 - has 2 connection objects with DC1, and DC3
DC3 - only 1 connection with DC3
Looks like DC2 is the site's "bridgehead server". I also found that DC2 is the ISTG (Intersite Topology Generator) for site A. Now, I exchange the roles between DC1 and DC2, so as, DC1 is having 2 connection objects to DC2 and DC3. The changes were allowed, but, when I select to "replicate now" on connection objects (with DC3), it doesn't show the normal AD domain service is replicated. Instead it shows:
one or more of these ad domain services connections between these domain controllers in different sites. AD DS will attend to replicate across these connections. For information about these connection, check support.
What's went wrong? What would be the "best practice" to decomm the old DC? Shall I just demote it and expect updates/changes made on all the ad? or else?
Thanks in advance.