I recently installed a new Server 2012 machine on a small network to replace our aging Server 2003 DC. I have completed the migration of Active Directory, DNS, FSMO roles, made the 2012 machine the schema master, etc. Everything has been running fine for a few days. The only roles still left are file and print server. Everywhere I have looked it is mentioned to remove the 2003 server from Global Catalog Server, demote it, and shut it down. The hardware is still OK and the domain and forest functional levels are at 2003. Is it OK to keep this 2003 server online as a failover DC to create some redundancy? Would I need to do anything specific to ensure they get along?
ASKER CERTIFIED SOLUTION
http://blogs.technet.com/b/askds/archive/2014/07/23/it-turns-out-that-weird-things-can-happen-when-you-mix-windows-server-2003-and-windows-server-2012-r2-domain-controllers.aspx from a quick google, it does look like some people out there have had issues with this configuration. Proceed with caution ;)
If you don't have any application dependency related windows server 2003 or functional level 2003 then you can replace windows server 2003 with 2012.
Thanks everybody. Nice to know it will work but it's a good point about the on-going vulnerability issues and patches down the road potentially causing problems with 2003 DCs. Appreciate it!