Hi,
I work for a large healthcare provider. We have 2012 DCs running at 2003 domain forest and functional levels. We have around 60 NT4 and Windows 2000 servers. When we removed the last 2003 DC, a couple of critical services broke on the legacy operating systems. We've put workarounds in place for the legacy services and lowered the default domain security setting. We're now looking at upgrading the domain and forest functional levels 2012, but have some concerns that doings so will break additional services, particularly around .NET apps.
The below indicates that NT4 and 2000 servers are not compatible with 2008+ higher level functional levels:
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/ee522994(v=ws.10)?redirectedfrom=MSDN#BKMK_OSInterop
Can someone provide some real world insight into:
- Whether upgrading AD forest and functional levels to 2012, will this have an impact on 2003 servers?
- At a base level, would they be able to logon OK?
- Would apps work as normal?
- Would we need to lower any security settings to accommodate 2003 servers?
- Later we’d like to upgrade to Windows 2016 forest and functional levels, would we have backwards compatibility issues with 2003, 2008 and 2012 servers?
-Is the upgrade to Windows 2016 challenging in terms of prerequisites and potential catches?
I'm well aware 2003 is not supported, what I'm after is whether anyone has experience of running 160+ 2003 servers at 2012 domain functional levels in an enterprise environment (i.e. 1000 servers+)
Thanks in advance,