How to increase the forest level from 2003 to 2008 with the least "consequences"?

Question

Active Directory

Good afternoon, everyone, in connection with the implementation of Microsoft Dynamics CRM 2016, it is required to change the forest operation mode from 2003 to at least 2008. The following problem arose, in the St. Petersburg branch machines on Windows Server 2003 are still used as DCs, because of this, the forest operation mode must be changed impossible. Forest root for example moscow.ru, domain since 2003 DC piter.ru, Moscow and St. Petersburg are different AD sites, trust relationships are established between domains, Exchange 2007 is used on both sites. I'm trying to come up with the simplest and safest solution to this problem. What's the best way to check all this?
Features: from the "working hands" in St. Petersburg, only a novice administrator who has never encountered an AD migration.

Answer 1

The St. Petersburg branch still uses Windows Server 2003 machines as DCs, which makes it impossible to change the forest mode.

Have you tried?
As far as I remember, the forest mode first changes from 2003 to 2008, then only on the 2008 server you can enable the DC role. You don't need a server to change the 2008 mode.
Why migrate? I see no problems - connect via RDP to DC and do it.

Answer 2

Plus, 2012 r2 saves you the hassle of manually expanding the schema.