With the new Server Manager that shipped with Windows Server 2012, and Remote Server Administration Tools for Windows 8, you can manage previous versions of the Server operating system, such was Windows 2003, 2008, and 2008R2. Some of the functionality will be limited, however, as these operating systems don't support all the new features in Windows Server 2012.
When you add these servers, you may see the following: “Verify WinRM 3.0 service is installed, running, and required firewall ports are open”
The new Server Manager uses Windows Report Management (WinRM) to communicate with servers, which is installed and enabled by default on all 2012 Servers. For 2008 and 2008R2 Operating Systems, you must download and install this: http://www.microsoft.com/en-us/download/details.aspx?id=34595
Once this is installed, and the server is rebooted – you must run a command to enable remote management: “winrm quickconfig”
At this point, you can refresh your Server Manager console, and you should see them come online and able to be managed:
The limitation for Server Manager on Windows 2003 systems is “online” or “offline” status. The limitation for 2008 and 2008R2 servers is that you cannot remotely add/remove windows roles and features, as that is a new capability for Windows Server 2012.
Worth taking a note of the known issue with WMF 3.0 on a server with a ConfigMgr Client before anyone blasts this across their estate.
Hopefully this will be resolved soon as it's brilliant being able to manage a downlevel OS with Server Manager.
@Steve; This is problem is solved in SP1 for SCCM 2012. SP1 is available for download for msdn and technet subscribers. It's not yet available on the volume license site though.
In PowerShell you can accomplish the same thing. This has the added benefit of enabling PowerShell remoting as well which is really useful.
PS:> Enable-PSRemoting -Force