Hi Sajeel,
This is a known enhancement bug. Windows 2008 R2 is not supported with any version of ACS irrespective of platform.
Acs 4.2.x doesn't support all newer versions of Windows 2008. It only supports the below listed version.
Supported Operating Systems section
--Windows Server 2008, Standard Edition
--Windows Server 2008, Enterprise Edition
--Japanese Windows Server 2008, Standard Edition, Service Pack 2
--Japanese Windows Server 2008, Enterprise Edition, Service Pack 2
Link for System requirement and supported version
http://www.cisco.com/en/US/docs/net_mgmt/cisco_secure_access_control_server_for_windows/4.2.1/Installation_Guide/windows/install.html#wp1041324
However, we have few option at this point which may suit your requirement:
1.] Rool back your AD to standard 2008 Non-R2.
2.] Replace AD with LDAP because we can use win 2008 R2 with LDAP as a protocol.
3.] Go for ACS 5.2 only for cases where we want DC to run on win 2008 R2
Related bugs and enhancement
------------------------------------------
Applicable where customer is trying to ACS windows or remote agent on the windows 2008 R2
CSCta35271 Support for Windows server 2008 R2
Applicable where customer is directing all the authentication request to AD/DC as 2008 R2
CSCtg37183 ACS 4.x doesn't support 2008 R2 Server for AD
CSCtg12399 ACS 5.1 did not support 2008 R2 Server for AD.
We have also seen this working in few instances but again it's not tested by Cisco so there may be issues that you may not afford in your production enviornment.
Regards,
Jatin
Do rate helpful posts-
~Jatin