The issue has been resolved. now the IP addresses and the Subnet infomation is displayed in the User Tracking Reports. The problem was, that no Layer 3 device was added in the LMS. as per the document:
ANI reads the ARP table from the Layer 3 devices it discovered to map the MAC addresses to IP addresses. If UserTracker shows the MAC addresses, and the IP address and hostname fields are empty, chances are that ANI does not discover the default gateway of the host correctly.
Added the Layer 3 switches, performed the Data Collection, Device Discovery and UT Acqusition and now the endhost reports are generated based on IP address.
following is the link for reference:
http://www.cisco.com/en/US/products/sw/cscowork/ps563/products_tech_note09186a0080094949.shtml#ts2b