Hello Adhi,

when you use any form of advanced DDR or virtual DDR that employs a virtual-template or a dialer the virtual-access is a dynamic interface that inherits some charasteristics from the logical interface and uses some physical resources (like B channels on a ISDN PRI or a ethernet or FE when using PPPoE client)

During the PPP session it is the Virtual-Access that gets the IP address in the IPCP negotiation.

When the PPP session terminates the virtual-access is removed as needed.

see the following link

http://www.cisco.com/en/US/docs/ios/dial/configuration/guide/dia_virtual_temp_ifs_ps6350_TSD_Products_Configuration_Guide_Chapter.html

Hope to help

Giuseppe