Nagesh,
You cannot configure sub-interfaces on the etherswitch module. Its not supported. I have tested this in the lab and like I suspected you are not able to create sub interfaces on the ports. You can either make them a "switchport" (layer 2) and then use the vlan interface and then associate that port with that vlan. Or to do the "no switchport" (layer 3) interface that you can assign an ip address to it. I get the invalid marker when I tried to do the int fa1/0/15.1 as an example
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#int fa1/0/15
Switch(config-if)#
Switch(config-if)#
Switch(config-if)#
Switch(config-if)#exit
Switch(config)#int fa1/0/15.1
^
% Invalid input detected at '^' marker.
Switch(config)#
HTH,Please rate if it does.
-amit singh