Solved!! solved!! solved!!
checkout the comments here first.if you dont find it working ,then reading down here may help.
this tutorial is for ut-300r2u modems with old firmware.
for tutorial on new firmware visit here.
i am not using the modem which is using this particular firmware.i got this method from a friend of mine who is successfully using [...]
PORTFORWARDING BSNL/DATAONE MODEM UT300R2U (OLD FIRMWARE)