I face exact-problem, bummber.
doomrocks --> looks like there are other routers after yours before finally reaching a bsnl-bridge. friggin bsnl cant afford to let users have their own level-2 IP.
as long as you see a 192.x.x.x.x in your gateway in modem.. you r shit outa luck.

or may be bribe some bsnl guy to portforward your port/ip.