If you are using a dialer to connect to the Internet, u r on bridged mode. By default MTNL configures your connection to PPPOE. And I presume you will be on PPPOE as u r not aware of the difference...
For port forwarding, check these links...
PortForward.com - Free Help Setting up Your Router or Firewall
https://broadband.forum/mtnl-broadband/1523-torrents/#post15408
https://broadband.forum/mtnl-broadband/1337-port-block-problem/#post13151
For port forwarding, check these links...
PortForward.com - Free Help Setting up Your Router or Firewall
https://broadband.forum/mtnl-broadband/1523-torrents/#post15408
https://broadband.forum/mtnl-broadband/1337-port-block-problem/#post13151