After a little googling, the AG241 doesn't allow telnet access in its default state.
I found
this page which has a custom-built firmware image that enables telnet access on the router (required for DMT tool).
I can't personally verify the safety / success of using this firmware, and the usual warnings apply about installing unsupported firmware on a device, it will also void your warranty should anything go wrong.
So it's up to you - remember the firmware is the core software that makes your router work, and I'm not suggesting you do this, merely pointing out that it is possible