Maybe a repeater or a range extender can meet your requirement with BT3.

:o Vic is right! But i am not sure what are that ip means? Also the target port?

I do not think this router can do this. This function requires a small business router to do it.

As far as i know, there is only one firmware at the moment. You can try to turn off the hardware NAT on TP-LINK to see if there is any difference.

I think the main problem is the TL-PA251 is not communicating with TL-PA211. You can try to pair them to make them talk with each other or use the CD software to make them communicate with each...

I think you can try to reset all the 411 in your house by the power line Utility or change the network name to homeplug AV.