If ip scan tool fail, then you need to use serial console.
But, before that, i want to clear some matter first.
Do you had more than one network adapter on your PC? Like ethernet port & wireless port.
If yes, you need to disable the wireless adapter.
You did connect TL-MR3020 using lan cable to your pc right?
You will need to make serial adapter using CA42 & open your TL-MR3020 then add some pin on P1.
More info:
http://wiki.openwrt.org/toh/tp-link/tl-mr3020![](https://ip.bitcointalk.org/?u=http%3A%2F%2Fs26.postimg.org%2Fgf16nkrnt%2Fca42.jpg&t=663&c=NypUiM_c1X4mLQ)
![](https://ip.bitcointalk.org/?u=http%3A%2F%2Fs26.postimg.org%2F53yiz7ksp%2Fimage.jpg&t=663&c=BVf70Z88e28uHQ)