Model :

Hardware Version :

Firmware Version :

ISP :

I have the following components of my system:
Modem (provided by ISP)
[*]"AP" Main Router (Asus RT-n66u)
[*]"RE1" Range Extender 1 (TL-WA830RE) - Universal Repeater
[*]"RE2" Range Extender 2 (TL-WA901ND) - Universal Repeater
These are physically set up in a linear chain, so the idea is that RE1 picks up the signal from AP and forwards to RE2. Meaning like this:

Modem --[wired]-- AP --[wireless]-- RE1 --[wireless]-- RE2

So, when setting up RE2, I scan for the signal to repeat and sure enough it picks up the signal from RE1. The question is though, the step after that I'm asked to enter the MAC Address of Main Router/AP(BSSID).
After selecting RE1, it prefills the MAC address of RE1. Is that correct?
[*]Or should I be entering the MAC address of the root AP?