It did it and set the IP but I wanted AP to extend my main router’s wifi.
That didn’t work on the same name.
I tried duplicating the old settings from my wr703n and now I check if the wlan0 crash again.
You can set up the ssid and password the same as your main router. I don’t know why it will not work.
OK, based on your latest responses, you might want to update your picture. For example, add a PC to the main router and clarify a needed communication to and from. Also, you could add that you want the same SSID.
Like it has been said before, WDS with two different router brands is iffy.
So, here are some more questions 
What are your attachments to your current main router (besides sunk cost)?
Would you be willing to purchase a second MT300N v2? ($25)
If budget was not an issue, I would recommend replacing both routers with the B1300. Those are what I use.
If you are willing to buy a second MT300N, this is what I would do. Then set up the two MT300 as a WDS pair using GL-inet firmware. I can attest that you can certainly change the SSID that Other Wireless B devices would connect to to match SSID=Home.
If you are willing to spend more, I would replace the Main router with a B1300. Then you can avoid purchasing MT300 (A), as MT300N (B) and the B1300 can directly form a WDS.
Sorry I wasn’t clear enough…
Yes, I have one PC connected via wifi to the main router and I wanted to have the same SSID all over the house.
I don’t really want to buy another router right now.
I didn’t have any problem with the wr703n running OpenWRT and WDS with the main router (TP-Link 841n).
The only reason I replaced the old 703n is the speed (only 150mbps) and it has low flash memory.
What I did now is to use Access Point (WDS) mode for the wifi and put it under LAN.
Now my main router is connecting to this AP and It’s working find by now.
Please upgrade to the latest testing firmware. You can download it from here. I tested the WDS mode with same SSID, it works fine.
This is online tutorial. More Settings - GL.iNet Docs
@kyson-lok
Ok, I’ll try.
But what WDS type this firmware using? AP or Client?
TP-Link seems to allow to configure only the client for WDS so my OpenWRT needs to be the AP.
It is AP client mode for MTK.