I'm renting accommodation where the landlord has an unsecured portal for networking, and in order to operate on the network a password is entered on the portal page that pops up when you first connect. After that, it never asks again for that device. When connected, I cannot seem to see any other devices on the subnet, so I purchased this router with the intention of using its wifi connection and LAN ports to run my own private subnet a) to ensure no-one else can poke about my devices and b) I can use normal security features for devices that can't see the login page.

However I've fallen at the first hurdle. I can set this to WISP mode, and seemingly connect to themain router, but I get no IP address on the WAN interface page, so I assume it's not playing ball with the main router. If I run the "detect" function, it claims "dynamic IP" is correct, but the dynamic IP setting is not yielding any fun.

I cannot find the main router's IP address, but the main router's IP range is 192.168.2.X and the TP-link is sitting on 192.168.0.1. When I try to change the TP-link IP to ..2.X it resets itself back to ..0.1 within 5 seconds. 

What's going on here?