narangashish29 :
Yes they are plugging their router into the lan ports to use it as an access point
but why does that cause disturbance...
dhcp runs on layer2 (LAN) and it provides ip/gateway info to devices.
plugging the cable from one LAN to another bridges them. It's a single LAN.
since the other router has nothing in the wan port it's gateway goes no where.
you only want 1 dhcp server and gateway per layer2.
dhcp needs to be turned off on the new AP.
if you are having issues accessing the web admin page, make sure you unplug it from the other LAN and plug one pc into it.
if you can't find the admin page still then do the same thing after a factory reset it. then configure the admin page to be on a free ip of the main router's subnet and turn off dhcp and configure a ssid/pw. apply changes for both at the same time.
main router 192.168.1.1/24 then make the admin 192.168.1.18 for the AP.