Graças a @ batistuta09, o link aqui me deu a resposta. Acontece que o adsl e meu roteador portátil estavam operando com os mesmos intervalos de IP. Eu mudei a faixa de IP do meu roteador portátil entregue e resolveu o problema.
Solution 3:Change the LAN IP address of the router. Most TP-Link routers use 192.168.1.1/192.168.0.1 as their default LAN IP address, it may be conflicting with the IP range of your existent ADSL modem/router. If so,the router is not able to communicate with your modem and cause you can’t access the Internet. To resolve the problem, we need to change the LAN IP address of the router to aviod such conflict, for example, 192.168.2.1.