https://www.net.princeton.edu/software/dhcp_probe/ http://odhcploc.sourceforge.net/ Mobile Android Xiaomi Redmi note 7 can not access internet. It can ping local LAN IP but it detect wrong gateway. Since 192.168.1.1 web access lead to wrong router (this one already disable DHCP). https://sites.google.com/site/quanghoangls/thong-bao/modem-router/cau-hinh-router-wifi-chay-ngang-hang-voi-modem Yee => It turned out that the 2nd Wifi Router setup incorrectly when it set LAN IP = 192.168.1.1 that same as Internet Modem.
Some tribes of the programmer clan.