@terziyski The condition is definitely like this: Optus DSL modem LAN port => AX3000 WAN port (Dynamic IP) The result is still that router cannot obtain IP address from modem.

@terziyski My ISP is Optus. I am sure that I tried all the steps from the guide. Nothing goes right.

I can access the internet correctly with my modem, but the router cannot. I tried all solutions on page https://www.tp-link.com/au/support/faq/138/, but it still doesn't work like the picture below