On an Asus RT-N12E_B1 router, in the menu, I get the hint:
The WAN IP is not the external IP. External IP-based services will not work. --> Change now
The router gets the internet from an Inteno fiber modem Lan1 port plugged to its WAN port.
How to get rid of this hint?
Taking the answer from the worthful comment above:
It's just a fact that you're behind CGNAT. Why do you want the hint gone? Switching to AP mode changes nothing.
From this follows that you can ignore the hint. It does not harm any device or network setup.
Change to AP mode by saving:
Thanks go to Error code: "The WAN IP is not the external IP. External IP-based services will not work." From Asus router.
Accept the next menu pop ups. I accepted two empty DNS fields as well, still wondering if that was right, seems so. Somehow I did not get further in the menu, so that I clicked to skip the Quick Internet Setup instead. But I could not enter the Asus menu anymore. After this, it takes at least 2 minutes until the changes take place. You might need to wait even a bit longer.
Then, the internet comes back, it works on all devices. Yet, you cannot enter the modem menu with the usual IP 192.168.1.1 anymore, and http://router.asus.com/ does not work either. To find the external IP of your modem and enter its menu, download the Device Discovery tool from Asus for your router model.
Path on Windows is: C:\Program Files (x86)\ASUS\Wireless Router\Device Discovery
Start Discovery.exe.
Enter the IP in your browser to enter your modem's menu, for example to look for a newer firmware or change back to the "Administration - Operation Mode" you had before.
The menu:
In my case, I could not check for newer firmware but I guess it was the latest anyway. I would still rather try an upgrade before doing the switch to AP operation mode, perhaps it works in "Wireless router mode (Default)" but not in "Access Point(AP) mode".
