Manage RT-AC88U router without an Internet connection

[AlHolden]

We have a RT-AC88U (and RT-AC68U on AIMesh) connected to the Frontier FIOS service. The AC88U is running 3.0.0.4.386_48263

Whenever I want to administer the router (using 192.168.0.1, or the router.asus.com address which replaces that IP), there's no response or a plain white page - unless the router has a working Internet connection.

Once the WAN is working, the router's admin pages all come up just fine.

This seems like a paradox, as I will never be able to administer the router (to fix a WAN configuration issue) when the router cannot contact the Internet.

Is there a setting I can change, which will allow me to admin the router from the LAN - when the WAN's not there?

[jzchen]

What is the IP address of the device/computer you are using ASUSwrt (web interface) on?

[AlHolden]

Hi and thanks, @jzchen 

I'm using any of our PCs on the LAN to connect to the RT-AC88U web interface, which assigns IPs via DHCP. Today this PC has been given IP 192.168.0.161.

When I connect this Win 11 PC to the router's IP of 192.168.0.1 - using Firefox 131.0.2 (64-bit) - I am immediately forwarded to http://router.asus.com where the main index.asp is displayed and I can manage the settings...

UNLESS the WAN connection has no real internet at the time - in which case the LAN browser attempt times out or displays a plain white page (no html source at all). That's the part which concerns me.

I've attached a simple diagram to visualize what's happening.

[jzchen]

If not already set as such, try setting the default gateway of the PC to 192.168.0.1, (the LAN IP of the router).

That's definitely a strange bug....

[AlHolden]

@jzchenwhen the Windows 11 machine connects to the Asus router via wi-fi and obtains the IP using DHCP, there does not appear to be anywhere to set the Gateway. However, the netstat command confirms :
Wireless LAN adapter Wi-Fi 2:
Connection-specific DNS Suffix . : akh6.com
IPv4 Address. . . . . . . . . . . : 192.168.0.161
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.0.1

I was guessing that the browser or router is trying to use some outside DNS server to resolve router.asus.com, when actually the router should just resolve it locally. But only the router holds the WAN DNS addresses, and the PCs are just using the router for DNS...

At least that's how it SHOULD be set up, but maybe there's some setting somewhere that's affecting this, and I just don't know where it is?