ASUS Router Dual WAN issues

Corporate Drone · April 11

I will try to make this as concise or at least as organized as possible

Equipment;

ASUS AC2900 router

TMO-G4SE cellular modem
Touchstone CMB200 cable modem

Pixel 6 phone

Windows 11 Pro PC

The TLDR;

I lose connection to the internet and failover doesn't work AND the admin center tells me the connected failover modem disconnects when this happens- like my cellular modem is idle no problems are reported but when it's under load it suddenly disconnects. When I get the primary connection back, the failover connection says it's back on standby again. I also can't always connect with to my router on my PC anymore. ERR_connection_timed_out is the page I get when I try to navigate to my router.

Problems;

For years I have been using a network setup that goes cable modem into WAN, cellular modem into LAN 4, with a pihole on LAN 3 acting as a pihole DNS server with no other containers only pihole and set up using recursive DNS from a tutorial I can't find again

I was never able to log in to the router on my cellphone, even when the cellphone used the wifi

The setup has a failover connection and was working fine- I almost never noticed an internet outage other than getting a text from my ISP telling me my internet was down which I would then use to have them give me credit for the lost service. This happened often enough that I get about $75 a year back from them. The system was working OK.

About two months ago the pihole started acting up- just being unable to update and suddenly could not log in to the web interface, only through Putty.

The pihole was removed, the DNS on the router initially got changed to Adguard but I started getting a red WAN light on my router and no connection so I shrugged my shoulders and switched router DNS to google to see if it would fix the issue. It was still an occasional problem.

What's happening now is when there's a failure on my cable modem, I lose internet AND in the admin center for the router, my cellular modem goes from "Cold, Standby" or "Hot, Standby" to "Disconnected". After a long wait, SOMETIMES it'll say Connected, but I still won't have internet and after a short interval, it'll disconnect again.
IF I just disable dual WAN, I can no longer connect to the router using my PC, and yet my phone (so long as it's on wifi) will now connect to the router when it would not before. Though I can't get to the router on my PC- I can get to the internet- just not 192.168.50.1 or asusrouter . com. If I log in to the router using my phone and enable dual WAN again, my PC can connect to the router again. ERR_connection_timed_out is the page I get when I try to get to my router.

I went to Tmobile thinking there was an issue with the modem- they've checked their modem and say it's fine.

Things I've tried;

Rebooting everything and also rebooting when changes are made

(When I can log in) updating the ASUS router DNS to "Assign from ISP"

Cable modem plugged in to WAN as the ONLY/Primary router- usually connection to the internet / only sometimes connection to the router on PC
Cellular modem in WAN port as the ONLY / primary router / Cable modem not plugged in at all - no connection to the internet / no connection to router on PC
Cellular modem in LAN 1 instead of LAN 4 as failover router / Cable modem in WAN but powered off - no connection to the internet / no connection to router on PC
Cellular modem gets a different known working cable as failover router in LAN 4 / Cable modem in WAN but powered off - no connection to the internet / no connection to router on PC
Connected to Cellular modem directly on my cellphone using wifi, bypassing router - yes connection to the internet (the router, being bypassed, no connection to the router is expected)

Things I think I should still try but don't have the equipment;

Use a different PC and see if it can get to 192.168.50.1 every time
Reconsider all my life choices and just find a beach in Mexico and live out my days there instead of this computer thing

Edits;

I'm not using VPN but I do have PIA installed, and also Vivaldi's default VPN. This issue of not being able to access my router persists regardless of if I'm on the VPN or if I'm using Edge without a VPN

I also can't access the networked mapped USB drives on the router from Explorer when things are having a fit but that's to be expected

I ended up taking everything off the network except for the PC, and pulling everything off except for the PC. With only the Cable modem in WAN I was able to get places and shut off Dual WAN. Added back the cellular modem and set up Dual WAN a second time. Things worked again. Then I tested the failover by unplugging power to the cable modem. Once again, the 2ndy network went from "Hot-Standby" to "Disconnected" until I went and plugged in the cable modem, waited for it to finish powering it on- then the 2ndy network went from "Disconnected" to "Hot-Standby" again. I have a sneaking suspicion that somewhere my router isn't liking the handover of the DNS / DHCP from the cable modem to the cellular modem due to a ??????? setting that maybe I changed while setting up the pihole which now isn't in the picture. But I'm not sure where to start. I have already replaced the pihole IP in the DNS settings I can find on the router with the easiest most reliable one I can think of which would be Google.

So I'm still stumped.

Corporate Drone · May 8

I finally got around to trying to fix this again.

One of the first things I did was check my firmware revision- and my firmware was a few versions old- it's updated now.

I also reset my cellular modem and reinstalled it according to the instructions it came with.

Then I updated the ports in Dual WAN setup- I switched my WAN to be my backup connection, and LAN 1 to be primary WAN connection

In this configuration, either modem is capable of being primary, either modem is capable of being secondary, and failover works.

After switching back to WAN being primary connection, and any LAN being secondary, the only connection that works is WAN and once that disconnects, backup drops too.

I'm at a loss as to why a configuration like this stopped working and now works in a completely counterintuitive way. The only way to get dual WAN back seems to be using the WAN port as secondary, and pick a LAN port to be primary.

If I use WAN as primary and LAN as secondary, as soon as WAN drops connection, so does LAN. LAN will show HOT-STANDBY until the cable is pulled for WAN. Then it suddenly shows as DISCONNECTED. If WAN is reconnected- then so does LAN and LAN goes cack to HOT-STANDBY again.

Both modems appear to be functioning, and the cables all appear to work fine too.

The reason I'm not wanting to just leave LAN as primary and WAN as secondary is that for some reason when the cable modem is in a LAN port it tops out at about 250 Mbps while if it's in the WAN port it hits 1.1 Gbps. The cellular modem tops out at 500 Mbps in the WAN port or 270 Mbps in the LAN port. I would assume this is a problem with the LAN ports and the router I mean this all points to that- but then again I wouldn't get the 1.1 Gbps result in the WAN port reported on the PC that's plugged into a LAN port if that were the case?