Asus router loses WAN connection frequently and fails to restore

[Jani-Petteri]

I've seen countless topics on different forums, including this one, about this very specific problem. I've tried most of the proposed fixes, but none worked. None of the topics I've seen concluded with problem solved, so I'm wondering if they are enduring, switched brand or just didn't post the answer. A common detail on all these problems is that there is an internet providing device, usually in bridge mode, on Asus WAN port and people suspect that it's a DHCP issue where the Asus router does not renew or other ways handle the lease correctly.

So, I have used my Asus DSL-AX82U with VDSL connection and it worked very well. Now the VDSL is no longer available, so the Asus now has a Huawei 4G router modem (B818-263 in bridge mode) connected to WAN port. Very often the connection between these two devices is interrupted. Interrupt happens usually daily, sometimes many times a day. WAN connection on Asus is interrupted, all other functions including WLAN operate normally. Huawei admin page will display all-good 4G connection. Asus network map displays not connected to internet, but when clicking on it, it will display WAN ip details and lease time as if they were OK. On the device, internet led is lit red. Rebooting Asus usually restores the connection. Speed is good when connection is working

I have WAN settings by default, using Automatic IP for PVC connection type. I have tried tweaking the settings, but the problem persists. The problems started on day 1 when I connected Huawei to Asus WAN port. I have had devices in Huawei WLAN, but it's a lot slower than Asus, so I prefer to use Asus as main gateway for my home. Asus also has many good features that I like. The Huawei is now in bridge mode (that disables most extra features) and WLAN disabled. The Huawei logging is stupid. It will not display any meaningful info on the admin site and when downloading "developer logs", I get a 200 kb corrupted zip package that I cannot open. Asus logs are mostly identical to all other people who posted this issue. I'm using latest firmware for this device, which is not older than 2 months.

Did anyone actually find a cure to this? Any suggestions?

My next bet would be to set Huawei out of bridging, setup DMZ and put the Asus there. This resolved at least some of these issues on one forum, but I'd rather use bridge mode because DMZ might open another can of worms. If that doesn't help, I'm forced to use Huawei WLAN and ditch the Asus as junk.

[jzchen]

May try adjusting the WAN DHCP Query frequency.  (I suggest try Normal for a day).  See if the issue continues:

https://www.asus.com/support/faq/1043591/

The article describes Continuous but I think it is too frequent.  If Normal makes it worse then try Continuous...

[Jani-Petteri]

Thanks for the reply. I've had it Aggressive and Normal. Normal failed today, I'm testing Continuous now. If that fails, I'll try the DMZ setup.

[Jani-Petteri]

That failed as expected. While viewing the settings to set up a DMZ, I realized that I don't actually need a DMZ because I don't need any connections from the outside. 

Right now I have set the following configuration. 4G is in normal operation mode (not bridged), wifi and DHCP are disabled. Modem has IP for LAN 192168.1.1. Asus router has been changed to static IP address (192.168.1.10), dns and default gateway points to 4G modem. Asus has DHCP enabled for 192.168.50.0 subnet and it should serve all local clients because no other device connects directly to the modem. DHCP dns and default gateway points to the router, that should redirect to modem. Lets see how this goes.

[jzchen]

Interesting, you seem to have created a double NAT, but if that works for you...

What DHCP Query setting did you decide works best out of the three:  Aggressive (default), Normal (my initial suggestion), Continuous (the article suggestion)?

[Jani-Petteri]

My gut feeling is that Normal query setting survived the longest before going down. Continuous was definitely fastest to go down.

One detail change to my configuration. I left Asus DHCP DNS setting as blank, not pointing at modem. It's a double NAT, but I hope this works without too much additional latency. The modem has its own firewall too, so I guess I'm double protected from internet. 🔥🧱😎 It takes at least a week before I can confidently say that it's stable.

[jzchen]

We have Frontier (an American aka USA) service.  I switched it to Normal and it started crashing.  But if you read the details on what Continuous, Aggressive, and Normal do, Normal seems the only reasonable choice, to not spam the ISP DHCP server.  So I changed it back to Normal (had to call my brother-in-law to reboot the router since it is a remote network that I manage).  Now it runs well a couple of months later.  Just a thought but it may not be the Normal DHCP setting that is causing the WAN loss...

I have a Gateway provided by AT&T here at our home.  Bridge mode is not available, only IP Passthrough.  Can not turn off DHCP server basically (my understanding), but my ASUS router gets WAN IP...

[Jani-Petteri · Accepted solution]

Static IP assigment failed today. Conclusion: NEVER BUY ASUS NETWORK PRODUCTS.

I need a workaround until new gear arrives, so I'll report if I manage a stable solution.

[Jani-Petteri]

I have set the Asus router in Adminstration -> Operation Mode -> selected: Access Point(AP) mode / AiMesh Router in AP mode. It should now be only a plain Wifi Access Point and a network switch with no routing features. I set the DHCP and routing to the 4G modem. The modem also has Wifi enabled to allow me to debug. This is not desirable configuration because now the Asus doesn't have QoS or firewall, both of which are more advanced than in the 4G modem.

And it failed again 😂 But now it was different. Asus internet led slowly blinks red/white. When I connected to the modem Wifi, I could not connect to internet. I have a suspicion that the modem might be to blame this time. Seems like booting either of the devices will reset the error.

Observation: It seems like the connection will always fail after being up for exactly 12 hours. At first when the Asus had WAN ip and its lease time was 24 h, when it broke, the remaining lease timer almost always displayed 12:59:59 or slightly less depending on how quicly I opened it. I guess one of the related devices either reports or handless the lease time incorrectly.