Having trouble with dual wan on RT-AX89X & Netgear CM2000, only works if you unplug the ethernet

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krellboy

Occasional Visitor
I have a new RT-AX89X (A2, running current as of 3/11/2021 firmware) attached to a Netgear CM2000 cable modem (via 10g port) and a cellular modem (ethernet) in the wan port.

Failover works fine if you unplug the cable modem ethernet port, but if you just unplug the coax it doesn't. If you have the coax unplugged (so it is in a failed-over (working) condition) and then plug the CM ethernet into the Asus it starts dropping the traffic going over the backup connection. When you do that this appears in the log:

Mar 11 20:15:32 dhcp client: bound 192.168.100.10/255.255.255.0 via 192.168.100.1 for 30 seconds.

(note the cable modem has a management interface on 192.168.100.1, so if the cable is down it looks like it starts handing out leases so you can talk to it directly)

I don't think this is an error, the modem is trying to re-test the main wan connection, but all of the traffic drops when this happens.

I'm pretty sure I've tried both ping and DNS as connectivity sensors and they act the same. It's having the ethernet plugged in that kills it.

Any ideas?
 

krellboy

Occasional Visitor
I've experimented a bit more, the problem (disconnecting from the running failover secondary) happens only if the primary has link AND is able to get an address somehow. This can be either a static or DHCP address. My cable modem starts an internal DHCP server when the cable is down (for provisioning), I just tried the moto version of the same modem and it does exactly the same thing. There is one more brand to try.
 

swhdash

New Around Here
I have a new RT-AX89X (A2, running current as of 3/11/2021 firmware) attached to a Netgear CM2000 cable modem (via 10g port) and a cellular modem (ethernet) in the wan port.

Failover works fine if you unplug the cable modem ethernet port, but if you just unplug the coax it doesn't. If you have the coax unplugged (so it is in a failed-over (working) condition) and then plug the CM ethernet into the Asus it starts dropping the traffic going over the backup connection. When you do that this appears in the log:

Mar 11 20:15:32 dhcp client: bound 192.168.100.10/255.255.255.0 via 192.168.100.1 for 30 seconds.

(note the cable modem has a management interface on 192.168.100.1, so if the cable is down it looks like it starts handing out leases so you can talk to it directly)

I don't think this is an error, the modem is trying to re-test the main wan connection, but all of the traffic drops when this happens.

I'm pretty sure I've tried both ping and DNS as connectivity sensors and they act the same. It's having the ethernet plugged in that kills it.

Any ideas?
I am having the exact same problem - if I physically break the connection between my Fiber modem and my AX86U, it will failover just fine to my DSL. If I disconnect the fiber from the modem (or if the connection otherwise goes down, which it has twice in the past two days), then the router shows it is disconnected, but won't switch over unless I reboot the router or pull the physical wire between the modem/router. I have played with the ping and DNS detection, but those seem to be unhelpful settings for this basic problem.
 

Tech9

Very Senior Member
Dual WAN fail over doesn't work on AC86U router as well. I use Cable and ADSL connections and unplugging the coax cable or phone line does not trigger fail over. Only unplugging the LAN cables does as you guys already observed. The test was done as an experiment after reading this thread. I need reliable Dual WAN fail over in few remote office places and they all run on Cisco RV345P routers.
 

swhdash

New Around Here
I am having the exact same problem - if I physically break the connection between my Fiber modem and my AX86U, it will failover just fine to my DSL. If I disconnect the fiber from the modem (or if the connection otherwise goes down, which it has twice in the past two days), then the router shows it is disconnected, but won't switch over unless I reboot the router or pull the physical wire between the modem/router. I have played with the ping and DNS detection, but those seem to be unhelpful settings for this basic problem.
So frustrating - our fiber connection has been going down about every 2 weeks, confirmed by the provider, and every time I've had to physically disconnect the AX86U from the modem to achieve a failover. I'm going to reach out to support to see if there's a ticket open on this issue as I can even reproduce by pulling the fiber cable from my modem while leaving the connection between modem and router.
 

SoCalReviews

Very Senior Member
I often have a similar problem on a Spectrum cable internet service. Sometimes the main internet is down but the ISP cable modem still shows a problematic but active internet to the ASUS router. Some services still work like VOIP but the web services are down. In those cases the failover doesn't get triggered unless I unplug the cable modem power cord or the Ethernet going to the router WAN port.

My work around is to have a switchable power cord used on the primary cable modem so I can easily power it off and manually trigger the failover to the secondary internet service. I switch the primary modem back on at a later time when full internet service is restored. Some ISPs offer a wireless data failover option with their business internet services.
 
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b-rubble

New Around Here
Confirming this is still a problem with Merlin 386.2.2 on RT-AX88U. My Comcast primary WAN went out 30 minutes ago and I just sat here and watched the GUI show the Primary WAN as "Disconnected" and my Secondary WAN as "Hot-Standby". Wouldn't switch over to secondary until I went into the WAN setting page and forced my primary WAN to the Secondary provider. FWIW - my mode is set to Fail Over with Allow Failback checked, Detect Interval 5, Failover Trigger 5, Failback Trigger 20, DNS Query and Ping both checked.
 

Tech9

Very Senior Member
Dual/Multi WAN Fail Over works well on Cisco RV3xx, Ubiquiti Edgerouter, TP-Link TL/E-R605, Peplink Balance, Drytek Vigor etc. If you really need reliable Fail Over, get one of those and run it before the Asus. Open all the ports to your router in DMZ or whatever is called there. I need Dual WAN Fail Over in my offices and I run Cisco routers. pfSense/OPNSense, IPFire, Untangle, Sophos/NG etc. appliances do it as well, but they are more complicated to setup.
 

swhdash

New Around Here
Confirming this is still a problem with Merlin 386.2.2 on RT-AX88U. My Comcast primary WAN went out 30 minutes ago and I just sat here and watched the GUI show the Primary WAN as "Disconnected" and my Secondary WAN as "Hot-Standby". Wouldn't switch over to secondary until I went into the WAN setting page and forced my primary WAN to the Secondary provider. FWIW - my mode is set to Fail Over with Allow Failback checked, Detect Interval 5, Failover Trigger 5, Failback Trigger 20, DNS Query and Ping both checked.
I have been working with Asus support, which so far has had me look at the two intro kb articles out there and reset my router to factory settings. The problem persists. Waiting back to hear next steps from them.
 

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