How to switch secondary WAN to Hot-Standby?

[Ubimo]

Hello
I use a Huawei LTE stick as a backup secondary WAN in case my primary WAN fails.
While the Dual-WAN, failover, and failback functionalities are working well, they are not fast enough.
How can I switch the secondary WAN to Hot-Standby mode?

 

[eibgrad]

What constitutes too slow? At least for my ASUS RT-AC68U, the default is 6 secs (3 sec interval * 2 consecutive failures). If you change too quickly, you may end up w/ a lot of false negatives.

[Wireless Router] How to configure the Auto Network Detection while enabling the Dual WAN? | Official Support | ASUS Global

 

[Tech9]

This thing may or may not fail over to Secondary ISP and may or may not fail back to Primary ISP after the service is restored. If it switches connections at all even being slow - don't touch, it won't get any better. Asus component, copy/paste over the years in different firmware, never fixed.

 

[ccleeland]

This thing may or may not fail over to Secondary ISP and may or may not fail back to Primary ISP after the service is restored. If it switches connections at all even being slow - don't touch, it won't get any better. Asus component, copy/paste over the years in different firmware, never fixed.

Is a correct interpretation of this that 'Dual WAN w/failover/fallback" is not reliable? I've never had the occasion to use it until the last month, when I signed up for ATT Fiber but still have Charter/Spectrum running to ensure I like ATT. Spectrum is set up as the secondary.

It definitely seems to failover to secondary, but I never see it failback. Not sure if that's because ATT is IP Passthrough rather than bridging?

In any case, I had my router set up to reboot weekly at 3am monday mornings, and noticed that my monday workday would start with the router on secondary and the primary on "cold standby", and I'd have to go manually pull the ethernet connection to the secondary (charter modem) in order to get a failback. I'm guessing that after a reboot, the DHCP on ATT side takes longer to come back up, so for now I've disabled the weekly reboot.

 

[Tech9]

Is a correct interpretation of this that 'Dual WAN w/failover/fallback" is not reliable?

Test your luck. None of the Asus routers I ever had in my hands were working properly with Dual WAN to 2x Ethernet ports.

 

[ccleeland]

Seems that the feature almost works correctly, but almost isn't good enough.

 

[Tech9]

Make sure you test it right. It works always with cables physically unplugged, but may fail with actual service outages.

 

[ccleeland]

@Tech9 in your experience, is the feature more reliable with a USB-based secondary?

I actually did experience a genuine service outage and it failed over, but the failback is definitely not reliable. This was for hookups via ethernet, though.

 

[Tech9]

is the feature more reliable with a USB-based secondary

I personally never had a real USB 4G modem to test with. Folks around reported better success with Ethernet + USB, but perhaps hardware compatibility factor is involved. The main issue with mobile backup is when the plan has limited data and the router doesn't fail back to restored primary WAN connection. It will drain the mobile plan data.

 

[ccleeland]

For various reasons I have multiple phones with mobile hotspot plans and fairly large monthly data allocations. I semi-tested with one of those phones tethered via USB, but I wouldn't call it a full validation--more of a "I wonder if it'll actually work?". Once I decide which of my broadband connections will stay around, I'll consider where the phone-based hotspot will be a hot standby or will simply be an option for manual standby support ("oh my service is down...better connect up the phone").

One (of the many) things that's lacking in the ASUS dual-wan implementation is any kind of notification of a WAN failure/failover. Also missing is the inability to manually kick it back to the primary from either CLI or GUI. It seems I *have* to physically disrupt service somehow.

 

[tournakos]

Hi all,
I am running the tests as you described above with a WAN/USB failover/failback setup and when I unplug the ethernet cable it indeed switches to USB after a while. Similarly, when I plug it back it switches back to ethernet after a while (definitely a bit longer than the expected 6 secs). I have NOT tested it with an actual outage that does not involve physically unplugging the cable but I kinda looks stupid to work in one case but not the other. Well done Asus.

Now my concern is that after the (successful) failback the secondary WAN remains in Hot-Standby (as opposed to cold-standby that it was before the switch), keeping the connection open and potentially draining 4G data. I have found no way to enforce cold standby and when I tried a reboot it actually got quite confused for a while until finally settling to the same as below. Any ideas as to why this is happening and I can ensure cold-standby? Any chance it actually reverts to cold standby on its own after a while? Even disabling and reenabling dual wan keeps it at hot standby.

 

[Tech9]

I have NOT tested it with an actual outage that does not involve physically unplugging the cable but I kinda looks stupid to work in one case but not the other.

Unfortunately, this is exactly what happens quite often and you may find your mobile data plan completely drained because the router failed to switch back to the Primary WAN after the service was restored. Don't trust this thing. Unplugging physically the cables from the Asus router is not a valid test. Unplug the ISP connection upstream instead (coax, copper, fiber... whatever technology is used), leave the ISP gateway running and observe the behavior on your Asus behind it.

 

[tournakos]

Unfortunately, this is exactly what happens quite often and you may find your mobile data plan completely drained because the router failed to switch back to the Primary WAN after the service was restored. Don't trust this thing. Unplugging physically the cables from the Asus router is not a valid test. Unplug the ISP connection upstream instead (coax, copper, fiber... whatever technology is used), leave the ISP gateway running and observe the behavior on your Asus behind it.

Yes I tried that and it didn’t even switch to secondary Nonetheless I hadnt the dns/ping check options enabled

 

[JGrana]

You might want to look into an Addon for a solution:

WANFailover - Dual WAN Failover ***v2 Release***

WAN Failover is designed to replace the factory ASUS WAN Failover functionality, this script will monitor the WAN Interfaces using a Target IP Address and pinging these targets to determine when a failure occurs. When a failure is detected in Failover Mode, the script will switch to the...

www.snbforums.com

 

[tournakos]

Guys I stand corrected, after enabling the dns and ping checks it appears to be working flawlessly. Apparently when these checks are off, asus only considers a disconnected cable a failover situation. When on, it worked fine and very quickly when I simulated a no connection situation with the main router and all cables plugged. It also reverted (failback) correctly. I attach a screenshot of my setup, I wonder if my detect interval is too short at 3 secs what issues this might cause in the future.

 

[Tech9]

Test your luck with it. Monitor your data plan.

 

[tournakos]

Test your luck with it. Monitor your data plan.

Will do although I dont care much given sim has unlimited data at a very low cost. One thing which is still unclear is how it decides to put the usb wan on cold or hot standby. Of course I prefer cold like it is now anyway, just wondering

 

[Offler2]

Adding my 2 cents if it might help

Since 3g/4g usb modems are usually small linux computers, you might run into different types of behavior depending on the settings on the USB. Few quirks:

Hardware:
I have DWM-222, connected to RT-AC68U.

a) If I set "Auto reconnect" to be enabled, USB modem might not recognize SIM after router reboot. Its because modem boot sequence finished some time ago, it just takes 5 watts from USB, connects to the LTE network and router would not be able neither manage card, nor access network.

b) If UPNP is disabled in Primary WAN, it will try to enable itself for USB and then disable in an endless cycle.
Found out because UPNP integration kept popping up in Home Assistant OS, even when it should be disabled.

Workaround is to enable UPNP for Primary WAN.

c) Setting anything else than "Auto" for network type might fail USB to be connected.

d) If USB dongle automatically sets its IP address to 192.168.1.1 on desktop you might end up in IP conflict instead of failover.
Avoid using USB modems like these, they are usually running a lot of bloatware with web interface and quite slow.


e) 4G modem which runs 150mbit download and 50mbit upload on desktop PC, runs 20-40mbit download and 10mbit upload when connected via router.
Not sure about the cause. I suspect USB port, maybe usb extension cable with external power source will resolve this. CPU utilization isnt that high, i might test it on USB 3.0 port...

f) You can send SMS via LTE modem:
connect via ssh/terminal and send following commands
echo -e "AT+CMGF=1\r" > /dev/ttyUSB2
echo -e "AT+CMGS=\"+phonenumber\"\r" > /dev/ttyUSB2
echo -e "Message\x1A" > /dev/ttyUSB2

Actual endpoind may vary, depending on your LTE modem, in my experience it varied in Cold and Hot standby.