Trying Dual Wan - Failover only

[Micgang]

Two days ago I set up dual wan on my AX 92u, utilizing the failover feature with auto switchback. I’m using T-Mobile HI gateway as the primary isp input and Fios as the standby. seems to be working correctly after two tests, both where I would unplug the primary isp wan cable to see how long it took to recognize the failure and make the switch To the backup. I didn’t time it, but it seemed to take 15-20 seconds. Plugging the primary wan cable back in triggered the router to switch back to the primary. I guess a couple of questions I have are…

Is this a reasonable way to test this?
Are there other routers that make the switch from primary to backup more quickly? For example, are there routers that would recognize the outage and switch almost instantly?

 

[L&LD]

Yes, seems like a reasonable test.

Other solutions may be quicker, but how important that is, is relative.

How often does your main WAN go down? Even if it's a few times a day, there are few situations where this would actually matter.

 

[Tech9]

Is this a reasonable way to test this?

No. It works reliably only when you physically unplug the cable. Dual WAN fail over is broken in Asuswrt. If you have the cables in place, but the service is lost, it may or may not fail over. After the service is restored it may or may not fail back. I've tested like 10 different Asus routers - all the same, unreliable.

 

[L&LD]

10 routers tested. Clap, clap. Oh, and these were the broken models you pick up for pennies, correct?

Many more Asus users are using Dual WAN than those with issues.

 

[Tech9]

SNB forum has Better Search available. Multiple threads with Dual WAN issues. @Micgang can test it for himself as well. It's easy to replicate. It works better with WAN + USB, but not with WAN + LAN. One possible workaround is setting 40+ attempts in Failover Trigger Condition. In 5-6 min time it eventually realizes the service is lost or restored. Still not guaranteed.

 

[eibgrad]

Loss of the physical connection is relatively easy to detect and to respond correctly. The problem is the more subtle issues of a still physically connected but either non-working or unreliable connection. Now things get tricky as to when things should failover (or fallback). In this context, "instant failover" isn't even a thing. Last thing you want is the router prematurely jumping back and forth based on bad assumptions. As I said, physical failure detection is easy in comparison, but the chances of that happening are quite rare too.

In short, pulling the plug or cable is one measure of whether it works at all, but NOT how well it's going to work in actual practice.

 

[Tech9]

Working Dual WAN routers by default switch after 3 attempts in 10 seconds interval, or in 30 seconds. My Cisco RV routers are set this way, probing both IP and DNS. TP-Link ER605 also works well with about 30 seconds reaction time. From home routers Synology rt2600ac, but the router is AC and expensive. I'm waiting for Asuswrt RC3 release to test again if there is any improvement. In current Asuswrt fail over eventually happens, but most of the time it doesn't fail back until the cable is unplugged. I don't have a USB modem to test WAN + USB. Some SNB folks say it works better.

 

[Micgang]

Thanks for all of the feedback. I’ll think about some tests that don’t involve unplugging the cables. I don’t really have some great need to have near instantaneous failover. Like many here, I just like to learn and try new things. My thinking here is that 5g home internet connections may not be as stable as a hard line, so a backup/failover would be handy on days I’m working from home. So far though I am impressed with how stable the 5g connection has been.

 

[Tech9]

For work from home you're good. Being physically there, if you lose the main ISP you can just unplug the cable or switch connections manually in GUI.

 

[henryr]

Two days ago I set up dual wan on my AX 92u, utilizing the failover feature with auto switchback. I’m using T-Mobile HI gateway as the primary isp input and Fios as the standby. seems to be working correctly after two tests, both where I would unplug the primary isp wan cable to see how long it took to recognize the failure and make the switch To the backup. I didn’t time it, but it seemed to take 15-20 seconds. Plugging the primary wan cable back in triggered the router to switch back to the primary. I guess a couple of questions I have are…

Is this a reasonable way to test this?
Are there other routers that make the switch from primary to backup more quickly? For example, are there routers that would recognize the outage and switch almost instantly?

Fore those interested in using Dual WAN rather than failover mode, where you want failover in the event of a WAN problem too.

I have the Asus T-AX86U with latest Merlin FW, and two WANs which I use in load balance mode. IPv4 only.

My Primary WAN is BT internet (FTTC) via modem (no double NAT). I consider it primary because it has lower latency. My secondary WAN is Virgin cable via Docsis modem (no double NAT). Higher latency but much higher bandwidths. I have a gaming PC main interface routing to the primary WAN, everything else routed to secondary WAN, including a second interface on the gaming PC which is used to upload (Twitch) streams.
It's not really load balancing, as all my outbound traffic choice of WAN is determined by the routing rules, which are:

192.168.50.163/32, all, Primary WAN
192.168.0.0/16, all, Secondary WAN

(I used a /16 as a mega catch all. No harm done.)

Firstly, unplugging the Primary WAN from the ASUS causes the secondary WAN to go down too (inexplicably...) for around 40 seconds. After that all devices including the gaming PC use the secondary WAN no problem. Reconnect Primary and it comes back into service immediately, and the gaming PC traffic is routed over it immediately too.

Unplug the secondary WAN cable next. Primary WAN stays up. All traffic is routed over primary after about 30 seconds. Reconnect secondary cable. All secondary traffic reverts back to it after about 30 seconds.

This basic failover and recovery is pretty OK for my needs, but I appreciate that it could behave very differently (worse) in the event that a different network issue occurs upstream from my cable-pulling (which others here have rightly pointed out).

tl:dr: Asus router load balanced WAN failover and recovery behaviour with routing rules in place does appear to work ok for cable pulls in a basic test.

 

[Tech9]

does appear to work ok for cable pulls

Yes, but it's you doing the failback/failover, not the router.

 

[henryr]

Yes, but it's you doing the failback/failover, not the router.

Yes, I'm putting the cable back in. It's the router then reverting the traffic back onto that original link again.

 

[Tech9]

Proper Dual WAN routers don't need cables pulled. The best Dual WAN home router is Synology rt2600ac. It's broken in Asus routers.

 

[Ranger802004]

If you have Merlin Firmware, check out this script package tool I put together. https://www.snbforums.com/threads/dual-wan-failover-script.78978/