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RT-AC86U & DFS Channels (EU Model)

Stuey3D

Regular Contributor
So I have recently purchased an RT-AC86U to replace my ageing RT-AC68U as I now have 30+ devices connected to my network and the 68U was starting to show its age a little bit (sometimes devices were sluggish, and a couple if times it locked up completely requiring a full power off and on)

The RT-AC86U is a very fast and capable router and adaptive QOS works a treat on it when compared to the older 68U, however I have noticed an odd issue on the 86U though and its that it wont hold on to the DFS channels always dropping back to channel 48.

On my 68U it practically lived on channel 100 all the time, and because every other wifi system in my local vicinity is ISP provided I was the only one using the DFS channels and it worked awesome With very good range. However on the 86U it chooses channel 108 and holds it for a random amount of time then will drop to 48 and never return back to 108. I know on DFS channels routers are meant to vacate a DFS channel when radar is detected but after 30 minutes they can return back, however the 86U never returns.

Normally I wouldn’t be fussed as wifi performance is still very decent however in my daughters bedroom its where you notice the change the most. When using DFS channels the routers can increase their transmit power and the difference is that on channels 100/108 the iDevices will sit on full wifi signal all the time rather than dropping to 2 bars and her Nintendo Switch will sit between 2-3 bars signal rather than 1-2 bars on channel 48.

My question is is this normal behaviour for the 86U I do live near a small airfield so radar would likely be detected, however I find it odd that the 68U didn’t release channel 100 yet the 86U wont stay on it for long. Is it because the 86U has a more sensitive antenna setup and is likely detecting radar that the 68U likely didn’t detect? Or do I have a faulty unit? Or is this just how the newer Asus Routers handle DFS channels?
 

jotzet79

New Around Here
So I have recently purchased an RT-AC86U to replace my ageing RT-AC68U as I now have 30+ devices connected to my network and the 68U was starting to show its age a little bit (sometimes devices were sluggish, and a couple if times it locked up completely requiring a full power off and on)

The RT-AC86U is a very fast and capable router and adaptive QOS works a treat on it when compared to the older 68U, however I have noticed an odd issue on the 86U though and its that it wont hold on to the DFS channels always dropping back to channel 48.

On my 68U it practically lived on channel 100 all the time, and because every other wifi system in my local vicinity is ISP provided I was the only one using the DFS channels and it worked awesome With very good range. However on the 86U it chooses channel 108 and holds it for a random amount of time then will drop to 48 and never return back to 108. I know on DFS channels routers are meant to vacate a DFS channel when radar is detected but after 30 minutes they can return back, however the 86U never returns.

Normally I wouldn’t be fussed as wifi performance is still very decent however in my daughters bedroom its where you notice the change the most. When using DFS channels the routers can increase their transmit power and the difference is that on channels 100/108 the iDevices will sit on full wifi signal all the time rather than dropping to 2 bars and her Nintendo Switch will sit between 2-3 bars signal rather than 1-2 bars on channel 48.

My question is is this normal behaviour for the 86U I do live near a small airfield so radar would likely be detected, however I find it odd that the 68U didn’t release channel 100 yet the 86U wont stay on it for long. Is it because the 86U has a more sensitive antenna setup and is likely detecting radar that the 68U likely didn’t detect? Or do I have a faulty unit? Or is this just how the newer Asus Routers handle DFS channels?
I have exactly the same behavior on my AX3000 / RT-AX58U: DFS channels are dismissed after radar activity has been detected. But then no more switching back to DFS channel where the transmission is much higher, and in general WiFI stability is much better. Also scheduled daily restarts do not improve the situation at all...

any hints what we can do here?
 

L&LD

Part of the Furniture
I don't think there is any solution here. Unless moving to an area where your router can't pick up DFS channel usage is an option.

Test the lower channels up to Control Channel 48 (rebooting after each change and waiting 10 minutes before testing) and doing the same with the higher Control Channels 149 and above.

Using Auto for anything is usually a compromise on stability, reliability, performance, and/or some combination of all three.
 

Stuey3D

Regular Contributor
When I posted this I was running Merlin 384.18 and now I am running 384.19 I am locked to channel 100 and this issue appears to be fixed for me.

On 384.18 it used to choose channel 108 or channel 64 and it was never very reliable, on some reboots It’d bounce between channel 108 and 64 randomly, other reboots it would choose 108 then drop to 48 and stay there, these issues usually presented themselves on the first day of being rebooted.

Now on 384.19 it chooses channel 100 nearly all the time and it appears to stay there perfectly, my uptime is nearly a week now and it hasn’t changed its still on 100 which on 384.18 is unheard of. Although on one occasion it did drop to 48 but never went back to 100 like I’d expect so I guess not completely working as it should, but definitely for me something changed in that firmware update.

All my settings are set to auto and I have disabled smart connect.
 

L&LD

Part of the Furniture
@Stuey3D, I hope the firmware upgrade solves your issues for good. But on 'Auto', you're just vulnerable to random issues as the WiFi environment in and around your home changes (and it does change constantly).

If you do find further issues (and you still do it seems, just less frequently), try testing manual Control Channels as suggested above to solve the issue.
 

Stuey3D

Regular Contributor
@Stuey3D, I hope the firmware upgrade solves your issues for good. But on 'Auto', you're just vulnerable to random issues as the WiFi environment in and around your home changes (and it does change constantly).

If you do find further issues (and you still do it seems, just less frequently), try testing manual Control Channels as suggested above to solve the issue.
Right now the router is working almost perfectly but I do have one issue with it and it’s that it decides it will reboot randomly.

When it’s up and running everything is working perfectly but just randomly it will reboot. I’m not sure if it’s a RAM usage issue or not. I have adaptive qos on, AIProtect on, Traffic Analyser On, AiMesh on. When the router is initially booted it has around 120MB of RAM free but over time that drops and this morning that had dropped to around 58-60MB then suddenly the router rebooted it had been up for 7days 10 hours at that point. That 7 days was the longest uptime I’ve had since I got the router too, because of experimenting and then nuking it and starting again so not sure if this is a one off or a regular problem. It had auto rebooted in the past pre nuking too, again just randomly.
 

L&LD

Part of the Furniture
Auto rebooting isn't a good sign of a stable router/network to me. I would be doing an M&M Config asap if you want a more reliable network. See the link in my signature below for that guide.
 

Stuey3D

Regular Contributor
Auto rebooting isn't a good sign of a stable router/network to me. I would be doing an M&M Config asap if you want a more reliable network. See the link in my signature below for that guide.
I’m still debating whether to switch back to the official release as I don’t really use many of the advanced features of Merlin‘s firmware, the only thing I use is FQ_Codel on the Adaptive QOS but even then I’m not sure how much of a performance boost that gives over stock firmware Adaptive_QOS.

I was starting to have odd little gremlins on the 68U which is what prompted me to get the 86U in the first place, I put the gremlins on the 68U down to the amount of devices (29-32 at any time) and the age of the router. The 86U does perform much better though.

As for this m&m config why is this needed? After the update to 384.19 I did the JFFS format and 3 reboots, then an initialise all settings from the GUI followed by a WPS button reset too, surely that has reset the router to out of the box fresh ready for setup? As I said before I had the rebooting issue when I first set it up too, I’m hoping its not a hardware issue.
 

tts

Occasional Visitor
I have AC68U and DFS enabled. I think I am always on 100, it never switched once.

Is there any log I can check on DFS/radar activity?
 

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