Asus Zenwifi XT8 5GHz-2 Band DFS Channel Backhaul Behavior

tomatopotatochilli

Occasional Visitor
I have the 2-pk XT8 Mesh system. The 2 routers are connected through the 5GHz-2 band as dedicated wireless backhaul. The channel used is DFS channel.

Now, if a DFS/Radar event happens and the channel can't be used, what is the behavior of the system, specifically the AiMesh satellite node? I am trying to understand the disruption for clients connected on all bands (2.4, 5-1, 5-2) to the satellite.

1. The 5Ghz-2 band will just switch to another non-DFS channel at the time with minimal interruption to any connected device? What if, channel is the manually selected?
2. The satellite will just switch to using 5Ghz-1 band as the backhaul for time being at cost of some performance hit?
3. The satellite will detect the backhaul being disconnected and declare itself offline - the client can switch to a different AP if available?
4. The satellite will stay online to clients but disconnected from main router hence causing an availability delay for minutes till the DFS channel clears again?
5. Some other behavior.

Please explain exactly what to expect. Thanks.
 

JagoUK

Regular Contributor
If a DFS event occurs. Router and Node move to another 5ghz-2 band on channel 100-140.

This happens if you have automatic or manual channel selection.

It will disable channel changing for 31mins.

This is a problem for 160mhz as it pushes you down to 80mhz. In effect stopping 4gbps backhaul.

5ghz-1 is NOT available for backhaul. Although it will temporarily use 2.4ghz to sync while 5ghz is disabled.

For this reason I returned my XT8'S.

See review in my signature for further explanation.
 

OzarkEdge

Part of the Furniture

JagoUK

Regular Contributor

OzarkEdge

Part of the Furniture
Ran the Ethernet cables back around the house
You, Sir, are a man of action! :)

I hope AiMesh 2.0 affords you another go at it.

OE
 

JagoUK

Regular Contributor
You, Sir, are a man of action! :)

I hope AiMesh 2.0 affords you another go at it.

OE
Well unless Asus give us 80+80 and amazon put it on sale again ill have to wait for the 6e Version.
 

tomatopotatochilli

Occasional Visitor
If a DFS event occurs. Router and Node move to another 5ghz-2 band on channel 100-140.

This happens if you have automatic or manual channel selection.

It will disable channel changing for 31mins.

This is a problem for 160mhz as it pushes you down to 80mhz. In effect stopping 4gbps backhaul.

5ghz-1 is NOT available for backhaul. Although it will temporarily use 2.4ghz to sync while 5ghz is disabled.

For this reason I returned my XT8'S.

See review in my signature for further explanation.
Thanks for confirming that the system will just move 5.2 band to another channel in all cases. So, I should expect an almost seamless transition in connectivity for my client devices. Right?

Now, even if 160Mhz drops to 80Mhz, it remains a 2400Mbps backhaul and in my environments, I expect it to actually provide 400-500Mbps which is ok if DFS events are rare.
 

JagoUK

Regular Contributor
No, when a DFS event is triggered it will knock 5ghz out for 2 mins and that channel for 31mins. 5ghz is always disabled for first 2 minutes of boot as it has to listen on DFS before broadcasting.

Max speed i got when located in place on 160mhz was 2800mbps. Even with routers a metre apart max speed was 3400mbps.

80mhz lowered speed to 1600mbps.

Max transfer speed on wireless AX 160mhz with NAS plugged into node transferring file to Samsung S10+ was 65MBps. Using an ethernet to USB-C into same phone was 100MBps.
 

tomatopotatochilli

Occasional Visitor
I'm less worried about speed drops as long as I get say 100-200Mbps+ during that time. Connectivity loss of 2 minutes is a much bigger problem.

Did you mean 5.2 Band will be out for 2 minutes or both 5.1 and 5.2? During that time what happens to a client connected on 5.1/2.4 to the satellite? Does it show connected but doesn't actually work?

Is there any way to simulate a DFS event in the router? Any logs you can point to where I can see if these events are happening and I haven't noticed?
 

JagoUK

Regular Contributor
I'm less worried about speed drops as long as I get say 100-200Mbps+ during that time. Connectivity loss of 2 minutes is a much bigger problem.

Did you mean 5.2 Band will be out for 2 minutes or both 5.1 and 5.2? During that time what happens to a client connected on 5.1/2.4 to the satellite? Does it show connected but doesn't actually work?

Is there any way to simulate a DFS event in the router? Any logs you can point to where I can see if these events are happening and I haven't noticed?
100-200mbps should be easily achievable.
I managed to stream a 120mb UHD 60fps.

IIRC both 5ghz get blocked for 2 mins. But only the 5ghz channel that detects the DFS event gets blocked for 31mins.

In my case it was a local weather radar.
The DFS channel gets blocked but I've never had it switch back to selected channel so it effectively stays blocked until you intervene.

You can see DFS events in the event log. Look for "RADAR" (doesn't always appear which i think is a bug)

Also look at review in my sig where I have written about this.
 

tomatopotatochilli

Occasional Visitor
I read your review (excellent and very useful) and checked logs in my router too.

The thing that is confusing me is if 5 band got blocked for 2 minutes, did you lose connectivity or 2.4 band handled it during that time?
 

JagoUK

Regular Contributor
I read your review (excellent and very useful) and checked logs in my router too.

The thing that is confusing me is if 5 band got blocked for 2 minutes, did you lose connectivity or 2.4 band handled it during that time?
5ghz gets blocked for 2mins and light goes yellow, backhaul and all other traffic is restricted to 2.4ghz then after 2mins goes back to white again and 5ghz works again.
The channel gets blocked for 31mins and not selectable.
 

tomatopotatochilli

Occasional Visitor
Ouch. Like you said in your review, I really don't want to return this unit.

Is this ASUS specific implementation issue of losing both 5.1/5.2 or required by DFS regulations in your area.?

I am in US and at least logs don't show any events in last day or so, but need to read up more. I wish they simply has a simulate DFS event through some tool/setting option, just so that I know what to expect when it happens.
 

JagoUK

Regular Contributor
Ouch. Like you said in your review, I really don't want to return this unit.

Is this ASUS specific implementation issue of losing both 5.1/5.2 or required by DFS regulations in your area.?

I am in US and at least logs don't show any events in last day or so, but need to read up more. I wish they simply has a simulate DFS event through some tool/setting option, just so that I know what to expect when it happens.
It is Asus aggressive DFS implementation.

If you want to test it then turn your router off then back on again and look in the wireless log.

Alternative is to manually pick each channel one by one and it will trigger this in the wireless log.
20200816_230937.jpg
 

JoWa

Occasional Visitor
The problem I have is that when XT8 drops to 2,4ghz.. it never goes back to 5ghz... I have tried to disable DFS... manually choose only 80mhz... disable 160mhz.. run AUTO 20/40/80/160.. running only 160mhz.. and more.. I tried it all.. but it always drops to 2,4 and never goes back.. I have a great signal quality between router and nod. So thats not the issue.
 

tomatopotatochilli

Occasional Visitor
If you don't have a DFS channel (verified with manual selection and wifi analyzer), then why does it drop to 2.4? For me, switching off smart connect and roaming assistant helped on the first day when I saw some switching to 2.4 randomly. No problem since then.
 

tomatopotatochilli

Occasional Visitor
Btw, following settings in the wifi driver (if available) really make a device stick to 5Ghz as long as the signal is not very weak. Really works well for me.

Set Preferred Band to 5Ghz
Set Roaming Aggressiveness to Highest

See if that solves your problem.

1599849595172.png
 

JoWa

Occasional Visitor
thanx for tip, but its not my computer thats the problem. Nod goes from GREAT 5ghz to WEAK 2,4 signal after a short while
 

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