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XT8 AX6600 Slow Wireless Backhaul

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tehdesolate

New Around Here
So I purchased a 2 pack of the ZenWifi XT8 (AX6600) and have it configured as such:

Router 1: Configured as a Router and main hub for the mesh node. WAN1 connected to Verizon FIOS ONT box. LAN1 services one low-usage endpoint.
Router 2: Configured as a mesh node and connected to the main hub (Router 1) via wireless backhaul (5GHz-2). I have a simple gigabit TP-Link switch attached to LAN1 that services multiple endpoints.

From Router 1's built-in speed test: ~850mbps down/up on a 1gbps FIOS connection.
From an endpoint wirelessly connected to 5GHz-1 on Router 1: ~600mbps down/up

Here's my problem: From an endpoint on the switch attached to Router 2 or from an endpoint wirelessly connected to Router 2: avg 260mbps down/up on 5GHz and avg 40mbps down, 20mbps up on 2.4GHz. This was 0.09mbps down/up earlier today on the 2.4GHz radio, which choked out my entire battalion of IOT devices hanging off of this router.

The routers are situated approx. 50 feet away from each other separated by one wall and a floor. I've disabled support for a/b/g and am only using N/AC/AX on all radios. QOS, Smart Connect, and all of the other useless bells and whistles are turned off. These routers are running fairly lean at about 5% CPU usage and 70% RAM usage. CPU usage spikes to about 15% during a speed test. Obviously these routers are not being taxed and aren't gasping for additional compute resources like I gasp for another hour of sleep when my alarm clock goes off in the morning. I've ruled out potential bottlenecks other than the backhaul link as well. All devices on the gig switch have 1gbps rated NICs. The routers are advertised as having a 5GHz-2 (EDIT: radio) rating of 4800mbps, but I'm barely squeezing out 5% of that on my 5GHz-1 net and a laughable 1% on my 2.4GHz net despite signal strength between the routers being rated as "Great" from the main hub's homepage. Firmware on both routers are current as of this posting. Based on this backhaul connection spec and lack of compute usage, I should reasonably expect parity between both routers at ~600mbps down/up, but this is not the case.

I've included the Wireless Log as well for review.

Has anyone else had this problem with the XT8 and have found either a workaround or a solution to this?
I'm eventually going to run CAT6 to both routers and connect them to a Catalyst 2960S so this issue will become OBE, but it would be nice to know if there was firmware available or a configuration change(s) I can make to fix this in the months between now and then.
 

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One of the 5Ghz radios seems to be using channel 165 that is only 20Mhz. Is this the backhaul radio (SSID: "7EB9E616192FD89E3D81BF3794254BDD"?
 
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It is. As another person commented in another thread, I tried forcing the backhaul to use 160Hz, but this didn't result in any positive change. The backhaul radio is set to 20/40/80/160 MHz (auto, for all intents and purposes). I set the channel manually to 165 as the local Dopler Radar likes to prowl the lower channels and bump my clients offline from time to time.
 
I would try setting the backhaul to a non-DFS 80Mhz channel (36 or 149) and see how it behaves. Trying to get 160Mhz channels working in an area with radars seems like an impossible task (until 6Ghz equipment arrives)
 
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Am using channel 44 for the 5GHz-1 radio, and channel 157 for the backhaul (5GHz-2 radio), both radios set to 80MHz. channel width. Getting faster speeds at the remote node on gigabit internet, more like 500+Mbps. I found that using 160MHz. channel width on the backhaul (5GH-2 radio) was a bunch slower than using 80MHz. channel, since the DFS channels apparently don't work well here.

Happy with the speed, considering using wireless backhaul.
 
Well, I see an improvement up to 360mbps on the 5GHz-1 net and a big increase up to 130mbps down, 20mbps up on the 2.4GHz net. While it's a significant improvement, it's not anywhere near what I should be getting. The speedtest from Router 1 is still just a smidge under 900 down and 830 up.
 
Just to be sure doublecheck that the XT8s are using different channels on 5GHz-1 and 5GHz-2 (not sure if the UI does the check already).
After this you might need to start trying different placements for the XT8s looking to improve performance by reducing distance and avoiding obstacles.
 
5GHz-1 is on channel 48 and 5GHz-2 is on channel 161. I'm thinking placement could be a potential issue, which I might be able to adjust later today. Router 2 is already mounted to the wall while Router 1 is not, so I could potentially relocate Router 1.
 
5GHz-1 is on channel 48 and 5GHz-2 is on channel 161. I'm thinking placement could be a potential issue, which I might be able to adjust later today. Router 2 is already mounted to the wall while Router 1 is not, so I could potentially relocate Router 1.
You know, if you use the Asus router smart phone app, and tap on the node on the Home page, you'll go to the page for the node. At the top it has an RSSI number, which gives you a feeling for how well connected the router and node are. Here, I see from -57 to -55dBm. Right at the moment it's -56dBm, and, as I said, the speed is good here. Using the node's RSSI should be a help in placement.
 
The particulars about the positioning of wireless access points and what interferes with its signals are within my scope of knowledge, but what escapes me is how HVAC interferes with it. Not that it simply does interfere, but how?

For example (see picture attached), I'm contemplating placing Router 1 on a bump-out wall section that serves as a riser for an HVAC duct highlighted in red. North is the exterior wall of the house, East and West sides point to the side of my home, and South points directly towards the interior of the home.

If I place the WAP on the South wall of the bump-out (green dot), how is the signal interfered with for devices south of the WAP? Does the HVAC return ducting bounce the signal back out and scatters it? Does it act like an echo chamber and scatters the signal throughout the duct work and introduces interference that way? I guess the simplest question would be: If I put the WAP on the south wall, will the HVAC ductwork behind the wall significantly interfere with the signal for devices south of the WAP?
 

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As a follow-up, I moved the router into its final resting place and saw an immediate jump in performance up to 600mb down and 500mb up over the wireless backhaul. It's been smooth sailing since then.

As a final opinion on the XT8, I'll say that the connection rating for the backhaul wireless link is deceiving.
 
You need to go through and manually set the backhaul channel to include dfs. If you can't have dfs because of radar, manually set it to 80mhz. Do not use the 20/40/80 auto option. I beleive this is where your issue lies. An 80mhz backhaul will still give you around 1.7gbps.

Try setting your 5ghz front haul channels to auto channel selection unless you know for sure the channel you are using has low utilisation or is clear.
 

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