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Asus XT8 Optimization Advice

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Spartacus

Occasional Visitor
I have a ZenWifi XT8 setup in my small one story home (~1800 sq ft). The node is connected via wired backhaul. I've segregated my IOT devices on a separate Guest Network and now I'm trying to decide how best to optimize the bands. Currently I have separate SSIDs for the 2.4 and 5GHz bands. I've further split the 5GHz-2 band to accept only AX connections.

My question is around the Wireless mode, Channel Bandwidth and Control Channel. Are these best set to auto or is it better to specify each? Is it better to set bandwidth to 20/40/80 or specify the bandwidth directly? Using Wifi Signal on my Mac, I'm noticing very short but significant speed drops that happen pretty regularly and it's driving me nuts trying to figure out the cause. Any informed advice would be greatly appreciated.
 
I think what you're describing is what's commonly called "ping spikes". SNB published a good article about that awhile back: Wi-Fi Ping Spikes: Causes and Fixes. That article recommends avoiding auto channel selection because of the possibility of service drops when the AP decides to choose another channel. However, IME the XT8 doesn't repeat ACS very often, so I suspect that isn't your problem. (The benefit of leaving it on is that you have a chance of your setup auto-adapting when your neighbor sets up a new WiFi system on what had been your clearest channel.)

As for bandwidth, the rule of thumb is that wider bandwidth transports data faster but at a lower signal-to-noise ratio. So if you have a lot of interference, the wider bandwidth settings are more prone to needing retransmissions, which might be the cause of the spikes you're seeing. If you don't actually need 80MHz bandwidth - say, your internet connection is only 100Mbps anyway - reducing the max bandwidth setting might be helpful.

However, first go read the above-linked article, and see if any of its other recommendations apply to your case.
 
Thank you tgl. I'll take a look. I have GB internet so lower bandwidth isn't a good option. I was wondering more if letting it choose was better than forcing it to 80 MHz. Could it potentially use the lower bandwidth when not strictly necessary?
 
Some will disagree but I advocate SmartConnect and auto channel. In a crowded environment setting 2.4 GHz to 20 MHz is a good idea. Use DFS if you can. 80 MHz on the 5GHz bands is OK.
You spent the money on a good router let it and the clients choose what is best for them.
 
I could be wrong, but I believe that the 20/40/80 setting means precisely to auto-adapt the channel bandwidth depending on traffic volume. I wouldn't move away from that setting without an extremely specific reason.

As bbunge says, in the 2.4GHz band you should leave it set on 20MHz, unless maybe you live out on a prairie somewhere. If you can see any other 2.4GHz networks then a 40MHz setting will create too much interference.

Anyway, to return to what I said yesterday, the way you're setting up the system seems to say that you don't want any roaming between channels/APs to happen. In that case, per the "ping spikes" article, you should turn off 802.11k features. In ASUS-speak that seems to boil down to disabling the roaming assistant.
 
I could be wrong, but I believe that the 20/40/80 setting means precisely to auto-adapt the channel bandwidth depending on traffic volume. I wouldn't move away from that setting without an extremely specific reason.

As bbunge says, in the 2.4GHz band you should leave it set on 20MHz, unless maybe you live out on a prairie somewhere. If you can see any other 2.4GHz networks then a 40MHz setting will create too much interference.

Anyway, to return to what I said yesterday, the way you're setting up the system seems to say that you don't want any roaming between channels/APs to happen. In that case, per the "ping spikes" article, you should turn off 802.11k features. In ASUS-speak that seems to boil down to disabling the roaming assistant.
Unfortunately, that doesn't seem to have done it. I turned off Roaming Assistant per the article but I'm still seeing the issue. I've attached an example of what I'm seeing.
 

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My question is around the Wireless mode, Channel Bandwidth and Control Channel. Are these best set to auto or is it better to specify each? Is it better to set bandwidth to 20/40/80 or specify the bandwidth directly? Using Wifi Signal on my Mac, I'm noticing very short but significant speed drops that happen pretty regularly and it's driving me nuts trying to figure out the cause. Any informed advice would be greatly appreciated.

Informed advice is a tall order... I make a lot of assumptions until determined otherwise.

I look to restrict Wireless Mode to only those required. With Smart Connect disabled, I can set 2.4/5.0 to N only/N-AC-AX mixed... current clients.

I look to maximize Channel Bandwidth for max capacity, subject to DFS/WiFi/other interference and weird firmware behavior/restrictions...

Given 2.4 travels far and is subject to crowd interference, convention is to be courteous and live with 20MHz bw on non-overlapping channels 1,6,11... avoid too much cross-channel interference, and co-channel interference that is too near/similar in power dBm.

For 5.0, you can try to shoe horn in 160MHz, but more likely than not, it won't fit... legacy clients may restrict you to using non-DFS control channels, limiting 160MHz to just one option. And if DFS doesn't cut you back to 80MHz, other interference may since 160MHz increases the potential for WiFi/other interference. So, I fix 80MHz and try to find the non-DFS control channel for client compatibility that affords the least noise and best client/node connections (ch 36-48,149-161). Auto channel seems to find the first acceptable channel and stay there, even when other channels may exhibit less noise and stronger client/node connections as seen in the Wireless Log. So, I check each candidate channel for best results, fix the best one, and then keep an eye on things over time. Fixing both bw and ch promises the most stability/least client disruption, imo.

If you want to set and forget and hope for the best user experience i.e. surrender, then let the router decide... set variable bw 20-40-80MHz (-160, too, if you KNOW it will work reliably in your DFS radio space) and ch Auto with/without DFS control channels depending on your clients. This approach may be less successful in a crowded radio space where other routers are doing the same thing... hopping channels and limiting bandwidth to avoid crowd interference. I prefer to determine what's going on around me and then camp out with fixed bw and ch.

This article Wi-Fi Ping Spikes: Causes and Fixes is a good read and seems to fit with my experience through trial and error, although the term 'Ping Spikes' is a bit too narrow, imo... I would more generally say 'client or user experience disruption'.

OE
 
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Informed advice is a tall order... I make a lot of assumptions until determined otherwise.

I look to restrict Wireless Mode to only those required. With Smart Connect disabled, I can set 2.4/5.0 to N only/N-AC-AX mixed... current clients.

I look to maximize Channel Bandwidth for max capacity, subject to DFS/WiFi/other interference and weird firmware behavior/restrictions...

Given 2.4 travels far and is subject to crowd interference, convention is to be courteous and live with 20MHz bw on non-overlapping channels 1,6,11... avoid too much cross-channel interference, and co-channel interference that is too near/similar in power dBm.

For 5.0, you can try to shoe horn in 160MHz, but more likely than not, it won't fit... legacy clients may restrict you to using non-DFS control channels, limiting 160MHz to just one option. And if DFS doesn't cut you back to 80MHz, other interference may since 160MHz increases the potential for WiFi/other interference. So, I fix 80MHz and try to find the non-DFS control channel for client compatibility that affords the least noise and best client/node connections. Auto channel seems to find the first acceptable channel and stay there, even when other channels may exhibit less noise and stronger client/node connections as seen in the Wireless Log. So, I check each candidate channel for best results, fix the best one, and then keep an eye on things over time. Fixing both bw and ch promises the most stability/least client disruption, imo.

If you want to set and forget and hope for the best user experience i.e. surrender, then let the router decide... set variable bw 20-40-80MHz (-160, too, if you KNOW it will work reliably in your DFS radio space) and ch Auto with/without DFS control channels depending on your clients. This approach may be less successful in a crowded radio space where other routers are doing the same thing... hopping channels and limiting bandwidth to avoid crowd interference. I prefer to determine what's going on around me and then camp out with fixed bw and ch.

This article Wi-Fi Ping Spikes: Causes and Fixes is a good read and seems to fit with my experience through trial and error, although the term 'Ping Spikes' is a bit too narrow, imo... I would more generally say 'client or user experience disruption'.

OE
Thanks OE! That's more consistent with what I've been reading (e.g. set max bw and force cleanest non-dfs channel). Still getting these damn "ping spikes" though despite turning off the Roaming Assistant. Is there another way to track down what's causing the issue?
 
Thanks OE! That's more consistent with what I've been reading (e.g. set max bw and force cleanest non-dfs channel). Still getting these damn "ping spikes" though despite turning off the Roaming Assistant. Is there another way to track down what's causing the issue?

I'm not particularly skilled at such troubleshooting, mostly because I lack the tools and training. My lay approach is to divide and conquer by process of elimination. As discussed in that article, a ping spike is a delay in transmission/reception that could be attributed to one of many different causes... so you need to be careful not to rule things in or out prematurely... and resist the temptation to assume the quick fix is a router setting. When troubleshooting, it can help to come at the problem from a different angle... a different test, a different client, etc... to avoid getting stuck on one line of reasoning that isn't moving you forward. Sometimes fixing a prerequisite eliminates the problem indirectly... like time to upgrade something instead of blindly struggling with it.

OE
 
Thanks again OE, I applied as much from the article as I could so I'll continue to poke around to see if I can figure out what's going on.
 
Spartacus, sorry to go off topic. You mentioned you have your IOT devices on a guest network. I guess that mean they are completely separated from your main network and only communicatie over the internet?

I'm asking because my IOT devices on the 2.4Ghz have terrible connections and keep dropping. It's driving my crazy to the point where I'm thinking about returning my XT8's. I just don't understand how these expensive machines have worse results than my cheap ISP router...

If setting them up on a guest network is the trick, then I would need that to have access to the main network as I have devices running locally on there, including my home automation server.
 

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