Poor performance with 2 Airport Extremes

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Level 1

12 points

Poor performance with 2 Airport Extremes

Hi,

We have an office with a ground and upper floors with identical latest model Airport Extreme (ac-compatible) on each. They are both at the latest firmware and are configured to just be wi-fi access points with no routing function (Bridge mode), IP v6 set at link-local only and each connected to the network via ethernet. Each has 2.4GHz and 5GHz versions of its own created network. Each is set to auto-select the channel(s) to use on each.

We are having intermittent, although increasing in frequency, performance issues with the upstairs Extreme, specifically, seeing network speed tests less than half the figures for a device connected to the downstairs Extreme’s wi-fi. Does anyone know why this scenario would result in this beyond there simply being a fault with the upstairs Extreme or its connections, or have any ideas on further trouble-shooting?

Regards,

GAM

iMac, macOS Sierra (10.12.6)

Posted on Jun 4, 2018 10:59 PM

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Answer 1

Top-ranking reply

LaPastenague

Level 9

67,262 points

Jun 6, 2018 1:09 AM in response to gamcall64

There is not enough screen resolution to really see the numbers clearly.

But it looks like signal is below -60db.. in some places below -70db.

You will not get decent speed with signal that low. And 5ghz is very poor tranmission through materials.. so you really do need to get closer or simply better ..

Swap the Extreme now and see if the problem follows the router.

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Answer 2

Tesserax

Level 10

157,896 points

Jun 6, 2018 12:40 PM in response to gamcall64

Thanks for posting the screenshot.

Signal-to-Noise Ratio (SNR) is one measure of Wi-Fi signal "quality." The basic formula is: SNR = Signal - Noise

In the screenshot, RSSI = Signal, so the formula would now read: SNR = RSSI - Noise

If I can read the image well enough, you got an RSSI of -82 and a noise value of -86, plugging them into the formula, you would get: SNR = -82 -(-86) = 4

Using the following SNR Guideline as reference, that value of 4 would represent "Little or no signal." You can't get much worse than that.

SNR Guideline

40+dB = Excellent signal
25dB to 40dB = Very good signal
30dB = Minimum range boundary (voice)
15dB to 25dB = Low signal
20dB = Minimum range boundary (data)
10dB to 15dB = Very low signal
5dB to 10dB = Little or no signal

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Answer 3

Jun 5, 2018 1:47 AM in response to gamcall64

Latest model Extreme can be up to 5 years old.. so how old are they?

To troubleshoot wireless is always difficult.

First job is to actually make sure the upstairs computers are connected to 5ghz upstairs.

Run the wireless diagnostics from one of your computers. The scan is the most important part of it. Open it out so you can see all the columns.. and check both signal and channel your computer is connected to.

Second thing I would do is swap upstairs and downstairs Extreme..

Does the problem follow the Extreme or stay in the same location? The former tells you something is wrong with the Extreme.. the second is likely caused by ethernet not working correctly.

Perhaps the best thing is to give us screenshots then of your results with both and we can then figure out the next test.

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Answer 4

Tesserax

Level 10

157,896 points

Jun 5, 2018 11:46 PM in response to gamcall64

The screenshot that LaPastenague provided is from the Wireless Diagnostics app. You can access this app by holding down the option key, and then, click on the Wi-Fi icon on the macOS menu bar. Once the app starts, do not click on Continue, but instead, select Window > Scan from the app's menu bar.

Ref: macOS Sierra: Use Wireless Diagnostics - Apple Support

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Answer 5

gamcall64 Author

Level 1

12 points

Jun 5, 2018 7:08 AM in response to LaPastenague

Hi there - thanks for your reply. The Extremes are at least 3 years old, I’d say.

Yes - testing clients have been connected to the 5Ghz, but also to the 2.4GHz (by design).

The scan is /var/tmp/WirelessDiagnostics_<serial>_<date-time>_<seq-no>/wifi_scan.txt, yes? What program are you using in that screenshot? Have you opened that file?

Yes - had considered swapping Extremes around.

Thanks,

GAM

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Answer 6

gamcall64 Author

Level 1

12 points

Jun 6, 2018 12:23 AM in response to Tesserax

Hi Tesserax,

Thanks for that. I had run the Wireless Diagnostics app, but I ran it by hitting Continue the first time, so I missed those other options “hidden” under the Window menu item. Below is a screenshot of the various windows of WD focussing on the Wifi network of concern (upstairs 5GHz). Part of the SSID has been redacted.

And yes - I have noted the AT country code Wifi network in our vicinity as a possible issue, but it also appears in the list when running WD against the downstairs network and as I said before, there are no issues there.

Thanks,

GAM

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Answer 7

gamcall64 Author

Level 1

12 points

Jun 10, 2018 11:35 PM in response to Bob Timmons

Thanks for your reply Bob, but I wasn't extending one airport with another. They were 2 base stations, each with their own created networks, as I thought I had described in my original post.

Regards,

GAM

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Answer 8

gamcall64 Author

Level 1

12 points

Jun 10, 2018 8:36 PM in response to Tesserax

Hi Tesserax,

Thanks again for your reply.

The value of the noise was 95 (not 86), so the SNR value is actually 13, which is still pretty low on that scale you cite and it points to the actual problem, which turned out to be the location.

Swapping the units didn't change the situation; i.e. the downstairs unit behaved as the upstairs one in the same location (and the upstairs unit had the same performance in the downstairs location as the downstairs one did). Once I put the upstairs extreme in another location the SNR value shot up, as did the quality of the signal and so transfer rate. Then I took my laptop to where the extreme previously was and watched all the stats plummet again, so I'm pretty sure I established cause and effect; i.e. the upstairs extreme was previously in a wi-fi "dead-zone" due to whatever factors are at play in that location. I noticed there were iron bars on the window of the room. Maybe there was a "Faraday Cage" effect? However - there were similar bars on the window in another room and I didn't see a similar drop in stats when I took my laptop in there.

Whatever - I'm pretty sure an extreme (or any Apple base station) can't be in that room and deliver any quality wi-fi.

Thanks,

GAM

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Answer 9

Jun 10, 2018 9:30 PM in response to gamcall64

....the upstairs extreme was previously in a wi-fi "dead-zone" due to whatever factors are at play in that location.

Users often forget, or do not realize that an "extending" AirPort can only "extend" the quality and speed of signal that it receives.

True, the extending AirPort can make the signal "stronger" by re-broadcasing it, but it will not make the signal go any faster. So, the signal strength will improve in the remote area, but the signal quality/speed will not.

That is why the general rule of thumb for an AirPort that will extend using wireless is an AirPort location that is about half-way between the "main" AirPort and the general area where you need more WiFi coverage. The general rule assumes that your walls are of normal construction.....not cement or plaster.....and that there are no mirrors (which are in effect large sheet metal obstructions) in the signal path between the AirPorts.

If top performance is your goal, the only way that this can be achieved is to connect the remote AirPort back to the main AirPort using a wired Ethernet cable connection. When you do this, then you can locate the remote AirPort exactly in the specific area where you need more coverage.....since there is zero loss through the Ethernet cable, at least up to about 325 feet or 100 meters.

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Poor performance with 2 Airport Extremes

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