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Retreat Center network under load - Interpreting RF saturation data

A model citizen

Retreat Center network under load - Interpreting RF saturation data

Hey all! My work has paid off and I have had two times in the last week or so where Ive had 85 max users, usually concentrated between a couple APs and things have been fine. The highest RF usage ive seen is in this first pic on this AP called Courseroom Indoor. Everything seems to be working fine. There is a session going on at this moment (a room full of people on this MR52 next door) Clients on that AP are all on 5ghz and im confused about where the 2.4ghz traffic is coming from on channel 1. 

 

Screen Shot 2019-08-02 at 11.39.11 AM.png

 

 

Looking at the mesh neighbors on that AP we see:

 

Screen Shot 2019-08-02 at 11.41.31 AM.png

 

Except neither of those APs are particularly active nor are they using this gateway as their gateway. They are using an adjacent one and are meshed to the other on 5ghz. Channel use is channel use but I thought Id still provide the background.

 

Which leads us to the RF spectrum interfering APs list:

 

Screen Shot 2019-08-02 at 11.45.36 AM.png

 

Ok Im not sure how to interpret this exactly but I have read this:
https://documentation.meraki.com/MR/Monitoring_and_Reporting/RF_Spectrum_Page_Overview

There does not seem to be anything that could reasonably cause interference to the point where I have a 50% saturated channel 1.

 

Im way out in the country and so my air is very RF clean. 

 

They just left the room, and now channel 1 has calmed down to like 12%. So their traffic was a factor, but nobody was on channel 1. What gives? 

Networking geek since high school where I got half of a CCNA. Played Marathon II and Infinity over localtalk.
Made many a network over the years, now de facto admin of a retreat center with some of this fine Meraki hardware.
Fortune 100 Tech veteran/refugee.
7 REPLIES 7
A model citizen

Re: Retreat Center network under load - Interpreting RF saturation data

There is now a new group of 15 on that AP and both bands now report "very low". So maybe a fluke? Seems odd.

Networking geek since high school where I got half of a CCNA. Played Marathon II and Infinity over localtalk.
Made many a network over the years, now de facto admin of a retreat center with some of this fine Meraki hardware.
Fortune 100 Tech veteran/refugee.
A model citizen

Re: Retreat Center network under load - Interpreting RF saturation data

OK now I have channel 157 as "jammed" or "very high" on an AP with literally no traffic. 

 

Here:

 

 

Screen Shot 2019-08-02 at 2.29.32 PM.pngThere are no 5ghz mesh neighbors as this is a gateway.Screen Shot 2019-08-02 at 11.41.31 AM.png

 

Doesn't look like much of note is happening here (i sorted by channel and there is nothing on 157)Screen Shot 2019-08-02 at 11.45.36 AM.png

 

 

Utilization report:

Screen Shot 2019-08-02 at 2.34.55 PM.png

 

 

 

So WTF is happening? 

 

 

Update: 5 min later is now completely flat again at "very low". Weird.

Networking geek since high school where I got half of a CCNA. Played Marathon II and Infinity over localtalk.
Made many a network over the years, now de facto admin of a retreat center with some of this fine Meraki hardware.
Fortune 100 Tech veteran/refugee.
Kind of a big deal

Re: Retreat Center network under load - Interpreting RF saturation data

@RumorConsumer  I have found the RF spectrium page in my own experience to not be that great. I have an MR18 at home and with one device connected and doing next to nothing the channel was maxing out.

 

In regard to the 2.4Ghz spectrum remember that there is a ton of non IT devices that interfere with this channel i.e. cordless phones, microwaves etc. 

Meraki CMNO, Ruckus WISE, Sonicwall CSSA, Allied Telesis CASE & CAI
Kind of a big deal

Re: Retreat Center network under load - Interpreting RF saturation data

There are a lot of things that use the 2.4Ghz spectrum.  Some common ones are:

* Bluetooth (so if you have a lot of users with devices and bluetooth turned on 2.4Ghz WiFi can be hurt)

* Cordless microphones (have run into this at events - you only find out about it when the mics get turned on).

* Some domestic speakers

* Cordless phones (not so likely in your case)

 

Then you can get devices that creae WiFi "personal area networks".  For example, I have a 360 degree camera and it uses 2.4Ghz WiFi when talking to my smart phone.  360 degree 4k video soaks up every bit of bandwidth it can.  It can chew a whole channel out on its own.

 

And I bet there are probably other personal devices that uses have that can eat up the bandwidth as well.

Building a reputation

Re: Retreat Center network under load - Interpreting RF saturation data

I wish I had an Ekahau sidekick so I could also verify what dashboard is saying about interference is actually correct.

The graph is surely wrong because the center channels are always wrong especially in the 2.4 GHz band.

There can of course be non-WiFi interferers on your channel and if they have a high duty cycle then yes, you could have a 'jammed' warning even with no WiFi clients in that area.

I've also complained to Meraki for almost two years now that they should fix the spectrum analyser page and include the damn UNII-2 bands.

A model citizen

Re: Retreat Center network under load - Interpreting RF saturation data

@BlakeRichardson But was the channel maxing out? And re 2.4ghz yes I am aware and I thought maybe something was causing that interference. There was a group of tech entrepreneurs using the property and its possible that one of them brought along something that made an annoying PAN as @PhilipDAth suggested. Also, as he mentioned, bluetooth I supposed could be a culprit with 60+ people with their phones all clustered together. Cordless mics weren't used. Doesn't mean there wasn't something.

Ok good to know guys thanks as always.

@GIdenJoe what does
>The graph is surely wrong because the center channels are always wrong especially in the 2.4 GHz band.

mean?
Networking geek since high school where I got half of a CCNA. Played Marathon II and Infinity over localtalk.
Made many a network over the years, now de facto admin of a retreat center with some of this fine Meraki hardware.
Fortune 100 Tech veteran/refugee.
Building a reputation

Re: Retreat Center network under load - Interpreting RF saturation data

If you look at the 2.4GHz graphic you’ll see that channel 6 RF output seems to be centered around channel 5 instead.

Also it’s unclear if signals from the same AP are ignored or not.  Since it uses a separate radio to scan it should also see it’s own transmitted signal.

 

Simply put we need

 

Info how the scanning works exactly

What It uses to project It onto the graph

A much higher resolution

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