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Occasional Contributor I

Question: SNR and Path Loss - Show AP ARM State

So I am trying to make sense of the neighbor SNR as seen from an AP.

 

My current knowledge may be way off here, but I interpret the lower SNR to be worse than the higher SNR. But then path loss is higher for the neighbors with lower SNR, so I am a bit confused by this. Am I completely off?

 

Can someone explain these columns? I can't seem to wrap my head around them. I understand the concept of SNR as it relates to the AP's signal in relation to the background noise. But how do these columns help in explaining wether or not a neighbor is interferring?

 See attached screenshot. Thanks in advance!

Background:
FW 6.5.0.4, Controller: 7010. AP's are a 5 AP135's and two AP92's.

Contributor II

Re: Question: SNR and Path Loss - Show AP ARM State

Since this command only shows you info form the Aruba AP neighbors (and not outside neighbors). It can be helpful to determining how close the AP's are from each other. 

 

Current Channel = 6

Neighbors on Channel 6 = 2 

Power levels on Neighbors on Channel 6 = 9 

SNR from Neighbors on Channel 6 = 6 and 7

 

When relating this output to an avg SNR your client should have. SNR > 25 @ 2.4ghz, and SNR > 30 @ 5ghz. You can tell that from the AP's perspective the neighbors on channel 6 are not anywhere close enough to create co-channel interference. 

 

You do have 2 neighbors with SNR of 25 on channel 1, which shows that there are 2 AP's fairly close by. I personally dont use this command to review the path loss column. 

 

Typically when I use this command I am targeting a certian area and want to get a baseline of my neighbors. This data can be skewed if there are physical obstructions between the AP's. If you can confirm that your Aruba neighbors dont have high SNR's and are still getting interference on 2.4. Then its either non-aruba SSID's, other frequences that overlap in the same specturm, or non-wifi interference.  

 

Hope this info helps provide a bit better understanding on how this command can be useful. 

Justin Kwasnik | ACMX# 598 | ACCX# 638
Occasional Contributor I

Re: Question: SNR and Path Loss - Show AP ARM State

That is a wonderful explaination Justink84! Thank you!

 

 It makes sense, and I will repeat it back to you so that I am sure that I understand it correctly. The AP sees the other two AP's on channel 6, but their SNR is 6db, so close enough to the noise floor to not be a problem. Had those same AP's had an SNR of 25 or greater, then that would be possible Co-Channel interference.

 

Thanks again!

Contributor II

Re: Question: SNR and Path Loss - Show AP ARM State

Correct Upstanding_Citizen.

 

Just wanted to remind you that this output is for Aruba AP neighbors only and does not include outside the enviornment. If you wanted to get an idea of all SSID's (aruba and non-aruba), you could run the following command. 

 

- show ap monitor ap-list ap-name <ap-name> sort chan,asc

 

Most of the time admins would want the frequencies to not have any interference at all. Although functions of ARM do require a specific level of interference to be present in order to change power levels on AP's and also channel changes (this also depends on how your ARM config is setup). 

 

If you had all of those AP's with an SNR of 25 or greater (more so SNR 30+), reguardless of what channel you were on. I would then state that your RF is fairly dense on 2.4 and it may be a good idea to disable a few radios (air monitors vs actually disabling). 

 

If you start seeing a number of AP's that are SNR 40+ then you may want to start reviewing power levels on neighbors, SSID TX Rates, and physical locations. Sometimes these stats can be skewed when AP's are surrounded by metal and other variables.  Client environmental issues can be very common when they can hear 4-5 AP's with all of the same signal strength. 

Justin Kwasnik | ACMX# 598 | ACCX# 638
Occasional Contributor I

Re: Question: SNR and Path Loss - Show AP ARM State

Thank you JustinK84! You have gone far and above at answering my question. I appreciate it!

 

 I willl definitely be using the "- show ap monitor ap-list ap-name <ap-name> sort chan,asc" command in the future.

Contributor II

Re: Question: SNR and Path Loss - Show AP ARM State

Happy to help, and good luck with everything!!

 

Just remove the "-" from the begining of the command, it was more so just to note a bullet point when I added the post.  You also dont need the chan,asc added at the end. Although it will sort everything for you by channel in ascending order. 

Justin Kwasnik | ACMX# 598 | ACCX# 638
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