Controllerless Networks

Occasional Contributor I

Need help understanding Client Match settings



I've been reading manuals and searching these forums/google for days now and i'm still bewildered by client match on IAP-225's running


I'm intimately familiar with this table having stared at it for quite some time: original.jpg


As well as having already referenced the user guide and:


and many others I don't remember the links for.


Anyways, my questions relate specifically to:

CM calculating interval

CM neighbor matching %

CM threshold

SLB mode


Every bit of documentation i've been able to dig up is completely obtuse in it's explanation of these features. Can somebody please explain in simple terms exactly what these options do? I'm looking for settings to encourage clients to move to the strongest AP within range as quickly as possible (especially 5GHz AC clients). With the default settings I have clients that will hang onto an AP with RSSI reaching -85 plus while sitting literally on top of another AP in the neighborhood.


Blindly tinkering with these settings my best results so far have been with:


CM calculating interval = 10

CM neighbor matching % = 90

CM threshold = 30

SLB mode = Channel



I haven't been able to find any information on what SLB mode does, the latest manual merely states what options are available without a clear explanation of how those options function. I'm also curious about Background spectrum monitoring, does it provide any benefits to how client match works? Are there any performance down sides to enabling it? Thank you for any help!

Guru Elite

Re: Need help understanding Client Match settings



Clientmatch is being hardened in the 4.2.x.x code, which was just released recently.  I would say to use the version of clientmatch that is in that train of code, because alot of things have been improved.


With that being said, the majority of clientmatch parameters are rarely changed from the defaults.


Here are your definitions:


- CM Calculating Interval - How often should I consider bandsteering or load-balancing clients.  Anything lower than 30 seconds could possibly speed up how fast clients are steered and load balanced, but could increase cpu with little benefit.

- CM Neighbor Matching percent is used for load balancing users.  75 means that 75% of the access points that can be viewed by another access point shares its RF domain, so a client can be load balanced among those access points.

- CM Threshold - If an access point in the same RF domain has "CM Threshold" above another access point in the same RF domain, clients will be sent to another access point.  It could be seen as the difference between an access point and the least loaded AP in the RF domain before clients are sent elsewhere.

- SLB Mode - Are we load balancing clients based on how many are on a channel, how many are on a specific radio or both?


You have to be careful, because ClientMatch is different between the Instant (IAP) and Controller-based (AOS) platforms, so you can get confused if you read the explanations for both at the same time.  Also, ClientMatch has recently been "hardenend" in the release of Instant, so that is probably the version you want to test it out on.  Typically the default parameters are not changed unless TAC says to, because it requires a full understanding to (1) understand what the knobs do and (2) to understand if changing them is getting you close to your result.


Based on your changed parameters:


- Anything under the 30 seconds for the CM calculating interval could cause higher CPU and it should not be changed:

- CM Neighbor matching should not be changed because increasing it to 90 percent means that you are increasing the possible APs in an RF domain, which means clients can be load balanced to access points that are out of their actual RF domain.

- Setting a CM threshold of 30 means the difference between the least populated and most populated clients in an RF domain must differ by 30 before load balancing would start.


Long story short, just stick with the defaults and you should be fine.


Background spectrum monitoring is normally turned on if you have issues and you need to see if there is any non-wifi interference.  Typically you would leave this off in regular production to save any overhead.  It does not work in conjunction with clientmatch, no.





Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.
Frequent Contributor I

Re: Need help understanding Client Match settings

Hi there, just confirming your last sentence. This means you can have Client Match or Background Spectrum Monitoring, but not both?



Guru Elite

Re: Need help understanding Client Match settings

This was a long reply. The last sentence does not stand on its own. Background Spectrum has to do with monitoring. Client match woukd have to do with APs serving clients moving clients based on need. Two different use cases.
Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.
Frequent Contributor I

Re: Need help understanding Client Match settings

Thanks for clarifying.

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