Wireless Access

Hi:

I attended an Atmosphere seminar in Boston yesterday (great conference!) and learned of two settings I’d like to take advantage of regarding band steering.

I was told there was a signal strength setting that determines if band steering happens at all. I believe the default was -45dBm, meaning that if a 2.4Ghz client had a signal of -45dBm or greater, it wouldn’t be band steered. I’d like to change this number, but I can’t find where to make that change. Can anyone help? (I have APs in dorm rooms, and students could be sitting right under the AP with a high signal strength, and never make it to 5Ghz)

Also, I was told that lowering 2.4 transmit power a bit can encourage clients to go to 5Ghz. Is this best done in the ARM profile section? I see a “Max TX EIRP” and “Min Tx EIRP” setting there. But I also see a “Transmit EIRP” setting under the 802.11a and 802.11g radio profiles. How do these interact? Which one wins?

And at the risk of asking too many questions in one posting, does anyone have best practice settings for these numbers in typical college environments? Dorm rooms, class rooms, auditoriums?

Thanks,

Tony

I would work with Aruba TAC if you're looking to change any ClientMatch settings.

In terms of the max power, you would do this in the ARM profile. The Max and Min should be 3db apart (ex: min 12, max 18).

On Aruba Solutions Exchange, there is a really great RF Optimization wizard:

https://ase.arubanetworks.com/solutions/id/75

Hi Tim:

You said: The Max and Min should be 3db apart (ex: min 12, max 18).

Just to verify, do you mean they should be 6dB apart?

Thanks,

Tony

Hi Tim:

Your original post did read 3dB of separation.

Yet the two numbers you posted (12dBm and 18dBm) are 6dB apart.

Which is correct?

Thanks,

Tony

Tony,

The band steer - G Max is -45, which means anything stronger than that it will not steer.  That figure pretty much represents a user standing directly under an access point.

The band steer A Min is -75, which means, the user must be seen by the a-band on the same AP at stronger than -75 to steer it.

You typically do not have to change those settings.  If you see a user continuously beeing steered to a and ending back up on g, you probably need to lower the g transmit power.  You would do it by lowering the ARM max TX EIRP in the ARM profile that is under the G radio.  The Transmit Eirp setting is only if you are NOT using ARM.

Hi Colin:

Can you tell me where to change the band steer - G Max?

In dorm rooms, a student can be sitting directly under an AP, and might never make it to 5Ghz.

Thanks,

Tony

Tony1234,

Again, I have never been in an environment that required that to be changed.  You first need to know:

- Is the user repeatedly connecting to G, because the power on the G band is too high?  If so, lower the power on the G band so that the client can select the A band way ahead of client-match kicking the user off onto the other band.

- If you modify the clientmatch settings, you could have users that constantly get kicked to A, but return to G, because your power is too high on G.  Your clients will notice this and it will be disruptive.  You need to reduce the power on G, first.

To see what your clients are doing on clientmatch do this:

config t

logging level debugging user subcat client-match

Then type:

show log user all | include client-match

That will allow you to understand why client-match is making decisions.  90% of RF issues can be helped or prevented by setting the correct power.  The remaining can be helped by Client Match on default settings after the client has already made a poor decision...

Hi Colin:

Thanks for all your help on this issue.

I’ve lowered my 2.4 transmit power to 9 to 12 dBm. But I have many dorm rooms where a student is sitting right under the AP.

I’ve done tests in these dorm rooms where the device connects at 2.4, and stays there.

If I change cm-band-g-max-signal to a setting like 30, the device gets steered to 5 Ghz.

In this setting, I’ve got an AP every 3rd dorm room (in some cases every dorm room), so I know that the 5 Ghz signal is adequate.

I’m still unclear why in this use case it’s a bad idea to change that setting. Can you elaborate?

Thanks,

Tony

Tony1234,

If it works for you, you can leave it at that.  Some people make changes to multiple settings at one time and they do not understand what is happening, as a result.