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CAPsMAN signal strength question

Sun Jan 12, 2020 12:54 pm


I'd have a question about reported signal strength in the CAPsMAN registration table:

I've a setup with a central router running CAPsMAN and 3 APs.
I'd like to prevent clients to connect to an AP with a weak signal - so i implemented the following access list:
As far as i understood correctly, -70dbm should be a good value for that.

My problem is: Clients report much better signal than the AP in the CAPsMAN registration table:
In that case, everything's still fine - but often, the signal strength reported by CAPsMAN is below the 70 and the client gets kicked from the best possible AP.
If i disable the access list, the client connects fine and reports a good signal strength - everything works although clients tend to connect to APs with bad connectivity or keep connected to an AP while moving with the same result.

What did i misinterpret?

Is 70 not the desired treshold value?
If i set it to 80 for example, clients again start to connect to bad APs - so the value seems to be important.
Maybe 75?

I am a little bit clueless ... every tip would be appreciated very much ;-)

Thanks in advance from Salzburg, Austria!

- Johannes
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Re: CAPsMAN signal strength question

Sun Jan 12, 2020 7:23 pm

Have in mind that if your client device connects to an AP with a bad signal the AP has nothing to do with that...
It is a bad decision from the client's device side...
Some are better in these decisions and some are not..!

What we do from the AP side is just to assist and help in a better roaming by disconnecting the client or in some cases stop him from connecting..

Anyways, i would set it to -80 and reduce the parameter "allow signal out of range" to 5 seconds..
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Re: CAPsMAN signal strength question

Mon Jan 13, 2020 7:47 pm

I think it is perfectly normal to have different values there.
- On client side you can see the strength of the signal received, signal transmitted by the AP. in this case the AP is the transmitter (TX) and the client is the receiver (RX)
- on CAPSMAN registration table you can see the strength of the signal received, signal transmitted by the client. The AP does not know at which power the client transmits, it can only see how much it receives. As you can see you have RX value.

Those values should be different as the AP and the client will transmit at different powers. It is also correct that the value received by the AP is lower than the one you can see on the client when you scan for SSIDs because the AP should have a higher transmit power than the client.
This is also one of the reasons it is much better to have multiple small APs spread around the house instead of one big router with big antennas in the middle. With the big antennas router you risk seeing good signal very far but your transmitted packets will have trouble reaching the router so overall you will experience bad connectivity.

Anyway, I am using -79 as the last good "accept" value and -80 as the start of the deny list in the capsman access list.
In Capsman I can see a log like "30:07:4D:B9:AA:30@cap3 disconnected, registered to other interface" so most modern devices will migrate to a better signal by themselves without hitting that access list. they just do some internal calculations and migrate to the best signal. other devices get kicked by capsman and must re-register.

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