@nzhang27 wrote:
So those channel numbers actually reflect a fact that the AP has been scanning and *meeting* other APs/stations at different channels?
Just for clarity, when I write (and our docs say) that the AP scans, it means that it moves off channel and dwells for some period of time and passively listens. The dwell time is not configuration (it used to be) and is generally assumed to be around 80ms, such that the AP can return the it's home channel before the next beacon needs to be sent. This takes place nominally once per 10 seconds (refer ARM profile scan time setting).
some caveats...
>> There is a notion of agressive scanning too - that just means that if the AP is idle it can go off channel before the 10 second expiry.
>> There are some cases where scanning is deferred, due to various checks such as VOIP call active, load etc, this is called "scan reject".
>> some channels are scanned more frequently than others, there is a notion of 'rare channels' and 'inbetween channels' etc that are scanned less frequently than say the main blocks of unii-1,2,2e,3, this is achieved using a weighting scheme:
(sg-7030) #show rf am-scan-profile default
AM Scanning profile "default"
-----------------------------
Parameter Value
--------- -----
Scan Mode all-reg-domain
Dwell time: Active channels 500
Dwell time: Regulatory Domain channels 250
Dwell time: non-Regulatory Domain channels 200
Dwell time: Rare channels 100
you can view the AP scanning behaviours using the command "show ap arm scan-times ap-name <>" -- the output is reasonably self explanatory; but if you have questions post back here.
Also your replies help me understand a lot, as well as brings a lot of new surfing and reading for me. Anyway, they are really helpful. Thank you.
no problem at all, glad to hear it's useful info.
regards
-jeff