Hello, everyone.
I haven’t found a corresponding NW lesson to this, so I am creating a new forum thread.
3.3.c Describe access point discovery and join process (discovery algorithms, WLC selection process)
I have some questions regarding the WLC discovery process that the OCG mentions:
An AP can be “primed” with up to three controllers—a primary, a second-
ary, and a tertiary. These are stored in nonvolatile memory so that the AP can
remember them after a reboot or power failure. Otherwise, if an AP has previ-
ously joined with a controller, it should have stored up to 8 out of a list of
32 WLC addresses that it received from the last controller it joined. The AP
attempts to contact as many controllers as possible to build a list of candidates.
From what I understand, regardless of what we configure, the AP will attempt to discover as many WLCs as possible?
Is this primary/second/ter configuration done on the AP or the WLC? If these 3 controllers are configured and an AP reboots and discovers all the WLCs, are these the first 3 controllers that it will attempt to join? Also, what is “tertiary”?
So does the WLC selection process work the following way?
- Try to join the primary WLC. If that fails, try the secondary one, and so on.
- If none of these 3 are configured, join the controller that you joined previously
- If you didn’t join any controller previously, join the least-loaded one.
Then again, this seems a bit different than what, for example Kevin Wallace says
He mentions something called a master controller?
My next question is
Otherwise, if an AP has previ-ously joined with a controller, it should have stored up to 8 out of a list of 32 WLC addresses that it received from the last controller it joined.
The controller tells the AP what other WLCs exist? A cisco doc says
Also, the LAP remembers the management IP address of its controller and the controllers present as mobility peers even across reboot. However, as soon as the AP joins another WLC, it only remembers the IP of that new WLC and its mobility peers and not the previous ones.
So if it does associate with a WLC, does the WLC also tell it what other WLCs there are?
It’s all getting randomly mixed up together and I unfortunately don’t get what happens when in which order.
Thank you.
David