topic Re: how Cisco AP decide which is better cisco wlc if there are many wl in Wireless

how Cisco AP decide which is better cisco wlc if there are many wlc.

jain.manish94 — Thu, 19 May 2022 07:07:21 GMT

Hello Team,

How one new cisco access point will decide which is better wlc for joining in case there are many wlc.

for example there 2 wlc at the central site and both are active active with ap license.

and AP have both wlc ip address using any kind of method like dhcp option 43 and dns.

Re: how Cisco AP decide which is better cisco wlc if there are many wl

Kasun Bandara — Thu, 19 May 2022 07:26:28 GMT

you can configure AP settings with WLC priority in WLC settings. if 2 WLCs are not in HA cluster, then my guess is AP will select 1st WLC which gives association. recommendation is to configure HA for 2 WLCs if possible.

Re: how Cisco AP decide which is better cisco wlc if there are many wl

jain.manish94 — Thu, 19 May 2022 07:36:12 GMT

I already said that this is new ap and my controller are in another location and aps are other locations but with the help of DHCP option ap knows both wlc ip address and which wlc it will join what is the criteria?

Re: how Cisco AP decide which is better cisco wlc if there are many wl

Kasun Bandara — Thu, 19 May 2022 07:49:28 GMT

this will give good explanation for your scenario

https://community.cisco.com/t5/wireless-mobility-documents/joining-process-of-an-cisco-access-point/ta-p/3149279

Re: how Cisco AP decide which is better cisco wlc if there are many wl

MHM Cisco World — Thu, 19 May 2022 07:51:46 GMT

good Q
there are two phase
hunt and discovery
hunt is AP collect the WLC IP for all WLC through DHCP DNS manual WLC config
discover is AP send discover to all WLC in hunt list

here
AP send join to
primary/secondary WLC first
master flag WLC
if all above is failed then tie breaker is WLC how much AP connect to it, AP select the lowest AP connect WLC.

Re: how Cisco AP decide which is better cisco wlc if there are many wl

jain.manish94 — Thu, 19 May 2022 08:14:50 GMT

thanku you very much but how aps knows that how many aps connect on which controller and which has less aps ?

Re: how Cisco AP decide which is better cisco wlc if there are many wl

JPavonM — Thu, 19 May 2022 09:32:04 GMT

The excess capacity is sent in the CAPWAP response packet from WLC.

From the process explained by cisco, I have found that AP use to join to WLC with lowest delay or the first that responded to discovery:

Look at the controller list and send a join request to a controller in this order (only if the AP received a discovery reply from it):

Primary Controller system name (previously configured on LAP)
Secondary Controller system name (previously configured on LAP)
Tertiary Controller system name (previously configured on LAP)
Master controller (if the LAP has not been previously configured with any Primary, Secondary, or Tertiary controller names. Used to always know which controller brand new LAPs join)
If none of the above are seen, load balance across controllers using the excess capacity value in the discovery response.
If two controllers have the same excess capacity, then send the join request to the first controller that responded to the discovery request with a discovery response.

Re: how Cisco AP decide which is better cisco wlc if there are many wl

Leo Laohoo — Thu, 19 May 2022 09:47:19 GMT

Depends on the firmware of the controller.

The AP will join the first controller it will receive a join success.

Again, this is highly dependent on the controller because if the controller has high CPU or buggy firmware the join request from the AP can/may get delayed.

Re: how Cisco AP decide which is better cisco wlc if there are many wl

MHM Cisco World — Thu, 19 May 2022 09:50:13 GMT

AP send discovery request
WLC reply with discovery response contain all
how much AP connect
how much max AP this WLC can support