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

jain.manish94
Spotlight
Spotlight

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. 

2 Accepted Solutions

Accepted Solutions

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.

View solution in original post

JPavonM
VIP
VIP

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):

  1. Primary Controller system name (previously configured on LAP)

  2. Secondary Controller system name (previously configured on LAP)

  3. Tertiary Controller system name (previously configured on LAP)

  4. 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)

  5. 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.

View solution in original post

8 Replies 8

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.

Please rate this and mark as solution/answer, if this resolved your issue
Good luck
KB

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?

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

Please rate this and mark as solution/answer, if this resolved your issue
Good luck
KB

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.

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

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

JPavonM
VIP
VIP

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):

  1. Primary Controller system name (previously configured on LAP)

  2. Secondary Controller system name (previously configured on LAP)

  3. Tertiary Controller system name (previously configured on LAP)

  4. 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)

  5. 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.

Leo Laohoo
Hall of Fame
Hall of Fame

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.

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