We have recently deployed a new vWLC in a separate datacentre. There is already one vWLC running in the network and all the access points were joined with the old vWLC.
As soon as new controller was setup and a mobility tunnel was created. some access points started moving to the new controller. There is no DHCP option 43 configured. There is no HA Primary secondary WLC configured for any access points. how does the access point know there is a new controller and lets join it. no reboot was given to any of the access points
Note: both controllers are virtual running 126.96.36.199
If its in the same subnet then AP will get the all information about all WLCs and collect in his database.
If you want to move All APs to old vWLC then you have to configure each APs HA tab with priamry and secondary IP/name of WLCs.
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Primary/secondary wasnt setup. both controller are in different subnet to each other and also in different subnet from the all the access point. The HA tab of the access point is blank. Primary/secondary backup in the global conigurataions of both the controller is also blank.
Is there a way to find out the reason how these access point joined the new controller. Or is there a way if these access points have any controller IP addresses saved in the database ?
You have mentioned that you have added the WLC on same mobility group right?
This would mean that via the process of broadcast that AP will know that there is another controller that just came online.
It is also possible that it learned that new WLC via DNS.
Since this new AP sees a new WLC and it has seen on its algorithm that this WLC doesn't have any load (APs associated), then it sees it as a better metric compared to the existing wlc you have.
You can avoid this unwanted hopping by hardcoding the primary WLC on the the HA tab of the APs.
Thanks for the response. This may make sense about the same mobility group causing this behavior. Is there any cisco documentation which explains the same ?
The discovery process on the Access points should define it.
It doesn't talk directly about mobility.
Again there are other options like layer 3 discovery via DHCP etc..
Try to SSH to the APs or if you have a log server then it would have shown the actual process.
Here's a link which can be good reference just for AP join process.