Two active WLCs without HA. which WLC is selecting to join from AP?

[eeebbunee]

Hi Professionals,

I'm trying to migrating my WLC from 2504(old) to 9800(new).
I have 40 APs for the office/plant and all APs are joined to old one.
My plan is disconnect joining from old one to new WLC one by one, which means 2504 and 9800 should be up and running in network.

Please see my plans:
- Old(2504) IP: 10.10.10.45/24 (8.3.143)
- New(9800): 10.10.10.55/24 (17.9.4a)
  These are in same subnet and 40 APs are also in same subnet. (10.10.10.0/24)

- New controller has AAA authentication by AP's serial number.
  (I'm not sure this one is enough not to make AP confusing -- such as which WLC I need to join.)
- All 40 APs are stick to old WLC no matter what.
- Register target AP's serial number to new controller's AAA.
- Access target AP (SSH) and provides 'capwap ap primary' to new WLC9800.
- target AP starts joining with process (OS upgrade will be proceeded, and once it happened it never go back to old.)

- Repeating until all APs successfully on board.

In my plans, is there anything you worried about?
What if I connect new AP to my network? Which WLC it will be joined?

If I do provide IP but doesn't provide 'capwap ap primary' command to new AP, it will find WLC by the broadcast.
Then which WLC do you think it will connected?

Is there any possibility that joined AP automatically tries to join new controller?

Thank you for your attention.  

[MHM Cisco World]

The one that have less AP join to it.

https://ipcisco.com/lesson/access-point-discovery-and-join-process/

MHM

[eeebbunee]

Thank you for your comment.
What if 30 APs are moved to new one and old controller lost power?
Rest 10 APs are automatically trying to join with new controller? or is it stays until primary come back?

[MHM Cisco World]

Will if you want to make AP to join nee WLC what you can do only enable master wlc option and AP will all join new AP.

For old wlc if it turnoff then AP discovered and try joint it.

MHM

[marce1000]

  - Summarizing shortcut : the best scenario is a single migration (step) where the old 2504 is powered off and the APs only have the leftover new controller to join 

 M.

[Leo Laohoo]

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@eeebbunee wrote:
I have 40 APs for the office/plant and all APs are joined to old one.

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What model are the APs?

[eeebbunee]

I have 1852 Series / 2800 Series / 3800 Series AP and those are all activating.

In case of AP issue, I got 9120 Series AP as well.
I have tested using 2802I model so far.

Thank you!

[balaji.bandi]

as @Leo Laohoo  asked - i will ask same question, what model of the AP, what Airos code running on old WLC, what IOS XE running on new WLC 9800

look the compatible matrix :

https://www.cisco.com/c/en/us/td/docs/wireless/compatibility/matrix/compatibility-matrix.html

For us to understand the issue correctly - one of AP console in to it and change the WLC IP address and reboot (by the how are you changing this WLC IP address - any tools like prime or cli ? or WLC GUI ?)

What if I connect new AP to my network? Which WLC it will be joined?

number of methods, if same LAN broadcast which ever WLC respond quicker that will be joined and other option DHCP Option 43.

to guide AP to join which WLC.

[eeebbunee]

My core switch (9300L) is working as a DHCP server using dhcp pool.
When I search 'DHCP option 43' I found this configurations:

1. Add the Option 43 line with this syntax:

   option 43 hex <hexadecimal string>

   The hexadecimal string in step 3 is assembled as a sequence of the TLV values for the Option 43 suboption: Type + Length + Value. Type is always the suboption code 0xf1. Length is the number of controller management IP addresses times 4 in hex. Value is the IP address of the controller listed sequentially in hex.

   For example, suppose there are two controllers with management interface IP addresses, 192.168.10.5 and 192.168.10.20. The type is 0xf1. The length is 2 * 4 = 8 = 0x08. The IP addresses translate to c0a80a05 (192.168.10.5) and c0a80a14 (192.168.10.20). When the string is assembled, it yields f108c0a80a05c0a80a14. The Cisco IOS command that is added to the DHCP scope is:

   option 43 hex f108c0a80a05c0a80a14

In this example,  the controller 192.168.10.5 has priority than controller 192.168.10.20?
So, if new AP is added to subnet, IP will be granted from IOS (192.168.10.x) and it goes to 192.168.10.5 controller directly? 
I still don't understand how this configuration choose controller I want. Please correct me.

Thank you so much.

[balaji.bandi]

Lets we understand what you doing correctly here :

'iam trying to migrating my WLC from 2504(old) to 9800(new).
I have 40 APs for the office/plant and all APs are joined to old one.

All the AP working in the condition - and you have check the compatible matrix with 9800 and all ok. as mentioned before post.

now your Both the WLC in the Lan with the IP mentioned.

For now 2 WLC in the LAN connected and working - 40AP are on the OLD WLC.

Choose 1 of the AP  you like to move to At 9800

use below guide from WLC GUI - add the new WLC in primary controller. save and reload

https://mrncciew.com/2013/04/07/ap-failover/

Connect console to AP and check any errors and joining process to understand what is wrong.

check below also best methods used when the AP taken out of the box :

https://mrncciew.com/2013/03/17/ap-registration/