Migration from WLC 3504 to WLC 9800-L

[c.darbellay]

Hello everyone,

Title lays my situation. I'm not sure about what I must do as this is my first migration. This post is a summary of what I think I know and plan to do, I'd like for users with more experience to just nudge me as to whether this is a garbage plan or if overall it should work. The old WLC will be disposed of

The "best way" according to Cisco ?

This Cisco documentation covers a migration from 3500 to 9800 with minimal downtime, very close to my need. 

from what I get it goes like so:

1. send the order to all (or a subset) APs to download a new AP image that will work on IOs XE but not AIR OS
   1. Until their reboot this wont prevent them from working
2. In the WLC, change the primary WLC IP for all needed APs to that of the new one (9800)
3. reboot the migrating APs
4. They should boot on their new image, detect their WLC and you're good to go

But I dont have all the same situation

What differs in my use case

Good

1. We don't care about downtime (schools closed for summer, we can afford 1/2 to a day of downtime)
   1. We also can do this in groups (80 or so APs shouldn't be too violent anyways)
2. I used the config converter to prepare the new WLC and had little issues, pretty neat tool
3. our APs are confirmed compatible with the WLC (although their current image is not)

Bad

1. This is my first ever migration and it's a jump from AireOS to IOS XE
   1. no documentation of my predecessor's migrations and they were different migrations anyways
2. SSH and global credentials are not setup on APs, the previous doc makes it clear you cant use the usual pre-load on this since you change basically the entire way the WLC works.
3. We are moving the APs and the WLC to another VLAN altogether

My plan is

1. enable SSH and specific credentials on all APs at a global scale
   1. do the rest of the upload process as in the provided documentation
2. Put the new WLC's new vlan IP as master, with no secondary IP.
   1. change the AP's VLAN so they discover their new primary
   2. cross my fingers

Should I expect this to work with some bumps, or is it really important that I do the migration all in my current VLAN and only then move the APs ? Again I don't care about downtime but I do care about not having to slowly scrub away some config that is destined to fail.

Thanks for reading.

[marce1000]

 - FYI : https://www.cisco.com/c/en/us/support/docs/wireless/wireless-lan-controller-software/217908-migrate-from-aireos-wlc-to-catalyst-9800.html

 M.

[c.darbellay]

That's a good link but it's the one I put in my post as a basis for my question

[Rasika Nayanajith]

I would first get 9800 with its new management IP and build configuration. below tool help you to develop some base config for 9800. 
https://cway.cisco.com/wlc-config-converter/ 

However note that in 9800, you do not require SVI for user vlans. Only management SVI required (unless you have specific needs of mDNS/DHCP option 82). Refer 9800 best practice config guide for more details
https://www.cisco.com/c/en/us/products/collateral/wireless/catalyst-9800-series-wireless-controllers/guide-c07-743627.html 

Also be familiar with new Tags &  Profiles concepts of new 9800. Below post may helps to begin with
https://mrncciew.com/2022/06/30/9800-tags/ 

I would check the compatibility matrix & if all your AP support 17.6.x then I would go with that. If you have wave 1 (x702 series) then stick with 17.3.x code train.
https://www.cisco.com/c/en/us/td/docs/wireless/compatibility/matrix/compatibility-matrix.html 

Once you build your 9800 with required config, I will failover one AP to test. Make sure all your SSID tested with important client types used in your environment. Once everything is good, you can plan for cutover at large scale.

HTH
Rasika
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