Layer 2 roaming between AireOS and 9800 IOS-XE WLC

[Michiel Vercoutter]

Hi,

I have a scenario where APs connected to 2 types of WLC (AireOS and IOS-XE) will co-exist in the same physical place. The APs use flexconnect and local switching.

Is IRCM necessary in this scenario? How seamless will intercontroller roaming be, with and without IRCM? Clients will stay in the same subnet after roaming because the same locally switched VLANs are configured on both WLCs.

Thank you!

[Arshad Safrulla · Accepted solution]

What is the AireOS WLC and the version it is running? There is no way you can have Layer 2 roaming between 9800 and AireOS. With IRCM you will get Layer 3 seamless roaming, without IRCM client will go through the whole association and authentication process again each time it roams. 

To o-exist AP's registered in different WLC's in same place you need to upgrade your AireOS WLC in to an IRCM capable image. Then build mobility tunnels with new 9800. 

Now comes the difficult part, 

1. RF group name need to match in both WLC's.
2. AP group names in 5508 must match policy, RF tags in 9800CL (RF profiles at both also must match)

by doing the above you can make sure that both the WLC's (AireOS and 9800) share the same RF plan which will help you to improve RRM, false alarms on rogue, interference by AP's registered to other WLC etc.

 it is also recommended that you use 2 different VLAN's for the SSID (SSID 1 - Aire OS WLC - VLAN10, SSID 2 - 9800 WLC - VLAN20)

Cisco Catalyst 9800 Wireless Controller-Aireos IRCM Deployment Guide - Cisco

[Michiel Vercoutter]

Thank you for taking the time to help!

Customer is running 2 5508 controllers and one 3504 controller. Version currently used is 8.5.161.0 (because some old APs must still be supported) but the plan is indeed to upgrade to the 8.5IRCM version and build mobility tunnels to the 9800CL WLCs.

Do you have any documentation regarding the fact that AP group and RF group names must match?

I have indeed read that it's recommended to use different VLANs but unfortunately this is not possible anymore in this deployment.

Could you confirm that IRCM is possible with both old and new controllers using flexconnect?

Thank you.

[Arshad Safrulla]

Here you go 

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-8/b_C9800_rrm_dg.html#:~:text=with%20normal%20deployments.-,C9800%20Brownfield%20RRM/RF%20Group%20configuration%20considerations,-Up%20until%20this

Upgrading 5508 will definitely have a downtime, why not push all the AP's at one window to new 9800's instead of doing it in 2 windows and decommission the 5508 or convert it as Anchors till the EOL. If you are planning to do the upgrade batch by batch, then select one roaming domain (one floor, one building etc.). Also do not deploy different AP models in one roaming domain, such as Catalyst 9100 AP's with Wave 1 or Wave 2 AP's in one single roaming domain.

My personal experience with last migration, we replaced one complete building with Catalyst AP's in one downtime window and recovered all the Wave 1 and Wave 2 AP's. Wave 1 AP's were sent to the least critical sites where we can easily afford a downtime (upgrade planned by the end of 2022), Wave 2 AP's were sent to the sites where we don't have enough Catalyst AP's to cover one single roaming domain (In certain buildings we had first 15 floors Catalyst AP's and next 10 floors Wave 2 AP's, certain small sites completely Wave 2 AP's). Obviously we scrapped all the x600 series AP's. We ended up overshooting the allocated budget for technicians, but as a partner it was our duty to design a properly working solution. Planning is the key here, work with your customer and made him understand that salt and pepper deployments will end up introducing lot of sticky clients and sub optimal roaming performance. Also moving forward migrating from Wave1(last supported IOS-XE code is 17.3.X) or Wave2 (EOL for all the indoor AP's announced) to catalyst AP's will be a piece of cake.

Also make sure that you have considered the antenna gain difference of old ap to new ap, coverage pattern, POE requirements etc. when doing one to one AP replacement.

We also had a strange scenario where we had 9130's and 9120's installed in mix in couple floors, where certain clients ended up preferring the 9130's always. Since it was impacting only clients from a certain vendor, and it was not critical we left it as it is for now. So please test your clients with new AP's understand their behavior also.

[Michiel Vercoutter]

Thank you for your input Arshadsaf