topic 8.3.133.0 WLC doing L3 roams instead of L2 in Wireless

8.3.133.0 WLC doing L3 roams instead of L2

RichardAtkin — Mon, 05 Jul 2021 15:10:14 GMT

I have a pair of WLCs, both with APs on, both serving Clients within the same, quite large, coverage area. Both WLCs are connected to all of the same VLANs, both are in the same Mobility Group, etc. The SSID we have uses WPA2-AES (802.1X) and we use Interface Groups (which are identical across both WLCs).

I have noticed that when people roam from one WLC to the other, they often do a L3 roam instead of a L2. Given that both WLCs are connected to all the same Subnets, why is an Inter-Controller L3 roam happening? It should do an Inter-Controller L2 roam and the Client's session should be transferred to the new WLC...

Anybody else got this problem? Or any insights on how to troubleshoot?

Cheers,

Richard

Re: 8.3.133.0 WLC doing L3 roams instead of L2

Scott Fella — Fri, 26 Jan 2018 15:54:02 GMT

What you should be seeing is the the client is mobile. Meaning that the original controller the client was on will anchor the traffic to the other controller. As long as the interface names and interface group names are identical, the client should roam and keep the same IP address and be placed on the same interface within the interface group.

Re: 8.3.133.0 WLC doing L3 roams instead of L2

RichardAtkin — Fri, 26 Jan 2018 15:56:59 GMT

Indeed - The client does appear as Mobile and the AP is listed as the other WLC's IP address.
This status though implies that the traffic flow is still passing through the original WLC, but if it's doing a proper inter-WLC L2 roam the original WLC should move its self out of the traffic path and pass ownership of the Client's session to the new WLC, right?

Re: 8.3.133.0 WLC doing L3 roams instead of L2

Scott Fella — Fri, 26 Jan 2018 16:23:59 GMT

No. The point of connection will be the foreign controller and the new point of presence will be the anchor. The client will still pass through the foreign.

Re: 8.3.133.0 WLC doing L3 roams instead of L2

RichardAtkin — Fri, 26 Jan 2018 16:32:59 GMT

That’s not my understanding and also not what this (below) says... Do you know of any documentation that supports your view of the original WLC always staying in the traffic flow, even when both WLCs have access to the same VLANs?

https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-1/Enterprise-Mobility-8-1-Design-Guide/Enterprise_Mobility_8-1_Deployment_Guide/cuwn.html#16463

Thanks,

Richard

Re: 8.3.133.0 WLC doing L3 roams instead of L2

Saravanan Lakshmanan — Fri, 26 Jan 2018 18:00:19 GMT

https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/Enterprise-Mobility-8-5-Design-Guide/Enterprise_Mobility_8-5_Deployment_Guide/cuwn.html#95243

when a client roams from an AP joined to one WLC to an AP joined to a different WLC. It also varies based on whether the WLCs are operating on the same VLAN. Figure 2-31 shows inter-controller roaming, which occurs when the WLCs interfaces or interface groups are supporting the same VLAN.

open TAC case.