I have read that the N+1 HA model provides redundancy for geographically separated data centers.
As of my implementation for the the N+1 HA in one site, I understand that it works in Layer 2, as we connect the WLC as a trunk, connect APs as an access and add the VLAN ID to every interface we add and then assign these interfaces to SSIDs.
But over WAN we are in Layer 3, how does the backup controller work with VLANs that it don't know about?
Regards.