We have a scenario in which we have multiple controllers in separate buildings (separate VLANs and two different mobility groups) with 200+ APs spread throughout the enterprise. Because of an old controller DNS entry and OTAP, it is probably safe to assume that every LWAPP AP has built a list that includes every controller in the enterprise -- including controllers in another VLAN.
Here is the problem: Recently, a controller at the primary building crashed and some AP's moved to a controller in the secondary building (different VLAN). When that happened, users began roaming between APs in mobility groups. Because of this, inter-subnet roaming did not occur, client IP addresses changed, and loss of connectivity ensued.
My question: Should we create one large mobility group between the two buildings (multiple VLANs) OR should we reset every AP back to default (to wipe the known controllers list), ensure that AP's in each building only know about controllers in that same building, and keep the two separate mobility groups.
I am seeking advice since having one large mobility group would mean possible tunneling back over our gigabit connection between the primary and secondary buildings.