I have 3 wireless lan controllers 4402, the IP Address of the Managament Interface of each WLC, it should be the same subnet than all the WLCs. For example:
WLC1 IP Management Interface 192.168.12.5
AP-Management Interface 192.168.12.6
WLC2 IP Management Interface 192.168.12.7
AP-Management Interface 192.168.12.8
WLC3 IP Management Interface 192.168.12.9
AP-Management Interface 192.168.12.11
It depends on your requirement. It is not at all mandatory to keep the management interfaces of all the controllers in same subnet.
You can very well configure mobility between all controllers even if they are in different subnet.
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