Scenario:

Business with multiple locations needing to manage Wi-Fi system from a centralized location, using one controller instead or hosting a CAPWAP controller on each site.  Is this possible?

Answer:

Yes, if there is a VPN connection established between the MAIN site and each individual BRANCH office.  To do this you will to use DHCP extended options.  Use DHCP option 138 for CAPWAP.

Example:

MAIN site has an NXC appliance which will be managing all the CAPWAP enabled APs on all sites.  The NXC has a local IP of 192.168.1.250.  This means that each BRANCH office DHCP server needs to be configured to use option 138 and point the CAPWAP traffic to 192.168.1.250 (NXC).  When wireless access points receive a DHCP address from their local network they will then point to 192.168.1.250 to register for management and receive configuration file.

If the BRANCH offices were using Zyxel gateways, this is what the DHCP server configuration would look like: