HI,
Except Local, other DHCP options will work with IAP VPN ( VPN terminating on Aruba Controller).
Here Centralised ( Centralised L2 and Centralised L3 ) means, IP address for the connected clients will be provided by the Aruba controller through the VPN ( all the clients of all IAPs )
Distributed means, IP address to the connected clients will be provided by the respective VC .
Here L2 or L3 means how the tunnel is created and what is the Gateway for the clients.
L2 means, Controller will be the Gateway ( May be any other at the Controller end) and traffic will be tunneled to the controller
L3 means, VC will be the Gateway and traffic will be routed to the controller through the VPN tunnel
Local means, if we want to have multiple DHCP scopes in the VC with out VPN tunnel we can configure Local type DHCP scopes