When Cisco device is configured as DHCP server and Aruba AP is acting as DHCP client then DHCP pool on Cisco box has to be configured in following manner:
ip dhcp pool For_Aruba_AP network <Network> <Subnet Mask> default-router <Default Gateway> option 60 ascii "ArubaAP"
//Configure above statement as it is. option 43 ascii "Wireless controller managerment IP address"
//You can configure IP address of two controllers saperated by comma(,).
Option 60 is Vendor Class Identifier Code.
Option 43 is MAnagement IP address of wireless controller.