The DHCP Authorized ARP feature enhances the Dynamic Host Configuration Protocol (DHCP) and Address Resolution Protocol (ARP) components of the Cisco IOS software to limit the leasing of IP addresses to mobile users to authorized users. This feature enhances security in public wireless LANs (PWLANs) by blocking ARP responses from unauthorized users at the DHCP server.
http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtautarp.html
