Вызвать arp -a не вариант? Тут пример есть http://codeguru.earthweb.com/cpp/i-n/network/networkinformation/print.php/c14635
пацаны, читаем мсдн... в ремарках про SendARP ... On Windows Vista, a new family of functions can be used to access, modify, and delete the ARP table entries when the Address member of the MIB_IPNET_ROW2 structure passed to these functions is an IPv4 address. The new functions include the following: GetIpNetTable2, CreateIpNetEntry2, DeleteIpNetEntry2, FlushIpNetTable2, and SetIpNetEntry2. ...