IP --> DHCP Server --> Leases --> Add new --> General="Pool_Name", MAC Address="MAC address of desired blocked", Server="Name of DHCP Server failing", Block access = yes, Address List = Black-list
IP --> DHCP Server --> Leases --> Add new --> General="Pool_Name", MAC Address="MAC address of desired blocked", Server="Name of DHCP Server failing", Block access = yes, Address List = Black-list