The Book

Any other clients with manually configured ip or with ip served from unauthorized dhcp server will be ignored. Do this by enabling “Add ARP for leases” on DHCP server. And on the eth interface that is hosting dhcp service choose option ARP: “reply-only”. That way you are instructing your router not to maintain arp table with unsolicited broadcast.. Only clients that are served by your dhcp will have an entry in arp table and router won't be able to send any frames to clients not found in arp table!