the invention ensures that a single and consistent reply is made to arp request in a system of connected ip networks . when an adapter becomes active , the owning host sends an arp advertisement into the network over the adapter . if the advertisement is also received at the sending host over a different adapter b , then the host knows that adapter b is on in the same physical network as adapter a and b can be designated as a backup adapter for a and a can be designated as backup adapter for b . if adapter a fails or becomes inactive , the host resets the backup adapter field for any adapter it owns for which a is marked as the backup adapter . if a backup adapter b has been designated for a , the host also sends an arp advertisement associating mac - b with ip - a . this allows network connections originally served via adapter a to continue non - disruptively over adapter b and it also provides access to the host for subsequent new connections . when adapter a becomes active again , the host sends a gratuitous arp advertisement that maps ip - a to mac - a . this allows adapter a to re - assume responsibility for responding to arp requests for ip - a .