Looks like it has to do with gratitious arp
http://wiki.wireshark.org/Gratuitous_ARP
-Does the target MAC address ever matter in requests? I gather Solaris uses ff:ff:ff:ff:ff:ff in its standard ARP requests and most other OSes use 00:00:00:00:00:00 instead. Is the use of the ff:ff:ff:ff:ff:ff MAC in the target address above significant in any way? Obviously having a destination address of ff:ff:ff:ff:ff:ff is critical.yes
RFC 3927, which is based on Gratuitous ARP, specifies 00:00:00:00:00:00 for the target MAC. However many simple TCP/IP stacks have an API which permits the specification of only one MAC value, and when the Ethernet Destination field is set to 'broadcast', the ARP target is also set 'broadcast'. Note: Normal ARP requests have the same value in the ARP Packet Target MAC address as in the Ethernet Destination field.