Using EtherCard library in a "tiny" LAN (without GW)

Hello,
I work on a project on an isolated Lan (at this time: one Arduino & my PC), all in fixed IP.
I try to send Udp packet; doesn't work.
Watching ethernet packets (by http://Analyzer.polito.it) I see that dest mac address alway0 000000!
Digging in source tcpip.cpp I read that packet is sent to mac address of the Gateway,
Of course don't work since I don't have GW.
I am starting modifying that (adding dmac parameter to udpPreparee & udpSend).
I will report the result soon, however, if you know that this work has already be done, please, give a link.
Regards.
PO.