On a related note, you can also have your card use a different MAC address
ifconfig eth1 hw ether deadbeef0001
(this needs do be done while the card is down for obvious reasons)
now your card will answer all arp requests with DE:AD:BE:EF:00:01.
The kernel performs this trick on most cards by setting the card into promiscuous mode and using software to filter out all MACs that aren't yours which stands to reason it would be slightly slower than just using your real MAC.
Author: Mike Baker