Arptables is used to set up, maintain, and inspect the tables of ARP rules
in the Linux kernel. It is analogous to iptables, but operates at the ARP
layer rather than the IP layer.

Currently, only support for specifying hardware addresses for Ethernet
is available. This tool is not luser-proof: you can specify an Ethernet 
source address and set hardware length to something different than 6, f.e.

Arptables Frequently (and less frequently) Asked Questions:
http://ebtables.sourceforge.net/arptables-faq.html

Note: an /etc/rc.d/init.d/arptables sysv-style script is included.