Cannot ping via MAC address. It looks like the ebuild does something unusual because when I manually compile the source from http://www.habets.pp.se/synscan/programs.php?prog=arping I can ping via MAC address, but the version portage installs cannot. In fact, the help output is very different. It looks like there are two versions: one written by Thomas Habets, and one maintained by Yoshifuji Hideaki. And the one in portage cannot ping via MAC address. They are both called arping so is there a way to add the other one and change it's ebuild name in order to distinguish the two?
Note that the ebuild refers to http://www.habets.pp.se/synscan/programs.php?prog=arping But it appears to install something different
net-analyzer/arping installs /usr/sbin/arping2 which is what you want to use. net-misc/iputils installs /sbin/arping which is the cause of your confusion.