Long, long ago, SunOS, and possibly other Unixes, considered x.x.x.0 as a broadcast address as well. (Or I should say more properly, an all-zeroes host address.

Long, long ago, SunOS, and possibly other Unixes, considered x.x.x.0 as a broadcast address as well. (Or I should say more properly, an all-zeroes host address.) It took a long, long time to shake that assumption out of all code, long after the OS had stopped using .0 that way. So this is yet another domino.