FWIW:  I get these same messages on a Sparc 1+ that is on a segment
with 2 logical IP subnets on it.  There is a cisco router connected
to it and it has a "secondary address" on the port.  The "other"
subnet (from netbsd's perspective) only has one machine on it right
now, and I get these messages about every 30-90 minutes on the
netbsd machine.  The message is always about the one station
on the other logical subnet.  It isn't really a problem, but
falls into the "annoying" category.

-Andrew