John Auld said:
> If the m0n0wall does respond, do you have stale arp entries the host where
> you run ping. Try arp -a and look for out of date arp entries. Try
> deleting
> the old arp entries if they are present.

Thanks John, that must have been it. Although the system I was pinging
from does not seem to have any cached arp for my m0n0wall (it is not on
the same physical network segment), there must be some other cache in the
network in my building (my subnet is controlled by a switch I have no
direct control over). In fact after a few hours m0n0wall stopped
responding to the wrong IP addresses. I'll have to take the issue up with
the people controlling that switch. Thanks for the help.


-- 
Giuseppe Vacanti
cosine Science & Computing BV (NL)
http://gvacanti.cosine.nl/