Excuse me for butting in, but why are there three parallel links from
your NetBSD box to this hub?  In the normal case the hub is all one
Ethernet domain.

The configuration you drew makes no sense to me at all.  Unless the
hub is a switching hub configured with three distinct VLANs, one for
each link from the NetBSD box, you might as well put the external
boxes A, B, and C directly onto the hub, with just one link from the
NetBSD box to the hub. I cant see how the two additional links are
achieving anything useful in your topology.



I havent looked at Matt's driver in ages, but it's just barely
possible that the autosense is consistently sending packets out each
port of the multiport card, close enough togehter in time that they
_always_ collide and so _always_ fail to autosense.  Or alternatively,
switching the PHY chips to 10Mbit could be confusing the hub for long
enough to break autosense on the other ports of the multiport card.