AIX 3.1 Ethernet problem - anyone seen this before?

[Pat_Barron at TRANSARC.COM]

I've been seeing a very strange problem with our RS/6000's and their
Ethernet interfaces; I was hoping someone here might have seen it, too,
and might be able to point me in the direction of a fix.

We believe that we have an Ethernet card or tranceiver someplace on our
network that is going bad, and is generating garbage Ethernet packets.
Specifically, packets longer than the maximum allowable Ethernet packet
length.  Our Suns react to this by printing a "giant packet" message on
the console and ignoring it.  A number of our RS/6000's react by having
their Ethernet interfaces silently lock up.  I'm not sure if they transmit
packets or not, but they certainly don't receive any.

Each occurence only affects some subset of our machines, and it doesn't
happen on the same set of machines every time.  But on the machines it
does happen on, their Ethernets lock up simultaneously, and it's definitely
correlated to the "giant packet" messages on the Sun.  The only fix we've
found is to reboot the system.

Anyone have any clues what's going on?  My best guess is that the giant
packet is causing the Ethernet card itself to get into a funky state.
Is there any way of resetting the Ethernet card (in terms of performing
a *hardware* reset on it) on the fly?  Any other suggested solutions?

Thanks,
--Pat.