embedded wrote:

We've found a way to get ping to fail all of the time by increasing
the size of the ping messages.  When we use the max in Windows of
65500, every ping to the first FCC1 Ethernet is dropped.  However,
when we ping with a size of 65500 to the second FCC2 Ethernet
everything is fine and all echos are successful.

In windows:
ping -l 64000 172.24.100.11  -t

It definitely seems to be a problem with the mpc, but I'm not sure
where to look.  Board? KErnel? boot loader?  The two Ethernet devices
should be configured identically, and looking through the kernel code,
it seems that there aren't any preferred treatment differences.  Could
the problem be in the bit-banging mdio control, or should I look
within fs_enet?  We've got this reproducing on all of our boards and
it could also reside in the board setup...

Does anyone with experience on the ep8248 and/or mpc8272 family,
fs_enet-* code have any ideas where I should look next?

It looks very similar to what I was seeing on ep8248 -- the first 
ethernet port would fail when attempting to receive back-to-back 
packets.  I didn't look into it too closely since I thought it was 
probably a board issue (I had only one, and the firmware never generated 
any traffic that resulted in back-to-back receives).

I'd be very interested if you ever figure out what's wrong.

-Scott