Sorry, I should have made that clearer. The setup originally was 3 computers:
Router-box
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boxa ------ | router-card-a router-card-b | ----- boxb
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Where boxa and boxb are each connected to the router box with a crossover
cable. It's about as simple as you can get to test a router, but right now
I'm just running tests between boxa and router-card-a, in hopes of getting
a repeatable measure of thruput. The router box has the second network
card in and working, but nothing plugged into it.
So routing shouldn't enter into it. Duplex shouldn't either, really; I
think the cards are at half duplex by default, but I'll double check
anyway. And no packets are being dropped, according to ifconfig. Also, it
happens in both directions, and it happens between router-card-b and boxb
as well, when I plug that in, and for that matter between boxa and boxb, in
both directions, if I string a crossover cable all the way across.
I am in the process of exploring all suggestions, and thank you all very
much for the feedback. Additional ideas are still quite welcome. I
confess I was hoping someone would just tell me to tweak a kernel setting,
but I guess I'll keep plugging away.
Thanks again
- greg tillman