Disable Route Optimization in Linux

[Bruce]

Greetings,

I'm working toward building up a couple of test fixtures that require me 
to generate multiple channels of Ethernet traffic.  I have some Perl 
code that will allow me to send and receive traffic using specified 
local and peer ports.  I seem to have only one problem that is 
preventing me from getting started.  Linux is optimizing all my traffic 
to go through the default port.

To be more specific, let's assume I have a 8 port switch to be tested.  
Assume I have two Linux boxes with a quad NIC card in each.  Assume the 
8 ports from the two quad NIC cards all get plugged into the switch.  To 
test each switch port I need to be able to generate traffic from all 8 
ports of the two quad NIC cards.  Linux optimizes my routes and sends 
all traffic through the default eth port, even when I specify another port.

Is there any way to turn off the router in Linux or at least override it 
with my desired routes?  I have tried many combinations of "route add", 
"route del", "ip route add x.x.x.x via y.y.y.y.  So far I am striking 
out.  Any help would be appreciated.

I am using Ubuntu 6.10 desktop on an Intel architecture box.

Thank you,
Bruce