I have a server and a box that cannot communicate, a server(fedora 12) with two nics on it, directly connected to say 192.168.1.0 and 192.168.2.0 the route table looks like this
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 192.168.1.1 255.255.255.0 UG 0 0 0 eth0
192.168.2.0 * 255.255.255.0 U 0 0 0 eth1
eth0 = 192.168.1.15
eth1 = 192.168.2.1
and a directly connected user (Mythdora) on the 192.168.2.0 network with ip 192.168.2.2 and route table like so
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.2.0 * 255.255.255.0 U 0 0 0 eth0
the cable is a crossover and it works all three nics work