You are setting 255.255.255.0 netmasks so the machines are expecting to find .1 .2 .3 machines on the local ethernet interfaces. I don't know why you are doing it like that, but what would fix your problem is getting the Linux router machine to do a proxy-arp. You can turn this on by echo'ing the apporiate incantation to proc. Documentation/proc.txt in your linux source directory should give you the details.
cheers, BM
