OS 10.5 - using wifi and ethernet

i have several imacs that i want to access the internet via the wifi and then funnel all other traffic to the hardwired ethernet. i have both an x serve and pc servers (which includes an exchange server)

i have the wifi set as top priority in the network settings followed by ethernet. connecting via afp is no problem seems bonjour or something is directing that type of traffic. i am having trouble connecting via smb to the pc servers. also, dont know how to tell entourage use the ethernet instead of wifi.

i have the dns of the wifi at a 172... and the ethernet is 10....

is there some software that will can act as a traffic filter?

thanks!
d